Below is a brief summary of the flat roof insulation requirements within Technical Handbook 6 (Energy) 2022. These requirements came into force on 1st February 2023.
New Dwellings – Technical Handbook 6 (Energy) 2022 (TH6 2022)
Under TH6 2022, all new domestic properties must meet targets for:
- carbon emissions; and
- delivered energy demand – this considers both the energy used in the dwelling.
To calculate specific targets for each, a standard specification is applied to a Notional Building of the same dimensions as the proposed dwelling to see how it would perform. Project teams can choose to vary from this specification providing the finished building meets all three of the above targets and that the U-values are better than specified worst case U-values.
The U-value for flat roofs used within the Notional Building specification is 0.09 W/m²K. The worst acceptable U-value for flat roofs is 0.12 W/m²K.
Existing Dwellings – Technical Handbook 6 (Energy) 2022 (TH6 2022)
TH6 2022 states that where a property is extended or converted, it should achieve the same worst-case U-value as for new builds (0.12 W/m²K for flat roofs). Where practical, renovated elements should also look to achieve this value but in all cases, renovated roofs should at least achieve a U-value of 0.35 W/m²K.
New Non-Domestic – Technical Handbook 6 (Energy) 2022 (TH6 2022)
Under TH6 2022, all new non-domestic properties must meet targets for carbon emissions and delivered energy demand. The U-values of the different elements must also meet specified worst-case U-values.
As with for new domestic buildings, the carbon emissions and primary energy targets are set by applying a set specification to a building of the same dimensions as the proposed project and seeing how it performs.
The roof U-value used within the Notional Building specification is 0.11 W/m2K. The worst acceptable U-value for flat roofs is 0.16 W/m2K.
Existing Non-Domestic – Technical Handbook 6 (Energy) 2022 (TH6 2022)
As with for existing domestic properties, TH6 2022 states that where a property is extended or converted, it should achieve the same worst-case U-value as for new builds (0.16 W/m²K for flat roofs). Where practical, renovated elements should also look to achieve this value but in all cases, renovated roofs should at least achieve a U-value of 0.35 W/m²K.
