What Is An R-Value?

R-values describe the thermal resistance of materials and construction elements to heat transfer and are measured in [m² ºC/W].

R-values are quoted as Material R-values for individual materials of given thickness and density Total R-values are for construction elements as the sum of the R-values of all the building. example: a wall will be made up of the thermal resistance of the outer wall cladding, the wall framing, insulation and inner wall lining. Air gaps and thermal bridges incorporated and also the surface thermal resistances. Total R-values must not be mistaken for the material R-value of insulation products. A wall insulated with an 'R 1.9'-Insulation product does not necessarily satisfy the requirement for a total R-value of R 1.9.

Air movement through wall insulation especially low density products has to be taken into account when estimating your total R-Value.