Foil-Tec - Suspended Timber

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) Overall thermal transmittance (U-value) of suspended floors should be calculated using BS EN ISO 13370.

In many cases Foiltec Double used in suspended timber floors will meet Building Regulations requirements with no additional measures.

  • Foil-Tec is rolled out with the shiny side facing upwards, over the joists
  • Foil-Tec is then nailed in place through the Foil-Tec Saddle Clips to main­tain required air gap – 4 per m²
  • The horizontal joints are overlapped by 100mm and are left open to allow any moisture accumulation to dissipate
  • Foil-Tec must be brought up (behind the skirting board) to 75mm
  • The decking is then fixed with screws (at 200mm centres) 37mm into the joists
P/A RatioU-Value (with 50mm Cavity)U-Value (with 100mm Cavity)
0.20.24 W/m²K0.22 W/m²K
0.40.30 W/m²K0.37 W/m²K
0.60.33 W/m²K0.30 W/m²K
0.80.34 W/m²K0.31 W/m²K
1.00.36 W/m²K0.32 W/m²K