The investigation reported herewith was confined to a consideration of factors which enter into the problem of moisture accumulation in insulated and uninsulated walls, with particular reference to fill-type insulation. Both analytical and experimental methods were employed.

In the analytical study, the relation which must exist among the principal factors when no moisture accumulation takes place was evaluated. The results of the study show that the water permeability of the cold side of the wall must be many times that of. the warm side to avoid moisture accumulation, even under ordinary conditions.