Performance gap in affordable housing comes under scrutiny

An analysis of the performance of new affordable homes has highlighted a variety of concerns, including issues with the use of some green technologies.

The analysis of 83 test dwellings on 28 affordable housing-led projects, was part of Innovate UK’s major building performance evaluation (BPE) programme. The programme sought to identify where the ‘performance gap’ arises, by evaluating and assessing post-construction and in-use performance of domestic and non-domestic buildings. This was done through forensic evaluation, including: fabric in-situ U-value testing, multi-stage air tightness testing, and long-term indoor air quality evaluation as well as post-construction reviews, occupant walkthroughs and post-occupancy evaluation.

The National Energy Foundation was commissioned to carry out analysis of the data from the 83 homes. The aim was to empower affordable providers to take a lead and become champions in combating the performance gap.

The study found a number of commissioning, operation and maintenance related issues with technologies, including:

  • Mechanical ventilation with heat recovery (MVHR): Operation and maintenance were found to be problematic, and system supply-extract was found to be unbalanced. The report says, “MVHR does not appear ready for widespread adoption within the social housing sector”
  • Solar thermal systems: There were instances of sub-optimal design and controls specifications resulting in incorrect set-up
  • Combined heat and power systems: These were found not to have user friendly controls.

The study also found:

  • On average, the fabric U-values exceeded the target set, with nine homes failing to meet the Building Regulations Part L backstop
  • The airtightness 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
  • 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 emerged as a powerful means of bridging the performance gap and presents opportunities in terms of transferring the skills gained into future developments.

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