Tuesday, 23 February 2016

Government report identifies Passivhaus as best meeting the 'Performance Gap' between design expectation and built performance

The recently published government report, 'Building Performance Evaluation Programme: Findings from domestic projects', conducted by Innovate UK (formally the Technology Strategy Board), set out to find out if low-carbon homes really were performing as energy-efficiently as predicted at the design stage, and if not, what was causing the 'performance gap'. 

The UK is legally bound to reduce greenhouse gases by 80% by 2050. Building better low-carbon homes will help the UK achieve this ambitious goal. 

The Innovate UK report, published earlier this month on the GOV.UK website, looked at data from a subset of 76 homes in the Innovate UK’s Building Performance Evaluation Programme (BPE). The properties chosen in the BPE are part of leading-edge developments across the UK where low-carbon design was a priority, and include two of Gale & Snowden Architects' recent residential projects, Knight's Place and Rowan House.

The report looks at three forms of low-carbon design (Passivhaus, Passive Solar and Traditional with renewable energy systems) and concludes that: 'homes built to Passivhaus standards achieved the best airtightness and insulation values, which means they had the lowest heat loss and the best thermal performance'.

Gale & Snowden was involved in the BPE programme, spending a period of over two years monitoring five Passivhaus flats at Knight's Place and Rowan House. Our previous blog post discussing the methods used to monitor the flats can be found here.

Knight's Place

The Innovate UK report found that Knight's Place came second across the schemes tested in airtightness results, achieving air permeabilities of 0.30m3/hr/m2 and 0.74m3/hr/m2 (at 50Pa) against a design of 0.41m3/hr/m2 (at 50Pa). The worst performing scheme was as much as 14.48m3/hr/m2 (at 50Pa) worse than designed. Credit goes to ISG Pearce Ltd. contractors for achieving such outstanding airtight construction.

Other findings in the report include:
  • Adopting Passivhaus principles can achieve very low energy use for space heating. Long-term low heating bills can repay the extra effort and attention needed onsite. 
  • Construction has a limited effect on electricity use. However, the use of low-power fittings, including lights, can reduce demand. Efficient construction provides a much bigger scope for savings in space heating. 

Having designed low-energy buildings for nearly 25 years, Gale & Snowden welcome the report's findings and will use the information and strategies outlined to build on their already vast experience in Passivhaus and low-energy design.

To read more about Passivhaus and energy-efficient design, visit our website. Gale & Snowden is registered with the Passivhaus Institute in Germany as a Certified Designer, as well as being a member of the Passivhaus Trust in the UK. Gale & Snowden also offer a Passivhaus design consultancy service, with more information available here.

Follow us on twitter for the latest updates @galeandsnowden

The full 38-page report can be downloaded from here, or read below:

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