u-values-and-building-regulations-for-insulating-your-home
Building Regulations, Standards and U-Values
The lower the U-Value the more insulation there is in a building element, (e.g a floor, ceiling or wall). Therefore the less heat loss.
Consequently, the higher the U-Value, the more heat loss you have in the home.
U-Values are important because there are certain standards according to the Building Regulations and Standards depending on location.
For example, Scotland buildings will need a lower U-Value due to the colder weather than England. Wales can get away with having a higher U-Value than England and Scotland because it is typically less cold.
The tables below show the suggested U-values in England, Wales and Scotland. Note the distinction between the domestic and non-domestic columns.
England
| Domestic | Non-domestic | |||||
| New Build | Existing Buildings | New Build | Existing Buildings | |||
| Best Starting Point (Fabric Only) | Extension | Refurbishment | Best Starting Point (Fabric Only) | Extension | Refurbishment | |
| Wall | 0.16 | 0.28 | 0.30 / 0.55 * | 0.22 | 0.28 | 0.30 / 0.55 * |
| Floor | 0.11 | 0.22 | 0.25 | 0.18 | 0.22 | 0.25 |
| Pitched Roof – Ceiling Level | 0.11 | 0.16 | 0.16 | 0.14 | 0.16 | 0.16 |
| Pitched Roof – Rafter Level | 0.11 | 0.18 | 0.18 | 0.14 | 0.18 | 0.18 |
| Flat Roof | 0.11 | 0.18 | 0.18 | 0.14 | 0.18 | 0.18 |
* A U-value of 0.55 W/m²·K is used for cavity insulation and 0.30 W/m²·K for internal or external wall insulation.
Wales
| Domestic | Non-domestic | ||||||
| New Build | Existing Buildings | New Build | Existing Buildings | ||||
| Best Starting Point (Fabric Only) | Extension | Refurbishment | Best Starting Point (Fabric Only) | Extension (Domestic in Character) | Extension (Other Buildings) | Refurbishment | |
| Wall | 0.16 | 0.21 | 0.30 / 0.55 * | 0.22 | 0.21 | 0.26 | 0.30 / 0.55 * |
| Floor | 0.11 | 0.18 | 0.25 | 0.18 | 0.18 | 0.22 | 0.25 |
| Pitched Roof – Ceiling Level | 0.11 | 0.15 | 0.16 | 0.14 | 0.15 | 0.15 | 0.16 |
| Pitched Roof – Rafter Level | 0.11 | 0.15 | 0.18 | 0.14 | 0.15 | 0.18 | 0.18 |
| Flat Roof | 0.11 | 0.15 | 0.18 | 0.14 | 0.15 | 0.18 | 0.18 |
* A U-value of 0.55 W/m²·K is used for cavity insulation and 0.30 W/m²·K for internal or external wall insulation.
Scotland
| Domestic | Non-domestic | |||||||
| New Build | Existing Buildings | New Build | Existing Buildings | |||||
| Best Starting Point (Fabric Only) | Extension & Refurbishment * | Conversion of Heated Buildings | Best Starting Point (Fabric Only) | Refurbishment, Extension & Conversion of Unheated Buildings | Conversion of Heated Buildings | |||
| A | B | |||||||
| Wall | 0.15 | 0.17 | 0.22 | 0.30 | 0.18 | 0.25 | 0.30 | |
| Floor | 0.13 | 0.15 | 0.18 | 0.25 | 0.15 | 0.20 | 0.25 | |
| Pitched Roof – Ceiling Level | 0.10 | 0.11 | 0.15 | 0.25 | 0.14 | 0.15 | 0.25 | |
| Pitched Roof – Rafter Level | 0.10 | 0.13 | 0.18 | 0.25 | 0.14 | 0.15 | 0.25 | |
| Flat Roof | 0.10 | 0.13 | 0.18 | 0.25 | 0.14 | 0.15 | 0.25 | |
* Column A is for extensions where the existing dwelling’s walls and roof U-values are worse than 0.70 W/m²·K in the walls and worse than 0.25 W/m²·K in the ceiling. Column B is for other extensions, upgraded existing thermal elements, non-exempt conservatories and conversion of unheated buildings.