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What is Thermal Comfort?

Thermal comfort is most easily explained as a feeling of personal satisfaction with the thermal environment, in other words, feeling neither cold nor hot.

Thermal comfort, also called human comfort, is an individual, subjective assessment and therefore can be difficult to measure. However, it plays an essential role in the design and maintenance of any facility with live occupants. For builders’ purposes, thermal comfort is defined by international comfort standards, the most important of which are ANSI/ASHRAE Standard 55, ISO 7730 and EN-15251.

ASHRAE Standard 55 establishes the ranges of indoor environmental conditions that are acceptable to achieve thermal comfort. This standard has been regularly updated since first published in 1966, with the latest revision in 2013. It estimates that for thermal comfort purposes, temperature could range from between approximately 67°F and 82°F (19.5°C and 27.8°C), though thermal comfort is determined by a combination of six factors:

  • Metabolic rate: The energy generated by the body — in other words, activity level
  • Clothing insulation: The level of insulation provided by the clothing an individual is wearing
  • Air temperature: The temperature of the air surrounding the occupant
  • Radiant temperature: The weighted average of all the temperatures from surfaces surrounding an occupant
  • Air speed: Rate of air movement given distance over time
  • Humidity: Moisture content in the air

In addition to HVAC systems, ceiling fans are known to play a big role in thermal comfort. Big Ass Fans® improve thermal comfort by providing steady air circulation. Though air movement does not lower room temperature, it creates a cooling effect of up to 10°F (6°C) when the breeze passes over the skin. And when the furnace is on, the fans slowly push the warm air that collects at the ceiling down without creating a draft, resulting in a more even temperature throughout a space.

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