Housebuilders ‘struggling’ with Part L

In a move towards achieving the Future Homes Standard in 2025, changes in Part L came into effect in June 2022. 18 months on, an Industry Viewfinder survey by Housebuilder & Developer (HBD) reveals over three-quarters (77%) of UK housebuilders find the new regulations challenging.

The report, ‘A Year On: Revisiting Changes to Part F & Part L’, was commissioned by HBD in association with a number of key industry manufactures including Keylite Roof Windows (Keylite). It explored UK housebuilders’ attitudes to the changes and the impact the new regulations had made on projects and buying habits.

The modifications to Part L include guidelines for the energy performance of roof windows, ensuring housebuilders specify appropriate glazing and insulation standards to minimise heat loss in all projects.

In accordance with Part L specifications, Keylite’s patented expanding thermal collar is integrated to maintain the window’s thermal integrity. This provides housebuilders with a cost-effective and time-efficient solution to create thermally efficient and comfortable homes.

Colin Wells, head of technical at Keylite, commented: “This latest study from HBD is very enlightening. It shows that over half (55%) of UK housebuilders found addressing Part L specification in relation to window U-values quite challenging, whilst almost a third (30%) found a cost increase of 1k-5k per unit due to Part L updates.

“Interestingly, the study also revealed that 72% of housebuilders said having a thermal collar installed alongside a roof window is ‘important’ or ‘very important’. Keylite’s patented integrated expanding thermal collar comes as standard in every roof window, improving airtightness and Psi Values for SAP. It also ensures the thermal integrity of the window and roof is as designed, thus removing the reliance on an additional thermal collar, helping housebuilders meet Part L regulations.”

To read the Industry Viewfinder study, ‘A Year On: Revisiting Changes to Part F & Part L’, please visit