Investment and Adaptation in Thermal comfort can increase 11% people performance and productivity while facing the heat and high humidity. Global Heat Alert ahead

Thermal comfort is the condition of mind that expresses subjective satisfaction with the thermal environment. The human body can be viewed as a heat engine where food is the input energy. The human body will release excess heat into the environment, so the body can continue to operate. The heat transfer is proportional to temperature difference. In cold environments, the body loses more heat to the environment and in hot environments the body does not release enough heat. Both the hot and cold scenarios lead to discomfort.

The concept of thermal comfort is closely related to thermal stress. This attempts to predict the impact of solar radiation, air movement, and humidity for military personnel undergoing training exercises or athletes during competitive events. Several thermal stress indices have been proposed, such as the Predicted Heat Strain (PHS) or the humidex. Generally, humans do not perform well under thermal stress. People's performances under thermal stress are about 11% lower than their performance at normal thermal wet conditions. Also, human performance in relation to thermal stress varies greatly by the type of task which the individual is completing. Some of the physiological effects of thermal heat stress include increased blood flow to the skin, sweating, and increased ventilation.

Thermal comfort is influenced by factors like air temperature, mean radiant temperature, relative humidity, air speed, metabolic rate, and clothing. Thermal conditions can affect learning, cognitive performance, task completion, disease transmission, and sleep.

Psychological adaptation

Thermal comfort as a "condition of mind" is defined in psychological terms. Among the factors that affect the condition of mind (in the laboratory) are a sense of control over the temperature, knowledge of the temperature and the appearance of the (test) environment. A thermal test chamber that appeared residential "felt" warmer than one which looked like the inside of a refrigerator.

Physiological adaptation

The body has several thermal adjustment mechanisms to survive in drastic temperature environments. In a cold environment the body utilizes vasoconstriction; which reduces blood flow to the skin, skin temperature and heat dissipation. In a warm environment, vasodilation will increase blood flow to the skin, heat transport, and skin temperature and heat dissipation. If there is an imbalance despite the vasomotor adjustments listed above, in a warm environment sweat production will start and provide evaporative cooling. If this is insufficient, hyperthermia will set in, body temperature may reach 40 °C (104 °F), and heat stroke may occur. In a cold environment, shivering will start, involuntarily forcing the muscles to work and increasing the heat production by up to a factor of 10. If equilibrium is not restored, hypothermia can set in, which can be fatal. Long-term adjustments to extreme temperatures, of a few days to six months, may result in cardiovascular and endocrine adjustments. A hot climate may create increased blood volume, improving the effectiveness of vasodilation, enhanced performance of the sweat mechanism, and the readjustment of thermal preferences. In cold or underheated conditions, vasoconstriction can become permanent, resulting in decreased blood volume and increased body metabolic rate

Behavioral adaptation

In naturally ventilated buildings, occupants take numerous actions to keep themselves comfortable when the indoor conditions drift towards discomfort. Operating windows and fans, adjusting blinds/shades, changing clothing, and consuming food and drinks are some of the common adaptive strategies. Among these, adjusting windows is the most common. Those occupants who take these sorts of actions tend to feel cooler at warmer temperatures than those who do not.

Important of human physiological process to identify Hypothermia/Hyperthermia

The human body always works to remain in homeostasis. One form of homeostasis is thermoregulation. Body temperature varies in every individual, but the average internal temperature is 37.0 °C (98.6 °F). Sufficient stress from extreme external temperature may cause injury or death if it exceeds the ability of the body to thermoregulate. Hypothermia can set in when the core temperature drops to 35 °C (95 °F). Hyperthermia can set in when the core body temperature rises above 37.5–38.3 °C (99.5–100.9 °F). Humans have adapted to living in climates where hypothermia and hyperthermia were common primarily through culture and technology, such as the use of clothing and shelter.

Satisfaction with the thermal environment is important because thermal conditions are potentially life-threatening for humans if the core body temperature reaches conditions of hyperthermia or hypothermia. Buildings modify the conditions of the external environment and reduce the effort that the human body needs to do in order to stay stable at a normal human body temperature, important for the correct functioning of human physiological processes.

In building science studies, thermal comfort has been related to productivity and health. Office workers who are satisfied with their thermal environment are more productive. The combination of high temperature and high relative humidity reduces thermal comfort and indoor air quality.

Indoor spaces that are not air conditioned can create indoor heat waves if the outside air cools but the thermal mass of the building traps the hotter air inside. Cedeño-Laurent et al. believe these may become worse as climate change increases the "frequency, duration, and intensity of heat waves" and will be harder to adjust to in areas that are designed for colder climate.

Mortality due to heat waves could be reduced if buildings were better designed to modify the internal climate, or if the occupants were better educated about the issues, so they can take action on time. Heatwave early warning and response systems are important elements of heat action plans.

Heat illness in rising temperatures

Since the 1970s, temperature on the surface of Earth has become warmer each decade. This increase happened faster than in any other 50-year period over at least the last 2000 years. Compared to the second half of the 19th century, temperature in the 21st century show a warming of 1.09 °C.

Extreme heat is a direct threat to health, especially for people over 65 years, children, people living in cities and those who have already existing health conditions. Rising global temperatures impact the health and well-being of people in multiple ways. In the last few decades, people all over the world have become more vulnerable to heat and experienced an increasing number of life-threatening heatwave events. Extreme heat has negative effects on mental health as well, raising the risk of mental health-related hospitalizations and suicidal.

People with cognitive health issues (e.g. depression, dementia, Parkinson's disease) are more at risk when faced with high temperatures and ought to be extra careful as cognitive performance has been shown to be differentially affected by heat. People with diabetes and those who are overweight, have sleep deprivation, or have cardiovascular/cerebrovascular conditions should avoid too much heat exposure.

Although heat itself is not a direct threat to health on its own, a combination of factors of rising temperatures can detriment one's health. The effects of heat on an individual's health is influenced by temperatures, humidity, exercise, hydration, age, pre-existing health status and also by occupation, clothing, behavior, autonomy, vulnerability, and sense of obligation.

Physical exercise is beneficial for reducing the risk the many illnesses and for mental health. At the same time the number of hours per day when the temperature is dangerously high for outdoor exercise has been increasing. The rising heat also impacts people's ability to work and the number of hours when it is not safe to work outdoors (construction, agriculture, etc.) has also increased.

There are two types of heat the body is adapted to, humid heat and dry heat, but the body adapts to both in similar ways. Humid heat is characterized by warmer temperatures with a high amount of water vapor in the air, while dry heat is characterized by warmer temperatures with little to no vapor, such as desert conditions. With humid heat, the moisture in the air can prevent the evaporation of sweat. Regardless of acclimatization, humid heat poses a far greater threat than dry heat; humans cannot carry out physical outdoor activities at any temperature above 32 °C (90 °F) when the ambient humidity is greater than 95%. When combined with this high humidity, the theoretical limit to human survival in the shade, even with unlimited water, is 35 °C (95 °F) – theoretically equivalent to a heat index of 70 °C (158 °F) Dry heat, on the other hand, can cause dehydration, as sweat will tend to evaporate extremely quickly. Individuals with less fat and slightly lower body temperatures can more easily handle both humid and dry heat.

Heat stress causes illness but also may account for an increase in workplace accidents, and a decrease in worker productivity. Worker injuries attributable to heat include those caused by: sweaty palms, fogged-up safety glasses, and dizziness. Burns may also occur as a result of accidental contact with hot surfaces or steam. In the United States, occupational heat stress is becoming more significant as the average temperatures increase but remains overlooked. There are few studies and regulations regarding heat exposure of workers.

In unusually hot conditions, all workers should be aware of their risk for heat illness and should ensure that they drink plenty of water and take breaks in cool places to avoid any severe impacts.