New Part L rules could force older systems out of new build, leader warns

Nigel Headford, director of Deceuninck Aluminium

The end of the Part L new build transition period could force manufacturers of legacy aluminium systems out of the new build sector, the director of Deceuninck Aluminium has warned. He explained that businesses supplying windows and doors into new build – including home extensions – have limited time to meet tougher standards of thermal performance.

The Part L new build transition period comes to an end on the 15 June 2023. Unless a project breaks ground before the transition period ends, all windows and doors supplied to site need to meet the higher standards of performance introduced in last year’s update to Part L: a notional U-value requirement for new-build windows and doors of 1.2W/m²K – but with a 12-month stay of execution.

“A frightening number of older aluminium systems can’t get down to U-values of 1.2W/m²K without using triple-glazed units, which comes with increased cost and weight, impacting on handling – and hardware,” said Nigel Headford, director of Deceuninck Aluminium. “Under the regulations, extensions are classed as new build, so the implications are significant.”

Nigel added that installers need to get to grips with regulatory change and ask the right questions of their suppliers, as liability for compliance sits with them. “The installer is responsible for compliance. Fabricators don’t know where ‘trade’ windows and doors end-up”, he said.

“You could have a single job which includes a houseful of windows going into a pre-existing part of a single property, and two or three going into an extension as part of the same project. In the pre-existing part of the home, the U-value requirement would be 1.4W/m²K so double glazing might be fine. Cross the threshold between the ‘old’ and new part of the building and the U-value will need to be 1.2W/m²K.”

Leaders of Deceuninck Aluminium have expanded the business’ product offer, launching an ultra-energy efficient Decalu88 flush casement window in March. The product achieves headline U-values of as low as 0.8W/m²k – a Passivhaus-equivalent level of performance – and 1.2W/m²k with a standard double-glazed unit.

“The new Decalu88 flush casement makes compliance simple,” Nigel continued. “It’s also Future-Homes-proof, getting down to U-values of as low as 0.8W/m²K if you step up to a triple-glazed unit – and that’s an aluminium window that’s flush inside and out.”

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