New study reveals insights into gaps in building performance

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The findings of an £8m study into the gaps between the expected and actual performance of buildings have been released

A new study has revealed insights into difference in performance of building after construction when compared to the expected outcomes during the design process.

This disparity is something that occurs across all building sectors. In a bid to understand why, the government’s innovation agency Innovate UK funded an £8m competition.

The Building Performance Evaluation (BPE) programme brought together leading industry practitioners to identify where gaps arise and why. This was achieved by evaluating and assessing the post-construction and in-use performance of both domestic and non-domestic buildings.

The project used detailed forensic evaluation to get its results. This included fabric in-situ U-value testing, multi-stage air tightness testing, long term indoor air quality evaluation, and post-construction reviews.

To collect the data, the project evaluated 52 new housing projects, of which 54 per cent (28 projects) were led by registered providers (RPs).

Innovate UK commissioned the technical team at the National Energy Foundation to analyse data from all 28 RP-led projects. This comprised of 83 test dwellings. From this it was hoped the results of the study would empower RPs to champion closing the performance gap between designed and built-as.

The study identified key success factors to improving the performance gap. It found that:

•             On average, the fabric U-values exceeded the target set, with nine properties failing to meet the Building Regulations PartL1A (Conservation of fuel and power in new dwellings) backstop.

•             The air tightness of 46 per cent of the BPE test dwellings was below the design intent hitting an average airtightness of 4.4 m3m- 2h-1 @ 50 Pa across all the properties evaluated, against an average design specification of 4.93 m3 h-1 m-2 @ 50 Pa.

•             A high number of commissioning, operation and maintenance-related issues were encountered, in particular where buildings had advanced services equipment configurations in place.

•             While underheating was less of an issue, overheating was more frequently reported. This was not only due to high levels of thermal insulation and airtightness but it was also dictated by window opening behaviour and sub-optimal building design and specification.

•             Overall, BPE emerges as a powerful means of bridging the performance gap and presents sizeable opportunities in terms of transferring the skills gained into future developments.

Energy Specialist Federico Seguro said: “The construction industry continues to wrestle with pinpointing and bridging the gap between the design of buildings and their ‘as-built’ performance; a gap that exists across all building sectors.

“Our meta-analysis of all of the BPE projects led by Registered Providers revealed the trigger points resulting in social housing projects failing to deliver on the designed performance targets, and identified a number of key issues for the future.

“Our research will empower Registered Providers who have the means to champion and combat the ‘performance gap’ in buildings, and allow them to apply lessons from the BPE to their new developments.”

The National Energy Foundation is already actively involved in a number of key areas identified in the study. As such the organisation developed an Assured Performance Process Framework in partnership with East Hampshire County Council and the Milton Keynes Development partnership.

Additionally, new tools and techniques have been put forward in collaboration with academia. This includes PULSE, which allows building performance evaluation to become more accessible and affordable.

The organisation has also been involved in asset management propositions and has worked closely with asset management teams within organisations with large portfolios. This includes VolDEC, iAIM and Suffolk County Council.

View the full report here: Insights from Social Housing Projects

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