Thermal comfort

The thermal comfort of a person depends on many conditions. The human body, considered as a thermodynamic system, produces mechanical work and low temperature heat, using food (fuel) and oxygen as input. In healthy conditions, the internal body temperature must be restricted within a very narrow range at about 37°C, otherwise the functionality of important organs like liver, spleen, etc., may be severely damaged. In order to achieve this goal, the rate of heat generation by the body must be equal to the rate of heat loss from it. The job of the human thermo-regulatory system is to control the heat balance. Carrying away of heat is mostly done by the skin by evaporating water (water vapor migration and transpiration), as well as by thermal conduction, convection and radiation. If it is difficult or impossible for the body to give away the surplus heat, a person feels uneasy and the climate is estimated as sultry or hot. If too much heat is carried off, e.g. by higher velocity of wind or room air, the surrounding is felt as to cold.

The tool "Comfort" has been developed to predict the comfort-feeling of a person. Thereby it uses the calculation methods according to the theory described by P.O. Fanger, who has developed a method to represent the thermal comfort depending on the following conditions:

• air temperature of the thermal zone,
  
• mean radiation temperature of the surrounding area,
  
• air velocity,
• air humidity,
• activity of the person,
• clothing of the person.

By fixing these variables the predicted mean vote (PMV) and the predicted percentage of dissatisfied (PPD) can be calculated. Thereby, the predicted mean vote is presented on a scale from -3 (cold) to +3 (hot):

Values outside this rage are graduated as too cold or too hot, respectively.

"Thermal comfort" includes a detailed description of the theory of P.O. Fanger and provides a calculator for PMV and PPD based on the above mentioned variables.

Acknowledgement
The program "Thermal comfort" was developed by Prof. F. Butera, Polytechnicum of Milano, Italia. The IDEA-consortium likes to thank Prof. Butera for the permission to include the program in IDEA.