# Part Q compliance

Part L compliance refers to meeting Part L of the UK Building Regulations — “Conservation of Fuel and Power” — which sets standards for energy efficiency in buildings.

For windows, this primarily means achieving required U-values (typically ≤1.4 W/m²K for new builds, ≤1.6 W/m²K for replacements in existing dwellings), incorporating low-emissivity (low-E) glazing, warm-edge spacers, and effective airtightness.

Heritage buildings can meet energy performance standards by using high-performance timber windows such as Accoya® with slimline double glazing and draught-proofing systems that maintain thermal efficiency and preserve historical features.