BREEAM Low carbon design

1 Aim and benefits
2 When to consider
3 Step by step guidance
4 Questions to ask while seeking compliance
5 Tools and resources
6 Tips and best practice
7 Typical evidence
- 7.1 Design Stage:
- 7.2 Post Construction Stage:
8 Applicable Schemes
9 Related articles on Designing Buildings Wiki

[edit] Aim and benefits

The aim of this issue is to encourage the adoption of design measures which reduce building energy consumption and associated carbon emissions and also minimise reliance on active building services systems.

There are three credits available:

The passive design analysis and free cooling credits are linked; it is not possible to achieve the free cooling credit without having first achieved the passive design analysis credit.

Free cooling has been highlighted in this issue as it relates particularly to reducing overheating for adaptation to climate change. It can also make the building much simpler to operate and maintain than one with mechanical cooling.

While not a specific requirement of BREEAM, it is recommended that the passive design analysis credit is achieved before targeting the Low Zero Carbon (LZC) Feasibility Study credit. This is line with the Energy Hierarchy which favours making building and systems more energy efficient before incorporating LZC technologies.

The LZC Feasibility Study credit is covered in a separate article.

[edit] When to consider

It is a requirement of the issue that, in order to maximise the potential benefit, the passive design analysis should be considered at the early stages of the project (RIBA Stage 2 or equivalent) when relevant issues are being considered and agreed.

The modelling required to demonstrate compliance is often undertaken by building services designers as they will be developing the required models as part of demonstrating Part L compliance and thermal performance of the building. As this model then forms the basis of the LZC Feasibility Assessment, the individual should be a member of the Chartered Institute of Building Services Engineers (CIBSE) and/or be an accredited energy assessor.

[edit] Step by step guidance

[edit] Passive Design Analysis (1 Credit)

This credit can only be awarded where the first credit within issue Hea 04 Thermal Comfort has been achieved.

The design team will be required undertake the following activities:

Calculate the energy demand and consumption for the proposed development using the base requirements as set out within the National Calculation Methodology (NCM) templates but without any passive measures included within the design.
Calculate the energy demand and consumption for the proposed development with passive design measures incorporated. Refer to CN4 of the BREEAM manual for the required content for the passive design analysis.
Produce a report that demonstrates that a meaningful reduction in the total energy demand has been undertaken. CN16 recommends that the passive design measures should contribute at least 5% of the overall building energy demand and/or CO2 emissions but it should be noted that if the analysis demonstrates that a greater reduction could have been achieved then the credit should be withheld. Knowledge Base Compliance Note KBCN00027 has further information and examples.
Provide documentary evidence (specifications/drawings/etc.) to confirm that the passive design measures have been incorporated into the building design.

More information can be found in the methodology section of this issue within the BREEAM Manual.

Refer also to the separate article on Passive Design: https://www.designingbuildings.co.uk/wiki/BREEAM_Passive_design

[edit] Free Cooling (1 Credit)

This credit can only be awarded where the first credit of this issue is achieved.

The design team will be required to include within the passive design analysis a free cooling assessment that identifies opportunities for the implementation of free cooling solutions.

The credit can only be awarded where the building users any of the free cooling strategies listed in CN5, i.e. that the building does not use any active cooling.

The assessment should cover all occupied spaces within the building. Small IT rooms and lift motor rooms are specifically excluded as these will often require ventilation/cooling to meet the equipment operational requirements. Likewise, the provision of mechanical ventilation for small areas such as kitchenettes and toilets is also acceptable.

A brief overview of the free cooling measures is included below:

Night Time Cooling (or purging): the facility to cool the building overnight through natural ventilation measures (e.g. openable windows or vents) in conjunction with exposed thermal mass elements.
Ground Coupled Air Cooling: an example of this is the incorporation of a thermal labyrinth into the building. Most effective where is there is a large temperature differential between day and night.
Displacement Ventilation: low-velocity air is delivered at low level into a space which then rises to high level as it heats up, resulting in a natural displacement of stale air. Suited to high-occupancy, open-plan spaces with high ceilings.
Ground Water Cooling: utilises water from a below ground source to provide cooling into the building. Requires less water than conventional cooling towers and performs reliably regardless of the weather or season.
Surface Water Cooling: utilises water from an above ground source (e.g. rivers or lakes) to provide cooling into the building.
Evaporative Cooling: uses water mist to provide cooling by drawing the heat from the hot air. Can achieve up to 90% savings when compared to conventional chillers.
Desiccant Dehumidification and Evaporative Cooling, using waste heat: description to be added
Absorption cooling, using waste heat: description to be added
Natural Ventilation: where the building is cooled solely via natural ventilation (e.g. openable windows/vents).

More information can be found in the methodology section of this issue within the BREEAM Manual.

See also the separate article on free cooling: https://www.designingbuildings.co.uk/wiki/BREEAM_Free_Cooling

[edit] Low zero carbon feasibility study (1 Credit)

While this credit is not dependent on the first two credits, the base case should include any passive design or free cooling measures adopted for the first two credits.

Refer to the BREEAM LZC technologies article for further details of this credit.

[edit] Questions to ask while seeking compliance

Were any passive design measures set prior to undertaking the analysis?
Has the passive design assessment been included in the RIBA Stage 2 scope?

[edit] Tools and resources

[edit] Tips and best practice

Some of the elements that form part of the passive design analysis may already have been set prior to RIBA Stage 2, e.g. site location (and therefore site weather and microclimate), building form and building orientation. In these instances the team should demonstrate the following:

For site location, either that the site was a specific client requirement that could not be changed or that, when the site was selected and options assessed, consideration was given to the potential passive design benefits.
For building form and orientation, it should be demonstrated that they were either dictated by site constraints or have been chosen to improve the building performance.

Where this cannot be demonstrated, the credit should be withheld.

For shell only and shell and core assessment, all relevant criteria of the passive design analysis appropriate to the building type and function apply.

For a shell only assessment, all relevant criteria of the free cooling credit appropriate to the building type and function apply but only the following free cooling strategies can be considered:

There are no changes to the criteria where the assessment is for a simple building.

[edit] Typical evidence

[edit] Design Stage:

Passive Design Analysis report including calculations produced during RIBA Stage 2 (or earlier)
Free Cooling Assessment report including calculations
Architectural drawings and specification
Building Services drawings and specification

[edit] Post Construction Stage:

As-built drawings
Assessor site survey

[edit] Applicable Schemes

The guidelines collated in this ISD aim to support sustainable best practice in the topic described. This issue may apply in multiple BREEAM schemes covering different stages in the life of a building, different building types and different year versions. Some content may be generic but scheme nuances should also be taken into account. Refer to the comments below and related articles to this one to understand these nuances. See this document for further guidelines.