Overview

American Society of Heating Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 55 (1992) defines thermal comfortas the condition of mind that expresses satisfaction with the thermal environment. This definition loosely translates to the question of whether the occupant feels too hot, too cold, or just right. The next step is to determine if the room is thermally comfortable. The simplest way is to ask all the occupants if they are satisfied with their thermal environment. However, this method may result in numerous thermostat adjustments and, as a worst case, reinstallation of the entire heating or cooling system. The ultimate goal is to predict the thermal comfort in a room without resorting to a polling system.

The six primary variables used to predict thermal comfort are activity level, clothing insulation value, air velocity, humidity, air temperature, and mean radiant temperature (Fanger, 1967). For most design situations, the room usage dictates the activity level and clothing insulation value. For example, an office situation implies sedentary activity with business attire. In contrast, an exercise room implies a high activity level with shorts and a T-shirt. In addition, the humidity depends on the heating or cooling system, generically referred to as a thermal distribution system, for the entire building, which may not be controlled at the room level. Usually, the air velocity is maintained at a level that avoids a draft...