Find the gap – insights into the ‘performance gap’ from social housing sector BPE projects

27th January 2016

There’s a growing appreciation of the gap that exists between the design of a building and its ‘as-built’ performance. This ‘performance gap’ occurs in buildings across all sectors, whether it’s social housing, commercial office space, public buildings or private residential dwellings.

The Building Performance Evaluation (BPE) programme was an £8 million competition funded by Innovate UK (formerly, Technology Strategy Board). Working with leading industry practitioners, the programme sought to identify where the ‘performance gap’ arises, by evaluating and assessing the post-construction and in-use performance of both domestic and non-domestic buildings. This was done through detailed forensic evaluation, including: fabric in-situ U-value testing, multi-stage air tightness testing, long-term indoor air quality evaluation as well as post-construction reviews, occupant walkthroughs and post-occupancy evaluation.

The programme included a total of 52 new housing projects, of which 54% (28 projects) were led by Registered Providers (RPs).

The National Energy Foundation’s Technical Team was commissioned by Innovate UK to undertake an analysis of the data arising from all 28 RP-led projects, which comprised 83 test dwellings. The ultimate objective of the study was to empower RPs to take a lead and become champions in combating the performance gap between designed and as-built.

Findings from the study identified:

  • Key success factors (where things worked well and not so well).
  • Practices which resulted in a significant performance gap.
  • The relative impact of specific attributes such as defects and building services on the performance gap.

In particular, the study 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% 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.
  • Whilst 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.

The National Energy Foundation is actively involved in a number of the key areas identified by the BPE:

  • An Assured Performance Process Framework developed in partnership with East Hampshire District Council and the Milton Keynes Development partnership.
  • New tools and techniques in collaboration with academia, such as PULSE that enable building performance evaluation to become more accessible and affordable.
  • New asset management propositions, working with asset management teams within organisations that own large portfolios on how best to manage and act on asset data – for example, VolDEC, iAIM and Suffolk County Council.

The Foundation will be presenting the findings of this work at the National Housing Maintenance Forum – a two-day conference devoted to housing maintenance that is expected to attract over 350 people with responsibility for maintenance and stock re-investment in repairs and maintenance contractors, suppliers and consultants.

The National Energy Foundation is also looking forward to the upcoming Building Data Exchange Hackathon run by Innovate UK where it will be sponsoring a challenge specifically aimed at leading programmers, coders and construction sector professionals interested in developing new tools, techniques and data visualisation work that will help building designers, specifiers, owners and users to find and act on the ‘performance gap’.

Energy Specialist, Federico Seguro, commented:

“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.”