The Building Performance Evaluation programme included leading industry practitioners and involved a detailed forensic evaluation of:
- Fabric in-situ U-value testing.
- Multi-stage air tightness testing.
- Long-term indoor air quality evaluation.
- Post-construction reviews.
- Occupant walkthroughs.
- Post-occupancy evaluation.
There were 52 new housing projects in total, of which 54% (28 projects) were led by registered providers. We were commissioned by Innovate UK to undertake an analysis of the data from these 28 projects, which covered a total of 83 test dwellings. We produced a report of our findings.
Our study identified:
- Key success factors (where things worked well and not so well).
- Practices which resulted in a significant energy 'performance gap'.
- The relative impact of specific attributes such as defects and building services on the 'performance gap'.
In particular, our 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, the Building Performance Evaluation programme is a powerful means of bridging the performance gap and presents sizeable opportunities in terms of transferring the skills gained into future developments.
Our meta-analysis 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 enable registered providers who have the means to champion and combat the ‘performance gap’ in buildings, and allow them to apply lessons from the Building Performance Evaluation programme to their new developments.