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Adaptive thermal comfort: A "whole-building" solution

The latest buzz in commercial building design has engineers integrating greater temperature control measures to enhance the comfort of occupants. Here’s how the concept works:

Adaptive thermal comfort, defined

Adaptive thermal comfort is a theory that suggests a human connection to the outdoors and control over the immediate environment allow them to adapt to (and even prefer) a wider range of thermal conditions than is generally considered comfortable.

Integrated into new building designs, this concept can also become part of a whole-building approach that can help frame sustainable standards for indoor climates.

In ASHRAE Standard 55, thermal comfort success in commercial buildings is defined as a comfort level that meets the needs of 80% of its occupants. Conventionally, these needs are met by creating a highly predictable and controlled environment through mechanical equipment, such as HVAC.

But thermal comfort depends on far more than just the temperature of the air—it also takes into consideration the environmental factors of mean radiant temperature, relative humidity and air velocity, and the incorporation of highly variable personal factors that include:

  • The amount of clothing being worn
  • A person’s resting metabolic rate
  • Level of physical activity

The theory also takes into account that people’s perceptions of the environment around them changes based on seasonal expectations of temperature and humidity, as well as their ability to control the conditions of their personal space.

While the ASHRAE standard recognizes the role of adaptive factors in establishing thermal comfort, it does not provide specific guidelines for increasing comfort levels in new buildings. There are measures you can take to increase individualized comfort levels through building design.

  • Increase the movement of air throughout the building
  • Adding more windows that can be opened from the inside and installing ceiling fans or desk fans can increase the flow of air throughout the building, allowing occupants to feel more comfortable in conditions that could otherwise feel too hot. However, since fresh, outdoor air can bring pollen, mold and other environmental irritants indoors, be sure to alternate periods of natural ventilation with energy-efficient cooling and high-efficiency air filters that help control the quality of indoor air.

  • Give occupants more control over their immediate environment
  • By offering more control over the indoor environment, for example, the ability to open windows or adjust a thermostat, occupants will be able to tolerate a wider range of temperature levels.

  • Control humidity levels
  • Humidity plays an important role in thermal comfort. Too much moisture in the air can cause physical discomfort and interfere with air quality. Keep levels balanced with a dehumidifier integrated into the HVAC system, such as the Humiditrol® dehumidification system for rooftop units, which controls humidity levels independent of temperature.

  • Encourage a corporate culture of comfort
  • Suggest that your clients implement a corporate culture that encompasses a whole-building approach to comfort. Asking employees to wear seasonally appropriate clothing and adjust accordingly to their own comfort levels will allow for higher set points during the cooling season, and lower set points during the heating season. Similarly, interior color choices and office furnishings can affect the comfort levels of occupants.

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