3.

4.

5.

6.

air temperature (dry-bulb)

mean radiant temperature

relative air velocity

water vapor pressure in ambient air

The basis of his analysis is the so-called general comfort equation which defines all combinations of the variables which will create thermal comfort. The importance of such equations lies in the fact that once proven valid, they can be used very quickly to determine the effect of changing any one of the six variables, something considerably more difficult by experimentation. His comfort equation was modified to define a variable predicted mean vote (PMV) and a scale similar to the one used in the Kansas State Studies was chosen:

The numerical values, however, are lower by 4. A scale is thus obtained which is easier to remember, as it is symmetrical around the zero point, so that a positive value corresponds to the warm side and a negative value to the cold side of neutral. In figure 22 the results are compared with the experimentally determined KSU comfort vote. As can be seen the agreement is

excellent for the comfort line (KSU = 0, PMV = 4) but not so

good for environmental conditions outside of the comfort range.

As mentioned previously, an advantage of an analytical model such as this is the capability of observing the effect of one of the six controllable parameters without having to conduct extensive experiments. For example, it may be unreal

istic to assume that during the summer subjects will wear the standard 0.6 clo clothing ensemble.

Certainly in hot weather

people would be more inclined to wear lighter clothing such as shorts and an open neck shirt with short sleeves. Data for this type of clothing ensemble (clo = 0.25) is compared with the standard Kansas State clothing ensemble in figure 23. The comparison shows what one might intuitively expect. For lighter clothing, subjects would report comfort at 4 or 5°F warmer temperature. It would be expected that they would vote cool at a somewhat higher temperature also (approximately 6°F). However, both subjects would vote hot at approximately the same temperature and relative humidity.

Consequently for the sake of energy conservation, one can justify higher temperature limits in the summer if lighter clothing is worn and lower temperature limits in the winter if more than the standard amount of clothing is worn. Figure 24 has been included here to show precisely by use of Fanger's analysis, how the "acceptable room temperature" can be

varied by changing the clothing.