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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 4.2)
| Element | Max. U-Value (W/m²K) |
|---|---|
| Walls | 0.18 |
| Floors | 0.18 |
| Pitched roof | 0.15 |
| Flat roof | 0.15 |
| Windows and roof windows | 1.4 (or WER Band B) |
| Rooflights | 2.2 |
| External doors | 1.4 |
Table 4.2 also covers replacement elements: a replacement must meet these values and be no worse than the element it replaces.
Renovated & Retained Thermal Elements (AD-L 2021, Table 4.3, column b)
| Element | Improved U-Value (W/m²K) |
|---|---|
| Roof (all types) | 0.16 |
| Wall (cavity insulation, where suitable) | 0.55 |
| Wall (internal or external insulation) | 0.30 |
| Floor | 0.25 |
Table 4.3 has no window or door rows: replacement windows and doors are new elements and fall under Table 4.2 (1.4 W/m²K).
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.
Correction
July 2026: The renovation table was corrected to Table 4.3 as printed in the 2021 edition incorporating 2023 amendments: a single roof row improved to 0.16 W/m²K replaces the previous 0.16/0.18 split, and window and door rows were removed because Table 4.3 contains none. Section headings were corrected to the right table numbers (extensions and new/replacement elements are Table 4.2, not 4.1; renovated and retained elements are Table 4.3).
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.
Frequently Asked Questions
Related Calculators
Insulation U-Values
Part L target U-values for walls, floors, roofs and windows with insulation thicknesses to achieve compliance.
Part L 2021 U-Value Targets
Part L 2021 target U-values for all building elements with notional dwelling values.
Part E Acoustic Ratings
AD-E sound insulation requirements: airborne DnT,w+Ctr and impact L'nT,w targets for separating walls and floors.
Part B Fire Resistance Ratings
AD-B fire resistance periods: 30, 60, 90, 120 min ratings by building type for walls, floors, doors and structural elements.
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Last updated: July 2026
Verified against UK standards · estimates only, confirm with your supplier.