Book excerpt: Moisture control is fundamental to the proper functioning of any building. Controlling moisture is important to protect occupants from adverse health effects and to protect the building, its mechanical systems and its contents from physical or chemical damage. Yet, moisture problems are so common in buildings, many people consider them inevitable. Excessive moisture accumulation plagues buildings throughout the United States, from tropical Hawaii to arctic Alaska and from the hot, humid Gulf Coast to the hot, dry Sonoran Desert. Between 1994 and 1998, the U.S. Environmental Protection Agency (EPA) Building Assessment Survey and Evaluation (BASE) study collected information about the indoor air quality of 100 randomly selected public and private office buildings in the 10 U.S. climatic regions.