The lambda value is the thermal conductivity of a material, expressed in W/mK. The lower this value, the less heat is conducted, and the better the material insulates.
The Rd value indicates the thermal insulating capacity of a material layer. The higher the Rd value, the better the insulation.
The Rd value is calculated as follows: Rd = insulation thickness (in m) / lambda value. Depending on the lambda value and thickness of the insulation board, you get the following Rd values for your façade.
Lambda value | 0,035 | 0,027 | ||
Thickness of insulation boards | Appearance with joint | Joint-free appearance(3) | Appearance with joint | Joint-free appearance(3) |
20 mm(1) | 0,57 m²K/W | 0,71 m²K/W | ||
30 mm(2) | 0,86 m²K/W | 1,00 m²K/W | 1,11 m²K/W | 1,30 m²K/W |
40 mm | 1,14 m²K/W | 1,29 m²K/W | 1,48 m²K/W | 1,67 m²K/W |
60 mm | 1,71 m²K/W | 1,86 m²K/W | 2,22 m²K/W | 2,41 m²K/W |
80 mm | 2,29 m²K/W | 2,43 m²K/W | 2,96 m²K/W | 3,15 m²K/W |
100 mm | 2,86 m²K/W | 3,00 m²K/W | 3,70 m²K/W | 3,89 m²K/W |
120 mm | 3,43 m²K/W | 3,57 m²K/W | 4,44 m²K/W | 4,63 m²K/W |
140 mm | 4,00 m²K/W | 4,14 m²K/W | 5,19 m²K/W | 5,37 m²K/W |
160 mm | 4,57 m²K/W | 4,71 m²K/W | 5,93 m²K/W | 6,11 m²K/W |
180 mm | 5,14 m²K/W | 5,29 m²K/W | 6,67 m²K/W | 6,85 m²K/W |
200 mm | 5,71 m²K/W | 5,86 m²K/W | 7,41 m²K/W | 7,59 m²K/W |
220 mm | 6,28 m²K/W | 6,43 m²K/W | 8,15 m²K/W | 8,33 m²K/W |
(1) Iso-Façade insulation board without tongue and groove, not ATG certified
(2) Not ATG certified
(3) ATG certification limited to single-family homes. Insulation boards without pre-milled joint lines (joint-free appearance) are standard 5 mm thicker than boards with joint lines.