Use this tool to look up the FBS 2026 notional building specification for any building element. Select an element to see its notional value under the Future Buildings Standard alongside the Part L 2021 notional value and the limiting (backstop) value that no element may exceed.
How this tool works
The notional building is a reference design used in SBEM calculations to set the target emission rate (TER) and target primary energy rate (TPER) for a new non-domestic building. The actual building must demonstrate performance equal to or better than the notional building to achieve compliance.
Limiting values are backstop thresholds for individual elements. Even where trade-offs are used elsewhere in the design, no single element may perform worse than its limiting value. This prevents excessively poor fabric being compensated by oversized renewables.
All values are taken from Approved Document L Volume 2, 2026 edition (Tables 4.1 and 4.2).
Related Pages
Notional Building Specification
Part L 2021 notional building specification (NCM 2021), how it works in SBEM, and what it means for your design.
Fabric Standards
Detailed breakdown of U-values, air permeability, and thermal bridging requirements under the FBS.
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