ABSTRACT
Since human beings spend more than 90% of their time indoors in developed countries, design of indoor environment is crucial to the comfort and welfare of the building occupants. However, this is not an easy task. Woods (1989) reported that about 800,000 to 1,200,000 commercial buildings in the United States containing 30-70 million workers have had problems related to the indoor environment. If the problems can be fixed through technologies, Fisk (2000) estimated that for the United States, the potential annual savings and productivity could be $15-$40 billion from reduced sick building syndrome symptoms, and $20-$200 billion from direct improvements in worker performance that are unrelated to health.
