Designing Buildings - User contributions [en]

Performance gap in low energy housing

2012-11-27T08:58:34Z

J65on:

= Introduction =

This article will look at the ways in which low energy buildings are currently regulated and discuss the opportunities that exist to adjust them to reflect user comfort and control in the future.

The current intent of policy is to ‘achieve comfortable low energy buildings’ (Tuohy, 2012), however 'comfort' as a term rarely appears in regulations or statutory minima. It does appear in design guides such as CIBSE guide A, however this is only a design guide and is not always fully implemented in every building built.

The building regulations are a requirement for every building and would be a perfect platform to include for thermal comfort however it does not address thermal comfort in any of the approved documents, they actually mostly seize to be a part of the building process when it is completed and occupied. This is a large problem for the industry as it encourages segregation between the design and build teams and the building occupiers.

The Good Homes Alliance conference 'Closing the Performance gap' showed that monitoring and post occupational evaluation (POE) are essential tools to ensure our low carbon homes are operating as designed, and are comfortable and healthy’ (Good Homes Alliance, 2011). Currently no ongoing post construction tests and checks are enabled through the building regulations, any surveys are usually academic or research motivated. (NHBC Foundation, 2012). This must be overcome if buildings are to move on. Derbyshire supports the need for change and for inclusion of a POE and argues that science cannot grow and evolve without a ‘testing of hypothesis through observed observation, the results of which are fed back into the body of knowledge to generate a new cycle of hypothesis, experiment and feedback’ (Derbyshire S. A., 2002).

<br/>

= Post occupational evaluation =

There are some organisations that do support the implementation of POE, one of the key objectives for the Usable Building Trust is ‘to make building performance evaluation a routine activity for design and building teams’ (Bordass, 2011) however it was noted that this was difficult as design and build teams were often reluctant to participate as the reputation of the designers or the builders could be put into doubt.<br/>

Schemes such as BREEAM also recognise the requirement for POE, under BREEAM New Construction 2011 it is a requirement that a BREEAM In Use assessment is undertaken for any building that achieves an Excellent or Outstanding rating (BRE Global Ltd, 2011). ‘BREEAM In-Use is a scheme to help building managers reduce the running costs and improve the environmental performance of existing buildings. It consists of a standard, easy-to-use assessment methodology and an independent certification process that provides a clear and credible route map to improving sustainability’ (BRE Global Ltd). Although it is designed as a tool to help improve the environmental performance of the building, it can help to bridge the gap between designer and occupant, where the occupant actually has to learn about the building, the way it works and is managed in order to pass the In Use assessment.

But if POE were undertaken, where would the fault lie if the building owners questioned why the building wasn’t performing as designed, the designers or the builders? The answer to this question is a bit of a minefield, however the answer may be that neither may be to blame and actually the building users are not using the building as designed. In the case of the BRE Environmental Office, it was designed as an exemplar case however the energy used in the building was around 90% higher than the designed energy demand (Ni Riain, Fisher, Mackenzie, & Littler, 2000). According to (Tuohy, 2012) there were ten key findings from the POE, eight of these were connected with the controls of the systems, one was that it was occupied differently to designed and the other that there was no energy performance data on display.

The main point to focus on here is the fact that the controls were not implemented as designed compromising user control over the environment, this is supported by (Juricic, Van Den Ham, & Kurvers, 2012) citing ‘user’s opportunity to influence their indoor climate is one of the most important keys to robustness’. However, again to can be difficult to determine whether the controls were incorrectly designed or whether they are being used incorrectly by the occupants. An example of this is as a Passivhaus assessor, this author is often asked whether the windows can be opened in a Passivhaus because the air tightness of the building is designed to be very low, the myth is that the windows shouldn’t be opened however the PHPP includes openable windows as an important control for mitigating overheating which is wholly dependent on the users knowledge of that control. It could be very easy for an occupant to be in an overheating home and leave the windows closed because they think it will affect the performance of the building and blame the building for not performing correctly without the correct operative knowledge.

<br/>

= improving standards =

Tuohy indicates that ‘there are policy initiatives aimed at improving industry processes such as: Soft Landings, BREEAM, LEED, Green Star, AGBR and BIM’ (Tuohy, 2012). The CLG’s Code for Sustainable Homes (CfSH) has also established itself as a ‘proving ground’ for new guidance and regulations, it is currently a voluntary standard except for social housing schemes in England. There are also some planning authorities that use the CfSH as a mandatory standard implementable through the planning system; this and voluntary schemes account for only covers 16% of total CfSH assessed homes (CLG, 2012).<br/>

This 'proving ground' allows new ideas or strategies to be implemented on a section of the industry before being rolled out to national policy. This has been proven in the past through the use of targets for carbon emission compliance over the regulations which in the May 09 version of the Code was required at 25% above the building Regulations Part L1a 2006, and Code 4 was 44% above. The revision of the building Regulation Part L1a 2010 revised the compliance level in SAP to be in line with this new figure, with the equivalent carbon reduction of 25% over Part L1a 2006. This is likely to carry on into the revision of Part L1a 2013 with a further 25% reduction (44% over Part L1a 2006) and the introduction of Fabric Energy Efficiency (FEE) standards (CLG, 2012) which was introduced into the CfSH in Nov 2010.

It has been recognised that user knowledge of how the buildings work is important to how a building functions, the CfSH has dedicated credits for the production of a Home User Guide in order ‘to promote the provision of guidance enabling occupants to understand and operate their home efficiently and make the best use of local facilities’ (CLG, 2010). BREEAM has similar credits for the production of a Building User Guide ‘to ensure delivery of a functional and sustainable asset designed and built in accordance with performance expectations’ (BRE Global Ltd, 2011), however BREEAM goes one step further and introduces credits for thermal comfort, the criteria being ‘to ensure that appropriate thermal comfort levels are achieved through design, and controls are selected to maintain a thermally comfortable environment for occupants within the building.’. This criteria for thermal comfort indicates a step change for thermal comfort and the importance that it is seen to have in the environmental credentials of a building. Should these credits prove implementable industry wide perhaps they may enter into the regulations the same way of the example above in the CfSH.

<br/>

= compliance =

Looking into the future of POE, in May 2011 the Minister for State for Housing and Local Government reaffirmed the UK Government commitment to zero carbon homes from 2016, stating that ‘the carbon footprint of new homes cannot be allowed to add to our overall carbon reduction targets. But this needs to be done in ways which are cost effective and which protects the viability of house building’ (The Rt Hon Grant Shapps, 2011)

The zero carbon hub explains that ‘The definition of zero carbon was originally envisaged to be Level 6 of the Code for Sustainable Homes, which has only been achieved in practice by a handful of exemplar schemes.’ (Zero Carbon Hub) CLG has released figures that show that only 128 homes in the UK have been certified at Post Construction Stage as Code Level 6 up to December 2011 (CLG, 2012). This is a very small minority of the 52,486 homes that have received a Post Construction Stage Code certificate. The Zero Carbon Hub explains that this is due to difficulties in the way the homes are assessed, explaining that homes need to be treated as their own ‘individual energy island’, which means that they must achieve net zero carbon on their own merits which generally will require the onsite production of renewable energy.

The current definition of zero carbon homes is no longer Level 6 of the Code for Sustainable Homes, and in fact it is not based on the Code at all. Instead the definition is based upon achieving a minimum level in Fabric Energy Efficiency, achieving a minimum level of Carbon Compliance and achieving net zero carbon through Allowable Solutions (Zero Carbon Hub, 2008). This will be implemented through the building regulations and through the Standard Assessment Procedure.

<br/>

= performance gap =

Although the definition of zero carbon has been revised so that it is no longer based on Code 6 of the Code for Sustainable Homes, the majority of those defined as net zero carbon have been through this definition, however there is cause to question whether homes designed to this standard are actually being built to this standard. This is referred to as the performance gap, where the calculated designed performance does not meet the as built performance. The NHBC foundation questions ‘the ability of the SAP assessment model to make an accurate prediction of the energy use of homes given the large number of variables and the accuracy of the data inputs’ (NHBC Foundation, 2012) however a large variety of reasons could contribute to the performance gap including the calculation methods, build quality, construction techniques, or user behaviour. Hernandez Neto supports this and states that ‘the user should have the expertise to choose the most suitable tool depending on the type of analysis being done’. (Hernandez Neto, Fiorelli, & Buoro, 2012). Unfortunately in the case of Building Regulation compliance only SAP and SBEM are the accepted methods of showing compliance, so perhaps it would be more appropriate to allow to be used a different software that may produce more accurate results.

The NHBC Foundation lists 7 areas to be considered in order to understand the reasons for how a performance gap arises, (NHBC Foundation, 2012) due to ongoing scuntination of the SAP calculation model, Zero Carbon Hub has concluded that SAP is the best model to continue to use to evaluate building performance and because the validity of data is verified through the use of OCDEAs, who must be a member of a licencing organisation that operated regular QA verification testing on calculations the expertise to input data correctly is present.

<br/>

= case studies =

Unfortunately because low energy homes are rare in the UK and even fewer are subject of Post Occupational Evaluation the actual performance is not known. The BUS supports this and states that benchmarking could take 3-5 years to populate (BUS, 2012).

Leaman states that real world research means that effects ‘are more difficult to predict, e.g. unanticipated operating modes for innovative technologies, or alterations in user behaviour’ (Bordass, Stevenson, & Leaman, Building Evaluation: Practice and Principles, 2010). This idea is supported by Vale, who states that ‘Post Occupation Evaluation (POE) could have a significant role in the lowering of environmental impacts, but the framing of domestic POE must embrace a rating of the occupants’ behaviour’ (Vale & Vale, 2010).<br/>

Occupant behaviour, however is not as simple as designing a building to supply a uniform temperature as in air conditioned buildings, although in a research study (Juricic, Van Den Ham, & Kurvers, 2012) found that there was no difference between the energy use in user orientated buildings than those designed ignoring user profiles and concluded that ‘the idea of giving the opportunity to the user to interact with the environment is not necessarily synonym with higher energy use’. This however does not mean that because the building uses the same amount of energy whether users are in control or not that the users achieve the same level of thermal comfort, (Nicol, Humphreys, & Roaf, Adaptive Thermal Comfort: Principles and Practice, 2012) state that ‘behaviour is an important role in our thermal interaction with the environmental’ including the changing of clothes, changes of posture and metabolic rates, moving to a different thermal environment and changing the current environment using thermal controls. It has been found that the range of temperatures that are acceptable is around 70% wider for natural ventilated building than for HVAC buildings showing that ‘higher levels of personal control makes users more tolerant of wider temperature swings’ (De Dear & Brager, 1998).

<br/>

= technology =

Tuohy also looks at new technologies that are often used in low energy buildings and describes ‘new technology systems do not work as well as predicted’ and that the ‘controls are poorly designed’ (Tuohy, 2012). (NHBC Foundation, 2012) also cites mechanical and electrical installations as one of its 7 factors that contribute to the performance gap. The actual efficiency of technologies is particularly problematic as it could have a large effect on the performance gap, as efficiency is effected by the whole system, ie the boiler, pipework and inline components. It has been found that an 86% efficient gas boiler performed as poorly as 55% when the whole system was taken into account (Zero Carbon Hub, 2010).<br/>

This is particularly true in relatively new technologies such as heat pumps, the figure 1 shows COP curves for a communal Ground Source Heat Pump system. It can be seen that the actual system efficiency is well below the expected (designed) efficiency and actually in the summer shows COP of just above 1 which is the efficiency of a standard electrical heating system. Electrical systems generally perform poorly in SAPs as the fuel factor used is 0.52kgCO2/kWh as opposed to gas which is 0.19kgCO2/kWh (DECC, 2010), the only reason heat pumps do well in SAPs as opposed to a gas system is that the COP of around 2.5 will bring the carbon emissions in line with that of gas. With the government pushing the use of these kind of technologies through SAP where heat pumps fairly easily gain high levels of carbon reduction and through the use of initiatives such as FITs and RHIs, the latter of which pays for heat energy produced using low carbon technologies such as heat pumps.

[[File:COP Graph.png|RTENOTITLE]]

Figure 1 COP curves for a communal Ground Source Heat Pump system (Zero Carbon Hub, 2010)

<br/>

= conclusion =

To conclude, the mechanisms to make low energy buildings both exist and are in use through formats such as the building regulations which are changing towards zero carbon which encourages the building of low energy buildings. There are some problems with the implementations of new low carbon heating systems such as heat pumps which don’t seem to match up the designed performance with the actual installed performance which leads to inconsistencies in the energy use in the buildings when compared with the designed energy use. This performance gap is known by the industry however the solutions to the problem are not yet implemented in a way that lessens the impact. The most critical of these is to learn from building utilised POE techniques.

So the real challenge is to make 'comfortable low energy buildings', the scientific idea of comfort is still fairly new however there are research projects ongoing that seek to identify the effect that thermal comfort has on the energy use of buildings. It does seem to be clear that the comfort of building occupants has a large effect on the success of the building and makes it even more important to implement POE to evaluate the effect that thermal comfort and user occupation patterns actually have on the building performance and allow future projects to learn from and improve on their design.
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= References and further reading =

<br/>Bordass, B. (2011). The Usable Buildings Trust and New Professionalism. ''Impact, Jan/Feb'', 16-17.

Bordass, B., Stevenson, F., & Leaman, A. (2010). Building Evaluation: Practice and Principles. ''Building Research and Information, 38:5'', 564-577.

BRE Global Ltd. (2011). ''BREEAM New Construction: Non Domestic Buildings Technical Manual SD5073 - 2.0:2011.'' Watford: BRE Global Ltd.

BRE Global Ltd. (n.d.). ''BREEAM In Use''. Retrieved 05 25, 2012, from BREEAM: [http://www.breeam.org/page.jsp?id=373 http://www.breeam.org/page.jsp?id=373]

BRE Trust. (2010). ''Energy Efficiency in New and Existing Buildings: Comparitive Costs and CO2 Savings.'' Watford: BRE Press.

BUS. (2012). ''The Building Use Studies (BUS) Occupant Survey: Origins and Approach Q&A.'' London: BUS.

CLG. (2010). ''Code for Sustainable Homes: Technical Guide November 2010.'' London: RIBA Publishing.

CLG. (2012). ''2012 Consultation on CHnages to the Building Regulations in England: Section Two Part L (COnservation of Fuel and Power).'' London: CLG.

CLG. (2012). ''Code for Sustainable Homes and Energy Peformance of Buildings: Cumulative and Quarterly Data for England, Wales and Northern Ireland up to the end of December 2011.'' CLG.

De Dear, R., & Brager, G. (1998). Developing an Adaptive Model of Thermal Comfort and Preference. ''ASHRAE Transactions, 104 (1)'', 145-167.

DECC. (2010). ''The Government’s Standard Assessment Procedure for Energy Rating of Dwellings: 2009 edition .'' Watford: BRE.

Derbyshire, S. (2003). Architecture, Science and Feedback. ''Journal of Building Research and Information''.

Derbyshire, S. A. (2002). Architecture, Science and Feedback. ''Building Research and Information''.

Edwards, B. (2010). ''Rough Guide to Sustainability.'' Bristol: RIBA Publishing.

Energy Savings Trust. (2008). ''Monitoring Energy and Carbon Performance in New Homes.'' London: Energy Savings Trust.

Good Homes Alliance. (2011). Closing the Performance Gap: Low Carbon 4 Real plus Feedback and Monitoring. ''Closing the Performance Gap: Low Carbon 4 Real plus Feedback and Monitoring.'' London.

Hernandez Neto, A., Fiorelli, F. A., & Buoro, A. B. (2012). Computational Analysis - Evaluation of the impact of the user expertise on the results of simulation tools. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

Juricic, S., Van Den Ham, E., & Kurvers, S. (2012). Relationship between Building Characteristics and Energy Use and Health and Comfort Perception. ''The Changing Context of COmfort in an Unpredictable World.'' Windsor: NCEUB.

Leaman, A. (2003). Post Occupational Evaluation. ''Gaia Research Sustainable Construction Continuing Proffesional Development (CPD) Seminars''. London: Building Use Studies.

Leaman, A., Stevenson, F., & Bordass, B. (2010). Building Evaluation: Practice and Principles. ''Building Research and Information, 38:5'', 564-577.

Lomas, K., & Kane, T. (2012). Summertime temperatures in 282 UK Homes: Thermal Comfort and Overheating Risk. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

NHBC Foundation. (2012, March 01). Retrieved 2012, from NHBC Foundation Blog: [http://nhbcfoundation.blogspot.co.uk/2012/03/house-builders-not-solely-to-blame-for.html http://nhbcfoundation.blogspot.co.uk/2012/03/house-builders-not-solely-to-blame-for.html]

NHBC Foundation. (2012). ''Low and Zero Carbon Homes: Understanding the Performance Challenge.'' Watford: BRE Press.

Ni Riain, C., Fisher, J., Mackenzie, F., & Littler, J. (2000). BRE's Environmental Building: Energy Performance in Use. ''20 20 Vision.'' Dublin: CIBSE/ASHRAE.

Nicol, F., Humphreys, M., & Roaf, S. (2012). ''Adaptive Thermal Comfort: Principles and Practice.'' Tonbridge: Greengate Publishing Services.

Nicol, F., Humphreys, M., Sykes, O., & Roaf, S. (1995). ''Standards for Thermal Comfort.'' Padstow: T. J. Press (Padstow) Ltd.

Roaf, S. (2004). ''Closing the Loop: Benchmarks for Sustainable Buildings.'' Cornwall: RIBA Enterprises Ltd.

Stevenson, F., & Leaman, A. (2010). Evaluating Housing Performance in Relation to Human Behaviour: New Challenges. ''Building Research and Information, 38:5'', 437-441.

The Rt Hon Grant Shapps, M. (2011, May 17). ''Buildings and the Environment''. Retrieved 2012, from CLG: [http://www.communities.gov.uk/statements/corporate/buildingsenvironment http://www.communities.gov.uk/statements/corporate/buildingsenvironment]

Tuohy, P. (2012). Why Advanced Buildings Don't Work. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

Tweed, C., & Dixon, D. (2012). Thermal Experience is an era of Low Energy Domestic Heating Systems. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

Vale, B., & Vale, R. (2010). Domestic Energy Use, Lifestyles and POE: Past Lessons for Current Problems. ''Building Research and Information, 38:5'', 578-588.

Zero Carbon Hub. (2008). ''Definition of Zero Carbon Homes and Non-Domestic Buildings Consultation .'' Zero Carbon Hub.

Zero Carbon Hub. (2010). ''Carbon Compliance for Tomorrow's New Homes: Closing the Gap Between Deisgned and Built Performance.'' London: Zero Carbon Hub.

Zero Carbon Hub. (n.d.). ''About''. Retrieved May 13, 2012, from Zero Carbon Hub: [http://www.zerocarbonhub.org/about.aspx?page=2 http://www.zerocarbonhub.org/about.aspx?page=2]

Zero Carbon Hub. (n.d.). ''Definition''. Retrieved May 12, 2012, from Zero Carbon Hub: [http://www.zerocarbonhub.org/definition.aspx http://www.zerocarbonhub.org/definition.aspx]

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[[Category:Student_architect_essay_competition]]

Performance gap in low energy housing

2012-11-13T17:32:13Z

J65on:

= Introduction =

The current intent of policy is to ‘achieve comfortable low energy buildings’ (Tuohy, 2012), however 'comfort' as a term rarely appears in regulations or statutory minima. It does appear in design guides such as CIBSE guide A, however this is only a design guide and is not always fully implemented in every building built.

The building regulations are a requirement for every building and would be a perfect platform to include for thermal comfort however it does not address thermal comfort in any of the approved documents, they actually mostly seize to be a part of the building process when it is completed and occupied. This is a large problem for the industry as it encourages segregation between the design and build teams and the building occupiers.

The Good Homes Alliance conference 'Closing the Performance gap' showed that monitoring and post occupational evaluation (POE) are essential tools to ensure our low carbon homes are operating as designed, and are comfortable and healthy’ (Good Homes Alliance, 2011). Currently no ongoing post construction tests and checks are enabled through the building regulations, any surveys are usually academic or research motivated. (NHBC Foundation, 2012). This must be overcome if buildings are to move on. Derbyshire supports the need for change and for inclusion of a POE and argues that science cannot grow and evolve without a ‘testing of hypothesis through observed observation, the results of which are fed back into the body of knowledge to generate a new cycle of hypothesis, experiment and feedback’ (Derbyshire S. A., 2002).

<br/>

= Post occupational evaluation =

There are some organisations that do support the implementation of POE, one of the key objectives for the Usable Building Trust is ‘to make building performance evaluation a routine activity for design and building teams’ (Bordass, 2011) however it was noted that this was difficult as design and build teams were often reluctant to participate as the reputation of the designers or the builders could be put into doubt.<br/>

Schemes such as BREEAM also recognise the requirement for POE, under BREEAM New Construction 2011 it is a requirement that a BREEAM In Use assessment is undertaken for any building that achieves an Excellent or Outstanding rating (BRE Global Ltd, 2011). ‘BREEAM In-Use is a scheme to help building managers reduce the running costs and improve the environmental performance of existing buildings. It consists of a standard, easy-to-use assessment methodology and an independent certification process that provides a clear and credible route map to improving sustainability’ (BRE Global Ltd). Although it is designed as a tool to help improve the environmental performance of the building, it can help to bridge the gap between designer and occupant, where the occupant actually has to learn about the building, the way it works and is managed in order to pass the In Use assessment.

But if POE were undertaken, where would the fault lie if the building owners questioned why the building wasn’t performing as designed, the designers or the builders? The answer to this question is a bit of a minefield, however the answer may be that neither may be to blame and actually the building users are not using the building as designed. In the case of the BRE Environmental Office, it was designed as an exemplar case however the energy used in the building was around 90% higher than the designed energy demand (Ni Riain, Fisher, Mackenzie, & Littler, 2000). According to (Tuohy, 2012) there were ten key findings from the POE, eight of these were connected with the controls of the systems, one was that it was occupied differently to designed and the other that there was no energy performance data on display.

The main point to focus on here is the fact that the controls were not implemented as designed compromising user control over the environment, this is supported by (Juricic, Van Den Ham, & Kurvers, 2012) citing ‘user’s opportunity to influence their indoor climate is one of the most important keys to robustness’. However, again to can be difficult to determine whether the controls were incorrectly designed or whether they are being used incorrectly by the occupants. An example of this is as a Passivhaus assessor, this author is often asked whether the windows can be opened in a Passivhaus because the air tightness of the building is designed to be very low, the myth is that the windows shouldn’t be opened however the PHPP includes openable windows as an important control for mitigating overheating which is wholly dependent on the users knowledge of that control. It could be very easy for an occupant to be in an overheating home and leave the windows closed because they think it will affect the performance of the building and blame the building for not performing correctly without the correct operative knowledge.

<br/>

= improving standards =

Tuohy indicates that ‘there are policy initiatives aimed at improving industry processes such as: Soft Landings, BREEAM, LEED, Green Star, AGBR and BIM’ (Tuohy, 2012). The CLG’s Code for Sustainable Homes (CfSH) has also established itself as a ‘proving ground’ for new guidance and regulations, it is currently a voluntary standard except for social housing schemes in England. There are also some planning authorities that use the CfSH as a mandatory standard implementable through the planning system; this and voluntary schemes account for only covers 16% of total CfSH assessed homes (CLG, 2012).<br/>

This 'proving ground' allows new ideas or strategies to be implemented on a section of the industry before being rolled out to national policy. This has been proven in the past through the use of targets for carbon emission compliance over the regulations which in the May 09 version of the Code was required at 25% above the building Regulations Part L1a 2006, and Code 4 was 44% above. The revision of the building Regulation Part L1a 2010 revised the compliance level in SAP to be in line with this new figure, with the equivalent carbon reduction of 25% over Part L1a 2006. This is likely to carry on into the revision of Part L1a 2013 with a further 25% reduction (44% over Part L1a 2006) and the introduction of Fabric Energy Efficiency (FEE) standards (CLG, 2012) which was introduced into the CfSH in Nov 2010.

It has been recognised that user knowledge of how the buildings work is important to how a building functions, the CfSH has dedicated credits for the production of a Home User Guide in order ‘to promote the provision of guidance enabling occupants to understand and operate their home efficiently and make the best use of local facilities’ (CLG, 2010). BREEAM has similar credits for the production of a Building User Guide ‘to ensure delivery of a functional and sustainable asset designed and built in accordance with performance expectations’ (BRE Global Ltd, 2011), however BREEAM goes one step further and introduces credits for thermal comfort, the criteria being ‘to ensure that appropriate thermal comfort levels are achieved through design, and controls are selected to maintain a thermally comfortable environment for occupants within the building.’. This criteria for thermal comfort indicates a step change for thermal comfort and the importance that it is seen to have in the environmental credentials of a building. Should these credits prove implementable industry wide perhaps they may enter into the regulations the same way of the example above in the CfSH.

<br/>

= compliance =

Looking into the future of POE, in May 2011 the Minister for State for Housing and Local Government reaffirmed the UK Government commitment to zero carbon homes from 2016, stating that ‘the carbon footprint of new homes cannot be allowed to add to our overall carbon reduction targets. But this needs to be done in ways which are cost effective and which protects the viability of house building’ (The Rt Hon Grant Shapps, 2011)

The zero carbon hub explains that ‘The definition of zero carbon was originally envisaged to be Level 6 of the Code for Sustainable Homes, which has only been achieved in practice by a handful of exemplar schemes.’ (Zero Carbon Hub) CLG has released figures that show that only 128 homes in the UK have been certified at Post Construction Stage as Code Level 6 up to December 2011 (CLG, 2012). This is a very small minority of the 52,486 homes that have received a Post Construction Stage Code certificate. The Zero Carbon Hub explains that this is due to difficulties in the way the homes are assessed, explaining that homes need to be treated as their own ‘individual energy island’, which means that they must achieve net zero carbon on their own merits which generally will require the onsite production of renewable energy.

The current definition of zero carbon homes is no longer Level 6 of the Code for Sustainable Homes, and in fact it is not based on the Code at all. Instead the definition is based upon achieving a minimum level in Fabric Energy Efficiency, achieving a minimum level of Carbon Compliance and achieving net zero carbon through Allowable Solutions (Zero Carbon Hub, 2008). This will be implemented through the building regulations and through the Standard Assessment Procedure.

<br/>

= performance gap =

Although the definition of zero carbon has been revised so that it is no longer based on Code 6 of the Code for Sustainable Homes, the majority of those defined as net zero carbon have been through this definition, however there is cause to question whether homes designed to this standard are actually being built to this standard. This is referred to as the performance gap, where the calculated designed performance does not meet the as built performance. The NHBC foundation questions ‘the ability of the SAP assessment model to make an accurate prediction of the energy use of homes given the large number of variables and the accuracy of the data inputs’ (NHBC Foundation, 2012) however a large variety of reasons could contribute to the performance gap including the calculation methods, build quality, construction techniques, or user behaviour. Hernandez Neto supports this and states that ‘the user should have the expertise to choose the most suitable tool depending on the type of analysis being done’. (Hernandez Neto, Fiorelli, & Buoro, 2012). Unfortunately in the case of Building Regulation compliance only SAP and SBEM are the accepted methods of showing compliance, so perhaps it would be more appropriate to allow to be used a different software that may produce more accurate results.

The NHBC Foundation lists 7 areas to be considered in order to understand the reasons for how a performance gap arises, (NHBC Foundation, 2012) due to ongoing scuntination of the SAP calculation model, Zero Carbon Hub has concluded that SAP is the best model to continue to use to evaluate building performance and because the validity of data is verified through the use of OCDEAs, who must be a member of a licencing organisation that operated regular QA verification testing on calculations the expertise to input data correctly is present.

<br/>

= case studies =

Unfortunately because low energy homes are rare in the UK and even fewer are subject of Post Occupational Evaluation the actual performance is not known. The BUS supports this and states that benchmarking could take 3-5 years to populate (BUS, 2012).

Leaman states that real world research means that effects ‘are more difficult to predict, e.g. unanticipated operating modes for innovative technologies, or alterations in user behaviour’ (Bordass, Stevenson, & Leaman, Building Evaluation: Practice and Principles, 2010). This idea is supported by Vale, who states that ‘Post Occupation Evaluation (POE) could have a significant role in the lowering of environmental impacts, but the framing of domestic POE must embrace a rating of the occupants’ behaviour’ (Vale & Vale, 2010).<br/>

Occupant behaviour, however is not as simple as designing a building to supply a uniform temperature as in air conditioned buildings, although in a research study (Juricic, Van Den Ham, & Kurvers, 2012) found that there was no difference between the energy use in user orientated buildings than those designed ignoring user profiles and concluded that ‘the idea of giving the opportunity to the user to interact with the environment is not necessarily synonym with higher energy use’. This however does not mean that because the building uses the same amount of energy whether users are in control or not that the users achieve the same level of thermal comfort, (Nicol, Humphreys, & Roaf, Adaptive Thermal Comfort: Principles and Practice, 2012) state that ‘behaviour is an important role in our thermal interaction with the environmental’ including the changing of clothes, changes of posture and metabolic rates, moving to a different thermal environment and changing the current environment using thermal controls. It has been found that the range of temperatures that are acceptable is around 70% wider for natural ventilated building than for HVAC buildings showing that ‘higher levels of personal control makes users more tolerant of wider temperature swings’ (De Dear & Brager, 1998).

<br/>

= technology =

Tuohy also looks at new technologies that are often used in low energy buildings and describes ‘new technology systems do not work as well as predicted’ and that the ‘controls are poorly designed’ (Tuohy, 2012). (NHBC Foundation, 2012) also cites mechanical and electrical installations as one of its 7 factors that contribute to the performance gap. The actual efficiency of technologies is particularly problematic as it could have a large effect on the performance gap, as efficiency is effected by the whole system, ie the boiler, pipework and inline components. It has been found that an 86% efficient gas boiler performed as poorly as 55% when the whole system was taken into account (Zero Carbon Hub, 2010).<br/>

This is particularly true in relatively new technologies such as heat pumps, the figure 1 shows COP curves for a communal Ground Source Heat Pump system. It can be seen that the actual system efficiency is well below the expected (designed) efficiency and actually in the summer shows COP of just above 1 which is the efficiency of a standard electrical heating system. Electrical systems generally perform poorly in SAPs as the fuel factor used is 0.52kgCO2/kWh as opposed to gas which is 0.19kgCO2/kWh (DECC, 2010), the only reason heat pumps do well in SAPs as opposed to a gas system is that the COP of around 2.5 will bring the carbon emissions in line with that of gas. With the government pushing the use of these kind of technologies through SAP where heat pumps fairly easily gain high levels of carbon reduction and through the use of initiatives such as FITs and RHIs, the latter of which pays for heat energy produced using low carbon technologies such as heat pumps.

[[File:COP Graph.png|RTENOTITLE]]

Figure 1 COP curves for a communal Ground Source Heat Pump system (Zero Carbon Hub, 2010)

<br/>

= conclusion =

To conclude, the mechanisms to make low energy buildings both exist and are in use through formats such as the building regulations which are changing towards zero carbon which encourages the building of low energy buildings. There are some problems with the implementations of new low carbon heating systems such as heat pumps which don’t seem to match up the designed performance with the actual installed performance which leads to inconsistencies in the energy use in the buildings when compared with the designed energy use. This performance gap is known by the industry however the solutions to the problem are not yet implemented in a way that lessens the impact. The most critical of these is to learn from building utilised POE techniques.

So the real challenge is to make 'comfortable low energy buildings', the scientific idea of comfort is still fairly new however there are research projects ongoing that seek to identify the effect that thermal comfort has on the energy use of buildings. It does seem to be clear that the comfort of building occupants has a large effect on the success of the building and makes it even more important to implement POE to evaluate the effect that thermal comfort and user occupation patterns actually have on the building performance and allow future projects to learn from and improve on their design.
<div>
<br/>

= References and further reading =

<br/>Bordass, B. (2011). The Usable Buildings Trust and New Professionalism. ''Impact, Jan/Feb'', 16-17.

Bordass, B., Stevenson, F., & Leaman, A. (2010). Building Evaluation: Practice and Principles. ''Building Research and Information, 38:5'', 564-577.

BRE Global Ltd. (2011). ''BREEAM New Construction: Non Domestic Buildings Technical Manual SD5073 - 2.0:2011.'' Watford: BRE Global Ltd.

BRE Global Ltd. (n.d.). ''BREEAM In Use''. Retrieved 05 25, 2012, from BREEAM: [http://www.breeam.org/page.jsp?id=373 http://www.breeam.org/page.jsp?id=373]

BRE Trust. (2010). ''Energy Efficiency in New and Existing Buildings: Comparitive Costs and CO2 Savings.'' Watford: BRE Press.

BUS. (2012). ''The Building Use Studies (BUS) Occupant Survey: Origins and Approach Q&A.'' London: BUS.

CLG. (2010). ''Code for Sustainable Homes: Technical Guide November 2010.'' London: RIBA Publishing.

CLG. (2012). ''2012 Consultation on CHnages to the Building Regulations in England: Section Two Part L (COnservation of Fuel and Power).'' London: CLG.

CLG. (2012). ''Code for Sustainable Homes and Energy Peformance of Buildings: Cumulative and Quarterly Data for England, Wales and Northern Ireland up to the end of December 2011.'' CLG.

De Dear, R., & Brager, G. (1998). Developing an Adaptive Model of Thermal Comfort and Preference. ''ASHRAE Transactions, 104 (1)'', 145-167.

DECC. (2010). ''The Government’s Standard Assessment Procedure for Energy Rating of Dwellings: 2009 edition .'' Watford: BRE.

Derbyshire, S. (2003). Architecture, Science and Feedback. ''Journal of Building Research and Information''.

Derbyshire, S. A. (2002). Architecture, Science and Feedback. ''Building Research and Information''.

Edwards, B. (2010). ''Rough Guide to Sustainability.'' Bristol: RIBA Publishing.

Energy Savings Trust. (2008). ''Monitoring Energy and Carbon Performance in New Homes.'' London: Energy Savings Trust.

Good Homes Alliance. (2011). Closing the Performance Gap: Low Carbon 4 Real plus Feedback and Monitoring. ''Closing the Performance Gap: Low Carbon 4 Real plus Feedback and Monitoring.'' London.

Hernandez Neto, A., Fiorelli, F. A., & Buoro, A. B. (2012). Computational Analysis - Evaluation of the impact of the user expertise on the results of simulation tools. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

Juricic, S., Van Den Ham, E., & Kurvers, S. (2012). Relationship between Building Characteristics and Energy Use and Health and Comfort Perception. ''The Changing Context of COmfort in an Unpredictable World.'' Windsor: NCEUB.

Leaman, A. (2003). Post Occupational Evaluation. ''Gaia Research Sustainable Construction Continuing Proffesional Development (CPD) Seminars''. London: Building Use Studies.

Leaman, A., Stevenson, F., & Bordass, B. (2010). Building Evaluation: Practice and Principles. ''Building Research and Information, 38:5'', 564-577.

Lomas, K., & Kane, T. (2012). Summertime temperatures in 282 UK Homes: Thermal Comfort and Overheating Risk. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

NHBC Foundation. (2012, March 01). Retrieved 2012, from NHBC Foundation Blog: [http://nhbcfoundation.blogspot.co.uk/2012/03/house-builders-not-solely-to-blame-for.html http://nhbcfoundation.blogspot.co.uk/2012/03/house-builders-not-solely-to-blame-for.html]

NHBC Foundation. (2012). ''Low and Zero Carbon Homes: Understanding the Performance Challenge.'' Watford: BRE Press.

Ni Riain, C., Fisher, J., Mackenzie, F., & Littler, J. (2000). BRE's Environmental Building: Energy Performance in Use. ''20 20 Vision.'' Dublin: CIBSE/ASHRAE.

Nicol, F., Humphreys, M., & Roaf, S. (2012). ''Adaptive Thermal Comfort: Principles and Practice.'' Tonbridge: Greengate Publishing Services.

Nicol, F., Humphreys, M., Sykes, O., & Roaf, S. (1995). ''Standards for Thermal Comfort.'' Padstow: T. J. Press (Padstow) Ltd.

Roaf, S. (2004). ''Closing the Loop: Benchmarks for Sustainable Buildings.'' Cornwall: RIBA Enterprises Ltd.

Stevenson, F., & Leaman, A. (2010). Evaluating Housing Performance in Relation to Human Behaviour: New Challenges. ''Building Research and Information, 38:5'', 437-441.

The Rt Hon Grant Shapps, M. (2011, May 17). ''Buildings and the Environment''. Retrieved 2012, from CLG: [http://www.communities.gov.uk/statements/corporate/buildingsenvironment http://www.communities.gov.uk/statements/corporate/buildingsenvironment]

Tuohy, P. (2012). Why Advanced Buildings Don't Work. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

Tweed, C., & Dixon, D. (2012). Thermal Experience is an era of Low Energy Domestic Heating Systems. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

Vale, B., & Vale, R. (2010). Domestic Energy Use, Lifestyles and POE: Past Lessons for Current Problems. ''Building Research and Information, 38:5'', 578-588.

Zero Carbon Hub. (2008). ''Definition of Zero Carbon Homes and Non-Domestic Buildings Consultation .'' Zero Carbon Hub.

Zero Carbon Hub. (2010). ''Carbon Compliance for Tomorrow's New Homes: Closing the Gap Between Deisgned and Built Performance.'' London: Zero Carbon Hub.

Zero Carbon Hub. (n.d.). ''About''. Retrieved May 13, 2012, from Zero Carbon Hub: [http://www.zerocarbonhub.org/about.aspx?page=2 http://www.zerocarbonhub.org/about.aspx?page=2]

Zero Carbon Hub. (n.d.). ''Definition''. Retrieved May 12, 2012, from Zero Carbon Hub: [http://www.zerocarbonhub.org/definition.aspx http://www.zerocarbonhub.org/definition.aspx]

<br/>
</div>

[[Category:Student_architect_essay_competition]]

Performance gap in low energy housing

2012-11-13T17:26:11Z

J65on:

How to make comfortable low energy buildings that work?

<br/>

The current intent of policy is to ‘achieve comfortable low energy buildings’ (Tuohy, 2012), however 'comfort' as a term rarely appears in regulations or statutory minima. It does appear in design guides such as CIBSE guide A, however this is only a design guide and is not always fully implemented in every building built. <br/>

The building regulations are a requirement for every building and would be a perfect platform to include for thermal comfort however it does not address thermal comfort in any of the approved documents, they actually mostly seize to be a part of the building process when it is completed and occupied. This is a large problem for the industry as it encourages segregation between the design and build teams and the building occupiers.

<br/>

The Good Homes Alliance conference 'Closing the Performance gap' showed that monitoring and post occupational evaluation (POE) are essential tools to ensure our low carbon homes are operating as designed, and are comfortable and healthy’ (Good Homes Alliance, 2011). Currently no ongoing post construction tests and checks are enabled through the building regulations, any surveys are usually academic or research motivated. (NHBC Foundation, 2012). This must be overcome if buildings are to move on. Derbyshire supports the need for change and for inclusion of a POE and argues that science cannot grow and evolve without a ‘testing of hypothesis through observed observation, the results of which are fed back into the body of knowledge to generate a new cycle of hypothesis, experiment and feedback’ (Derbyshire S. A., 2002).

<br/>

There are some organisations that do support the implementation of POE, one of the key objectives for the Usable Building Trust is ‘to make building performance evaluation a routine activity for design and building teams’ (Bordass, 2011) however it was noted that this was difficult as design and build teams were often reluctant to participate as the reputation of the designers or the builders could be put into doubt. <br/>

Schemes such as BREEAM also recognise the requirement for POE, under BREEAM New Construction 2011 it is a requirement that a BREEAM In Use assessment is undertaken for any building that achieves an Excellent or Outstanding rating (BRE Global Ltd, 2011). ‘BREEAM In-Use is a scheme to help building managers reduce the running costs and improve the environmental performance of existing buildings. It consists of a standard, easy-to-use assessment methodology and an independent certification process that provides a clear and credible route map to improving sustainability’ (BRE Global Ltd). Although it is designed as a tool to help improve the environmental performance of the building, it can help to bridge the gap between designer and occupant, where the occupant actually has to learn about the building, the way it works and is managed in order to pass the In Use assessment.

<br/>

But if POE were undertaken, where would the fault lie if the building owners questioned why the building wasn’t performing as designed, the designers or the builders? The answer to this question is a bit of a minefield, however the answer may be that neither may be to blame and actually the building users are not using the building as designed. In the case of the BRE Environmental Office, it was designed as an exemplar case however the energy used in the building was around 90% higher than the designed energy demand (Ni Riain, Fisher, Mackenzie, & Littler, 2000). According to (Tuohy, 2012) there were ten key findings from the POE, eight of these were connected with the controls of the systems, one was that it was occupied differently to designed and the other that there was no energy performance data on display. <br/>

The main point to focus on here is the fact that the controls were not implemented as designed compromising user control over the environment, this is supported by (Juricic, Van Den Ham, & Kurvers, 2012) citing ‘user’s opportunity to influence their indoor climate is one of the most important keys to robustness’. However, again to can be difficult to determine whether the controls were incorrectly designed or whether they are being used incorrectly by the occupants. An example of this is as a Passivhaus assessor, this author is often asked whether the windows can be opened in a Passivhaus because the air tightness of the building is designed to be very low, the myth is that the windows shouldn’t be opened however the PHPP includes openable windows as an important control for mitigating overheating which is wholly dependent on the users knowledge of that control. It could be very easy for an occupant to be in an overheating home and leave the windows closed because they think it will affect the performance of the building and blame the building for not performing correctly without the correct operative knowledge.

<br/>

Tuohy indicates that ‘there are policy initiatives aimed at improving industry processes such as: Soft Landings, BREEAM, LEED, Green Star, AGBR and BIM’ (Tuohy, 2012). The CLG’s Code for Sustainable Homes (CfSH) has also established itself as a ‘proving ground’ for new guidance and regulations, it is currently a voluntary standard except for social housing schemes in England. There are also some planning authorities that use the CfSH as a mandatory standard implementable through the planning system; this and voluntary schemes account for only covers 16% of total CfSH assessed homes (CLG, 2012). <br/>

This 'proving ground' allows new ideas or strategies to be implemented on a section of the industry before being rolled out to national policy. This has been proven in the past through the use of targets for carbon emission compliance over the regulations which in the May 09 version of the Code was required at 25% above the building Regulations Part L1a 2006, and Code 4 was 44% above. The revision of the building Regulation Part L1a 2010 revised the compliance level in SAP to be in line with this new figure, with the equivalent carbon reduction of 25% over Part L1a 2006. This is likely to carry on into the revision of Part L1a 2013 with a further 25% reduction (44% over Part L1a 2006) and the introduction of Fabric Energy Efficiency (FEE) standards (CLG, 2012) which was introduced into the CfSH in Nov 2010.

<br/>

It has been recognised that user knowledge of how the buildings work is important to how a building functions, the CfSH has dedicated credits for the production of a Home User Guide in order ‘to promote the provision of guidance enabling occupants to understand and operate their home efficiently and make the best use of local facilities’ (CLG, 2010). BREEAM has similar credits for the production of a Building User Guide ‘to ensure delivery of a functional and sustainable asset designed and built in accordance with performance expectations’ (BRE Global Ltd, 2011), however BREEAM goes one step further and introduces credits for thermal comfort, the criteria being ‘to ensure that appropriate thermal comfort levels are achieved through design, and controls are selected to maintain a thermally comfortable environment for occupants within the building.’. This criteria for thermal comfort indicates a step change for thermal comfort and the importance that it is seen to have in the environmental credentials of a building. Should these credits prove implementable industry wide perhaps they may enter into the regulations the same way of the example above in the CfSH.

<br/>

Looking into the future of POE, in May 2011 the Minister for State for Housing and Local Government reaffirmed the UK Government commitment to zero carbon homes from 2016, stating that ‘the carbon footprint of new homes cannot be allowed to add to our overall carbon reduction targets. But this needs to be done in ways which are cost effective and which protects the viability of house building’ (The Rt Hon Grant Shapps, 2011)

The zero carbon hub explains that ‘The definition of zero carbon was originally envisaged to be Level 6 of the Code for Sustainable Homes, which has only been achieved in practice by a handful of exemplar schemes.’ (Zero Carbon Hub) CLG has released figures that show that only 128 homes in the UK have been certified at Post Construction Stage as Code Level 6 up to December 2011 (CLG, 2012). This is a very small minority of the 52,486 homes that have received a Post Construction Stage Code certificate. The Zero Carbon Hub explains that this is due to difficulties in the way the homes are assessed, explaining that homes need to be treated as their own ‘individual energy island’, which means that they must achieve net zero carbon on their own merits which generally will require the onsite production of renewable energy.

The current definition of zero carbon homes is no longer Level 6 of the Code for Sustainable Homes, and in fact it is not based on the Code at all. Instead the definition is based upon achieving a minimum level in Fabric Energy Efficiency, achieving a minimum level of Carbon Compliance and achieving net zero carbon through Allowable Solutions (Zero Carbon Hub, 2008). This will be implemented through the building regulations and through the Standard Assessment Procedure.

Although the definition of zero carbon has been revised so that it is no longer based on Code 6 of the Code for Sustainable Homes, the majority of those defined as net zero carbon have been through this definition, however there is cause to question whether homes designed to this standard are actually being built to this standard. This is referred to as the performance gap, where the calculated designed performance does not meet the as built performance. The NHBC foundation questions ‘the ability of the SAP assessment model to make an accurate prediction of the energy use of homes given the large number of variables and the accuracy of the data inputs’ (NHBC Foundation, 2012) however a large variety of reasons could contribute to the performance gap including the calculation methods, build quality, construction techniques, or user behaviour. Hernandez Neto supports this and states that ‘the user should have the expertise to choose the most suitable tool depending on the type of analysis being done’. (Hernandez Neto, Fiorelli, & Buoro, 2012). Unfortunately in the case of Building Regulation compliance only SAP and SBEM are the accepted methods of showing compliance, so perhaps it would be more appropriate to allow to be used a different software that may produce more accurate results.

<br/>

The NHBC Foundation lists 7 areas to be considered in order to understand the reasons for how a performance gap arises, (NHBC Foundation, 2012) due to ongoing scuntination of the SAP calculation model, Zero Carbon Hub has concluded that SAP is the best model to continue to use to evaluate building performance and because the validity of data is verified through the use of OCDEAs, who must be a member of a licencing organisation that operated regular QA verification testing on calculations the expertise to input data correctly is present.

<br/>

Unfortunately because low energy homes are rare in the UK and even fewer are subject of Post Occupational Evaluation the actual performance is not known. The BUS supports this and states that benchmarking could take 3-5 years to populate (BUS, 2012).

Leaman states that real world research means that effects ‘are more difficult to predict, e.g. unanticipated operating modes for innovative technologies, or alterations in user behaviour’ (Bordass, Stevenson, & Leaman, Building Evaluation: Practice and Principles, 2010). This idea is supported by Vale, who states that ‘Post Occupation Evaluation (POE) could have a significant role in the lowering of environmental impacts, but the framing of domestic POE must embrace a rating of the occupants’ behaviour’ (Vale & Vale, 2010). <br/>

Occupant behaviour, however is not as simple as designing a building to supply a uniform temperature as in air conditioned buildings, although in a research study (Juricic, Van Den Ham, & Kurvers, 2012) found that there was no difference between the energy use in user orientated buildings than those designed ignoring user profiles and concluded that ‘the idea of giving the opportunity to the user to interact with the environment is not necessarily synonym with higher energy use’. This however does not mean that because the building uses the same amount of energy whether users are in control or not that the users achieve the same level of thermal comfort, (Nicol, Humphreys, & Roaf, Adaptive Thermal Comfort: Principles and Practice, 2012) state that ‘behaviour is an important role in our thermal interaction with the environmental’ including the changing of clothes, changes of posture and metabolic rates, moving to a different thermal environment and changing the current environment using thermal controls. It has been found that the range of temperatures that are acceptable is around 70% wider for natural ventilated building than for HVAC buildings showing that ‘higher levels of personal control makes users more tolerant of wider temperature swings’ (De Dear & Brager, 1998).

<br/>

Tuohy also looks at new technologies that are often used in low energy buildings and describes ‘new technology systems do not work as well as predicted’ and that the ‘controls are poorly designed’ (Tuohy, 2012). (NHBC Foundation, 2012) also cites mechanical and electrical installations as one of its 7 factors that contribute to the performance gap. The actual efficiency of technologies is particularly problematic as it could have a large effect on the performance gap, as efficiency is effected by the whole system, ie the boiler, pipework and inline components. It has been found that an 86% efficient gas boiler performed as poorly as 55% when the whole system was taken into account (Zero Carbon Hub, 2010). <br/>

This is particularly true in relatively new technologies such as heat pumps, the figure 1 shows COP curves for a communal Ground Source Heat Pump system. It can be seen that the actual system efficiency is well below the expected (designed) efficiency and actually in the summer shows COP of just above 1 which is the efficiency of a standard electrical heating system. Electrical systems generally perform poorly in SAPs as the fuel factor used is 0.52kgCO2/kWh as opposed to gas which is 0.19kgCO2/kWh (DECC, 2010), the only reason heat pumps do well in SAPs as opposed to a gas system is that the COP of around 2.5 will bring the carbon emissions in line with that of gas. With the government pushing the use of these kind of technologies through SAP where heat pumps fairly easily gain high levels of carbon reduction and through the use of initiatives such as FITs and RHIs, the latter of which pays for heat energy produced using low carbon technologies such as heat pumps.

[[File:COP Graph.png|RTENOTITLE]]

Figure 1 COP curves for a communal Ground Source Heat Pump system (Zero Carbon Hub, 2010)

<br/>

To conclude, the mechanisms to make low energy buildings both exist and are in use through formats such as the building regulations which are changing towards zero carbon which encourages the building of low energy buildings. There are some problems with the implementations of new low carbon heating systems such as heat pumps which don’t seem to match up the designed performance with the actual installed performance which leads to inconsistencies in the energy use in the buildings when compared with the designed energy use. This performance gap is known by the industry however the solutions to the problem are not yet implemented in a way that lessens the impact. The most critical of these is to learn from building utilised POE techniques.

<br/>

So the real challenge is to make 'comfortable low energy buildings', the scientific idea of comfort is still fairly new however there are research projects ongoing that seek to identify the effect that thermal comfort has on the energy use of buildings. It does seem to be clear that the comfort of building occupants has a large effect on the success of the building and makes it even more important to implement POE to evaluate the effect that thermal comfort and user occupation patterns actually have on the building performance and allow future projects to learn from and improve on their design.
<div>
<br/>

References and further reading

<br/>Bordass, B. (2011). The Usable Buildings Trust and New Professionalism. ''Impact, Jan/Feb'', 16-17.

Bordass, B., Stevenson, F., & Leaman, A. (2010). Building Evaluation: Practice and Principles. ''Building Research and Information, 38:5'', 564-577.

BRE Global Ltd. (2011). ''BREEAM New Construction: Non Domestic Buildings Technical Manual SD5073 - 2.0:2011.'' Watford: BRE Global Ltd.

BRE Global Ltd. (n.d.). ''BREEAM In Use''. Retrieved 05 25, 2012, from BREEAM: [http://www.breeam.org/page.jsp?id=373 http://www.breeam.org/page.jsp?id=373]

BRE Trust. (2010). ''Energy Efficiency in New and Existing Buildings: Comparitive Costs and CO2 Savings.'' Watford: BRE Press.

BUS. (2012). ''The Building Use Studies (BUS) Occupant Survey: Origins and Approach Q&A.'' London: BUS.

CLG. (2010). ''Code for Sustainable Homes: Technical Guide November 2010.'' London: RIBA Publishing.

CLG. (2012). ''2012 Consultation on CHnages to the Building Regulations in England: Section Two Part L (COnservation of Fuel and Power).'' London: CLG.

CLG. (2012). ''Code for Sustainable Homes and Energy Peformance of Buildings: Cumulative and Quarterly Data for England, Wales and Northern Ireland up to the end of December 2011.'' CLG.

De Dear, R., & Brager, G. (1998). Developing an Adaptive Model of Thermal Comfort and Preference. ''ASHRAE Transactions, 104 (1)'', 145-167.

DECC. (2010). ''The Government’s Standard Assessment Procedure for Energy Rating of Dwellings: 2009 edition .'' Watford: BRE.

Derbyshire, S. (2003). Architecture, Science and Feedback. ''Journal of Building Research and Information''.

Derbyshire, S. A. (2002). Architecture, Science and Feedback. ''Building Research and Information''.

Edwards, B. (2010). ''Rough Guide to Sustainability.'' Bristol: RIBA Publishing.

Energy Savings Trust. (2008). ''Monitoring Energy and Carbon Performance in New Homes.'' London: Energy Savings Trust.

Good Homes Alliance. (2011). Closing the Performance Gap: Low Carbon 4 Real plus Feedback and Monitoring. ''Closing the Performance Gap: Low Carbon 4 Real plus Feedback and Monitoring.'' London.

Hernandez Neto, A., Fiorelli, F. A., & Buoro, A. B. (2012). Computational Analysis - Evaluation of the impact of the user expertise on the results of simulation tools. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

Juricic, S., Van Den Ham, E., & Kurvers, S. (2012). Relationship between Building Characteristics and Energy Use and Health and Comfort Perception. ''The Changing Context of COmfort in an Unpredictable World.'' Windsor: NCEUB.

Leaman, A. (2003). Post Occupational Evaluation. ''Gaia Research Sustainable Construction Continuing Proffesional Development (CPD) Seminars''. London: Building Use Studies.

Leaman, A., Stevenson, F., & Bordass, B. (2010). Building Evaluation: Practice and Principles. ''Building Research and Information, 38:5'', 564-577.

Lomas, K., & Kane, T. (2012). Summertime temperatures in 282 UK Homes: Thermal Comfort and Overheating Risk. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

NHBC Foundation. (2012, March 01). Retrieved 2012, from NHBC Foundation Blog: [http://nhbcfoundation.blogspot.co.uk/2012/03/house-builders-not-solely-to-blame-for.html http://nhbcfoundation.blogspot.co.uk/2012/03/house-builders-not-solely-to-blame-for.html]

NHBC Foundation. (2012). ''Low and Zero Carbon Homes: Understanding the Performance Challenge.'' Watford: BRE Press.

Ni Riain, C., Fisher, J., Mackenzie, F., & Littler, J. (2000). BRE's Environmental Building: Energy Performance in Use. ''20 20 Vision.'' Dublin: CIBSE/ASHRAE.

Nicol, F., Humphreys, M., & Roaf, S. (2012). ''Adaptive Thermal Comfort: Principles and Practice.'' Tonbridge: Greengate Publishing Services.

Nicol, F., Humphreys, M., Sykes, O., & Roaf, S. (1995). ''Standards for Thermal Comfort.'' Padstow: T. J. Press (Padstow) Ltd.

Roaf, S. (2004). ''Closing the Loop: Benchmarks for Sustainable Buildings.'' Cornwall: RIBA Enterprises Ltd.

Stevenson, F., & Leaman, A. (2010). Evaluating Housing Performance in Relation to Human Behaviour: New Challenges. ''Building Research and Information, 38:5'', 437-441.

The Rt Hon Grant Shapps, M. (2011, May 17). ''Buildings and the Environment''. Retrieved 2012, from CLG: [http://www.communities.gov.uk/statements/corporate/buildingsenvironment http://www.communities.gov.uk/statements/corporate/buildingsenvironment]

Tuohy, P. (2012). Why Advanced Buildings Don't Work. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

Tweed, C., & Dixon, D. (2012). Thermal Experience is an era of Low Energy Domestic Heating Systems. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

Vale, B., & Vale, R. (2010). Domestic Energy Use, Lifestyles and POE: Past Lessons for Current Problems. ''Building Research and Information, 38:5'', 578-588.

Zero Carbon Hub. (2008). ''Definition of Zero Carbon Homes and Non-Domestic Buildings Consultation .'' Zero Carbon Hub.

Zero Carbon Hub. (2010). ''Carbon Compliance for Tomorrow's New Homes: Closing the Gap Between Deisgned and Built Performance.'' London: Zero Carbon Hub.

Zero Carbon Hub. (n.d.). ''About''. Retrieved May 13, 2012, from Zero Carbon Hub: [http://www.zerocarbonhub.org/about.aspx?page=2 http://www.zerocarbonhub.org/about.aspx?page=2]

Zero Carbon Hub. (n.d.). ''Definition''. Retrieved May 12, 2012, from Zero Carbon Hub: [http://www.zerocarbonhub.org/definition.aspx http://www.zerocarbonhub.org/definition.aspx]

<br/>
</div>

[[Category:Student_architect_essay_competition]]

Performance gap in low energy housing

2012-11-13T17:07:26Z

J65on:

Page formatting for WIKI & references pending...

<br/>

Tuhoy indicates that the current intent of policy is to ‘achieve comfortable low energy buildings’ (Tuohy, 2012), however comfort rarely appears in regulations or statutory minima. It does appear in deisgn guides such as CIBSE guide A however this is only a design guide and is not always fully implemented in every building built. The building regulations are a requirement for every building and would be a perfect platform to include for thermal comfort however it does not address thermal comfort in any of the approved documents, they actually mostly seize to be a part of the building process when it is completed and occupied. This is a large problem for the industry as it encourages segregation between the design and build teams and the building occupiers.

The Good Homes Alliance conference Closing the Performance gap showed that monitoring and post occupational evaluation (POE) are essential tools to ensure our low carbon homes are operating as designed, and are comfortable and healthy’ (Good Homes Alliance, 2011). Currently no ongoing post construction tests and checks are enabled through the building regulations, any surveys are usually academic or research motivated. (NHBC Foundation, 2012). This must be overcome if buildings are to move on. Derbyshire supports the need for change and for inclusion of a POE and argues that science cannot grow and evolve without a ‘testing of hypothesis through observed observation, the results of which are fed back into the body of knowledge to generate a new cycle of hypothesis, experiment and feedback’ (Derbyshire S. A., 2002).

There are some organizations that do support the implementation of POE, one of the key objectives for the Usable Building Trust (UBT) is ‘to make building performance evaluation a routine activity for design and building teams’ (Bordass, 2011) however it was noted that this was difficult as design and build teams were often reluctant to participate as the reputation of the designers or the builders could be put into doubt. Schemes such as BREEAM also recognize the requirement for POE, under BREEAM New Construction 2011 it is a requirement that a BREEAM In Use assessment is undertaken for any building that achieves an Excellent or Outstanding rating (BRE Global Ltd, 2011). ‘BREEAM In-Use is a scheme to help building managers reduce the running costs and improve the environmental performance of existing buildings. It consists of a standard, easy-to-use assessment methodology and an independent certification process that provides a clear and credible route map to improving sustainability’ (BRE Global Ltd). Although it is designed as a tool to help improve the environmental performance of the building, it can help to bridge the gap between designer and occupant, where the occupant actually has to learn about the building, the way it works and is managed in order to pass the In Use assessment.

But if POE were undertaken, where would the fault lie if the building owners questioned why the building wasn’t performing as designed, the designers or the builders? The answer to this question is a bit of a minefield, however the answer may be that neither may be to blame and actually the building users are not using the building as designed. In the case of the BRE Environmental Office, it was designed as an exemplar case however the energy used in the building was around 90% higher than the designed energy demand (Ni Riain, Fisher, Mackenzie, & Littler, 2000). Accordingly to (Tuohy, 2012) there were ten key findings from the POE, eight of these were connected with the controls of the systems, one was that it was occupied differently to designed and the other that there was no energy performance data on display. The main point to focus on here is the fact that the controls were not implemented as designed compromising user control over the environment, this is supported by (Juricic, Van Den Ham, & Kurvers, 2012) citing ‘user’s opportunity to influence their indoor climate is one of the most important keys to robustness’. However, again to can be difficult to determine whether the controls were incorrectly designed or whether they are being used incorrectly by the occupants. An example of this is as a Passivhaus assessor I am often asked whether the windows can be opened in a Passivhaus because the air tightness of the building is designed to be very low, the myth is that the windows shouldn’t be opened however the PHPP includes openable windows as an important control for mitigating overheating which is wholly dependent on the users knowledge of that control. It could be very easy for an occupant to be in an overheating home and leave the windows closed because they think it will affect the performance of the building and blame the building for not performing correctly without the correct operative knowledge.

Tuohy indicates that ‘there are policy initiatives aimed at improving industry processes such as: Soft Landings, BREEAM, LEED, Green Star, AGBR and BIM’ (Tuohy, 2012). The CLG’s Code for Sustainable Homes (CfSH) has also established itself as a ‘proving ground’ for new guidance and regulations, it is currently a voluntary standard except for social housing schemes in England. There are also some planning authorities that use the CfSH as a mandatory standard implementable for the planning system; this and voluntary schemes account for only covers 16% of total CfSH assessed homes (CLG, 2012). This allows new ideas or strategies to be implemented on a section of the industry before being rolled out to national policy. This has been proven in the past through the use of targets for Carbon emission compliance over the regulations which in the May 09 version of the Code was required at 25% above the building Regulations Part L1a 2006, and Code 4 was 44% above. The revision of the building Regulation Part L1a 2010 revised the compliance level in SAP to be in line with this new figure, with the equivalent carbon reduction of 25% over Part L1a 2006. This is likely to carry on into the revision of Part L1a 2013 with a further 25% reduction (44% over Part L1a 2006) and the introduction of Fabric Energy Efficiency (FEE) standards (CLG, 2012) which was introduced into the CfSH in Nov 2010.

It has been recognized that user knowledge of how the buildings work is important to how a building functions, the CfSH has dedicated credits for the production of a Home User Guide in order ‘to promote the provision of guidance enabling occupants to understand and operate their home efficiently and make the best use of local facilities’ (CLG, 2010). BREEAM has similar credits for the production of a Building User Guide ‘to ensure delivery of a functional and sustainable asset designed and built in accordance with performance expectations’ (BRE Global Ltd, 2011), however BREEAM goes one step further and introduces credits for thermal comfort, the criteria being ‘to ensure that appropriate thermal comfort levels are achieved through design, and controls are selected to maintain a thermally comfortable environment for occupants within the building.’. This criteria for thermal comfort indicates a step change for thermal comfort and the importance that it is seen to have in the environmental credentials of a building. Should these credits prove implementable industry wide perhaps they may enter into the regulations the same way of the example above in the CfSH.

Looking into the future of POE, in May 2011 the Minister for State for Housing and Local Government reaffirmed the UK Government commitment to zero carbon homes from 2016, stating that ‘the carbon footprint of new homes cannot be allowed to add to our overall carbon reduction targets. But this needs to be done in ways which are cost effective and which protects the viability of house building’ (The Rt Hon Grant Shapps, 2011)

The zero carbon hub explains that ‘The definition of zero carbon was originally envisaged to be Level 6 of the Code for Sustainable Homes, which has only been achieved in practice by a handful of exemplar schemes.’ (Zero Carbon Hub) CLG has released figures that show that only 128 homes in the UK have been certified at Post Construction Stage as Code Level 6 up to December 2011 (CLG, 2012). This is a very small minority of the 52,486 homes that have received a Post Construction Stage Code certificate. The Zero Carbon Hub explains that this is due to difficulties in the way the homes are assessed, explaining that homes need to be treated as their own ‘individual energy island’, which means that they must achieve net zero carbon on their own merits which generally will require the onsite production of renewable energy.

The current definition of zero carbon homes is no longer Level 6 of the Code for Sustainable Homes, and in fact it is not based on the Code at all. Instead the definition is based upon achieving a minimum level in Fabric Energy Efficiency, achieving a minimum level of Carbon Compliance and achieving net zero carbon through Allowable Solutions (Zero Carbon Hub, 2008). This will be implemented through the building regulations and through the Standard Assessment Procedure.

Although the definition of zero carbon has been revised so that it is no longer based on Code 6 of the Code for Sustainable Homes, the majority of those defined as net zero carbon have been through this definition, however there is cause to question whether homes designed to this standard are actually being built to this standard. This is referred to as the performance gap, where the calculated designed performance does not meet the as built performance. The NHBC foundation questions ‘the ability of the SAP assessment model to make an accurate prediction of the energy use of homes given the large number of variables and the accuracy of the data inputs’ (NHBC Foundation, 2012) however a large variety of reasons could contribute to the performance gap including the calculation methods, build quality, construction techniques, or user behaviour. Hernandez Neto supports this and states that ‘the user should have the expertise to choose the most suitable tool depending on the type of analysis being done’. (Hernandez Neto, Fiorelli, & Buoro, 2012). Unfortunately in the case of Building Regulation compliance only SAP and SBEM are the accepted methods of showing compliance, so perhaps it would be more appropriate to allow to be used a different software that may produce more accurate results.

The NHBC Foundation lists 7 areas to be considered in order to understand the reasons for how a performance gap arises, (NHBC Foundation, 2012) due to ongoing scuntination of the SAP calculation model, Zero Carbon Hub has concluded that SAP is the best model to continue to use to evaluate building performance and because the validity of data is verified through the use of OCDEAs, who must be a member of a licensing organization that operated regular QA verification testing on calculations the expertise to input data correctly is present.

Unfortunately because low energy homes are rare in the UK and even fewer are subject of Post Occupational Evaluation the actual performance is not known. The BUS supports this and states that benchmarking could take 3-5 years to populate (BUS, 2012).

Leaman states that real world research means that predicting effects ‘are more difficult to predict, e.g. unanticipated operating modes for innovative technologies, or alterations in user behaviour’ (Bordass, Stevenson, & Leaman, Building Evaluation: Practice and Principles, 2010). This idea is supported by Vale, who states that ‘Post Occupation Evaluation (POE) could have a significant role in the lowering of environmental impacts, but the framing of domestic POE must embrace a rating of the occupants’ behaviour’ (Vale & Vale, 2010). Occupant behaviour, however is not as simple as designing a building to supply a uniform temperature as in air conditioned buildings, although in a research study (Juricic, Van Den Ham, & Kurvers, 2012) found that there was no difference between the energy use in user orientated buildings than those designed ignoring user profiles and concluded that ‘the idea of giving the opportunity to the user to interact with the environment is not necessarily synonym with higher energy use’. This however does not mean that because the building uses the same amount of energy whether users are in control or not that the users achieve the same level of thermal comfort, (Nicol, Humphreys, & Roaf, Adaptive Thermal Comfort: Principles and Practice, 2012) state that ‘behaviour is an important role in our thermal interaction with the environmental’ including the changing of clothes, changes of posture and metabolic rates, moving to a different thermal environment and changing the current environment using thermal controls. It has been found that the range of temperatures that are acceptable is around 70% wider for natural ventilated building than for HVAC buildings showing that ‘higher levels of personal control makes users more tolerant of wider temperature swings’ (De Dear & Brager, 1998).

Tuohy also looks at new technologies that are often used in low energy buildings and describes ‘new technology systems do not work as well as predicted’ and that the ‘controls are poorly designed’ (Tuohy, 2012). (NHBC Foundation, 2012) also cites mechanical and electrical installations as one of its 7 factors that contribute to the performance gap. The actual efficiency of technologies is particularly problematic as it could have a large effect on the performance gap, as efficiency is effected by the whole system, ie the boiler, pipework and inline components. It has been found that an 86% efficient gas boiler performed as poorly as 55% when the whole system was taken into account (Zero Carbon Hub, 2010). This is particularly true in relatively new technologies such as heat pumps, the figure 1 shows COP curves for a communal Ground Source Heat Pump system. It can be seen that the actual system efficiency is well below the expected (designed) efficiency and actually in the summer shows COP of just above 1 which is the efficiency of a standard electrical heating system. Electrical systems generally perform poorly in SAPs as the fuel factor used is 0.52kgCO2/kWh as opposed to gas which is 0.19kgCO2/kWh (DECC, 2010), the only reason heat pumps do well in SAPs as opposed to a gas system is that the COP of around 2.5 will bring the carbon emissions in line with that of gas. With the government pushing the use of these kind of technologies through SAP where heat pumps fairly easily gain high levels of carbon reduction and through the use of initiatives such as FITs and RHIs, the latter of which pays for heat energy produced using low carbon technologies such as heat pumps.

[[File:COP Graph.png]]

Figure 1 COP curves for a communal Ground Source Heat Pump system (Zero Carbon Hub, 2010)

<br/>

<br/>

So to conclude, the mechanisms to make low energy buildings exist and is in use through formats such as the building regulations which are changing towards zero carbon which encourages the building of low energy buildings. There are some problems with the implementations of new low carbon heating systems such as heat pumps which don’t seem to match up the designed performance with the actual installed performance which leads to inconsistencies in the energy use in the buildings when compared with the designed energy use. This performance gap is known by the industry however the solutions to the problem are not yet implemented in a way that lessens the impact. The most critical of these is to learn from building utilised POE techniques.

So the real challenge is to make comfortable low energy buildings, the science idea of comfort is still fairly new however there are research projects ongoing that seek to identify the effect that thermal comfort has on the energy use of buildings. It does seem to be clear that the comfort of building occupants has a large effect on the success of the building and makes it even more important to implement POE to evaluate the effect that thermal comfort and user occupation patterns actually have on the building performance and allow future projects to learn from and improve on their design.
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<br/>Bordass, B. (2011). The Usable Buildings Trust and New Professionalism. ''Impact, Jan/Feb'', 16-17.

Bordass, B., Stevenson, F., & Leaman, A. (2010). Building Evaluation: Practice and Principles. ''Building Research and Information, 38:5'', 564-577.

BRE Global Ltd. (2011). ''BREEAM New Construction: Non Domestic Buildings Technical Manual SD5073 - 2.0:2011.'' Watford: BRE Global Ltd.

BRE Global Ltd. (n.d.). ''BREEAM In Use''. Retrieved 05 25, 2012, from BREEAM: [http://www.breeam.org/page.jsp?id=373 http://www.breeam.org/page.jsp?id=373]

BRE Trust. (2010). ''Energy Efficiency in New and Existing Buildings: Comparitive Costs and CO2 Savings.'' Watford: BRE Press.

BUS. (2012). ''The Building Use Studies (BUS) Occupant Survey: Origins and Approach Q&A.'' London: BUS.

CLG. (2010). ''Code for Sustainable Homes: Technical Guide November 2010.'' London: RIBA Publishing.

CLG. (2012). ''2012 Consultation on CHnages to the Building Regulations in England: Section Two Part L (COnservation of Fuel and Power).'' London: CLG.

CLG. (2012). ''Code for Sustainable Homes and Energy Peformance of Buildings: Cumulative and Quarterly Data for England, Wales and Northern Ireland up to the end of December 2011.'' CLG.

De Dear, R., & Brager, G. (1998). Developing an Adaptive Model of Thermal Comfort and Preference. ''ASHRAE Transactions, 104 (1)'', 145-167.

DECC. (2010). ''The Government’s Standard Assessment Procedure for Energy Rating of Dwellings: 2009 edition .'' Watford: BRE.

Derbyshire, S. (2003). Architecture, Science and Feedback. ''Journal of Building Research and Information''.

Derbyshire, S. A. (2002). Architecture, Science and Feedback. ''Building Research and Information''.

Edwards, B. (2010). ''Rough Guide to Sustainability.'' Bristol: RIBA Publishing.

Energy Savings Trust. (2008). ''Monitoring Energy and Carbon Performance in New Homes.'' London: Energy Savings Trust.

Good Homes Alliance. (2011). Closing the Performance Gap: Low Carbon 4 Real plus Feedback and Monitoring. ''Closing the Performance Gap: Low Carbon 4 Real plus Feedback and Monitoring.'' London.

Hernandez Neto, A., Fiorelli, F. A., & Buoro, A. B. (2012). Computational Analysis - Evaluation of the impact of the user expertise on the results of simulation tools. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

Juricic, S., Van Den Ham, E., & Kurvers, S. (2012). Relationship between Building Characteristics and Energy Use and Health and Comfort Perception. ''The Changing Context of COmfort in an Unpredictable World.'' Windsor: NCEUB.

Leaman, A. (2003). Post Occupational Evaluation. ''Gaia Research Sustainable Construction Continuing Proffesional Development (CPD) Seminars''. London: Building Use Studies.

Leaman, A., Stevenson, F., & Bordass, B. (2010). Building Evaluation: Practice and Principles. ''Building Research and Information, 38:5'', 564-577.

Lomas, K., & Kane, T. (2012). Summertime temperatures in 282 UK Homes: Thermal Comfort and Overheating Risk. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

NHBC Foundation. (2012, March 01). Retrieved 2012, from NHBC Foundation Blog: [http://nhbcfoundation.blogspot.co.uk/2012/03/house-builders-not-solely-to-blame-for.html http://nhbcfoundation.blogspot.co.uk/2012/03/house-builders-not-solely-to-blame-for.html]

NHBC Foundation. (2012). ''Low and Zero Carbon Homes: Understanding the Performance Challenge.'' Watford: BRE Press.

Ni Riain, C., Fisher, J., Mackenzie, F., & Littler, J. (2000). BRE's Environmental Building: Energy Performance in Use. ''20 20 Vision.'' Dublin: CIBSE/ASHRAE.

Nicol, F., Humphreys, M., & Roaf, S. (2012). ''Adaptive Thermal Comfort: Principles and Practice.'' Tonbridge: Greengate Publishing Services.

Nicol, F., Humphreys, M., Sykes, O., & Roaf, S. (1995). ''Standards for Thermal Comfort.'' Padstow: T. J. Press (Padstow) Ltd.

Roaf, S. (2004). ''Closing the Loop: Benchmarks for Sustainable Buildings.'' Cornwall: RIBA Enterprises Ltd.

Stevenson, F., & Leaman, A. (2010). Evaluating Housing Performance in Relation to Human Behaviour: New Challenges. ''Building Research and Information, 38:5'', 437-441.

The Rt Hon Grant Shapps, M. (2011, May 17). ''Buildings and the Environment''. Retrieved 2012, from CLG: [http://www.communities.gov.uk/statements/corporate/buildingsenvironment http://www.communities.gov.uk/statements/corporate/buildingsenvironment]

Tuohy, P. (2012). Why Advanced Buildings Don't Work. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

Tweed, C., & Dixon, D. (2012). Thermal Experience is an era of Low Energy Domestic Heating Systems. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

Vale, B., & Vale, R. (2010). Domestic Energy Use, Lifestyles and POE: Past Lessons for Current Problems. ''Building Research and Information, 38:5'', 578-588.

Zero Carbon Hub. (2008). ''Definition of Zero Carbon Homes and Non-Domestic Buildings Consultation .'' Zero Carbon Hub.

Zero Carbon Hub. (2010). ''Carbon Compliance for Tomorrow's New Homes: Closing the Gap Between Deisgned and Built Performance.'' London: Zero Carbon Hub.

Zero Carbon Hub. (n.d.). ''About''. Retrieved May 13, 2012, from Zero Carbon Hub: [http://www.zerocarbonhub.org/about.aspx?page=2 http://www.zerocarbonhub.org/about.aspx?page=2]

Zero Carbon Hub. (n.d.). ''Definition''. Retrieved May 12, 2012, from Zero Carbon Hub: [http://www.zerocarbonhub.org/definition.aspx http://www.zerocarbonhub.org/definition.aspx]

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[[Category:Student_architect_essay_competition]]

Performance gap in low energy housing

2012-11-13T17:03:14Z

J65on:

Page formatting for WIKI & references pending...

<br/>

Tuhoy indicates that the current intent of policy is to ‘achieve comfortable low energy buildings’ (Tuohy, 2012), however comfort rarely appears in regulations or statutory minima. It does appear in deisgn guides such as CIBSE guide A however this is only a design guide and is not always fully implemented in every building built. The building regulations are a requirement for every building and would be a perfect platform to include for thermal comfort however it does not address thermal comfort in any of the approved documents, they actually mostly seize to be a part of the building process when it is completed and occupied. This is a large problem for the industry as it encourages segregation between the design and build teams and the building occupiers.

The Good Homes Alliance conference Closing the Performance gap showed that monitoring and post occupational evaluation (POE[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[1]|alt=[1]]]) are essential tools to ensure our low carbon homes are operating as designed, and are comfortable and healthy’ (Good Homes Alliance, 2011). Currently no ongoing post construction tests and checks are enabled through the building regulations, any surveys are usually academic or research motivated. (NHBC Foundation, 2012). This must be overcome if buildings are to move on. Derbyshire supports the need for change and for inclusion of a POE and argues that science cannot grow and evolve without a ‘testing of hypothesis through observed observation, the results of which are fed back into the body of knowledge to generate a new cycle of hypothesis, experiment and feedback’ (Derbyshire S. A., 2002).

There are some organizations that do support the implementation of POE, one of the key objectives for the UBT[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[2]|alt=[2]]] is ‘to make building performance evaluation a routine activity for design and building teams’ (Bordass, 2011) however it was noted that this was difficult as design and build teams were often reluctant to participate as the reputation of the designers or the builders could be put into doubt. Schemes such as BREEAM[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[3]|alt=[3]]] also recognize the requirement for POE, under BREEAM New Construction 2011 it is a requirement that a BREEAM In Use assessment is undertaken for any building that achieves an Excellent or Outstanding rating (BRE Global Ltd, 2011). ‘BREEAM In-Use is a scheme to help building managers reduce the running costs and improve the environmental performance of existing buildings. It consists of a standard, easy-to-use assessment methodology and an independent certification process that provides a clear and credible route map to improving sustainability’ (BRE Global Ltd). Although it is designed as a tool to help improve the environmental performance of the building, it can help to bridge the gap between designer and occupant, where the occupant actually has to learn about the building, the way it works and is managed in order to pass the In Use assessment.

But if POE were undertaken, where would the fault lie if the building owners questioned why the building wasn’t performing as designed, the designers or the builders? The answer to this question is a bit of a minefield, however the answer may be that neither may be to blame and actually the building users are not using the building as designed. In the case of the BRE Environmental Office, it was designed as an exemplar case however the energy used in the building was around 90% higher than the designed energy demand (Ni Riain, Fisher, Mackenzie, & Littler, 2000). Accordingly to (Tuohy, 2012) there were ten key findings from the POE, eight of these were connected with the controls of the systems, one was that it was occupied differently to designed and the other that there was no energy performance data on display. The main point to focus on here is the fact that the controls were not implemented as designed compromising user control over the environment, this is supported by (Juricic, Van Den Ham, & Kurvers, 2012) citing ‘user’s opportunity to influence their indoor climate is one of the most important keys to robustness’. However, again to can be difficult to determine whether the controls were incorrectly designed or whether they are being used incorrectly by the occupants. An example of this is as a Passivhaus assessor I am often asked whether the windows can be opened in a Passivhaus because the air tightness of the building is designed to be very low, the myth is that the windows shouldn’t be opened however the PHPP includes openable windows as an important control for mitigating overheating which is wholly dependent on the users knowledge of that control. It could be very easy for an occupant to be in an overheating home and leave the windows closed because they think it will affect the performance of the building and blame the building for not performing correctly without the correct operative knowledge.

Tuohy indicates that ‘there are policy initiatives aimed at improving industry processes such as: Soft Landings, BREEAM, LEED, Green Star, AGBR and BIM’ (Tuohy, 2012). The CLG’s Code for Sustainable Homes (CfSH)[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[4]|alt=[4]]] has also established itself as a ‘proving ground’ for new guidance and regulations, it is currently a voluntary standard except for social housing schemes in England. There are also some planning authorities that use the CfSH as a mandatory standard implementable for the planning system; this and voluntary schemes account for only covers 16% of total CfSH assessed homes (CLG, 2012). This allows new ideas or strategies to be implemented on a section of the industry before being rolled out to national policy. This has been proven in the past through the use of targets for Carbon emission compliance over the regulations which in the May 09 version of the Code was required at 25% above the building Regulations Part L1a 2006, and Code 4 was 44% above. The revision of the building Regulation Part L1a 2010 revised the compliance level in SAP[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[5]|alt=[5]]] to be in line with this new figure, with the equivalent carbon reduction of 25% over Part L1a 2006. This is likely to carry on into the revision of Part L1a 2013 with a further 25% reduction (44% over Part L1a 2006) and the introduction of FEE[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[6]|alt=[6]]] standards (CLG, 2012) which was introduced into the CfSH in Nov 2010.

It has been recognized that user knowledge of how the buildings work is important to how a building functions, the CfSH has dedicated credits for the production of a Home User Guide in order ‘to promote the provision of guidance enabling occupants to understand and operate their home efficiently and make the best use of local facilities’ (CLG, 2010). BREEAM has similar credits for the production of a Building User Guide ‘to ensure delivery of a functional and sustainable asset designed and built in accordance with performance expectations’ (BRE Global Ltd, 2011), however BREEAM goes one step further and introduces credits for thermal comfort, the criteria being ‘to ensure that appropriate thermal comfort levels are achieved through design, and controls are selected to maintain a thermally comfortable environment for occupants within the building.’. This criteria for thermal comfort indicates a step change for thermal comfort and the importance that it is seen to have in the environmental credentials of a building. Should these credits prove implementable industry wide perhaps they may enter into the regulations the same way of the example above in the CfSH.

Looking into the future of POE, in May 2011 the Minister for State for Housing and Local Government reaffirmed the UK Government commitment to zero carbon homes from 2016, stating that ‘the carbon footprint of new homes cannot be allowed to add to our overall carbon reduction targets. But this needs to be done in ways which are cost effective and which protects the viability of house building’ (The Rt Hon Grant Shapps, 2011)

The zero carbon hub explains that ‘The definition of zero carbon was originally envisaged to be Level 6 of the Code for Sustainable Homes, which has only been achieved in practice by a handful of exemplar schemes.’ (Zero Carbon Hub) CLG has released figures that show that only 128 homes in the UK have been certified at Post Construction Stage as Code Level 6 up to December 2011 (CLG, 2012). This is a very small minority of the 52,486 homes that have received a Post Construction Stage Code certificate. The Zero Carbon Hub explains that this is due to difficulties in the way the homes are assessed, explaining that homes need to be treated as their own ‘individual energy island’, which means that they must achieve net zero carbon on their own merits which generally will require the onsite production of renewable energy.

The current definition of zero carbon homes is no longer Level 6 of the Code for Sustainable Homes, and in fact it is not based on the Code at all. Instead the definition is based upon achieving a minimum level in Fabric Energy Efficiency, achieving a minimum level of Carbon Compliance and achieving net zero carbon through Allowable Solutions (Zero Carbon Hub, 2008). This will be implemented through the building regulations and through the Standard Assessment Procedure.

Although the definition of zero carbon has been revised so that it is no longer based on Code 6 of the Code for Sustainable Homes, the majority of those defined as net zero carbon have been through this definition, however there is cause to question whether homes designed to this standard are actually being built to this standard. This is referred to as the performance gap, where the calculated designed performance does not meet the as built performance. The NHBC foundation questions ‘the ability of the SAP assessment model to make an accurate prediction of the energy use of homes given the large number of variables and the accuracy of the data inputs’ (NHBC Foundation, 2012) however a large variety of reasons could contribute to the performance gap including the calculation methods, build quality, construction techniques, or user behaviour. Hernandez Neto supports this and states that ‘the user should have the expertise to choose the most suitable tool depending on the type of analysis being done’. (Hernandez Neto, Fiorelli, & Buoro, 2012). Unfortunately in the case of Building Regulation compliance only SAP and SBEM are the accepted methods of showing compliance, so perhaps it would be more appropriate to allow to be used a different software that may produce more accurate results.

The NHBC Foundation lists 7 areas to be considered in order to understand the reasons for how a performance gap arises, (NHBC Foundation, 2012) due to ongoing scuntination of the SAP calculation model, Zero Carbon Hub has concluded that SAP is the best model to continue to use to evaluate building performance and because the validity of data is verified through the use of OCDEAs[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[7]|alt=[7]]], who must be a member of a licensing organization that operated regular QA[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[8]|alt=[8]]] verification testing on calculations the expertise to input data correctly is present.

Unfortunately because low energy homes are rare in the UK and even fewer are subject of Post Occupational Evaluation the actual performance is not known. The BUS supports this and states that benchmarking could take 3-5 years to populate (BUS, 2012).

Leaman states that real world research means that predicting effects ‘are more difficult to predict, e.g. unanticipated operating modes for innovative technologies, or alterations in user behaviour’ (Bordass, Stevenson, & Leaman, Building Evaluation: Practice and Principles, 2010). This idea is supported by Vale, who states that ‘Post Occupation Evaluation (POE) could have a significant role in the lowering of environmental impacts, but the framing of domestic POE must embrace a rating of the occupants’ behaviour’ (Vale & Vale, 2010). Occupant behaviour, however is not as simple as designing a building to supply a uniform temperature as in air conditioned buildings, although in a research study (Juricic, Van Den Ham, & Kurvers, 2012) found that there was no difference between the energy use in user orientated buildings than those designed ignoring user profiles and concluded that ‘the idea of giving the opportunity to the user to interact with the environment is not necessarily synonym with higher energy use’. This however does not mean that because the building uses the same amount of energy whether users are in control or not that the users achieve the same level of thermal comfort, (Nicol, Humphreys, & Roaf, Adaptive Thermal Comfort: Principles and Practice, 2012) state that ‘behaviour is an important role in our thermal interaction with the environmental’ including the changing of clothes, changes of posture and metabolic rates, moving to a different thermal environment and changing the current environment using thermal controls. It has been found that the range of temperatures that are acceptable is around 70% wider for natural ventilated building than for HVAC buildings showing that ‘higher levels of personal control makes users more tolerant of wider temperature swings’ (De Dear & Brager, 1998).

Tuohy also looks at new technologies that are often used in low energy buildings and describes ‘new technology systems do not work as well as predicted’ and that the ‘controls are poorly designed’ (Tuohy, 2012). (NHBC Foundation, 2012) also cites mechanical and electrical installations as one of its 7 factors that contribute to the performance gap. The actual efficiency of technologies is particularly problematic as it could have a large effect on the performance gap, as efficiency is effected by the whole system, ie the boiler, pipework and inline components. It has been found that an 86% efficient gas boiler performed as poorly as 55% when the whole system was taken into account (Zero Carbon Hub, 2010). This is particularly true in relatively new technologies such as heat pumps, the figure 1 shows COP[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[9]|alt=[9]]] curves for a communal Ground Source Heat Pump system. It can be seen that the actual system efficiency is well below the expected (designed) efficiency and actually in the summer shows COP of just above 1 which is the efficiency of a standard electrical heating system. Electrical systems generally perform poorly in SAPs as the fuel factor used is 0.52kgCO2/kWh as opposed to gas which is 0.19kgCO2/kWh (DECC, 2010), the only reason heat pumps do well in SAPs as opposed to a gas system is that the COP of around 2.5 will bring the carbon emissions in line with that of gas. With the government pushing the use of these kind of technologies through SAP where heat pumps fairly easily gain high levels of carbon reduction and through the use of initiatives such as FITs and RHIs, the latter of which pays for heat energy produced using low carbon technologies such as heat pumps.

[[File:COP Graph]]

Figure 1 COP curves for a communal Ground Source Heat Pump system (Zero Carbon Hub, 2010)

So to conclude, the mechanisms to make low energy buildings exist and is in use through formats such as the building regulations which are changing towards zero carbon which encourages the building of low energy buildings. There are some problems with the implementations of new low carbon heating systems such as heat pumps which don’t seem to match up the designed performance with the actual installed performance which leads to inconsistencies in the energy use in the buildings when compared with the designed energy use. This performance gap is known by the industry however the solutions to the problem are not yet implemented in a way that lessens the impact. The most critical of these is to learn from building utilized POE techniques.

So the real challenge is to make comfortable low energy buildings, the science idea of comfort is still fairly new however there are research projects ongoing that seek to identify the effect that thermal comfort has on the energy use of buildings. It does seem to be clear that the comfort of building occupants has a large effect on the success of the building and makes it even more important to implement POE to evaluate the effect that thermal comfort and user occupation patterns actually have on the building performance and allow future projects to learn from and improve on their design.
<div>
<br/>

<br/>Bordass, B. (2011). The Usable Buildings Trust and New Professionalism. ''Impact, Jan/Feb'', 16-17.

Bordass, B., Stevenson, F., & Leaman, A. (2010). Building Evaluation: Practice and Principles. ''Building Research and Information, 38:5'', 564-577.

BRE Global Ltd. (2011). ''BREEAM New Construction: Non Domestic Buildings Technical Manual SD5073 - 2.0:2011.'' Watford: BRE Global Ltd.

BRE Global Ltd. (n.d.). ''BREEAM In Use''. Retrieved 05 25, 2012, from BREEAM: [http://www.breeam.org/page.jsp?id=373 http://www.breeam.org/page.jsp?id=373]

BRE Trust. (2010). ''Energy Efficiency in New and Existing Buildings: Comparitive Costs and CO2 Savings.'' Watford: BRE Press.

BUS. (2012). ''The Building Use Studies (BUS) Occupant Survey: Origins and Approach Q&A.'' London: BUS.

CLG. (2010). ''Code for Sustainable Homes: Technical Guide November 2010.'' London: RIBA Publishing.

CLG. (2012). ''2012 Consultation on CHnages to the Building Regulations in England: Section Two Part L (COnservation of Fuel and Power).'' London: CLG.

CLG. (2012). ''Code for Sustainable Homes and Energy Peformance of Buildings: Cumulative and Quarterly Data for England, Wales and Northern Ireland up to the end of December 2011.'' CLG.

De Dear, R., & Brager, G. (1998). Developing an Adaptive Model of Thermal Comfort and Preference. ''ASHRAE Transactions, 104 (1)'', 145-167.

DECC. (2010). ''The Government’s Standard Assessment Procedure for Energy Rating of Dwellings: 2009 edition .'' Watford: BRE.

Derbyshire, S. (2003). Architecture, Science and Feedback. ''Journal of Building Research and Information''.

Derbyshire, S. A. (2002). Architecture, Science and Feedback. ''Building Research and Information''.

Edwards, B. (2010). ''Rough Guide to Sustainability.'' Bristol: RIBA Publishing.

Energy Savings Trust. (2008). ''Monitoring Energy and Carbon Performance in New Homes.'' London: Energy Savings Trust.

Good Homes Alliance. (2011). Closing the Performance Gap: Low Carbon 4 Real plus Feedback and Monitoring. ''Closing the Performance Gap: Low Carbon 4 Real plus Feedback and Monitoring.'' London.

Hernandez Neto, A., Fiorelli, F. A., & Buoro, A. B. (2012). Computational Analysis - Evaluation of the impact of the user expertise on the results of simulation tools. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

Juricic, S., Van Den Ham, E., & Kurvers, S. (2012). Relationship between Building Characteristics and Energy Use and Health and Comfort Perception. ''The Changing Context of COmfort in an Unpredictable World.'' Windsor: NCEUB.

Leaman, A. (2003). Post Occupational Evaluation. ''Gaia Research Sustainable Construction Continuing Proffesional Development (CPD) Seminars''. London: Building Use Studies.

Leaman, A., Stevenson, F., & Bordass, B. (2010). Building Evaluation: Practice and Principles. ''Building Research and Information, 38:5'', 564-577.

Lomas, K., & Kane, T. (2012). Summertime temperatures in 282 UK Homes: Thermal Comfort and Overheating Risk. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

NHBC Foundation. (2012, March 01). Retrieved 2012, from NHBC Foundation Blog: [http://nhbcfoundation.blogspot.co.uk/2012/03/house-builders-not-solely-to-blame-for.html http://nhbcfoundation.blogspot.co.uk/2012/03/house-builders-not-solely-to-blame-for.html]

NHBC Foundation. (2012). ''Low and Zero Carbon Homes: Understanding the Performance Challenge.'' Watford: BRE Press.

Ni Riain, C., Fisher, J., Mackenzie, F., & Littler, J. (2000). BRE's Environmental Building: Energy Performance in Use. ''20 20 Vision.'' Dublin: CIBSE/ASHRAE.

Nicol, F., Humphreys, M., & Roaf, S. (2012). ''Adaptive Thermal Comfort: Principles and Practice.'' Tonbridge: Greengate Publishing Services.

Nicol, F., Humphreys, M., Sykes, O., & Roaf, S. (1995). ''Standards for Thermal Comfort.'' Padstow: T. J. Press (Padstow) Ltd.

Roaf, S. (2004). ''Closing the Loop: Benchmarks for Sustainable Buildings.'' Cornwall: RIBA Enterprises Ltd.

Stevenson, F., & Leaman, A. (2010). Evaluating Housing Performance in Relation to Human Behaviour: New Challenges. ''Building Research and Information, 38:5'', 437-441.

The Rt Hon Grant Shapps, M. (2011, May 17). ''Buildings and the Environment''. Retrieved 2012, from CLG: [http://www.communities.gov.uk/statements/corporate/buildingsenvironment http://www.communities.gov.uk/statements/corporate/buildingsenvironment]

Tuohy, P. (2012). Why Advanced Buildings Don't Work. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

Tweed, C., & Dixon, D. (2012). Thermal Experience is an era of Low Energy Domestic Heating Systems. ''The Changing Context of Comfort in an Unpredictable World.'' Windsor: NCEUB.

Vale, B., & Vale, R. (2010). Domestic Energy Use, Lifestyles and POE: Past Lessons for Current Problems. ''Building Research and Information, 38:5'', 578-588.

Zero Carbon Hub. (2008). ''Definition of Zero Carbon Homes and Non-Domestic Buildings Consultation .'' Zero Carbon Hub.

Zero Carbon Hub. (2010). ''Carbon Compliance for Tomorrow's New Homes: Closing the Gap Between Deisgned and Built Performance.'' London: Zero Carbon Hub.

Zero Carbon Hub. (n.d.). ''About''. Retrieved May 13, 2012, from Zero Carbon Hub: [http://www.zerocarbonhub.org/about.aspx?page=2 http://www.zerocarbonhub.org/about.aspx?page=2]

Zero Carbon Hub. (n.d.). ''Definition''. Retrieved May 12, 2012, from Zero Carbon Hub: [http://www.zerocarbonhub.org/definition.aspx http://www.zerocarbonhub.org/definition.aspx]

<br/>

----
<div id="ftn1">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[1]|alt=[1]]] COP Graph
</div><div id="ftn2">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[2]|alt=[2]]] The Usable Buildings Trust (UBT) is an organisation with charity status which was set up to evaluate building performance in use.
</div><div id="ftn3">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[3]|alt=[3]]] BREEAM is the Building Research Establishments Environmental Assessment Method that is used for new and existing non domestic buildings and existing homes
</div><div id="ftn4">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[4]|alt=[4]]] The Code for Sustainable Homes is an environmental assessment method that is used for new build homes to assess their environmental credentials on a 6 star rating systems.
</div><div id="ftn5">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[5]|alt=[5]]] Standard Assessment Procedure is the Governments approved calculation method for compliance with Building Regulations Approved Document Part L1a
</div><div id="ftn6">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[6]|alt=[6]]] Fabric Energy Efficiency Standard (FEES) is a standard based on the energy efficiency of the fabric in kWh/m<sup>2</sup>/Yr which was introduced under ENE2 in the Nov 10 version of CfSH
</div><div id="ftn7">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[7]|alt=[7]]] OCDEA – On Construction Domestic Energy Assessors are trained to carry out SAP assessment for new build homes and the production of Energy Performance Certificates (EPCs)
</div><div id="ftn8">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[8]|alt=[8]]] QA – Quality Assurance testing designed to ensure OCDEAs are completing SAP calculations within prescribed tolerances
</div><div id="ftn9">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[9]|alt=[9]]] Coefficient of performance (COP) is a measure of the efficiency of the heat pump, a COP of 3.2 is equivalent to 320% efficient system
</div></div>

[[Category:Student_architect_essay_competition]]

File:COP Graph.png

2012-11-13T16:59:37Z

J65on:

Performance gap in low energy housing

2012-11-13T08:52:25Z

J65on:

Page formatting for WIKI & references pending...

<br/>

Tuhoy indicates that the current intent of policy is to ‘achieve comfortable low energy buildings’ (Tuohy, 2012), however comfort rarely appears in regulations or statutory minima. It does appear in deisgn guides such as CIBSE guide A however this is only a design guide and is not always fully implemented in every building built. The building regulations are a requirement for every building and would be a perfect platform to include for thermal comfort however it does not address thermal comfort in any of the approved documents, they actually mostly seize to be a part of the building process when it is completed and occupied. This is a large problem for the industry as it encourages segregation between the design and build teams and the building occupiers.

The Good Homes Alliance conference Closing the Performance gap showed that monitoring and post occupational evaluation (POE[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[1]|alt=[1]]]) are essential tools to ensure our low carbon homes are operating as designed, and are comfortable and healthy’ (Good Homes Alliance, 2011). Currently no ongoing post construction tests and checks are enabled through the building regulations, any surveys are usually academic or research motivated. (NHBC Foundation, 2012). This must be overcome if buildings are to move on. Derbyshire supports the need for change and for inclusion of a POE and argues that science cannot grow and evolve without a ‘testing of hypothesis through observed observation, the results of which are fed back into the body of knowledge to generate a new cycle of hypothesis, experiment and feedback’ (Derbyshire S. A., 2002).

There are some organizations that do support the implementation of POE, one of the key objectives for the UBT[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[2]|alt=[2]]] is ‘to make building performance evaluation a routine activity for design and building teams’ (Bordass, 2011) however it was noted that this was difficult as design and build teams were often reluctant to participate as the reputation of the designers or the builders could be put into doubt. Schemes such as BREEAM[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[3]|alt=[3]]] also recognize the requirement for POE, under BREEAM New Construction 2011 it is a requirement that a BREEAM In Use assessment is undertaken for any building that achieves an Excellent or Outstanding rating (BRE Global Ltd, 2011). ‘BREEAM In-Use is a scheme to help building managers reduce the running costs and improve the environmental performance of existing buildings. It consists of a standard, easy-to-use assessment methodology and an independent certification process that provides a clear and credible route map to improving sustainability’ (BRE Global Ltd). Although it is designed as a tool to help improve the environmental performance of the building, it can help to bridge the gap between designer and occupant, where the occupant actually has to learn about the building, the way it works and is managed in order to pass the In Use assessment.

But if POE were undertaken, where would the fault lie if the building owners questioned why the building wasn’t performing as designed, the designers or the builders? The answer to this question is a bit of a minefield, however the answer may be that neither may be to blame and actually the building users are not using the building as designed. In the case of the BRE Environmental Office, it was designed as an exemplar case however the energy used in the building was around 90% higher than the designed energy demand (Ni Riain, Fisher, Mackenzie, & Littler, 2000). Accordingly to (Tuohy, 2012) there were ten key findings from the POE, eight of these were connected with the controls of the systems, one was that it was occupied differently to designed and the other that there was no energy performance data on display. The main point to focus on here is the fact that the controls were not implemented as designed compromising user control over the environment, this is supported by (Juricic, Van Den Ham, & Kurvers, 2012) citing ‘user’s opportunity to influence their indoor climate is one of the most important keys to robustness’. However, again to can be difficult to determine whether the controls were incorrectly designed or whether they are being used incorrectly by the occupants. An example of this is as a Passivhaus assessor I am often asked whether the windows can be opened in a Passivhaus because the air tightness of the building is designed to be very low, the myth is that the windows shouldn’t be opened however the PHPP includes openable windows as an important control for mitigating overheating which is wholly dependent on the users knowledge of that control. It could be very easy for an occupant to be in an overheating home and leave the windows closed because they think it will affect the performance of the building and blame the building for not performing correctly without the correct operative knowledge.

Tuohy indicates that ‘there are policy initiatives aimed at improving industry processes such as: Soft Landings, BREEAM, LEED, Green Star, AGBR and BIM’ (Tuohy, 2012). The CLG’s Code for Sustainable Homes (CfSH)[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[4]|alt=[4]]] has also established itself as a ‘proving ground’ for new guidance and regulations, it is currently a voluntary standard except for social housing schemes in England. There are also some planning authorities that use the CfSH as a mandatory standard implementable for the planning system; this and voluntary schemes account for only covers 16% of total CfSH assessed homes (CLG, 2012). This allows new ideas or strategies to be implemented on a section of the industry before being rolled out to national policy. This has been proven in the past through the use of targets for Carbon emission compliance over the regulations which in the May 09 version of the Code was required at 25% above the building Regulations Part L1a 2006, and Code 4 was 44% above. The revision of the building Regulation Part L1a 2010 revised the compliance level in SAP[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[5]|alt=[5]]] to be in line with this new figure, with the equivalent carbon reduction of 25% over Part L1a 2006. This is likely to carry on into the revision of Part L1a 2013 with a further 25% reduction (44% over Part L1a 2006) and the introduction of FEE[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[6]|alt=[6]]] standards (CLG, 2012) which was introduced into the CfSH in Nov 2010.

It has been recognized that user knowledge of how the buildings work is important to how a building functions, the CfSH has dedicated credits for the production of a Home User Guide in order ‘to promote the provision of guidance enabling occupants to understand and operate their home efficiently and make the best use of local facilities’ (CLG, 2010). BREEAM has similar credits for the production of a Building User Guide ‘to ensure delivery of a functional and sustainable asset designed and built in accordance with performance expectations’ (BRE Global Ltd, 2011), however BREEAM goes one step further and introduces credits for thermal comfort, the criteria being ‘to ensure that appropriate thermal comfort levels are achieved through design, and controls are selected to maintain a thermally comfortable environment for occupants within the building.’. This criteria for thermal comfort indicates a step change for thermal comfort and the importance that it is seen to have in the environmental credentials of a building. Should these credits prove implementable industry wide perhaps they may enter into the regulations the same way of the example above in the CfSH.

Looking into the future of POE, in May 2011 the Minister for State for Housing and Local Government reaffirmed the UK Government commitment to zero carbon homes from 2016, stating that ‘the carbon footprint of new homes cannot be allowed to add to our overall carbon reduction targets. But this needs to be done in ways which are cost effective and which protects the viability of house building’ (The Rt Hon Grant Shapps, 2011)

The zero carbon hub explains that ‘The definition of zero carbon was originally envisaged to be Level 6 of the Code for Sustainable Homes, which has only been achieved in practice by a handful of exemplar schemes.’ (Zero Carbon Hub) CLG has released figures that show that only 128 homes in the UK have been certified at Post Construction Stage as Code Level 6 up to December 2011 (CLG, 2012). This is a very small minority of the 52,486 homes that have received a Post Construction Stage Code certificate. The Zero Carbon Hub explains that this is due to difficulties in the way the homes are assessed, explaining that homes need to be treated as their own ‘individual energy island’, which means that they must achieve net zero carbon on their own merits which generally will require the onsite production of renewable energy.

The current definition of zero carbon homes is no longer Level 6 of the Code for Sustainable Homes, and in fact it is not based on the Code at all. Instead the definition is based upon achieving a minimum level in Fabric Energy Efficiency, achieving a minimum level of Carbon Compliance and achieving net zero carbon through Allowable Solutions (Zero Carbon Hub, 2008). This will be implemented through the building regulations and through the Standard Assessment Procedure.

Although the definition of zero carbon has been revised so that it is no longer based on Code 6 of the Code for Sustainable Homes, the majority of those defined as net zero carbon have been through this definition, however there is cause to question whether homes designed to this standard are actually being built to this standard. This is referred to as the performance gap, where the calculated designed performance does not meet the as built performance. The NHBC foundation questions ‘the ability of the SAP assessment model to make an accurate prediction of the energy use of homes given the large number of variables and the accuracy of the data inputs’ (NHBC Foundation, 2012) however a large variety of reasons could contribute to the performance gap including the calculation methods, build quality, construction techniques, or user behaviour. Hernandez Neto supports this and states that ‘the user should have the expertise to choose the most suitable tool depending on the type of analysis being done’. (Hernandez Neto, Fiorelli, & Buoro, 2012). Unfortunately in the case of Building Regulation compliance only SAP and SBEM are the accepted methods of showing compliance, so perhaps it would be more appropriate to allow to be used a different software that may produce more accurate results.

The NHBC Foundation lists 7 areas to be considered in order to understand the reasons for how a performance gap arises, (NHBC Foundation, 2012) due to ongoing scuntination of the SAP calculation model, Zero Carbon Hub has concluded that SAP is the best model to continue to use to evaluate building performance and because the validity of data is verified through the use of OCDEAs[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[7]|alt=[7]]], who must be a member of a licensing organization that operated regular QA[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[8]|alt=[8]]] verification testing on calculations the expertise to input data correctly is present.

Unfortunately because low energy homes are rare in the UK and even fewer are subject of Post Occupational Evaluation the actual performance is not known. The BUS supports this and states that benchmarking could take 3-5 years to populate (BUS, 2012).

Leaman states that real world research means that predicting effects ‘are more difficult to predict, e.g. unanticipated operating modes for innovative technologies, or alterations in user behaviour’ (Bordass, Stevenson, & Leaman, Building Evaluation: Practice and Principles, 2010). This idea is supported by Vale, who states that ‘Post Occupation Evaluation (POE) could have a significant role in the lowering of environmental impacts, but the framing of domestic POE must embrace a rating of the occupants’ behaviour’ (Vale & Vale, 2010). Occupant behaviour, however is not as simple as designing a building to supply a uniform temperature as in air conditioned buildings, although in a research study (Juricic, Van Den Ham, & Kurvers, 2012) found that there was no difference between the energy use in user orientated buildings than those designed ignoring user profiles and concluded that ‘the idea of giving the opportunity to the user to interact with the environment is not necessarily synonym with higher energy use’. This however does not mean that because the building uses the same amount of energy whether users are in control or not that the users achieve the same level of thermal comfort, (Nicol, Humphreys, & Roaf, Adaptive Thermal Comfort: Principles and Practice, 2012) state that ‘behaviour is an important role in our thermal interaction with the environmental’ including the changing of clothes, changes of posture and metabolic rates, moving to a different thermal environment and changing the current environment using thermal controls. It has been found that the range of temperatures that are acceptable is around 70% wider for natural ventilated building than for HVAC buildings showing that ‘higher levels of personal control makes users more tolerant of wider temperature swings’ (De Dear & Brager, 1998).

Tuohy also looks at new technologies that are often used in low energy buildings and describes ‘new technology systems do not work as well as predicted’ and that the ‘controls are poorly designed’ (Tuohy, 2012). (NHBC Foundation, 2012) also cites mechanical and electrical installations as one of its 7 factors that contribute to the performance gap. The actual efficiency of technologies is particularly problematic as it could have a large effect on the performance gap, as efficiency is effected by the whole system, ie the boiler, pipework and inline components. It has been found that an 86% efficient gas boiler performed as poorly as 55% when the whole system was taken into account (Zero Carbon Hub, 2010). This is particularly true in relatively new technologies such as heat pumps, the figure 1 shows COP[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[9]|alt=[9]]] curves for a communal Ground Source Heat Pump system. It can be seen that the actual system efficiency is well below the expected (designed) efficiency and actually in the summer shows COP of just above 1 which is the efficiency of a standard electrical heating system. Electrical systems generally perform poorly in SAPs as the fuel factor used is 0.52kgCO2/kWh as opposed to gas which is 0.19kgCO2/kWh (DECC, 2010), the only reason heat pumps do well in SAPs as opposed to a gas system is that the COP of around 2.5 will bring the carbon emissions in line with that of gas. With the government pushing the use of these kind of technologies through SAP where heat pumps fairly easily gain high levels of carbon reduction and through the use of initiatives such as FITs and RHIs, the latter of which pays for heat energy produced using low carbon technologies such as heat pumps.

file:///C:/Users/JPage/AppData/Local/Temp/msohtmlclip1/01/clip_image002.jpg

Figure 1 COP curves for a communal Ground Source Heat Pump system (Zero Carbon Hub, 2010)

So to conclude, the mechanisms to make low energy buildings exist and is in use through formats such as the building regulations which are changing towards zero carbon which encourages the building of low energy buildings. There are some problems with the implementations of new low carbon heating systems such as heat pumps which don’t seem to match up the designed performance with the actual installed performance which leads to inconsistencies in the energy use in the buildings when compared with the designed energy use. This performance gap is known by the industry however the solutions to the problem are not yet implemented in a way that lessens the impact. The most critical of these is to learn from building utilized POE techniques.

So the real challenge is to make comfortable low energy buildings, the science idea of comfort is still fairly new however there are research projects ongoing that seek to identify the effect that thermal comfort has on the energy use of buildings. It does seem to be clear that the comfort of building occupants has a large effect on the success of the building and makes it even more important to implement POE to evaluate the effect that thermal comfort and user occupation patterns actually have on the building performance and allow future projects to learn from and improve on their design.
<div><br/>
----
<div id="ftn1">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[1]|alt=[1]]] Post Occupation Evaluation (POE) is an exercise in determining the performance of the building in use
</div><div id="ftn2">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[2]|alt=[2]]] The Usable Buildings Trust (UBT) is an organisation with charity status which was set up to evaluate building performance in use.
</div><div id="ftn3">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[3]|alt=[3]]] BREEAM is the Building Research Establishments Environmental Assessment Method that is used for new and existing non domestic buildings and existing homes
</div><div id="ftn4">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[4]|alt=[4]]] The Code for Sustainable Homes is an environmental assessment method that is used for new build homes to assess their environmental credentials on a 6 star rating systems.
</div><div id="ftn5">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[5]|alt=[5]]] Standard Assessment Procedure is the Governments approved calculation method for compliance with Building Regulations Approved Document Part L1a
</div><div id="ftn6">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[6]|alt=[6]]] Fabric Energy Efficiency Standard (FEES) is a standard based on the energy efficiency of the fabric in kWh/m<sup>2</sup>/Yr which was introduced under ENE2 in the Nov 10 version of CfSH
</div><div id="ftn7">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[7]|alt=[7]]] OCDEA – On Construction Domestic Energy Assessors are trained to carry out SAP assessment for new build homes and the production of Energy Performance Certificates (EPCs)
</div><div id="ftn8">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[8]|alt=[8]]] QA – Quality Assurance testing designed to ensure OCDEAs are completing SAP calculations within prescribed tolerances
</div><div id="ftn9">
[[File:///C:/Users/JPage/Dropbox/University/Advanced Thermal Comfort Studies/Assessment/ATCS Paper Report.docx|[9]|alt=[9]]] Coefficient of performance (COP) is a measure of the efficiency of the heat pump, a COP of 3.2 is equivalent to 320% efficient system
</div></div>

[[Category:Student_architect_essay_competition]]

Performance gap in low energy housing

2012-11-12T14:29:58Z

J65on: Protected "How to make comfortable low energy buildings that work?": Competition Entry ([edit=author] (indefinite) [move=author] (indefinite))

Tuhoy indicates that the current intent of policy is to ‘achieve comfortable low energy buildings’ (Tuohy, 2012), however comfort rarely appears in regulations or statutory minima. It does appear in deisgn guides such as CIBSE guide A however this is only a design guide and is not always fully implemented in every building built. The building regulations are a requirement for every building and would be a perfect platform to include for thermal comfort however it does not address thermal comfort in any of the approved documents, they actually mostly seize to be a part of the building process when it is completed and occupied. This is a large problem for the industry as it encourages segregation between the design and build teams and the building occupiers.

The Good Homes Alliance conference Closing the Performance gap showed that monitoring and post occupational evaluation (POE[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftn1|[1]]]) are essential tools to ensure our low carbon homes are operating as designed, and are comfortable and healthy’ (Good Homes Alliance, 2011). Currently no ongoing post construction tests and checks are enabled through the building regulations, any surveys are usually academic or research motivated. (NHBC Foundation, 2012). This must be overcome if buildings are to move on. Derbyshire supports the need for change and for inclusion of a POE and argues that science cannot grow and evolve without a ‘testing of hypothesis through observed observation, the results of which are fed back into the body of knowledge to generate a new cycle of hypothesis, experiment and feedback’ (Derbyshire S. A., 2002).

There are some organizations that do support the implementation of POE, one of the key objectives for the UBT[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftn2|[2]]] is ‘to make building performance evaluation a routine activity for design and building teams’ (Bordass, 2011) however it was noted that this was difficult as design and build teams were often reluctant to participate as the reputation of the designers or the builders could be put into doubt. Schemes such as BREEAM[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftn3|[3]]] also recognize the requirement for POE, under BREEAM New Construction 2011 it is a requirement that a BREEAM In Use assessment is undertaken for any building that achieves an Excellent or Outstanding rating (BRE Global Ltd, 2011). ‘BREEAM In-Use is a scheme to help building managers reduce the running costs and improve the environmental performance of existing buildings. It consists of a standard, easy-to-use assessment methodology and an independent certification process that provides a clear and credible route map to improving sustainability’ (BRE Global Ltd). Although it is designed as a tool to help improve the environmental performance of the building, it can help to bridge the gap between designer and occupant, where the occupant actually has to learn about the building, the way it works and is managed in order to pass the In Use assessment.

But if POE were undertaken, where would the fault lie if the building owners questioned why the building wasn’t performing as designed, the designers or the builders? The answer to this question is a bit of a minefield, however the answer may be that neither may be to blame and actually the building users are not using the building as designed. In the case of the BRE Environmental Office, it was designed as an exemplar case however the energy used in the building was around 90% higher than the designed energy demand (Ni Riain, Fisher, Mackenzie, & Littler, 2000). Accordingly to (Tuohy, 2012) there were ten key findings from the POE, eight of these were connected with the controls of the systems, one was that it was occupied differently to designed and the other that there was no energy performance data on display. The main point to focus on here is the fact that the controls were not implemented as designed compromising user control over the environment, this is supported by (Juricic, Van Den Ham, & Kurvers, 2012) citing ‘user’s opportunity to influence their indoor climate is one of the most important keys to robustness’. However, again to can be difficult to determine whether the controls were incorrectly designed or whether they are being used incorrectly by the occupants. An example of this is as a Passivhaus assessor I am often asked whether the windows can be opened in a Passivhaus because the air tightness of the building is designed to be very low, the myth is that the windows shouldn’t be opened however the PHPP includes openable windows as an important control for mitigating overheating which is wholly dependent on the users knowledge of that control. It could be very easy for an occupant to be in an overheating home and leave the windows closed because they think it will affect the performance of the building and blame the building for not performing correctly without the correct operative knowledge.

Tuohy indicates that ‘there are policy initiatives aimed at improving industry processes such as: Soft Landings, BREEAM, LEED, Green Star, AGBR and BIM’ (Tuohy, 2012). The CLG’s Code for Sustainable Homes (CfSH)[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftn4|[4]]] has also established itself as a ‘proving ground’ for new guidance and regulations, it is currently a voluntary standard except for social housing schemes in England. There are also some planning authorities that use the CfSH as a mandatory standard implementable for the planning system; this and voluntary schemes account for only covers 16% of total CfSH assessed homes (CLG, 2012). This allows new ideas or strategies to be implemented on a section of the industry before being rolled out to national policy. This has been proven in the past through the use of targets for Carbon emission compliance over the regulations which in the May 09 version of the Code was required at 25% above the building Regulations Part L1a 2006, and Code 4 was 44% above. The revision of the building Regulation Part L1a 2010 revised the compliance level in SAP[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftn5|[5]]] to be in line with this new figure, with the equivalent carbon reduction of 25% over Part L1a 2006. This is likely to carry on into the revision of Part L1a 2013 with a further 25% reduction (44% over Part L1a 2006) and the introduction of FEE[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftn6|[6]]] standards (CLG, 2012) which was introduced into the CfSH in Nov 2010.

It has been recognized that user knowledge of how the buildings work is important to how a building functions, the CfSH has dedicated credits for the production of a Home User Guide in order ‘to promote the provision of guidance enabling occupants to understand and operate their home efficiently and make the best use of local facilities’ (CLG, 2010). BREEAM has similar credits for the production of a Building User Guide ‘to ensure delivery of a functional and sustainable asset designed and built in accordance with performance expectations’ (BRE Global Ltd, 2011), however BREEAM goes one step further and introduces credits for thermal comfort, the criteria being ‘to ensure that appropriate thermal comfort levels are achieved through design, and controls are selected to maintain a thermally comfortable environment for occupants within the building.’. This criteria for thermal comfort indicates a step change for thermal comfort and the importance that it is seen to have in the environmental credentials of a building. Should these credits prove implementable industry wide perhaps they may enter into the regulations the same way of the example above in the CfSH.

Looking into the future of POE, in May 2011 the Minister for State for Housing and Local Government reaffirmed the UK Government commitment to zero carbon homes from 2016, stating that ‘the carbon footprint of new homes cannot be allowed to add to our overall carbon reduction targets. But this needs to be done in ways which are cost effective and which protects the viability of house building’ (The Rt Hon Grant Shapps, 2011)

The zero carbon hub explains that ‘The definition of zero carbon was originally envisaged to be Level 6 of the Code for Sustainable Homes, which has only been achieved in practice by a handful of exemplar schemes.’ (Zero Carbon Hub) CLG has released figures that show that only 128 homes in the UK have been certified at Post Construction Stage as Code Level 6 up to December 2011 (CLG, 2012). This is a very small minority of the 52,486 homes that have received a Post Construction Stage Code certificate. The Zero Carbon Hub explains that this is due to difficulties in the way the homes are assessed, explaining that homes need to be treated as their own ‘individual energy island’, which means that they must achieve net zero carbon on their own merits which generally will require the onsite production of renewable energy.

The current definition of zero carbon homes is no longer Level 6 of the Code for Sustainable Homes, and in fact it is not based on the Code at all. Instead the definition is based upon achieving a minimum level in Fabric Energy Efficiency, achieving a minimum level of Carbon Compliance and achieving net zero carbon through Allowable Solutions (Zero Carbon Hub, 2008). This will be implemented through the building regulations and through the Standard Assessment Procedure.

Although the definition of zero carbon has been revised so that it is no longer based on Code 6 of the Code for Sustainable Homes, the majority of those defined as net zero carbon have been through this definition, however there is cause to question whether homes designed to this standard are actually being built to this standard. This is referred to as the performance gap, where the calculated designed performance does not meet the as built performance. The NHBC foundation questions ‘the ability of the SAP assessment model to make an accurate prediction of the energy use of homes given the large number of variables and the accuracy of the data inputs’ (NHBC Foundation, 2012) however a large variety of reasons could contribute to the performance gap including the calculation methods, build quality, construction techniques, or user behaviour. Hernandez Neto supports this and states that ‘the user should have the expertise to choose the most suitable tool depending on the type of analysis being done’. (Hernandez Neto, Fiorelli, & Buoro, 2012). Unfortunately in the case of Building Regulation compliance only SAP and SBEM are the accepted methods of showing compliance, so perhaps it would be more appropriate to allow to be used a different software that may produce more accurate results.

The NHBC Foundation lists 7 areas to be considered in order to understand the reasons for how a performance gap arises, (NHBC Foundation, 2012) due to ongoing scuntination of the SAP calculation model, Zero Carbon Hub has concluded that SAP is the best model to continue to use to evaluate building performance and because the validity of data is verified through the use of OCDEAs[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftn7|[7]]], who must be a member of a licensing organization that operated regular QA[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftn8|[8]]] verification testing on calculations the expertise to input data correctly is present.

Unfortunately because low energy homes are rare in the UK and even fewer are subject of Post Occupational Evaluation the actual performance is not known. The BUS supports this and states that benchmarking could take 3-5 years to populate (BUS, 2012).

Leaman states that real world research means that predicting effects ‘are more difficult to predict, e.g. unanticipated operating modes for innovative technologies, or alterations in user behaviour’ (Bordass, Stevenson, & Leaman, Building Evaluation: Practice and Principles, 2010). This idea is supported by Vale, who states that ‘Post Occupation Evaluation (POE) could have a significant role in the lowering of environmental impacts, but the framing of domestic POE must embrace a rating of the occupants’ behaviour’ (Vale & Vale, 2010). Occupant behaviour, however is not as simple as designing a building to supply a uniform temperature as in air conditioned buildings, although in a research study (Juricic, Van Den Ham, & Kurvers, 2012) found that there was no difference between the energy use in user orientated buildings than those designed ignoring user profiles and concluded that ‘the idea of giving the opportunity to the user to interact with the environment is not necessarily synonym with higher energy use’. This however does not mean that because the building uses the same amount of energy whether users are in control or not that the users achieve the same level of thermal comfort, (Nicol, Humphreys, & Roaf, Adaptive Thermal Comfort: Principles and Practice, 2012) state that ‘behaviour is an important role in our thermal interaction with the environmental’ including the changing of clothes, changes of posture and metabolic rates, moving to a different thermal environment and changing the current environment using thermal controls. It has been found that the range of temperatures that are acceptable is around 70% wider for natural ventilated building than for HVAC buildings showing that ‘higher levels of personal control makes users more tolerant of wider temperature swings’ (De Dear & Brager, 1998).

Tuohy also looks at new technologies that are often used in low energy buildings and describes ‘new technology systems do not work as well as predicted’ and that the ‘controls are poorly designed’ (Tuohy, 2012). (NHBC Foundation, 2012) also cites mechanical and electrical installations as one of its 7 factors that contribute to the performance gap. The actual efficiency of technologies is particularly problematic as it could have a large effect on the performance gap, as efficiency is effected by the whole system, ie the boiler, pipework and inline components. It has been found that an 86% efficient gas boiler performed as poorly as 55% when the whole system was taken into account (Zero Carbon Hub, 2010). This is particularly true in relatively new technologies such as heat pumps, the figure 1 shows COP[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftn9|[9]]] curves for a communal Ground Source Heat Pump system. It can be seen that the actual system efficiency is well below the expected (designed) efficiency and actually in the summer shows COP of just above 1 which is the efficiency of a standard electrical heating system. Electrical systems generally perform poorly in SAPs as the fuel factor used is 0.52kgCO2/kWh as opposed to gas which is 0.19kgCO2/kWh (DECC, 2010), the only reason heat pumps do well in SAPs as opposed to a gas system is that the COP of around 2.5 will bring the carbon emissions in line with that of gas. With the government pushing the use of these kind of technologies through SAP where heat pumps fairly easily gain high levels of carbon reduction and through the use of initiatives such as FITs and RHIs, the latter of which pays for heat energy produced using low carbon technologies such as heat pumps.

file:///C:/Users/JPage/AppData/Local/Temp/msohtmlclip1/01/clip_image002.jpg

Figure 1 COP curves for a communal Ground Source Heat Pump system (Zero Carbon Hub, 2010)

So to conclude, the mechanisms to make low energy buildings exist and is in use through formats such as the building regulations which are changing towards zero carbon which encourages the building of low energy buildings. There are some problems with the implementations of new low carbon heating systems such as heat pumps which don’t seem to match up the designed performance with the actual installed performance which leads to inconsistencies in the energy use in the buildings when compared with the designed energy use. This performance gap is known by the industry however the solutions to the problem are not yet implemented in a way that lessens the impact. The most critical of these is to learn from building utilized POE techniques.

So the real challenge is to make comfortable low energy buildings, the science idea of comfort is still fairly new however there are research projects ongoing that seek to identify the effect that thermal comfort has on the energy use of buildings. It does seem to be clear that the comfort of building occupants has a large effect on the success of the building and makes it even more important to implement POE to evaluate the effect that thermal comfort and user occupation patterns actually have on the building performance and allow future projects to learn from and improve on their design.
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<div id="ftn1">
[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftnref1|[1]]] Post Occupation Evaluation (POE) is an exercise in determining the performance of the building in use
</div><div id="ftn2">
[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftnref2|[2]]] The Usable Buildings Trust (UBT) is an organisation with charity status which was set up to evaluate building performance in use.
</div><div id="ftn3">
[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftnref3|[3]]] BREEAM is the Building Research Establishments Environmental Assessment Method that is used for new and existing non domestic buildings and existing homes
</div><div id="ftn4">
[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftnref4|[4]]] The Code for Sustainable Homes is an environmental assessment method that is used for new build homes to assess their environmental credentials on a 6 star rating systems.
</div><div id="ftn5">
[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftnref5|[5]]] Standard Assessment Procedure is the Governments approved calculation method for compliance with Building Regulations Approved Document Part L1a
</div><div id="ftn6">
[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftnref6|[6]]] Fabric Energy Efficiency Standard (FEES) is a standard based on the energy efficiency of the fabric in kWh/m<sup>2</sup>/Yr which was introduced under ENE2 in the Nov 10 version of CfSH
</div><div id="ftn7">
[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftnref7|[7]]] OCDEA – On Construction Domestic Energy Assessors are trained to carry out SAP assessment for new build homes and the production of Energy Performance Certificates (EPCs)
</div><div id="ftn8">
[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftnref8|[8]]] QA – Quality Assurance testing designed to ensure OCDEAs are completing SAP calculations within prescribed tolerances
</div><div id="ftn9">
[[file:///C:/Users/JPage/Dropbox/University/Advanced%20Thermal%20Comfort%20Studies/Assessment/ATCS%20Paper%20Report.docx#_ftnref9|[9]]] Coefficient of performance (COP) is a measure of the efficiency of the heat pump, a COP of 3.2 is equivalent to 320% efficient system
</div></div>

[[Category:Student_architect_essay_competition]]

Performance gap in low energy housing

2012-11-12T14:27:37Z

J65on: Created page with " Tuhoy indicates that the current intent of policy is to ‘achieve comfortable low energy buildings’ (Tuohy, 2012), however comfort rarely appears in regulations or statutory..."

User:J65on

2012-11-12T14:12:51Z

J65on:

My name is Jason Page; I am an architectural assistant specialising in low energy housing projects, I have a wide range of experience through planning and working drawing packages.

I have been trained in carrying out energy assessments, including SAP calculations, Code for Sustainable Homes assessments, PassivHaus assessments and Psi Value calculations.

I have experience working on one of the first zero carbon developments to be certified Code level 6 in the country.

I am currently studying towards an MSc in Architecture, Energy and Sustainability at London Metropolitan University, London which finishes in 2013

I can be contacted on JRP0040@my.londonmet.ac.uk or jason.page@ingletonwood.co.uk

User:J65on

2012-11-12T14:06:46Z

J65on: Created page with " My name is Jason Page; specialising in low energy housing projects, I have a wide range of experience through planning and working drawing packages. I have experience working o..."

My name is Jason Page; specialising in low energy housing projects, I have a wide range of experience through planning and working drawing packages.

I have experience working on one of the first zero carbon developments to be certified Code level 6 in the country.

I have been trained in carrying out energy assessments, including SAP calculations, Code for Sustainable Homes assessments, PassivHaus assessments and Psi Value calculations.

I am currently studying towards an MSc in Architecture, Energy and Sustainability at London Metropolitan University, London which finishes in 2013

I can be contacted on JRP0040@my.londonmet.ac.uk