Making energy calculations more accurate with HQM

[edit] Introduction

When developers and assessors start using HQM, one of the first things they look at is how their projects are doing in energy. This isn’t surprising seeing as it’s the issue with most credits. And it’s an easily quantifiable aspect of sustainability that can be assigned a cost. As with all the issues in the “My Home” section of Home Quality Mark, it works alongside the “Delivery” (previously Knowledge Sharing) section to ensure that the design is delivered to the occupants of the home (see how HQM recognises delivery and quality, here). The benefits of energy efficiency are also clear; lower carbon, lower running costs for consumers and healthier homes that keep us warm throughout the year (when also combined with measures to prevent uncomfortably warm temperatures in summer, of course!).

SAP is the calculation methodology to show compliance against the minimum standards of Building Regulations. HQM recognises performance that is above these minimum standards, and we want to provide a greater level of accuracy to the consumer and others using the scheme (such as the financial sector, planners and more). To do this, the calculation methodology needs to be different, as it is doing a different job. At the same time, we also don’t want to add significant burden on developers, by making them complete a new calculation from scratch.

We are currently consulting on the next version of Home Quality Mark, with regards to improving the accuracy of the calculation. The main change we are proposing is;

To use up-to-date Carbon and Primary Energy factors to more accurately determine energy efficiency. This will better recognise decarbonisation of the national grid.

[edit] How HQM already makes energy calculations more accurate

The HQM energy calculation already has a number of key features to improve the accuracy of energy predictions, because it:

[edit] Uses local weather conditions

HQM uses localised weather data to more accurately reflect the effects of weather on a home’s energy performance, compared to SAP, which uses a national average. Weather is one thing we can’t control when it comes to buildings, so this is important for producing an accurate calculation.

[edit] Considers energy usage of lighting, appliances and water heating

As HQM’s energy methodology is a variation of BREDEM [1], it means additional inputs can be added to improve the accuracy of the calculations. Using EU energy labels for appliances and details of light fittings that are actually installed, HQM acknowledges the benefits of low-energy products and gives a more realistic scenario based on the design details of the home. If this information isn’t available, default assumptions are made because even if they aren’t specified by the developer, they will be installed once occupants move in.

[edit] Uses a triple metric approach to give a holistic, overarching energy score.

By combining primary energy, CO2 emissions and heating & cooling demand, HQM’s energy methodology provides a holistic view of overall energy efficiency, in one metric.

This is an adapted version of the triple-metric approach used by BREEAM, which benefits from over 25 years of experience and knowledge of the worldwide assessment methodology for sustainable development.

[edit] Awards credits for cost, separately.

Energy efficiency and energy costs are not the same thing. The costs that consumers are charged in-practice can vary significantly, depending on the systems in place (e.g. heating and hot water), even if they are relatively efficient.

[edit] Produces HQM energy credits for each, individual home.

An HQM rating gives consumers and personal finance organisations, a way of comparing individual homes, including their energy efficiency and expected running costs. Energy performance of the home is therefore based on the individual home, as with Energy Performance Certificates (EPCs), instead of an average, which is allowed for compliance with Building regulations Part L, when assessing multiple homes in some cases.

[edit] Leads the way towards zero Carbon

We believe that lots of small changes can have an overall big impact, so HQM awards credits on a scaled approach across the scheme. For energy, HQM awards some credits for performance slightly beyond Building Regulations ‘notional dwelling’ all the way up to 100% improvement over regulation baselines and beyond, to recognise homes that off-set their regulated and unregulated energy use with low and zero carbon technologies.

HQM therefore recognises improvements in energy performance, all the way up to the few projects currently able to achieve best-practice zero carbon levels. We expect these standards to evolve over time, to recognise improvements and innovations made in industry and with low and zero carbon technologies.

[edit] Incorporates shared heated common areas.

Heated common areas shared by homes can contribute a significant proportion of a home’s energy demand, which can be overlooked in the building design.

Where these areas are present, HQM incorporates them in its energy calculation to give a holistic evaluation of the whole building and the assessed home’s relative energy usage associated with these spaces.

It does this by using outputs from SBEM that are already required by Building Regulations where these common areas are present.

[edit] It’s owned by BRE

This means we can update the methodology to reflect up to date best-practice and research, much faster than regulatory tools. This allows developers to keep ahead of the curve by using HQM.

[edit] Streamlining the assessment

Improving the accuracy of the calculation is important, but we also need to be mindful that developers and designers should not be have significant extra burden. For HQM ONE we are proposing to:

[edit] Streamline the HQM energy methodology

By removing the ‘foundation route’ option, we are proposing to simplify how credits are calculated and make outputs from HQM more comparable. If inputs for lighting, appliances and water heating aren’t available, appropriate defaults will be automatically assumed.

And HQM already helps to streamline assessment by:

[edit] Simplifying the process of certification by using data that are already there!

We’ve worked with SAP software providers so where their software is recognised by us (Elmhurst, FSAP, NHER), they can produce XML outputs that feed directly into our own HQM assessment tool. This means HQM assessors don’t have to do loads of extra work to use the HQM energy methodology because it starts with SAP, which is required for all new homes as part of complying with Building Regulations anyway.

[edit] Using the HQM engine to help calculate high temperature risk

Again, building on the inputs already required by SAP, the HQM energy methodology can be used to calculate credits in the ‘Temperature’ assessment issue. This provides a first-pass risk assessment as to whether prevention measures or dynamic simulation modelling are needed, and builds on Appendix P in SAP (overheating). This provides a more comprehensive evaluation of overheating risk by considering factors that aren’t already included in SAP, such as local environment and potential barriers to natural ventilation (e.g. noise or security risks).

[1] The BRE Domestic Energy Model (BREDEM) is a methodology for calculating the energy use and fuel requirements of dwellings based on their characteristics. It is suitable for use in research work, such as stock modelling. It shares some features with the SAP methodology, but allows users to adjust inputs which are fixed in SAP, making it better suited to certain analysis tasks. See here for more info: bre.co.uk/page.jsp?id=3176 https://www.bre.co.uk/page.jsp?id=3176

[edit] Related articles on Designing Buildings Wiki

• 5 things you need to know about HQM ONE.
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• BRE Buzz articles on Designing Buildings Wiki.
• BRE Buzz.
• BREEAM.
• Differences between HQM Beta and HQM ONE.
• Home Quality Mark.
• HQM ONE.
• Improving home quality with HQM ONE.