Fabric Performance & U-Values

The building fabric, its walls, roof, floor and windows, decides how much heat escapes in winter and enters in summer, and therefore how large the heating and cooling systems have to be to compensate. Controlling losses at the fabric is almost always cheaper over a building's life than oversizing the plant to fight them, which is why "fabric first" is the founding principle of low-energy building. This lesson introduces the U-value, the fabric-first logic, and where a building's heat actually goes.