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Part L – Building Regulations in England (Conservation of Fuel and Power).

Changes to Part L from 15th June 2022

Why is Part L changing?

The UK is looking to reduce its carbon footprint and improve the efficiency of buildings so they emit less carbon.

The construction industry is required to reduce carbon emissions from buildings by 75% by 2025 in order to help reach the target of net zero by 2025.

This is part of a phased approach, with a reduction of 30% in carbon emissions required from June 2022.

Who is Responsible for Ensuring that the Requirements of Part L are met?

Builders, Installers and homeowners are required to comply with Building Regulations.

Part L Regulations for Refurbishment of Existing Properties

From June, windows and doors fitted in England have to meet stricter standards, with a maximum U-value of 1.4 W/(m2k), or Window Energy Rating B.

Doors with less than 60% glass, need to achieve a minimum Doorset Energy Rating B, and DSER C for doors with more than 60% glazing.

Alternatively, a U value of 1.4 W/(m2k) for all doors is another suitable method of compliance.

Part L Regulations for New Build Properties

The requirements for New Build properties are calculated differently because the whole structure is taken into account, eg walls, roof, windows and doors. SAP calculations are made to assess overall thermal performance of a property, taking into account such things as thermal properties, space heating and air tightness.

Windows are required to meet a U-value of 1.2 W/(m2k) and doors with a glazed area of more than 60% need to achieve 1.2. All other doors need to achieve 1.0.

U-Value Summary Table

  New Dwellings
New Dwellings
Limiting U-Value*
Existing Dwellings
Windows 1.2 1.6 1.4
(where glazed area is more than 60%)
1.2 1.6 1.4
Other Doors 1.0 1.6 1.4

*In new dwellings where the thermal performance of other parts of the dwelling has been calculated through a SAP calculation to allow for a lower thermal performance of the windows, a lower U-value may be specified for windows with a limiting U-value of 1.6.

Frequently Asked Questions

1) When does Part L come into force?

Part L comes into force on 15th June 2022 in England. All installations after this date need to comply.

2) Does Document L apply to all buildings?

Yes but there are different requirements for new build and existing properties.

3) Does Document L apply to New Build homes?

Document L does not apply to work subject to a building notice, full plans application or initial notice submitted before 15th June 2022, provided that work for each building is started before 15th June 2023.

4) How do I make sure the windows and doors I fit comply with Part L?

The windows and doors you order will arrive with BFRC stickers on them which detail the specific energy rating of that product.  When ordering please specify if the windows are for new dwellings to ensure they are made to the correct specification. 

5) Are there any rules regarding enlarging a window or creating a new one?

Yes. If a window is enlarged or a new one created, either of the following should be met.

  1. The area of the windows roof windows, rooflights and doors should not exceed 25% of the total floor area of the dwelling.
  2. If the area of windows, roof windows, rooflights and doors exceeds 25% of the total floor area of the dwelling, compensating measures should be taken to improve the energy efficiency of the dwelling.

6) Does Part L apply to Wales?

New Part L rules for Wales have not yet been released so the current rules apply to England only.

7) Does document L apply to all buildings?

Document L Volume 1 applies to ‘dwellings’. A dwelling is described as a self-contained unit.

All the information on this page relates to Document L Volume 1 so only relates to self-contained homes.

8) What about blocks of flats with shared communal rooms or rooms for residential purposes?

For halls of residence, hotels, residential homes, hostels etc please refer to Approved Document L Volume 2: Buildings other than dwellings.

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