Document mpXpRyrJnRR3n8GQZmRqNy1yB

212 CHAPTER 12__________ 1948 Guide -Note.--Both summer and winter comfort zones apply to inhabitants of the United States onJy. Applica tion of winter comfort line is further limited to rooms heated by central station systems of the convection type. The line does not apply to rooms heated by radiant methods. Application of summer comfort line is limited to homes, offices and the like, where the occupants become fully adapted to the artificial air con ditions. The linedoes not apply to theaters, department stores, and the like where the exposure is less than 3 hours. The optimum summer comfort line shown pertains to Pittsburgh and to other dties in the northern portion of the United States and Southern Canada, and at elevations not in excess of 1000 ft above sea level. An increase of one deg CT should be made approximately per 5 deg reduction in north latitude. Tests10 made at the A.S.H.V.E. Research Laboratory in very hot conditions with subjects doing light work were in very close agreement with the effective temperature chart. Other work16 under similar environmental conditions, but with subjects walking 3 mph and carrying 20 lb packs indicated that the effective temperature lines should be more nearly horizontal. It therefore appears that the slope of the ET lines may vary: depending upon the rate of work being performed. Fig. 10, shows the A.S.H.V.E. Comfort Chart1S. The summer and winter comfort zones indicate conditions under which 50 per cent or more of the people are comfortable. The summer comfort zone extends from 66 ET to. 75 ET; a maximum of 98 per cent of the subjects were com- iPhysiological Principles 213 fortable at 71 :ET. The winter, comfort zone extends from 63 ET to .71 ET with a maximum of 97. per cent, feeling comfortable .at.66 ET. The 71 ET and'66 ET lines are referred to, respectively, as the summer and winter comfort.lines. : The comfort zones and lines as shown' in Fig. 10 are based on research prior to 1932. Later studies 19 by the A.S.H.V.E. Research Laboratory . * indicate a desirable winter effective temperature of 67 deg, arid this finding is confirmed by current practice. The shape of the curve showing the per cent of subjects comfortable in winter also j ustifies this conclusion, since a drop of only one degree from the 66 ET fine.seriously reduced the percentage of subjects comfortable. Systems should be designed to assure comfort for the maximum possible number . The comfort zones in Fig. 10 are located between the 30 per cent and 70 per cent relative humidity lines. There is some evidence that the zones could be extended somewhat beyond these limitations. Radiation from occupants to room surfaces and between the occupants has an important bearing on the feeling of warmth and may alter to some measurable degree the optimum conditions for comfort previously in- v dicated. Since the mean radiant temperature of a space is affected by X^cold walls and windows, as well as by the warm surfaces of heating units placed within the room or imbedded in the walls, these factors must be compensated. Likewise, in densely occupied spaces, such as classrooms, theaters and auditoriums, temperatures somewhat lower than those indicated by the comfort line may be desirable because of counter radiation between the bodies of occupants in close proximity to each other. Such radiation will also elevate the mean radiant temperature of the room. Many field studies 19 have been made to determine the optimum indoor effective temperature for both winter and summer in several metropolitan districts of the United States and Canada in cooperation with the manage ments of offices employing large numbers of workers (Fig. 11)-.- On the whole women of all age groups studied prefer an effective temperature for comfort 1.0 deg higher than men. All men and women.over 40. years of age prefer a temperature. 1 deg ET higher than that, desired by, persons below this age. The persons serving in all of these studies were repre sentative of office workers dressed for air conditioned spaces in the summer season and engaged in the customary office activity. On the basis of present kriowledge, for different geographical regions and age groups, the most popular temperature varies from a low of 66 deg ET in winter.to a high of 73 deg ET in summer. The spread for summer comfort is 69 to 73 deg ET. The A.S.H.V.E. Technical Advisory Committee' on Sensations, of Comfort, ascribes a spread of 3 deg in the optimum effective temperature for summer cooling to geographical location. However, it should be recognized that variations in sensation of comfort among individuals may be greater for any given location, as shown in Fig. 11, than variations due to a difference in geographical location. The available information in dicates that changes in weather conditions over a period of a few-, days do not alter the optimum indoor temperature. In general, people experiencing low or high temperatures over an extended period of time become acclimated to lower or higher indoor temperatures respectively. Sudden chilling (shock) of persons entering a cooled and air conditioned space during the summer months, may at times be important. It is due to the rapid evaporation of perspiration which accumulated on the skin