During the last quarter of 2024, it was good to see so many people agreeing with AluK in the media on the topic of U-Value compliance (or lack of it!) in this industry. We led the way in pointing out that some of the calculations being cascaded down the supply chain by other systems companies simply didn’t add up. I’d like to think it’s a lack of knowledge that’s behind some of the issues that we see and not a case of companies trying to play the system; but either way, we’re pleased that there now seems to be a real groundswell of support for our view that suppliers need to be doing much more to make sure customers aren’t risking non-compliance by relying on information which is simply not accurate.
Even beyond the issue of miscalculations though, there are still some myths circulating about how you can achieve compliance, which I also think it’s important for us to correct:
Myth 1
Energy ratings (DSERs and WERs) can be used to show Part L compliance for new build developments.
Wrong! Energy ratings can only be used for replacement product installations and in extensions.
Myth 2
The CEN standard window shown in BS EN 14351 (1230 x 1480 single opener) can be used to demonstrate compliance with U-Values.
Wrong! There is no option to use the CEN standard configuration window in Part L. U-Values should be assessed using the methods set out in the Building Research Establishment’s BR443 and applied to both the glass and the frame. For windows in dwellings, that means either calculated using the actual size and configuration, or calculated for a standard 1230 x 1480 window with one of the following standard configurations:
- a central horizontal divider with one fixed and one opening light for a vertical sliding sash
- no divider for a roof window
- a central vertical divider and one fixed and one opening light for a casement
Myth 3
Bifold doors can be shown to comply via the U-Value route using a French door sample configuration.
Wrong! Part L states ‘When a single U-Value is calculated for a product range of doors, the configuration of the door chosen for the calculation should be the worst performing in the product range. The calculation has to be carried out either using the actual size and configuration of the door or using one of the following standard sizes:
- 1.23m (+/-25%) wide x 2.18m (+/-25%) high for doors less than 3.6m2
- 2.00m (+/-25%) wide x 2.18m (+/-25%) high for doors more than 3.6m2
Myth 4
I don’t need a CE/UKCA mark for windows and doors which I place on the market, provided they comply with Building Regs (inc Part L)
Wrong! All windows and doors placed on the market in the UK must be CE/UKCA marked and thermal performance is one of the essential characteristics which must be declared on that mark. This is a legal requirement.
And these are just the myths which apply to installing windows and doors in homes. Beyond that, there is still confusion around the methods which can be used in commercial buildings. Essentially, for buildings like student accommodation and care homes where occupancy levels and internal heat gains are similar to dwellings, then the calculations can be based on the same BRE443 rules. But for other commercial windows, standard sizes and configurations cannot be used and calculations can only be based on the actual size and configuration.
AluK is committed to driving up standards right across the industry – and compliance is a major part of that. We recognise that Part L is challenging, but it’s certainly not insurmountable. Sliding doors, for instance, are fairly difficult to improve due to the thermal breaks in the sashes and frames being off-set from each other. However, there are many modern systems out there, such as our new S140 Lift and Slide system, which have been developed with various thermal break enhancements to enable them to comply with existing and future Building Regulations. On the other hand, there are some systems that have been around for many years which don’t have the same enhancements - and it’s difficult to see how these systems comply.
Full details on all of AluK’s third party accredited Part L compliant products – all calculated to the correct sizes and configurations on our products page
