This work presents an experimental and analytical investigation of heat and mass transfer with condensation in a fibrous insulation slab, one side of which is exposed to high temperature and high humidity, and the other side bounded by a cold surface. The analysis carried out is based on a model in which condensation occurs on the cold surface and in the interior of the fibrous insulation, and condensate falls away under gravity. Predicted heat transfer coefficients agreed well with experimental data at atmospheric pressure and temperatures up to 100 degrees C. It was also indicated by the analysis that the convective contribution is appreciable in higher pressure and temperature environments.