Thermal & Energy Efficiency

As the consultation closes on changes to Part L and Part F of Building Regulations for England, what energy efficiency detailing can be expected to change and how to track it?

A call to include build quality guidance notes in revised Part L regulations are expected to come into effect later this year. The proposal has been included in the 98-page Ministry for Housing, Communities and Local Government (MHCLG) consultation document which forms the first step towards the Future Homes Standard, which should be in place by 2025.

The guidance notes would give practical, technical advice on how builders could address the performance gap and reduce thermal bridging, while ensuring airtightness doesn't harm the structure of the building. The document spends several pages looking at the impact of insulation gaps and the need to address thermal bridging to reduce CO2 loss.

Actis UK and Ireland Technical Director Thomas Wiedmer, who has worked on the company's response to the document, says construction details should get further attention within the build quality section, saying: "Construction detailing is one of the biggest issues causing the performance gap. Tying projects up with specific details used is important to close the gap between designed and expected performance and we would go even further and suggest that a registration scheme could help to drive the importance of following these details on site."

A building with insulation which is effective on paper can still see huge heat loss of 20 to 30% if thermal bridging occurs. The only way to avoid such a scenario is for construction details to be thermally approved and followed through on site. Actis has worked closely with the LABC to create a 'fool-proof' method by which builders can minimise heat loss in this way and in 2019 created a new set of Registered Construction Details (RCD). 

The new RCD, part of a selection aimed at helping builders achieve as-built performance, provide construction details and checklists of points to look out for during design and on site. They offer instant access to online tutorials to help them reduce heat leakage through weak junctions – the weak points of an insulated building envelope – and thus design out thermal ridging. The details offer a combination of specific detail, good practice and points to watch, together with a range of modelled psivalues using different build ups which exceed expected industry standards. The RCD drawings and documents can be fed into specifications for projects and are also accessible on the go. "Energy efficiency standards should always be based on reducing the need for energy first and in particular limiting the heat loss through thermal elements," adds Thomas Wiedmer.

"That is through achieving excellent U-values, reducing thermal bridging and improving airtightness – the fabric first principle."

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