Neil Jefferson, director of the NHBC and chief executive of the Zero Carbon Hub
Despite the lack of decisions by the government on Part L of the Building Regulations and its zero carbon policy, there was one ministerial announcement at Ecobuild last week that will lead to action in a vital area – closing any gap between the expected and as-built energy performance, and therefore CO2 performance, of new homes.
Building regulations minister Don Foster has commissioned the Zero Carbon Hub to lead an industry-wide project to examine the construction process - from design and planning to testing and verification - to help identify areas where an energy use “performance gap” might be occurring.
The Hub had previously recommended that compliance should be based on “as built” and not “as designed” performance and this announcement is a helpful step in the right direction.
With so much work already going into improving the energy efficiency of new homes, it is fundamental that we can demonstrate what is being achieved and deliver the performance from new homes that consumers expect. If there are specific areas of underperformance, we need to understand why so action can be taken.
The reasons for underperformance are likely to not be limited, as is often assumed, to the construction team. Perhaps development of on-site quality assurance processes (an area we could usefully learn about from Passivhaus) could minimise end-of-line testing of new homes - particularly as some of the available post-construction tests can be problematic.
Key questions include consideration of the SAP assessment tool that is used to predict performance, together with the quality of the input data.
Emerging data also shows a fair degree of under-performance of materials and systems used in new homes and perhaps it should come
as no surprise that laboratory testing is unable to replicate real life conditions.
It is a credit to the industry that there is so much willingness from so many organisations and individuals to participate in this work and I hope that tackling this issue provides a real focus for continuing improvement and better communication across industry.