Limiting Area Weighted Maximum U-values (also known as Backstop U-values)

Limiting Area Weighted Maximum U-values (also known as backstop U-values) are the maximum permissible U-values for specific building elements, like walls and windows, set by building regulations. They act as a limit on the thermal performance of individual components to ensure a minimum standard of insulation, even if the overall building meets its carbon emission targets through other means, such as energy-efficient technology. These values are more lenient than the "notional" or target U-values, but if a Limiting Area Weighted Maximum value is used, the building must compensate by achieving better performance in other areas.