scope:

The theoretical background for the effects of moisture on heat transfer, which is given here, is valid for all types of materials, but the applications and detailed guidelines have been developed with a specific type of material in mind: masonry with medium or high thermal conductivity. This document is restricted to moisture contents in the hygroscopic range, where moisture content is in equilibrium with 95 % relative humidity or lower. For most building materials, moisture content in equilibrium with air having up to 95 % relative humidity is usually below the threshold value where the flow of liquid takes place. This value is often called critical saturation, when expressed as the fraction of voids with liquid, or critical moisture content when expressed as a specific moisture content. For higher moisture contents, reference is made to ISO 10051. Preferred moisture contents are: a) in equilibrium with 50 % relative humidity (due to the requirements in the material specifications); b) in equilibrium with 80 % relative humidity (because this level is sometimes considered as "the practical moisture content").