Human
thermal comfort is defined by
ASHRAE as the state of mind that expresses satisfaction with the surrounding environment (ASHRAE Standard 55). Maintaining thermal comfort for occupants of buildings or other enclosures is one of the important goals of
HVAC design engineers.
Thermal comfort is affected by heat conduction, convection, radiation, and evaporative heat loss. Thermal comfort is maintained when the heat generated by human metabolism is allowed to dissipate, thus maintaining thermal equilibrium with the surroundings. Any heat gain or loss beyond this generates a sensation of discomfort.[1] It has been long recognised that the sensation of feeling hot or cold is not just dependent on air temperature alone.
Thermal comfort is very important to many work-related factors. It can affect the distraction levels of the workers, and in turn affect their performance and productivity of their work. Also, thermal discomfort has been know to lead to Sick Building Syndrome symptoms. [2][3] The US EPA BASE study found that higher indoor temperatures, even within the recommended thermal comfort range, increased worker symptoms[4]. The occurrence of symptoms increased much more with raised indoor temperatures in the winter than in the summer due to the larger difference created between indoor and outdoor temperatures.
Factors determining thermal comfort include
