Thermal comfort

Thermal comfort

Human thermal comfort is defined by ASHRAE as the state of mind that expresses satisfaction with the surrounding environment (ASHRAE Standard 55). Maintaining thermal comfort for occupants of buildings or other enclosures is one of the important goals of HVAC design engineers. Thermal comfort is affected by heat conduction, convection, radiation, and evaporative heat loss. Thermal comfort is maintained when the heat generated by human metabolism is allowed to dissipate, thus maintaining thermal equilibrium with the surroundings. Any heat gain or loss beyond this generates a sensation of discomfort. [ [ Welcome To Home Energy Magazine Online ] ] It has been long recognised that the sensation of feeling hot or cold is not just dependent on air temperature alone.

Factors determining thermal comfort

Factors determining thermal comfort include:
* Air temperature
* Mean radiant temperature
* Air movement / velocity (see wind chill factor)
* Relative humidity (see also perspiration)
* Insulative clothing
* Activity levels.

Thermal stress

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. Values are expressed as the Wet Bulb Globe Temperature or Discomfort Index. [] [ [ About the WBGT and Apparent Temperature Indices ] ]

Operative temperature

The ideal standard for thermal comfort can be defined by the operative temperature. This is the average of the air dry-bulb temperature and of the mean radiant temperature at the given place in a room. In addition, there should be low air velocities and no 'drafts', little variation in the radiant temperatures from different directions in the room, humidity within a comfortable range, and air temperatures in a height of 0.1 m above the floor should not be more than 2 °C lower than than the temperature at the place of the occupant's head. The temperatures should also not change too rapidly across neither space nor time.

In addition to environmental conditions, thermal comfort depends on the clothing and activity level of a person. The amount of clothing is measured against a standard amount that is roughly equivalent to a typical business suit, shirt, and undergarments. Activity level is compared to being seated quietly, such as in a classroom.

This standard amount of insulation required to keep a resting person warm in a windless room at 70 °F (21.1 °C) is equal to one Clo. Clo units can be converted to R-value in SI units (K/(W/m²) or RSI) by multiplying Clo by 0.155 (1 Clo = 0.155 RSI). (In imperial units 1 Clo corresponds to an R-value of 0.88 °F ft²hr/Btu.)


These factors were explored experimentally in the 1970s. Many of these studies led to the development and refinement of ASHRAE Standard 55 and were performed at Kansas State University by Ole Fanger and others. Perceived comfort was found to be a complex interaction of these variables. It was found that the majority of individuals would be satisfied by an ideal set of values. As the range of values continued to deviate from ideal, increasingly fewer people were satisfied. This observation could be expressed statistically as the % of individual who expressed satisfaction by "comfort conditions" and the "predicted mean vote" (PMV)

ee also

* P. Ole Fanger
* Room air distribution
* Psychrometrics
* Air conditioning
* Building insulation
* Mahoney tables


* "Thermal Comfort", P. O. Fanger, McGraw-Hill, New York, 1970.
* Thermal Comfort chapter, Fundamentals volume of the "ASHRAE Handbook", ASHRAE, Inc., Atlanta, GA, 2005.

External links

* [ Determination Of Thermal Comfort Temperature]

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Comfort (disambiguation) — Comfort may refer to: Comfort (album), by the rock group Failure Comfort (fabric softener) Comfort Air, German airline Comfort food Comfort noise, artificial background noise used in radio and wireless communications to fill the silent time in a… …   Wikipedia

  • Thermal mass — Thermal mass, in the most general sense, is any material that has the capacity to store heat. The following discussion pertains to its functional application in ecologically sustainable building construction. When used correctly, it can… …   Wikipedia

  • Comfort zone (disambiguation) — Comfort zone may refer to: Comfort zone (also Comfort Zone Theory), a behavioural state within which a person operates in an anxiety neutral condition Comfort Zone, an album by the Canadian punk band Sector Seven Comfort zone (astronomy) (CZ, or… …   Wikipedia

  • Thermal bridge — Temperature distribution in a thermal bridge A thermal bridge, also called a cold bridge,[1] is a fundamental of heat transfer where a penetration of the insulation layer by a highly conductive or noninsulating material takes place in the… …   Wikipedia

  • Thermal insulation — The term thermal insulation can refer to materials used to reduce the rate of heat transfer, or the methods and processes used to reduce heat transfer.Heat energy can be transferred by conduction, convection, radiation or when undergoing a phase… …   Wikipedia

  • Thermal (energy) Storage —   A technology that lowers the amount of electricity needed for comfort conditioning during utility peak load periods. A buildings thermal energy storage system might, for example, use off peak power to make ice or to chill water at night, later… …   Energy terms

  • Human Thermal Environments — is a branch of the discipline Ergonomics, concerned with the thermal comfort (i.e. whether a person feels too cold, hot, sticky etc.) of human beings in any, but especially in their working environment.Convective, conductive, radiative and… …   Wikipedia

  • Richmond Pamukkale Thermal Hotel (Pamukkale) — Richmond Pamukkale Thermal Hotel country: Turkey, city: Pamukkale (Pamukkale) Richmond Pamukkale Thermal Hotel Location Located in the city of Pamukkale, the Richmond Pamukkale Thermal Hotel unites the home comfort and provides you with a… …   International hotels

  • Danubius Thermal Hotel Sarvar-Bukfurdo (Bukfurdo) — Danubius Thermal Hotel Sarvar Bukfurdo country: Hungary, city: Bukfurdo (Sarvar) Danubius Thermal Hotel Sarvar Bukfurdo The Danubius Thermal Hotel Sarvar Bukfurdo is located in the middle of a botanical garden and is surrounded by hundred years… …   International hotels

  • Colossae Thermal Spa Hotel Pamukkale (Pamukkale) — Colossae Thermal Spa Hotel Pamukkale country: Turkey, city: Pamukkale (City) Colossae Thermal Spa Hotel Pamukkale Location Colossae Thermal Spa Hotel Pamukkale is located at the town of Karahayit, which is a sub administrative unit of the city of …   International hotels