Properties of common insulating materials
Keywords: insulation, insulation, insulation, materials, property, performance, performance, lambda coefficient, calculation, losses, loss, heat balance…
All lambda are given in W / (mK)
Calculation of the thermal resistance of a wall or a wall
The thermal resistance is given by the following formula:
R = e / lambda
With e = wall thickness in m
and lambda = coefficient of heat loss of the materials used.
For walls made up of several layers of materials the thermal resistances add up, thus for a wall made up of 2 materials 1 and 2:
Total R = R1 + R1 = e1 / lambda1 + e2 / lambda2
We thus obtain R in m2.K / W which is not very significant, on the other hand its inverse: W / m2.K it is: it is the thermal transmission in Watts (in other words: the thermal losses) of the wall per degree of difference in T ° and m2 of the wall.
A thermal resistance at least equal to 2 is considered as standard insulation.
Example for an insulated wall with a resistance of 3:
- R = 3
- Outdoor temperature: 5 ° C
- Indoor temperature: 19 ° C
The losses by conduction in the wall will therefore be equal to (19-5) * 1 / 3 = 4,66 W per m2 of surface of this wall. If the wall is 40m2 the heating power to be supplied is therefore 4,66 * 50 = 233 Watts to maintain the interior temperature at 19 ° C, assuming that this is the only heat loss from this room.
This is a first simple approach to carry out the thermal balance of a house (other losses occur by convection, air renewal, thermal bridges, carpentry, etc.).
Learn more see the 2005 Thermal Regulation: RT2005
Lambda conduction coefficients for common materials
Wood and materials of plant origin
Industrial insulating materials for petrochemicals
Natural soils and floor coverings
The most common metals
Other materials and gases