This paper investigates the influence of waterproof fabrics on heat and moisture transfer through a clothing system. The water vapor permeability (WVP) for the outside layer was derived from published experimental data, and was considered to be a factor influencing the mass transfer coefficient at the boundary exposed to the environment. The analysis was carried out by using a mathematical model that describes the coupled heat and moisture transfer in porous textiles. The numerical simulation reveals a significant influence of water proof fabrics on the dynamic moisture content distribution in fabrics⁄fibers, moisture vapor condensations and the liquid transfer behavior inside the clothing. The research has shown the potential usage of the mathematical simulation in evaluating the performance of different waterproof and breathable fabrics in clothing systems, as well as the potential usage in the product development of functional apparel.