Kevin Underwood, BWF Technical Director discusses why it was very much welcomed when DLUHC published an amended version of Approved Document L volume 1 that gave external timber doorsets and timber windows a further year complying with the current recommendations before having to comply with the new figures from the 15th June 2023
The updates made in June to approved documents L and F have imposed significant changes on the performance of external doorsets and windows to be used in England. While these changes will affect both windows and doorsets destined for new build properties and those to be used for renovation and improvement projects, this article looks at the effects the changes have on external doorsets and windows supplied for use in existing dwellings e.g. houses and flats.
The Department for Levelling Up, Housing and Communities (DLUHC) published amendments to approved documents L and F which came into effect on 15th of June. These will change the recommendations for the thermal performance and the provision of background ventilation through trickle ventilators that are needed to comply with building regulations.
The original values and timescales published by DLUHC raised concerns within the woodworking industry that many products used in the market would not be able to be adapted in time to comply with the new recommendations. Among these concerns was that there was not enough development time to redesign the products to give higher levels of performance, customers had already been given quotations for products that might not comply when they were ordered, and imported products on long lead times may not be compliant when they arrived in the UK. There were also concerns that the carbon benefits of using timber-based products may not be realised as customers could be pushed towards products that emit more carbon in their manufacturing process. It was very much welcomed when DLUHC published an amended version of Approved Document L volume 1 that gave external timber doorsets and timber windows a further year complying with the current recommendations before having to comply with the new figures from the 15th June 2023. It should be noted that this extension has not been given to products for use in new build properties.
Approved Document L covers the recommendations to conserve fuel and power with volume 1 applying to building work on both new build and existing dwellings e.g. houses and flats. For work on existing dwellings the U-values for both external doorsets and windows that must be achieved to comply with the building regulations have been lowered meaning these products are required to permit less energy to transfer through them from the warm, heated environment inside the property to the colder environment outside. There are two measurements that are used to show the energy efficiency of external doorsets and windows,
a) U-values, a lower U-value shows that less heat will be transferred from a warm environment to a cooler environment. U-values are also an essential characteristic for conformity marking (e.g. CE and UKCA marking) and must be published on the manufacturers declaration of performance.
b) Energy Ratings, which not only take into consideration the U-value of the product but also allow for the energy required to heat cold air that may enter the warmer environment through the product and the heating effect of sunlight passing through the glazing. Energy Ratings apply to both Windows (WER) and doorsets (DSER).
Before the changes come into effect the limiting U-value for windows is 1.6 W/m2K or a WER in band C or better, and for doorsets the limiting U-value is 1.8 W/m2K or a DSER in band E or better. After the changes that come into effect on the 15th June 2023 the limiting values for timber windows will be a U-value of 1.4 W/(m2.K) or a WER in band B , and those for timber doorsets will be a U-value of 1.4 W/(m2.K) or a minimum DSER in band C for doorsets with more than 60% of the internal faced glazed or a minimum DSER of band B for all other doors.
Approved document F covers the recommendations for the provision of ventilation. The significant change that the new publication introduces is the need to provide background ventilation in all replacement windows even if the original windows in the dwelling were not fitted with background ventilators. If, however, it can be shown that fitting the new windows without background ventilators has not reduced the ventilation of the dwelling to a level below that which was achieved before the new windows were fitted, then the windows without ventilators would be accepted but this is likely to be difficult to demonstrate and may require a pressure test of the dwelling, both before the new windows are fitted and after they are fitted, to show that the ventilation of the dwelling was not reduced.
