Volume 39, Issue 4 (July 2011)
Considerations for Controlling Condensation in High-Humidity Buildings: Lessons Learned
Condensation problems in general use (i.e., non-humidified) buildings such as offices, schools, and condominiums typically manifest themselves as visible staining on window and door perimeters or minor dripping from overhead components. The relatively low interior moisture levels that are typical of these types of buildings are generally insufficient to cause severe water damage in the short term. At the other end of the spectrum, high-humidity buildings such as museums and natatoriums can suffer extreme damage due to condensation, sometimes within weeks, not years, of completion. High interior moisture levels and, in many cases, differential air pressures, contribute to condensation in both visible locations, such as windows and curtain walls, and concealed locations within walls and roofs. Signs of concealed condensation such as dripping water or rust stains may only become visible after moderate to heavy damage has already occurred within the enclosure. These problems are typically more severe in cold climates, but high-humidity buildings may experience condensation problems in mild climates, where such issues are often not considered by designers due to the lack of prolonged cold weather during the winter. This paper will review the severe and immediate condensation problems that are unique to high-humidity buildings, including surface condensation and concealed condensation due to air leakage through the enclosure. It discusses the theoretical mechanisms by which condensation forms in building enclosures, and illustrates these concepts through various case studies in both cold and mild climates. This paper will focus on design strategies for avoiding problems, but also discusses remedial work to existing buildings, drawing on the author’s experience with the investigation and repair of high-humidity buildings.