Demonstrating compliance with Part L

By John McComb, technical services director, Reynaers Aluminium UK

In June 2022 new rules come into force aimed at improving the thermal and energy efficiency performance of our homes and commercial buildings. The changes are part of the Government’s wider push to achieve zero-net carbon emissions by 2050.

For context, home energy use accounts for more than 25% of the UK’s carbon emissions and therefore is a major contribution to climate change, with a typical house losing 10% of its heat through the windows. Increasing the thermal efficiency standards of windows and doors in new and existing houses, as well as in commercial buildings, will significantly reduce heat loss and have a direct impact on reducing carbon emissions and nudge us closer to achieving these net-zero target.

The new standards, which come into play on 15 June are a just a steppingstone however in lieu of much bigger changes which will become law in 2025. From June any new houses or commercial buildings must be fitted with windows and doors that produce 31% less emissions than those installed today. Whereas after 2025 they will need to emit 75% less carbon.

As a manufacturer of aluminium window and door systems, we’ve been analysing our entire range of products to ensure they comply with the new standards. There are typically three ways in which manufacturers can show that their products and systems comply – U-values, hot box testing and BFRC ratings.

From June all windows or doors installed in new dwellings or buildings must have a­­­­­­ U-value rating of 1.6 – a significant drop of 0.4 from the previous standard.

However, any replacement windows or doors installed into existing buildings are required to demonstrate a U-value rating of 1.4 (down from 1.6) OR notably, a Band B WER. Similarly, replacement doors with >60% internal glazing must have a U-value of 1.4 or Band C WER.

Keeping ahead of the regulations

Over the last year Reynaers has been rigorously benchmarking its existing and planned new products to ensure they comply with the updated standards.

This involved a detailed FEA analysis using specific thermal modelling software to calculate the thermal performance and U-value. Reynaers is also working towards gaining full BFRC (British Fenestration Rating Council) approval status to ensure our customers have the utmost confidence in their purchasing decision that our products and systems are fully compliant with Part L 2022.

Some of our most popular products are well ahead in terms of their thermal efficient properties, giving fabricators and installers confidence when embarking on new and replacement projects.

The SL68, slimline window has a U-value rating of 1.4 and a Band A energy rating so can be used in all cases with absolute reassurance. While the CF68, one of our best-selling folding doors, has a U-value rating of 1.43 and Band B energy rating so can be used in all new and replacement situations. Indeed, some of our products, such as the MasterPatio system, already exceed the current requirements with a U-value of 1.39 and energy rating of Band B, again providing fabricators and specifiers with the reassurance that the products are fully compliant and more than fit for purpose.

However, the scope of the changes to Part L due to be imposed in 2025 will inevitably see a significant change in the way windows and doors are manufactured and will likely be the stimulus for the biggest change to construction methods in recent history.