FHS Fabric Specification Lookup
Use this free tool to look up the confirmed U-values and air permeability requirements for new dwellings under the Future Homes Standard. Select a building element to see the limiting and notional values.
For full details on Part L fabric changes, see our comprehensive guide to FHS Part L changes.
FHS Fabric Performance Values
Look up the fabric U-values and air permeability requirements for new dwellings under the Future Homes Standard. Backstop values (the absolute maximum permitted) are unchanged from Part L 2021. The key changes are to the notional dwelling values that designs must target. FHS notional values are from the consultation response (March 2026); the final notional buildings document has not yet been published.
Select a building element above to see its performance requirements.