Flooring U-values	Semi Detached House
Perimeter Length to Area Ratio U-Value W/m²K 1:1 0.25 0:9 0.25 0:8 0.25 0:7 0.24 0:6 0.23 0:5 0.23 0:4 0.21 0:3 0.20 0:2 0.17 0:1 0.12

The heat loss in a floor is greater at the exposed perimeter edge of the floor. To calculate the U-Value, the exposed perimeter edge to area ratio needs to be worked out e.g. — a 100m² area, semi-detached house with 3 external walls of 10m each has a perimeter edge to area ratio of 0.3 (i.e. 30m ÷ 100m² = 0.3) which, using Foil-Tec Double, gives a U-Value of 0.2 W/m²K. NB: The calculation method used presumes the perimeter walls are insulated to 0.35 W/m²K.