The BRE Green Guide defines the ‘functional unit’ for applicable materials, which may be assessed under the Mat 01 Issue:
- Functional unit for External Walls:
1m² of external wall construction, to satisfy current Building Regulations, and a U value of 0.3 W/m²K. Where relevant, the specification will also include an internal wall finish. - Variation for retail/industrial:
1m² of external wall construction, to satisfy current Building Regulations, and a U value of 0.3 W/m²K.
Louvres on a facade provide a role outside of the ‘functional unit’ and hence can be excluded from the calculations for the external wall.
Only elements forming part of the ‘functional unit’ need to be included in the external wall.
