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Page reviewed 02/02/2026
On 1st February 2023, revised versions of the Technical Handbooks came into force containing key amendments to several sections including Section 3 (Environment), Section 6 (Energy) and Section 7 (Sustainability).
Guidance on the previous versions of the Technical Handbooks (Section 6 2015) is retained at the bottom of this page for reference.
There are two Technical Handbooks for Section 6 (Energy):
Certain works on existing buildings may also be covered by the requirements of Section 6 (Energy). These include:
In these cases, the Technical Handbooks set out area-weighted average U-values for different elements (shown below). Where possible, project teams should look to meet the area weighted values, however, the Technical Handbook also recognises that this may be impractical for some refurbishment work. It sets out alternative approaches which may be used where this is the case. This includes reviewing any work on traditional, heritage or listed properties in line with 'Guide for Practitioners 6 – Conversion of Traditional Buildings' (refer to the relevant Technical Handbook for further details). In all cases, where improvement work is carried out, project team should look to meet, or better, the individual element backstops shown below.
There are two Technical Handbooks for Section 6 (Energy):
Each document sets out what, in ordinary circumstances, may be accepted as a reasonable provision for compliance with the energy efficiency requirements of the Building Standards for the type of building work in question.
The Technical Handbooks include a number of key metrics which all new build dwellings and non-domestic buildings must meet. These are:
The targets for Delivered Energy and Carbon Emissions are set via modelling software (SAP for domestic, SBEM for non-domestic). An energy assessor inputs the building dimensions into the software. The software will then apply a set Notional Building specification to a theoretical building of the same dimensions. From this, it generates the performance targets that the actual building and building specification are compared against.
Project teams are still free to diverge from the Notional Building specification providing the building meets the key metrics outlined above. In many cases, however, the Notional Building specifications form the starting point for building fabric specifications.
The fabric values from the domestic and non-domestic Notional Building specifications, and worst-case U-values are shown in the table below.
Element type | Domestic | Non-domestic | ||
Notional Building (W/m2K) | Area weighted worst case U-values (W/m2K) | Notional Building (W/m2K) | Area weighted worst case U-values (W/m2K) | |
Wall | 0.15 | 0.17 | 0.15 | 0.21 |
Floor | 0.12 | 0.15 | 0.13 | 0.18 |
Roof | 0.09 | 0.12 | 0.11 | 0.16 |
Element type | Domestic area-weighted average U-value (W/m2K) | Non-domestic area-weighted average U-value (W/m2K) | Individual element backstops (W/m2K) |
Wall | 0.17 | 0.21 | 0.70 |
Floor | 0.15 | 0.18 | 0.70 |
Roof | 0.12 | 0.16 | 0.35 |
Project teams can also choose to adopt two alternative approaches for extensions:
These can allow the U-values of certain elements (i.e. individual walls) to be relaxed providing this is compensated elsewhere. In all cases, the U-values should be no worse than 0.70 W/m2K for walls and floors or 0.35 W/m2K for roofs.
Element type | New build -Notional Building (W/m2K) | Existing buildings - extension & refurbishment * - A (W/m2K) | Existing buildings - extension & refurbishment * - B (W/m2K) | Conversion of heated buildings (W/m2K) |
Wall | 0.17 | 0.17 | 0.22 | 0.30 |
Floor | 0.15 | 0.15 | 0.18 | 0.25 |
Pitched roof - insulated at ceiling level | 0.11 | 0.11 | 0.15 | 0.25 |
Pitched roof - insulated at rafter level | 0.11 | 0.13 | 0.18 | 0.25 |
Flat roof | 0.11 | 0.13 | 0.18 | 0.25 |
* Column A is for extensions where the existing dwelling's walls and roof U-values are worse than 0.70 W/m²K in the walls and worse than 0.25 W/m²K in the ceiling. Column B is for other extensions, upgraded existing thermal elements, non-exempt conservatories and conversion of unheated buildings.
Element type | New build - Notional Building - heated & naturally ventilated (W/m2K) | New build - Notional Building - cooled & mechanically ventilated (W/m2K) | Existing buildings - refurbishment, extension & conversion of unheated buildings (W/m2K) | Existing buildings - conversion of heated buildings (W/m2K) |
Wall | 0.23 | 0.20 | 0.25 | 0.30 |
Floor | 0.22 | 0.20 | 0.20 | 0.25 |
Pitched roof - insulated at ceiling level | 0.18 | 0.16 | 0.15 | 0.25 |
Pitched roof - insulated at rafter level | 0.18 | 0.16 | 0.15 | 0.25 |
Flat foof | 0.18 | 0.16 | 0.15 | 0.25 |
Our suite of CPD training presentations can be delivered in-person or virtually. CPDs are available for Section 6 Scotland, as well as Part L England and Part L Wales, covering new and existing dwellings and buildings.
Try our free online U-value calculator to calculate the thickness of material needed to meet the new levels of thermal performance. With a number of roof, wall and floor constructions, the calculator is quick and easy to use.