Part L U-Value Targets History (2006-2021)
U-value requirements by year for walls, floors, roofs, windows, and doors, referencing Approved Document L: Conservation of Fuel and Power — editions from 2006 through to 2021 (effective 15 June 2022).
New Dwelling U-Value Targets by Year (Notional Dwelling Values)
| Element | 2006 | 2010 | 2013 | 2021 |
|---|---|---|---|---|
| External walls | 0.35 | 0.30 | 0.18 | 0.18 |
| Party walls | N/A | 0.20 | 0.00 | 0.00 |
| Ground floors | 0.25 | 0.25 | 0.13 | 0.13 |
| Pitched roof (insulation at ceiling) | 0.25 | 0.20 | 0.13 | 0.11 |
| Pitched roof (insulation at rafter) | 0.25 | 0.20 | 0.13 | 0.11 |
| Flat roof | 0.25 | 0.20 | 0.13 | 0.11 |
| Windows (whole unit) | 2.00 | 1.60 | 1.40 | 1.20 |
| External doors | 2.00 | 1.80 | 1.40 | 1.00 |
All values in W/m²K. These are notional dwelling values for SAP assessment. Elemental backstop values may differ.
Extension & New Thermal Elements (AD-L 2021, Table 4.1)
| Element | Max. U-Value (W/m²K) |
|---|---|
| Walls | 0.18 |
| Floors | 0.18 |
| Pitched roof | 0.15 |
| Flat roof | 0.15 |
| Windows, roof windows, rooflights | 1.4 |
| External doors | 1.4 |
Replacement Thermal Elements (AD-L 2021, Table 4.2)
| Element | Max. U-Value (W/m²K) |
|---|---|
| Cavity wall (full-fill or partial fill) | 0.55 |
| External wall (other) | 0.30 |
| Floor | 0.25 |
| Pitched roof (ceiling level) | 0.16 |
| Pitched roof (rafter level) | 0.18 |
| Flat roof | 0.18 |
| Windows, roof windows, rooflights | 1.4 |
| External doors | 1.4 |
Scotland & Northern Ireland
Scotland follows Technical Handbook Section 6 (Energy) with its own U-value targets that may differ from England. The 2024 Scottish regulations introduced tighter standards. Northern Ireland uses Technical Booklet F2 with values broadly similar to earlier editions of AD-L. Wales has its own edition of Approved Document L. Always check the applicable jurisdiction.
Related Calculators
Use the U-Value Calculator for build-up calculations, or the Insulation U-Values reference for insulation thickness guidance.
Always check the latest edition of Approved Documents on the Planning Portal (planningportal.co.uk) as regulations are updated periodically.
How We Calculate This
Frequently Asked Questions
Related Calculators
Concrete Mix Ratios
Standard UK concrete mix ratios explained with quantities per cubic metre and guidance on when to use each.
Insulation U-Values
Part L target U-values for walls, floors, roofs and windows with insulation thicknesses to achieve compliance.
UK Brick Dimensions
Standard UK brick sizes, coordinating dimensions and bricks per square metre for common bond patterns.
UK Cable Sizes
BS 7671 cable sizes and current ratings for common UK domestic circuits and installations.
Last updated: April 2026
All calculations are estimates. Verify with your supplier.