30 Metal canopies
A flat roof from the tool's Metal roofs group. With the layers below it has a U-value of 3.30 W/m²K, is 156 mm thick, and has about 116 kgCO₂e/m² of embodied carbon.
- U-value
- 3.30W/m²K
- Overall thickness
- 156mm
- Embodied carbon
- 116kgCO₂e/m²
- Fire
- A2 or better
Against the Building Regulations
| New home in | U-value limit | This build-up, 3.30 |
|---|---|---|
| England | 0.16 W/m²K | Misses by 3.14 |
| Wales | 0.13 W/m²K | Misses by 3.17 |
| Scotland | 0.12 W/m²K | Misses by 3.18 |
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. 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 | Aluminium rainscreen panel | 3 | 160 | 0.000 | 54.0 | A1 |
| 2 | Unventilated cavity or dab gap | 150 | – | 0.163 | 0 | – |
| 3 | Aluminium rainscreen panel | 3 | 160 | 0.000 | 54.0 | A1 |
| Total, with surface resistances | 156 | 0.303 | 116.4 |
U-value worked out to BS EN ISO 6946 from the total resistance. Carbon is stages A1 to A3 for the layers, including 8.3 kgCO₂e/m² for steel rails or purlins.
Moisture and rain
Traces only Under 10 g/m² at most, which the tool treats as negligible. Surface factor 0.18 (needs over 0.72 and at least 0.75).
Rain: Not checked for exposure zone 2 (moderate).
Other metal roofs
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.