In 1994, ASHRAE's comfort index accommodated evaporative air conditioning, which allows slightly higher regions of humidity. This index uses two wet-bulb temperature lines (i.e., 18–20 1C) to set the limits of winter and summer comfort zones, respectively. Comfort index was adjusted for use in the developing countries like Thailand. However its intuitive nature makes it difficult for quantitative evaluation of thermal comfort. A “thermally comfortable” environment is the ideal thermal environment for people to work in such that people perform their work efficiently. Although it is possible to create conditions in work places that will make a majority of people comfortable, it is almost impossible to please everyone [41].