What is the Heat Loss Coefficient (HLC)?

The Heat Loss Coefficient (HLC) quantifies the total rate of heat loss from a building through its fabric (walls, roof, floor, windows, doors) and ventilation. It is expressed in Watts per Kelvin (W/K) and represents the sum of:

1. Fabric heat loss (calculated via U-values × surface areas)
2. Ventilation heat loss (air changes × volume × heat capacity of air)