Humans require energy to perform work and produce heat to maintain an internal body temperature of around 37°C.
If the core body temperature is reduced by more than about 1°C hypothermia sets in; if it increases by more than
about 1°C the person may suffer a heat stroke [13]. The higher the activity level, the more heat is produced. If too
much heat is produced, then the body will sweat, which causes discomfort. If too little heat is produced blood will
be withdrawn from the hands and feet, skin temperature will fall and the person feels cold and uncomfortable [14].
Besides, clothing interferes with our ability to lose heat to the environment. Thermal comfort is very much
dependent on the insulating effect of clothing on the wearer. The insulation of clothing is measured in units of CLO
(1 CLO = 0.155 m2 K/W; the units are those of internal resistance) [3].