Most of the industry will be aware that these documents are seen as a “ stepping stone ” or interim step to further improvements as we approach the Government ’ s target of Net Zero in 2050 . Indeed , the Government timeline would suggest that work on the next stage will commence mid-2022 ( see the Roadmap to the Future Homes Standard below ) with implementation through the next development of the Future Homes Standard in 2025 .

The latest version of AD L for dwellings shows significant changes in ‘ U ’ Values and in particular the requirements for new build which must be assessed using the latest version of SAP10 ( Standard Assessment Procedure ) with a notional Whole window value of 1.2 W / m ² K with a backstop value of 1.6 W / m ² K .

The SAP calculations is for the whole building so in order to allow the use of windows that are

higher than the notional value but no more than the backup of 1.6 , insulation has to be improved elsewhere e . g . roof insulation . It would be fair to suggest that building contractors will be looking for their window supplier to attain the notional value or as close as possible .

As mentioned previously , this is an interim step and discussions with DLUHC would suggest that the future for Whole Window ‘ U ’ Values in new dwellings will see a notional value below 1 W / m ² K which would require major changes in both window profiles and glazing for many companies .

For existing dwellings or the replacement market , the new AD L requires windows to reach a minimum of 1.4 W / m ² K or WER B , doors with over 60 % glazing to also achieve 1.4 W / m ² K or DSER B and other doors to reach 1.4 W / m ² K or DSER B . So again , it falls on the window companies to make the necessary improvements

. On a brighter note it has been suggested that the next stage for replacement windows will not be as strict as new dwellings and could perhaps be somewhere around 1.2 W / m ² K but that will only be known when the next updates are published .

During discussions with GGF members , there have been several major issues raised . Examples would be , the extremely short transition period i . e . 6 months . Recently , the timber window and door industry were given an additional 12 months ( 15th June 2023 ) to comply , which is a very uneven playing field for the PVCu and Aluminium companies and is an issue we have raised with DLUHC .

Secondly , despite the importance the DLUHC has placed on the Industry making these Energy Efficient changes , they have continually refused to provide incentives such as reducing VAT or providing funding through Grants to the Homeowners to incentivise

the upgrading of homes . The recent and largely unsuccessful Green Homes Grant described replacement windows as a secondary level of improvement with only the extreme of exchanging single with double glazing being eligible and for a limited amount of funding . The necessary investment to upgrade machinery and systems companies will need to outlay , should be supported by Government in some way .

However , in recent positive discussions , the GGF ’ s Technical Team , in consultation with members of the GGF Systems House and Aluminium Groups , highlighted an issue to DLUHC regarding the way that U Value calculations were to be made for ‘ non-standard ’ Doors , especially bi-folding and sliding glass doors . Under the new Approved Document L , the GGF highlighted that it would be impossible for some larger multi-pane doors to comply with the uplifted regulations ,

due to conflicts in the proposals to calculate U values .

After discussions took place with DLUHC , the government department agreed to amend the basis for calculating U Values for non-standard doors , in particular larger bi-folding and sliding patio types . These include a further door size of 2000 x 2180 for multi leaf doors , together with a tolerance of 25 % on the sizes that can be used . The amendments bring the calculations more in line with BS EN 14351 .

The DLUHC were very responsive to very responsive to the GGF proposals and made the amendments to the calculation formula as quickly as it was possible to do so . This gives us great confidence that the GGF and FENSA will remain a trusted voice within the industry as it is the only change made to any of the Approved Documents published last December .

www . ggf . org . uk