Clothing level (clo) is one of the essential criteria used to regulate the 'occupants' satisfaction, along with the operative temperature, airspeed, relative humidity, and metabolic rate in the ASHRAE-55 CBE Thermal Comfort Tool.More often than not, thermal discomfort is due to inappropriately high clothing levels of indoor occupants. This study highlighted the influence of clothing insulation in achieving optimal thermal comfort. The influence of clothing insulation included posture, physical activity, climate, clothing fit, bedding system, season, gender, age level, building type, and indoor and outdoor temperature variations. Therefore, the clothing level per human individual was widely different and should be considered carefully in the design and operation of the built environment.
