Thermal adaptation is the ability of the human body to adjust to temperatures. The human body works to maintain the core body temperature at 37° celsius. The loss or gain of heat from the environment activates the thermal regulators in the body to warm or cool respectively. The thermal regulation system in our body functions intending to keep ourselves at a comfortable temperature. The core of our body passes on heat to the skin to maintain comfort during cold climates, while during hot climates the nervous system activates the sweat glands to cool down the body by evaporation of sweat from the layers of skin. Humans are comfortable in a wider range of temperature and beyond this range is the feeling of hot or cold. This state of either feeling is the result of the intent to maintain the core body temperature that is affected by the environment. Humans minimize the alteration in body temperature by wearing supportive clothing, using ceiling fans, hot and cold air- conditioners.   

People in colder climates have a comfortable temperature range on the lower side due to their body thermally adapting to the climate. When a person from a warmer region travels to a colder climate, they may require more insulating clothes to maintain comfort than a person used to the colder climate. One of the reasons for this discrepancy is due to the person from a warmer region being thermally adapted for the warmer climate. It has been studied that it takes about 7 to 14 days with 2 hours of daily exposure for the human body to adapt to the new temperature environment. The converse of this scenario is also possible, where the person adapted to a colder climate, may sweat more in hot climates until their body adapts to the newer conditions. 

There can be also a time lag in thermal adaptability during the beginning of a new season in some regions as it may take a few days for the body to adapt to the temperature of the new season. If the temperature gradient is faster than the thermal adaptability then the initial few days may feel hotter or colder than the actual environment. This scenario may be observed as at the start of the summer for about 14 days, most of the occupants in an indoor space would be thermally uncomfortable at a certain temperature. After the 14 days, their bodies would have thermally adapted to the warmer climate so thermal comfort could be achieved even at a higher temperature. Natural ventilation and passive strategies with the account of thermal adaptability played a critical role in controlling thermal comfort in people before inventing ceiling fans and air conditioners. With the world’s population approaching 8 billion people and people cramming into small spaces for shelter in urban areas, it’s becoming increasingly difficult for them to rely solely on natural ventilation and passive strategies. 

Thermal adaptability must be taken into account while formulating all thermal comfort strategies. In tropical places with warm climates like India people need not completely rely on air conditioners, since they feel comfortable at a relatively higher temperature. Hence, adopting a combination of ACs with 5-star energy rated BLDC ceiling fans and passive thermal strategies like climate-conscious building design could be beneficial to save money, energy, and the environment retaining sufficient thermal comfort. 

Maintaining even one degree of temperature higher in thermal comfort appliances like ACs, Air coolers, and ceiling fans would have a significant reduction in energy consumption. In ACs, a one-degree higher temperature setting offers about 5 % energy savings, in BLDC ceiling fans operating at medium speed offer about 50% energy savings. The combination of ACs with BLDC ceiling fans combination tends to offer much more energy savings.  

Cooling or warming more than the required temperature makes the thermal regulator function work unnecessarily to maintain the core temperature. This may lead to subtle shifts in the thermal adaptability mechanism and energy loss. 

The phenomenon of thermal adaptability is useful in the formulating of thermal comfort strategies for minimizing energy consumption, maintaining health, and save the environment. 

References: 

[1] Adapting to climate extremes 

[2] Human adaptation to hot and cold environments