Document 71Q2op3mjgxr43mgZ0x2JQ08g

68 CHAPTER 6 1959 Guide physiological Principles 69 variations in sensation of comfort among individuals may be greater for any given location than variations due to a differ ence in geographical location. The available information indi cates that changes in weather conditions over a period of a few days do hot alter toe optimum indoor temperature. Laboratory studies of Keeton and others,8 and years of practical field experience show that the adjustments in the heat'regulatory mechanisms of healthy people on entering and leaving air-conditioned spaces are prompt, easy, and safe. Sudden sensation of coolness on entering a cooled room from the hot street.is asociated with sweat on the skin and in the clothing.' Several minutes are required for the skin tempera ture to'fall and the free moisture to disappear.'Even am bulatory heart patients endure such changes with ease. The use of the word shock to describe any part of these adjust ments is unwarranted. Upon leaving an air-cooled space and re-entering a hot atmosphere,- sudden wanning occurs. Experiments at the ASHAE Research Laboratory8 and elsewhere" indicated no demonstrable harm to a healthy individual. Adaptation oc curred as soon as normal perspiration was established. Mild exercise shortened the adaptation time. Most healthy, sedentary, and slightly active men and women, normally clothed and in uniform environments, with air velocities of the order of 25 fpm, are thermally com fortable the year around when the dry-bulb air temperature is in the range 73 to 77 F and the relative humidity is in the range of 25 to 60 percent.8 Satisfactory comfort conditions for persons at work8 vary, depending upon the rate of work and the amount of clothing worn. In general, the greater the degree of activity, the lower the effective temperature necessary for comfort. Clothing has been evaluated for its overall insulation effects by a physical unit, the do which equals 0.116 C deg per (kilogram calorie) (square meter) (hour).8 Yaglou" criticizes the concept of overall insulation, and points out that different parts of the body require different amounts of insulation. The literature on effects of clothing is difficult to coordinate at the present time, as much of it is still in military service reports which, are yet to be published and amplified. For prematurely boro infants, the optimum temperature varies from 100 to 75 F, depending upon the stage of develop ment. The optimum relative humidity for these infants is placed at 65 percent.8 No data are yet available on the op- 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 op timum conditions for comfort previously indicated. Since the mean radiant temperature of a space is affected by cold walls and windows, as well as by the warm surfaces of hating units-placed within the room or embedded in the walls, these factors must be compensated. Likewise, in densely occupied spaces, such as classrooms, theaters, and auditoriums, tem peratures somewhat lower than those indicated by the com fort line may be desirable because of counter-radiation be tween the bodies of occupants in close proximity to each other. Such radiation will also elevate the m***" radiant temperature of the room. Many field studies8 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 managements of offices employing large numbers of workers (Fig. 11). On the whole, women of all age groups studied prefer an effective tempera ture 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 per sons serving in all of these studies were representative of office workers dressed for air-conditioned spaces in the sum mer season, and engaged in the customary office activity. On the hasis of present knowledge, for different geographi cal regions and age groups, the most popular temperature varies from a low of 66 ET in winter to a high of 73 ET in summer. The spread for summer comfort is 69 to 73 ET. A spread of 3 deg in the optimum effective temperature for summer cooling is ascribed to geographical location. However, A. Clothing: Customary indoor dotting. B. Activity: Sedenioiy or fight awsnfar work. C Hooting Method*.- Conrochoo type, Le., worm ait, direct deom or tot wafer radiators, plenum qdesu. Fig. 9 .... Effective Temperature Chart Showing Normal Scale of Effective Temperature, Applicable to Inhabitants of the United States Under Following Conditions: r\