HOME QUALITY MARK HERALDS NEW ERA OF QUALITY IN HOUSEBUILDING – BUT IT’S A WORK IN PROGRESS – Ben Wallbridge, Energy & Sustainability Assessor, Darren Evans Assessments

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The Home Quality Mark (HQM) has now officially joined the highly successful BREEAM family of quality and sustainability standards, stepping into the shoes of the now defunct Code for Sustainable Homes as a voluntary national housebuilding rating scheme which pretty much covers all of the bases. This comprehensive new standard incorporates elements of BREEAM and the Code but in its nascent and still developing form how workable is it?

The scheme was soft launched as a beta version last October which is a fully functioning standard but with the industry being actively encouraged by BRE to feedback from their experience of using it in practice to help hone the final version. This very open developmental approach is welcome however it does mean that the Mark as it stands is still something of a work in progress.

Developing a simple star system which makes sense to the two key audiences of consumers and housebuilders is laudable, but behind the ratings are a complex matrix of criteria for gaining credits which go way beyond the building itself to provide wide-ranging detail on a house’s credentials. These range from wellbeing issues such as air quality, transport and amenities to resilience, energy costs and post-construction fabric testing.

The layout and methodology of the HQM Technical Manual will feel familiar to assessors who have worked with the CfSH or BREEAM but seems even more intuitive and informative with three overarching sections: ‘Our surroundings’, ‘My home’ and ‘Knowledge Sharing’. For each there are indicators graphically represented with their importance in the scheme and the credits awarded – the indicators being cost, health & wellbeing and environmental footprint. These feed into the final certificate which informs the end user about their home.

Numerous study sites have been initiated by BRE which are informing the technical and operational feedback into the scheme although the number of HQM registered sites under the beta launch has not been released. The fact that registrations are free for six months should help encourage forward-thinking developers and clients to get involved.

Although the beta version of HQM is a fully functioning scheme, the BRE are welcoming feedback on all levels. While it is unlikely that the fundamental mechanisms and layout of the scheme will change drastically, it’s possible the first non-beta edition of the Technical Manual will have slight differences in terms of elements such as credit weightings, evidence requirements, or section wordings.

The initiative was launched nearly a year ago at EcoBuild 2015 and will have a strong presence at Ecobuild 2016 including sponsoring the first day of the event which focuses on housing. This will keep the new scheme in the forefront of the industry’s mind and help everyone to become more familiar and more knowledgeable about HQM going forward.

At HQM’s launch at last year’s Ecobuild Tony Barton, Executive Chair of consultant Sustainable Homes proclaimed that he “expected it to fly off the shelves, because we know the demand is there.” It may take time for it to usher in a new era of quality in housebuilding with builders using a star rating as a differentiator in the marketplace and housebuyers benefitting from an independent guarantee that their new home is not only well designed and built, cheaper to run, healthier and more sustainable. It is an exciting initiative with a lot of potential but with only 59 assessors currently qualified to use it in practice, it is a case of watch this space.

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CLEARING UP CONFUSION AROUND THE CRITERION 3 CHECK ON SUMMER HEAT GAIN Marcus Eves, Sustainability Consultant, Darren Evans Assessments

DEA blog - sunSummer overheating has been a hot topic in recent months, however the Building Regulations do make provision for limiting the effects of solar gain. Unfortunately despite being a requirement for compliance with Part L2A of the Building Regulations, the importance of the Criterion 3 check on how much buildings are being heated via windows is often overlooked and misunderstood.

Whilst we are all familiar with the requirements of Criterion 1 (Compliance with the Building Emission Rate), Criterion 3 (Limiting the Effects of Solar Gains in Summer) always seems to get forgotten about. And when it comes to finding a route to achieving compliance it can leave some confused and frustrated.

In commercial buildings compliance with the emissions targets is straightforward, proceeding through the reliable time-honoured menu; lower the U-values, improve the building services, enhance the controls and finally consider renewables. However many are unfamiliar with how the Criterion 3 check is performed in SBEM (the BRE’s Simplified Building Energy Model for non-domestic buildings). When it comes to compliance the implications of this can be drastic.

For the purposes of Part L, a ‘limiting solar gain check’ is performed for Criterion 3 compliance where the aggregated solar gains between April and September must be below a certain benchmark. It is crucial to understand that this does not mean a straightforward overheating check is carried out and is related to solar gain via windows only. Provisions must be taken to limit internal temperature rise due to solar gain in summer; this will reduce or eliminate the need for air conditioning or mechanical ventilation which will increase the building’s energy demand.

In Part L 2006 the Criterion 3 check carried out in the SBEM was based on overheating assessment and therefore any zones which were mechanically cooled were exempt. This gave a quick fix to developers: if a zone failed Criterion 3, a cooling system was added and a pass could be demonstrated. This is not the case anymore. Mechanical plant cannot simply be introduced to offset an issue as a result of poor façade design.

Consideration needs to be given to the design of the building very early on to limit solar gains entering the spaces. There are three main factors to consider:

  • window size and orientation;
  • solar protection through internal or external shading or improved glass specification;
  • high thermal capacity.

When the Criterion 3 limit is exceeded by a small amount – up to 30% – consider the glazing specification and blinds. Windows with lower G-values will restrict the amount of solar radiation entering the space. Blinds will also have the same effect, but these are not appropriate for all spaces.

When the Criterion 3 limit is exceeded by a larger amount (up to 50%) consideration must be given to the glazed area proposed. A reduction in the number of openings or their size may be required. If curtain walling is proposed, spandrel panels can be introduced to reduce the area of glass but keep the overall feel of the building.

Finally external shading must be considered; such as the introduction of overhangs to windows, vertical or horizontal fins, or brise soleil. This will have significant impact on the building form and so will require resubmissions to planning, therefore it’s vital the impact of Criterion 3 compliance is identified at the earliest stage.

It must be noted that if external shading is required, SBEM does not take this fully into account. A full overheating study using a bespoke Dynamic Simulation Model will be required in order to demonstrate to building control that the internal comfort conditions will be met.

In summary, recognising that compliance Criterion 3 is restricted to solar gain from windows, it is important to also acknowledge there is a trade-off between maximising the benefit of daylight and limiting solar gains. Also it is essential to recognise the impact of Criterion 3 compliance prior to planning submission and that the introduction of building services such as air conditioning or mechanical ventilation are not a fix. Lastly, achieving compliance can be expensive and in some instances affect a building’s form.