Thermal comfort represents the state of mind that expresses satisfaction with the ambient thermal environment and is established through a subjective evaluation.
Studies show that people of different cultures generally have different comfort zones; even people belonging to the same family can feel comfortable in different conditions, and keeping everyone comfortable at the same time is not an easy matter.
Regarding levels of thermal satisfaction, the Berkeley Center for the Built Environment states "Current standards specify a 'comfort zone' representing the optimal range and combinations of thermal factors (air temperature, radiant temperature, air velocity, humidity) and personal factors (clothing and activity level) that should satisfy at least 80% of a building's occupants."
This is the goal outlined by ASHRAE in the industry comfort gold standard:
Standard 55, Environmental thermal conditions for human occupation. ASHRAE Standard 55 also specifies what thermal conditions are considered suitable to create comfort for occupants.
Thermal comfort inside buildings depends on the level of building insulation, the efficiency of heating/cooling, ventilation and air conditioning systems and the level of automation and integration of other building systems.