Organic Insulation Materials, the Effect on Indoor Humidity, and the Necessity of a Vapor Barrier

Examples of organic insulation products are cellulose fiber, other plant fiber, and animal wool. These materials, which are all very hygroscopic, are associated with certain assertions about their building physical behavior that need to be verified.Examples of such assertions are: "A vapor barrier is not needed when using organic insulation materials" and "Organic insulation materials have a stabilizing effect on the indoor humidity".The paper presents some numerical analyses of the hygrothermal behavior of wall constructions and the occupied spaces they surround when an organic insulation material is used.

The following two main problems are analyzed:· The risk of interstitial condensation in typical building constructions with different vapor retarders when either conventional or organic insulation materials are used.· The influence on diurnal and seasonal indoor humidity variations when using either inorganic or organic insulation materials in the surrounding walls.