A strategy for assessing the thermal resistance of a wet insulation material has been developed. A computer program has been developed to calculate the effects of moisture flow and phase changes. Laboratory experiments in a guarded hot plate apparatus with moist mineral fiber insulation have been conducted. There was satisfactory agreement between the computer calculations and the experimental results.

The practical thermal resistance of mineral fiber insulation in two applications has been studied using the aforementioned strategy:

1. Insulation with accidental high moisture content caused by leakage, rain penetration, and so on. A typical example is insulation on the exterior of basement walls.

2. Insulation with trapped moisture inside impermeable vapor barriers. This situation is sometimes found in roof insulation.

A conclusion was that phase changes in some cases were important energy transfer mechanisms and therefore must be considered.