Deceuninck Aluminium has declared its Decalu88 bi-folding door achieves U-values of 1.2W/m2K with double glazed units, comfortably meeting new requirements for newbuild as well as home improvement under Part L from June this year, without using triple glazed units.
From June 2022, replacement doors with a >60% glazed area will need to achieve an overall U-value of 1.4W/m2K, while newbuild equivalents will need to achieve an overall U-value of 1.2W/m2K and when the Future Homes and Buildings Standard comes into force in 2025, these figures are expected to drop even further.
“Older systems were designed for a double-glazed unit, so there’s a maximum width of unit you can get into the frames,” director Nigel Headford explained, “So, the question is not about the number of panes of glass, but how deep you can go, and with older systems you are typically limited to a 28mm-32mm unit.
“If a triple glazed unit was used to improve the thermal performance, consideration would also need to be made for the extra weight placed on the hardware. Most bifolding doors on the market have a maximum weight of 100kg-150kg,” Nigel said. “So, if you are going to put in triple glazing then you are probably going to go over that maximum weight, which is going to limit the size of the door.”
