LO-2281 (RP 118) -- The Revised Modal Comfort Envelope PDF

A thermal sensation has been defined as "a conscious experience resulting from exposure to a class of variables making up the thermal environment;"l these variables include the dry-bulb temp, water vapor pressure (relative humidity), mean radiant temp and air velocity. In what is probably the most comprehensive study of the thermal sensation to date, Rohles and Nevins2 exposed 800 men and 800 women in groups of 10 subjects each to '20 dry bulb temps (60 to 98F in increments of 2F) at each of 8 relative humidities (15, 25, 35, 45, 55, 65, 75, and 85%) for 3 hours. Other factors of the thermal environment were kept constant: the mean radiant temp was equal to the air temp and the air velocity was less than 50 ft/min. Activity level of the subiects and clothing, two variables which contribute to the adaptation of the subjects to the thermal environment, were also the same for all subjects. The activity was sedentary and all participants were uniformly dressed in an ensemble having an insulative value of 0.6 clo. The thermal sensations were reported after one hour and every half hour thereafter on a seven-point scale in which 7 =hot; 6 = warm; 5 =slightly warm; 4 =comfortable; 3 =slightly cool; 2 = cool; and 1 = cold.

The results of these 160 tests showed that the thermal sensation undergoes sensory adaptation which is not unlike other sensory responses, and approximately 1.5 hours is required for men to adapt to a change in their thermal environment compared to a much faster time for women. In addition, the results demonstrated that temperature RH. Rohles, Jr. is Professor and Associate Director, Institute for Environmental Research, Kansas State University, Manhattan KS. This paper was prepared for presentation at the ASHRAE Spring Conference, Regina, Saskatchewan, Canada, May 16-18, 1973. The research project was sponsored by TC 2.1 (Physiology & Human Environment). 52 exerts an influence in how men feel almost seven times that of relative hl.lmidity, whereas for women temperature exerts 9 times the influence of relative humidity on their thermal sensation. When these results are considered in light of the two parameters of the thermal environment under study, namely, temp and relative humidity, the question immediately arises concerning the effecb of the remaining variables of the thermal environment. And, in fact, to examine these factors in any way like in the study described above is prohibitive both from the standpoint of time and money (each of the 1600 subjects was paid five dollars $5.00).