Wall Drying in Hot and Humid Climates

Abstract

Moisture and subsequent mold problems in buildings are a serious and increasing concern for the building industry. Moisture intrusion in buildings is especially pertinent in hot and humid climates because the climate conditions provide only limited drying potential while at the same time providing a high potential for mold growth. To reduce moisture accumulation in wall systems, it is important to design wall systems that not only reduce moisture intrusion, but also allow drying. Yet often a wall's ability to dry is not considered during the design or material selection process. No cladding system or installation is perfect, therefore wall systems should be designed with the assumption that some moisture will enter and then consider the effects and how that moisture can be managed. This paper explores the mechanisms of wall drying, focusing on how wood frame walls dry in hot, humid climates. This paper describes laboratory drying studies of conventional sheathing / weather resistive barrier systems under a variety of temperature and humidity conditions including those typical of hot humid climates. Additionally, a computer simulation is used to examine the implications of drying to the interior, drying to the exterior, or drying to both the interior and exterior. Traditional rules of thumb for construction in hot humid climates rely on drying to the interior, but we will show that walls can and do dry to the exterior in these climates.