Approved Document L - Wales
On 23rd November 2022, a revised version of Part L to the Building Regulations came into force for domestic properties in Wales. On 29th March 2023, a revised version of Part L also came into force for non-domestic properties. These are supported by new Approved Documents L (ADL 2022).
Guidance on the previous versions of the Approved Documents to Part L to the Building Regulations (ADL 2014) is retained at the bottom of this page for reference. For domestic properties, this guidance will only apply to individual units where plans were submitted by 23rd November 2022 and work on the unit commenced by 23rd November 2023. For non-domestic properties, the guidance only applies where plans for the unit were submitted by 29th March 2023 and work began before 29th March 2024.
ADL 2022 - In force from 23rd November 2022 (domestic) and 29th March 2023 (non-domestic)
There are two Approved Documents L for Part L:
Approved Document L1 2022 - Domestic
Approved Document L 2022 - Non-domestic
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.
New buildings
The Approved Documents include a number of key metrics which all new build dwellings and non-domestic buildings must meet. These are:
- Primary Energy - which considers both the energy used within the building and the energy used in upstream activities to prepare the fuel.
- Carbon Emissions - which sets the maximum expected operational carbon emissions from a building.
- Minimum Energy Efficiency Rating (MEER) - which requires dwellings to achieve a SAP rating of 81 or better (domestic only).
- Worst-case U-values (area weighted) - which set the worst possible U-values that walls, floors and roofs can achieve.
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 Dwelling/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 meet 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 tables below.
Domestic
Element type | Notional Building (W/m2K) | Area weighted worst case U-values (W/m2K) |
Wall | 0.13 | 0.18 (0.21 - flats and apartments) |
Floor | 0.11 | 0.15 |
Roof | 0.11 | 0.13 |
Non-domestic
The Notional Building specification for non-domestic properties varies depending on whether the space is used for side-lit, top-lit or un-lit activities. This is in reference to natural lighting within a space. Spaces for side-lit activities will primarily use windows for daylighting – this includes offices, schools, healthcare facilities etc. Spaces which are top-lit will typically include warehouses and distribution centres, where there are minimal or no heat demands, so the building fabric has less of an impact on overall energy demands.
Element type | Notional building - side-lit and unlit activities (W/m2K) | Notional Building - side-lit and unlit activities (spaces with mechanical cooling (W/m2K) | Notional Building - top-lit activities (W/m2K) | Area weighted worst case U-values (W/m2K) |
Wall | 0.22 | 0.26 | 0.26 | 0.26 |
Floor | 0.22 | 0.22 | 0.22 | 0.22 |
Roof | 0.18 | 0.18 | 0.18 | 0.20 |
Existing buildings
Certain works on existing buildings may also be covered by the requirements of ADL1. The requirements vary depending on whether it is a new element or a renovated element.
New elements
New elements includes cases where:
- a new thermal element is added (such as a dormer window)
- a thermal element is replaced (such as re-roofing)
- an extension (conservatories and porches are typically exempt).
On these projects, thermal elements will typically be expected to meet, or improve on, the maximum U-values shown in the table below.
Element type | Domestic - maximum U-value (ADL1 2022) (W/m2K) | Non-domestic - maximum U-value (ADL2 2022) (W/m2K) | |
Buildings that are essentially domestic in character (W/m2K) | All other non-domestic buildings (W/m2K) | ||
Flat roof | 0.13 | 0.15 | 0.18 |
Pitched roof - insulated at ceiling level | 0.13 | 0.15 | 0.15 |
Pitched roof - insulated at rafter level | 0.13 | 0.15 | 0.18 |
Wall | 0.18 | 0.21 | 0.26 |
Floor | 0.15 | 0.18 | 0.22 |
Some flexibility is given for certain applications, such as where fitting floor insulation may create an access problem. Consequential Improvements may also apply to the existing building depending on the type of work being carried out (typically for extensions).
Project teams can also choose to adopt two alternative approaches:
- U-value trade off approach; or
- Equivalent Primary Energy and carbon emissions target approach.
These approaches are available for all works carried out on existing dwellings and for material change of use, change in energy status and extensions on non-domestic properties. They 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 the limiting U-values (0.70 W/m2K - walls and floors, 0.35 W/m2K – roofs).
See the relevant Approved Document for further details on Consequential Improvements, design flexibility or the alternative approaches.
Renovated elements
Renovated elements include cases where:
- there is a material change of use;
- an unheated space is converted; or
- where more than 50% of the surface of an individual element is renovated (for example, by applying cladding, render or a waterproof membrane) or more than 25% of the surface area of the external envelope is renovated (for example, by fitting drylining).
Ideally, this work should look to achieve the improved values shown in the table above as a minimum. Where this isn’t technically feasible, or will not provide payback within 15 years, you should look to achieve the best possible U-values which are achievable. In all cases, you should reach, or improve upon, the limiting values shown in the second column for domestic properties or third for non-domestic.
Element type | Limiting U-values for retained fabric (W/m2K) | Maximum U-values - domestic (ADL1 2022) - area weighted average (W/m2K) | Maximum U-values - non-domestic (ADL2 2022) - area weighted average (W/m2K) |
Pitched roof - insulated at ceiling level | 0.35 | 0.16 | 0.16 |
Pitched roof - insulated at rafter level | 0.35 | 0.16 | 0.18 |
Flat roof or roof with integral insulation | 0.35 | 0.16 | 0.18 |
Wall - cavity insulation | 0.70 | 0.55 | 0.55 |
Wall - internal or external insulation | 0.70 | 0.30 | 0.30 |
Floor | 0.70 | 0.25 | 0.25 |
CPD training for Part L
Our suite of CPD training presentations can be delivered in-person or virtually. CPDs are available for Part L Wales, as well as Part L England and Section 6 for Scotland, covering new and existing dwellings and buildings.
U-value calculator
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.
ADL 2014 - superseded 23rd November 2023 (domestic) and 29th March 2023 (non-domestic)
There are four Approved Documents L (ADL), published by the Welsh Government (Llywodraeth Cymru):
Approved Document L1A: Conservation of fuel & power in new dwellings (ADL1A);
Approved Document L1B: Conservation of fuel & power in existing dwellings (ADL1B);
Approved Document L2A: Conservation of fuel & power in new buildings other than dwellings (ADL2A)
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 Regulations for the type of building work in question.
The tables below show the suggested U-values in Wales.
Domestic
| New build - Notional Building (W/m²K) | Existing buildings - extension (W/m²K) | Existing buildings - refurbishment (W/m²K) |
Wall | 0.18 | 0.21 | 0.30/0.55* |
Floor | 0.13 | 0.18 | 0.25 |
Pitched roof - insulated at ceiling level | 0.13 | 0.15 | 0.16 |
Pitched roof - insulated at rafter level | 0.13 | 0.15 | 0.18 |
Flat roof | 0.13 | 0.15 | 0.18 |
*A U-value of 0.55 W/m²K is used for cavity insulation and 0.30 W/m²K for internal or external wall insulation.
Non-domestic
| New build - Notional Building (W/m²K) | Existing buildings - extension (domestic in character) (W/m²K) | Existing buildings - extension (other buildings) (W/m²K) | Existing buildings - refurbishment (W/m²K) |
Wall | 0.26 | 0.21 | 0.26 | 0.30 / 0.55 * |
Floor | 0.22 | 0.18 | 0.22 | 0.25 |
Pitched roof - insulated at ceiling level | 0.18 | 0.15 | 0.15 | 0.16 |
Pitched roof - insulated at rafter level | 0.18 | 0.15 | 0.18 | 0.18 |
Flat roof | 0.18 | 0.15 | 0.18 | 0.18 |
* A U-value of 0.55 W/m²K is used for cavity insulation and 0.30 W/m²K for internal or external wall insulation.
Page updated 02/06/2025