Dwellings & Buildings
Added Floor Area
Existing Elements
Your U-value meets or exceeds the Part L requirement for this element type. You can proceed with Building Control submission.
Your U-value is within 10% of the limit. Consider improving insulation to provide a safety margin for on-site variations.
Your U-value exceeds the Part L limit. You'll need to add insulation or compensate elsewhere in the design.
New homes must produce 31% less CO2 than Part L 2013. This is achieved primarily through improved fabric performance and low-carbon heating.
Wall U-values reduced from 0.26 to 0.18 W/m²K, floors from 0.18 to 0.13 W/m²K, and roofs from 0.16 to 0.11 W/m²K for new builds.
Part L 2021 is a stepping stone to the 2025 Future Homes Standard, which will require 75-80% lower emissions than current levels.
Introduction of primary energy as a metric alongside carbon emissions, accounting for the energy required to generate electricity.
Part L 2021 sets limiting U-values for new builds: walls 0.18 W/m²K, floors 0.13 W/m²K, roofs 0.11 W/m²K, and windows 1.2 W/m²K. For extensions, the targets are less stringent: walls 0.28, floors 0.18, pitched roofs 0.16/0.18, flat roofs 0.18, windows 1.4 W/m²K.
Part L 2021 introduces significantly stricter U-value targets and a new "fabric first" approach. New build requirements reduced by approximately 30% (e.g., walls from 0.26 to 0.18 W/m²K). The 2021 regulations also introduce the Future Homes Standard pathway.
Yes, Part L applies to renovations when replacing or substantially renovating thermal elements. The renovation U-value for walls is 0.30 W/m²K, floors 0.25 W/m²K, and roofs 0.16 W/m²K. These are more relaxed than new build targets but must still be met when practical.
If the limiting U-value cannot practically be achieved (e.g., due to structural constraints), you may need to compensate elsewhere in the design to achieve equivalent carbon emissions. This is done through SAP calculations showing overall compliance. Building Control can accept technical justification for relaxations in renovation projects.