Changes to Document L
Aluprof UK
Sustainable, high-performance aluminium windows, doors, and facades for commercial and residential use.
What is Document L?
Part L is a building regulation that concerns construction projects that are new, or result in the change of use of a dwelling or all other buildings in England. It sets the standards for the energy performance and carbon emissions of new and existing buildings.
Why the changes to Document L?
The UK Government has pledged to achieve carbon neutrality in our homes by 2050 with their Future Homes Standard (FHS) that has been introduced in the 2019 Spring Statement. That commitment means that our homes will only use carbon-neutral energy from renewable sources, likely to remain electricity, however, a hydrogen option in the next decade is still likely. To reduce the energy demand we need to insulate our homes to a high level and ensure they stay warm in winter and cool in summer without using excessive energy. In December 2021, the Government took the first step of the Future Homes Standard by announcing the new Building Regulations where the second stage will take place in January 2025.
The recent change to Document L, Conservation of Fuel & Power, of the Building Regulations which came into effect on the 15th of June 2022 is the first step toward carbon neutrality. Housing developments which have obtained planning permission before the 15th June 2022 can continue to adhere to the previous Approved Document L as long as the development starts on site before 15th June 2023.
Whilst the whole building fabric will need to achieve much higher U-Values with the unveiled regulations, Aluprof fenestration products, which include windows, doors, overhead glazing and curtain wall systems, are already available in achieving class-leading insulation values and Passivhaus Standards.
Current statistics
According to LETI Climate Emergency Retrofit Guide, 27% of our carbon emissions in the UK come from heating our buildings, with 18% coming from our domestic building stock. 80% of our homes that will be needed in 2050 have already been built and we are still building homes today that are not in line with net zero standards. Currently, energy demand in our homes ranges from 90 to 170 kWh/m2 energy consumption per year, in 2050 we need to have our homes between 40 to 60 kWh/m2 per year for the increased renewable energy supply to meet demand. The UK will achieve this by taking a ‘whole building approach', increasing overall thermal insulation whilst reducing air permeability and cold bridging.
In a 2022 survey by Statista, 79% of dwellings in the UK use gas, a fossil fuel, for heating, and only 9% currently use electricity, which can come from renewables, for heating. Increasing insulation will reduce demand with the long-term target of just using renewable energy sources by 2050, therefore achieving carbon neutrality.
What has changed?
Previously the 2016 Approved Document L split the requirements for thermal performance into four documents:
The new documents have been combined into just two volumes:
Building Regulations in England
From an architect's perspective
For new dwellings, specifiers will need to design with new target rates with updated thermal performance for the glazing. There are two methodologies, using the ‘Notional Dwelling’ as detailed in SAP, or using the ‘Limiting Standards’ as detailed in Section 4 of the documents.
Using the ‘Notional Dwelling’ specifiers have a listed series of U values that each element of their building has to adhere to. Glazing has a maximum Uw value of 1.2 W/m2K. There are also limits on the g value, LT and orientation of the glazing.
Using the ‘Limiting Standards’, the maximum thermal performance of glass is 1.4 W/m2K, however, a higher performance glazing will most likely be needed. The ‘Limiting Standards’ methodology provides a greater scope of design freedom to specifiers allowing for more diverse designs that still adhere to the approved document.
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From a home improvement perspective
For replacement windows in the existing house or house extensions, Table 4.2 of Approved Document L Volume 1 offers the required minimum thermal performance values.
Part of Table 4.2
*The upstand that a rooflight is to be installed on, should have a max U value of 0.35 W/m2K.
When replacing glazing within an existing dwelling the new window or glass door must have a performance that is no worse than what is being replaced. In a traditional building, there could be limitations on the changes that can be made to the glazing. Maintaining the character of the existing building can be achieved by using glazing with a maximum Ug value (centre pane performance) of 1.2 W/m2K or by using a low emissivity secondary glazing.
If enlarging a window or door opening, the percentage of the proposed glazing area against the total floor area needs to be checked. If the area of all glazing, including roof glazing, exceeds 25% of the total floor area of the dwelling, a further increase in thermal performance will be required.
Conservatories or glass porches are classed as an addition to a dwelling, which sit outside the main walls and are separated by insulated external doors and are not heated by the dwellings’ heating system.
These glazed additions will be exempt from the energy efficiency requirements under regulation 21 as long as it meets the following criteria:
If the conservatory or porch does not meet these criteria, then the thermal performance requirements are applicable for a normal extension.
Associated Documents
Alongside the changes to Part L changes to Part F, ventilation, have been made and a new Part O introduced to control overheating in dwellings.
Crucial considerations
Avoiding cold bridging in new and replacement window installation is crucial in ensuring that the performance of the glazing installed is realised. Frames of modern aluminium systems offer high thermal insulation and are slim. The use of high insulation cavity closers or robust detailing is required.
What next
Specifier or installer, Aluprof UK have both the advanced systems and construction knowledge to support the correct installation of any facade system. Support and guidance is a phone call or email away.
This Approved Document L update to the performances of dwellings is a first step towards the much more stringent performance criteria that will come into effect in 2025 as part of the government’s Future Homes Standard. Aluprof will continue to advise and support customers through these changes.
Aluprof UK
Aluprof UK are forward looking company and are active member of the UK’s Passivhaus Trust with Passivhaus certified systems. Aluprof UK are currently specified on a wide range of buildings designed to meet the demands of thermally efficient buildings or Passivhaus standards.
To request more information on the Future Homes Standard, Part L Document and our Part L-ready products and systems, please get in touch with one of our project consultants via [email protected] or call us on +44(0)161 941 4005