TradeCalculator.co.uk
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.
Next up: related pages
Frequently Asked Questions
The 2021 edition of Approved Document L Volume 1 (effective 15 June 2022 in England) sets notional dwelling U-values of: walls 0.18 W/m²K, floors 0.13 W/m²K, pitched roof 0.11 W/m²K, flat roof 0.11 W/m²K, windows 1.2 W/m²K, and doors 1.0 W/m²K. These are the values used in the notional dwelling for SAP calculations — actual targets may vary depending on the whole-dwelling assessment.
Notional wall U-values (used in SAP target calculation) have tightened: 0.35 W/m²K in 2006 → 0.30 in 2010 → 0.18 in 2013 (unchanged at 0.18 in the 2021 edition). The limiting (elemental backstop) value was higher: 0.30 in 2013, tightened to 0.26 in 2021. So the 2013 notional of 0.18 did not require all walls to reach 0.18 — but it did raise the whole-dwelling target. Full-fill cavity insulation in a standard cavity wall may no longer be sufficient alone to pass the whole-dwelling SAP target — additional insulation (partial fill plus internal/external, or wider cavities) is often needed.
Extensions and new thermal elements in existing dwellings must meet AD L 2021 Table 4.2: walls 0.18, floors 0.18, roof 0.15 (one value for all roof types), windows 1.4 (or WER Band B), doors 1.4, rooflights 2.2. Replacement elements (for example re-roofing or new windows) must also meet Table 4.2 and be no worse than the element they replace. Renovating or upgrading a RETAINED existing element uses the separate Table 4.3: roof 0.16, cavity-filled wall 0.55, internally or externally insulated wall 0.30, floor 0.25.
Elemental U-values are the maximum permitted values for individual building elements (backstop values). Notional U-values are used in the SAP calculation for the notional dwelling — the building as designed must achieve at least as good overall energy performance as the notional dwelling. You can trade off between elements (e.g. better walls to compensate for poorer windows) as long as the overall target is met.
Was this calculator helpful?
Last updated: July 2026
Verified against UK standards · estimates only, confirm with your supplier.