This paper reports on an improved model of coupled heat and moisture transfer with phase change and mobile condensates in fibrous insulation. The new model considered the moisture movement induced by the pressure gradient, a super-saturation state in condensing region as well as the dynamic moisture absorption of fibrous materials and the movement of liquid condensates. The results of the new model were compared and found in good agreement with the experimental ones. (C) 2003 Elsevier Ltd. All rights reserved.