When we are talking about Thermal comfort, it is most easily explained as a feeling of personal satisfaction with the environment around an individual, in other words, feeling neither cold nor hot.
Thermal comfort is an individual, subjective assessment and therefore can be difficult to measure. However, it plays an essential role in the day-to-day quality of life for nearly every living organism on the planet. In our case, humans and what we can and cannot do depending on the thermal environment around us.
This is crucial when it comes to the design and maintenance of any building that is occupied with people. Because of the subjective nature of the 'feeling' and different individuals tolerances, thermal comfort has been defined by an international comfort standard. The most relevant and important 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 by the researchers at The Center for the Built Environment Berkeley who have a strong belief about how the future of thermal comfort will look.
The standards estimate that for thermal comfort purposes, the temperature could range from between approximately 67°F and 82°F, and lists out the 6 main factors that determine thermal comfort:
- Metabolic rate: The energy generated by the body — or in other terms, our internal and external activity level
- Clothing insulation: The level of insulation provided by the clothing an individual chooses to wear
- Air temperature: The temperature of the air surrounding an individual
- Surface temperature: The weighted average of all the temperatures from surfaces surrounding an occupant
- Air Velocity: Rate of air movement given distance over time, like fans and open windows
- Humidity: Moisture content in the air