Document JN8gL3mrZ7Bmm5EQE59qoqLeO

246 CHAPTER 12 '1953 Guide effective temperature for sedentary persons, as determined at the A.S.H.V.E. Research Laboratory, is 67-68 ET. As explained in Chapter 6 for so-called still air conditions, a relative humidity of approximately 50 percent is required to produce an effective temperature of 68 ET when the dry-bulb temperature is 72.5 F. However, even where provision is made for artificial humidification, the relative humidity is seldom maintained higher than 40 percent during the ex- F ig . 1. sotherm s of W in t e r O utdoor D e s ig n T e m p e r a tu r eI Heating Load 247 tremely cold weather, arid where no provision is made for humidification, the relative humidity may be 20 percent or less. Consequently, in using the figures listed in Table 2, consideration should be given to' the actual relative humidity-'to be maintained, if provision is to be made for humidifi cation. If no humidification is to be provided, the higher temperatures may not even produce comfort on cold days; if huiiidity is to be main tained at 50 percent, the lower temperatures will apply. In rooms having large glass areas, when surt is not shining, or in rooms with walls having a high transmission coefficient, the lowered surface tem perature will cause a feeling of coolness even though the air temperature in the room is at of above the temperatures indicated in the table. In rooms of this character, it is desirable to design for even higher temperatures than, those listed, unless a compensating higher temperature surface is installed to offset the low temperature surfaces. Table 2. Winter Inside Dry-Bulb Temperatures Usually Specified* Type of Building Deg F Type of Building Deg F Schools-- 68-72 Toilets and baths............................................... Wardrobe and locker rooms........................... Dining and lunch rooms................................. Playrooms.............................................................. 70 65-68 66 65-70 60-65 75 Hospitals-- Private rooms....................................................... Private rooms (surgical).................................. 70-72 70-80 Wards.................................... Toilets............................................. 68 66 68 70-80 Theaters-- 68 Hotels-- Dining rooms...................................................... Kitchens and laundries.................................. Toilets and service rooms............................. 70 66 65-68 68 Houes........................................................................................ Stores....................................................................................... 70-72 65-68 120 110 60-65 Paint Shops........................................................................ 80 * The most comfortable dry-bulb temperature to be maintained depends on the relative humidity and air motion. These three factors considered together constitute what is termed the effective temperature. (See Chapter 6.) When relative humidity is not controlled separately, optimum dry-bulb temperature for comfort will be slightly higher than shown in Table 2. The inside temperatures specified in Table 2 may be used for panel heated spaces as well as for spaces heated by warm air, radiators, or con vectors. It is true that warm panel surfaces tend to produce a comfortable environment at a lower room air temperature than when warm panels are not present, but field experience in the United States has indicated that actual reductions in air temperature are slight in operatiori. Temperature at Proper Level. In making the actual heat loss compu tations, however, for the various rooms in a building it is often necessary to modify the temperatures given in Table 2 so that the air temperature at the proper level will be used. By air temperature at the proper level is meant, in the case of walls, the air temperature at the mean height be tween floor and ceiling; in the case of glass, the air temperature at the mean height of the glass; in the case of roof or ceiling, the air temperature at the mean height of the roof or ceiling above the floor of the heated room; and in the case of floors, the air temperature at the floor level. Temperature at Ceiling. The air temperature at the ceiling is generally higher than at the breathing level due to stratification of air resulting from the tendency of the warmer or less dense air to rise. An allowance for this fact should be made in calculating ceiling heat losses, particularly in the