Cavity wall, partial-fill PIR
An external wall from the tool's Typical UK walls group. With the layers below it has a U-value of 0.17 W/m²K, is 380 mm thick, and has about 70 kgCO₂e/m² of embodied carbon.
- U-value
- 0.17W/m²K
- Overall thickness
- 380mm
- Embodied carbon
- 70kgCO₂e/m²
- Fire
- Worst class E
Against the Building Regulations
| New home in | U-value limit | This build-up, 0.17 |
|---|---|---|
| England | 0.26 W/m²K | Meets it |
| Wales | 0.18 W/m²K | Meets it |
| Scotland | 0.17 W/m²K | Meets it |
These are the limits for a single element in a new home. In England a new home usually needs better figures to pass the whole-house target, about 0.18 for walls. All UK U-value limits.
Section, drawn to scale
Layers, outside to inside
| # | Layer | mm | λ, W/mK | R, m²K/W | kgCO₂e/m² | Fire class |
|---|---|---|---|---|---|---|
| 1 | Brick, outer leaf | 102.5 | 0.77 | 0.133 | 41.5 | A1 |
| 2 | Unventilated cavity, foil-faced one side | 50 | – | 0.445 | 0 | – |
| 3 | PIR board | 100 | 0.022 | 4.545 | 11.1 | E |
| 4 | Medium-density block | 100 | 0.51 | 0.196 | 14.0 | A1 |
| 5 | Unventilated cavity or dab gap | 15 | – | 0.171 | 0 | – |
| 6 | Plasterboard | 12.5 | 0.21 | 0.060 | 3.5 | A2-s1,d0 |
| Total, with surface resistances | 380 | 5.720 | 70.1 |
U-value worked out to BS EN ISO 6946 from the total resistance. Carbon is stages A1 to A3 for the layers.
Moisture and rain
Traces only Under 10 g/m² at most, which the tool treats as negligible. Surface factor 0.96 (needs over 0.71 and at least 0.75).
Rain: Zone 2 of max 3 for exposure zone 2 (moderate).
Other typical UK walls
Figures come from the Build-up Atlas's own calculation, with generalised values for typical products, for an England new home with default settings. They are indicative, for design and teaching: check the manufacturer's declared values and the current regulations for your project. Rules and standards last checked 21 October 2026.