New Part L 2021 – England
Changes are being made to Building Regulation Part L (England).
Part L 2021: Conservation of Fuel and Power takes effect on 15th June 2022 for use in England.
It does not apply to work subject to a Building Notice, Full Plans Application or Initial Notice submitted before this date, provided work commences on site before 15th June 2023.
Outline of the Main Changes
Part L (England) 2021 reduces the number of Approved Document volumes from four to two:
- Volume 1: Dwellings
- Volume 2: Buildings Other Than Dwellings
Work to existing buildings is now incorporated into these two volumes rather than being covered within separate documents.
New Dwellings – Roof U-Values
| Requirement | Current | From 15.06.2022 |
|---|---|---|
| Notional Building U-Value | 0.13 | 0.11 |
| Limiting U-Value | 0.20 | 0.16 |
Existing Dwellings – Roof U-Values
| Application | Current | From 15.06.2022 |
|---|---|---|
| Replacement Roofs & Extensions | 0.18 | 0.15 |
| Renovations & Retained Roofs (where current U-value is worse than 0.35) | 0.18 | 0.16 |
Buildings Other Than Dwellings – New Build Roof U-Values
| Building Type | Current | From 15.06.2022 |
|---|---|---|
| Notional Building – Side Lit / Unlit | 0.18 | 0.15 |
| Notional Building – Top Lit | 0.18 | 0.18 |
| Limiting U-Value | 0.25 | 0.18 |
Buildings Other Than Dwellings – Refurbishment Projects
| Application | Current | From 15.06.2022 |
|---|---|---|
| New or Replacement Roof (including extensions under 100m²) | 0.18 | 0.18 |
| Renovations & Retained Roofs | 0.18 | 0.18 |
Important Notes
- Top-lit buildings are those that primarily use roof glazing as a source of daylight, such as warehouses and sports halls.
- Side-lit buildings primarily rely on windows.
- Extensions to buildings other than dwellings greater than 100m² and greater than 25% of the existing building area are treated as new buildings.
- Some Building Control Officers may interpret a re-deck as a replacement roof.
- Replacement of the waterproofing membrane is defined as a roof renovation.
- Where more than 50% of an individual roof area is renovated, or more than 25% of the building envelope is renovated, the entire roof should be upgraded.
- If achieving the target U-value is not technically or economically feasible, insulation should be upgraded as far as reasonably possible.
- Retained roofs are existing roofs that become positioned above a new habitable space or a change of building use.
Rooflights
The revised Part L requirements generally allow less stringent rooflight U-values than previously.
However, a completely new requirement has been introduced stating that any rooflight upstands constructed on site (and not integral to the rooflight itself) must achieve a maximum U-value of 0.35W/m²K.
Photovoltaic Systems
PV systems have now been incorporated into the Notional Building specification within Part L (England) 2021.
Dwellings – Notional Building Requirements
- Houses: kWp = 40% of ground floor area (including unheated spaces) ÷ 6.5
- Flats: kWp = 40% of dwelling floor area ÷ (6.5 × number of storeys in the block)
- Systems should face South East or South West.
Buildings Other Than Dwellings – Notional Building Requirements
Foundation Area = Conditioned Area ÷ Number of Storeys in the Whole Building.
- Top-lit areas not heated by a heat pump: 20% of foundation area.
- Side-lit / unlit areas not heated by a heat pump: 40% of foundation area.
- Where heated by a heat pump, percentages are pro-rated according to the proportion of heating demand met by the heat pump.