Document yra6QbD2GNX3zpbK0n8GvdO96

122 Chapter 6 1945 Guide Temperatures for other cities may. be obtained from local weather bureau records1. The design temperatures shown in Fig. 1 are generally repre sentative of the practice in various sections of the United States, although in some instances, due to local conditions of altitude or exposure, the design temperatures may vary somewhat from those indicated. The A.S.H.V.E. Technical Advisory Committee on Weather Design Conditions has recommended the adoption for heating of an outside design temperature which is equalled or exceeded during 97M per cent of the hours in December, January, February, and March, but the work of compiling the temperatures for the various localities is not yet com pleted. INSIDE TEMPERATURES The inside air temperature which must be maintained within a building is understood to be the dry-bulb temperature at the breathing line, 5 ft'. Table 2. Winter Inside Dry-Bulb Temperatures Usually. Specified* Type of Building Deg F Type of Building . Deg F Schools-- Toilets and baths.---------- -....... Wardrobe and locker rooms.... Dining and lunch rooms ....... Natatoriums- .......... .............. 70-72 68-72 55-65 70 65-68 66 65-70 6(K65 75 Hospitals-- Private rooms......... .................... Operating rooms............... -....... Kitchens and laundries............ Bathrooms.... ............................... 70-72 70-80 70-95 68 66 68 70-80 Theaters-- Toilets.- ................................ 68-72 68-72 68 Hotels-- Bedrooms arid baths.-- __:...... Dining rooms._________________ Ballrooms._______________ 1........ Toilets and service rooms......... 70 70 66 65-68 68. Homes.-- . . . ....... ................ Stores.. - ............................... Public buildings.___ ,__________ Warm air baths. ................... Steam baths_____ !_______ ___ --. Factories and machine shops.. Foundries and boiler shops.... Paint shops._______:------------------- 70-72 65-68 68-72 120 110 60-65 50^60 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 2.) above the floor, or the 30-in. line, and not less than 3 ft from the outside walls. Inside air temperatures, usually- specified, vary in accordance with the use to which the building is to be put and Table 2 presents values which conform to good practice. The proper dry-bulb temperature, to be maintained depends upon the relative humidity and air motion, as explained in Chapter 2. In other words, a person may feel warm or cool at the same dry-bulb temperature, depending on the relative humidity and air motion. The optimum winter effective temperature for sedentary persons, as determined at the A.S.H.V.E. Research Laboratory, is 66 deg. As explained in Chapter 2 for so-called still air conditions, a relative humidity of approximately.50 per cent is required to produce an effective `Carnegie Institute of Technology. Bulletin, An Analysis of Winter Temperatures for One Hundred and Twenty Cities, by Clark M. Humphreys. ' Heating Load 123 temperature of 66 deg when the dry-bulb temperature is 70 F. However, even where provision is made for artificial humidification, the relative humidity is seldom maintained higher than 40 per cent during the ex tremely cold weather, and where no provision is made for humidification, the relative humidity may be 20 per cent or less. Consequently, in using the figures listed in Table 2, consideration should be given to whether provision is to be made for humidification, and if so, the actual relative humidity to be maintained. 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 case of high ceilings. However, the exact allowance to be made may be somewhat difficult to determine as it depends on many factors, including (1) the type of heating system, (2) ceiling height, and (3) the insideoutside temperature differential. The type of heating system is par, ticularly important as the temperature gradient from floor to breathinglevel to ceiling may depend to a large' extent on whether direct radiation, unit heaters or warm air is used, and in the latter case, whether the circu' lation is by gravity, auxiliary fan- or forced air. Although with properly adjusted air flow the temperature differential with unit heaters can be reduced to a minimum, it is also possible with improper adjustment that the temperature differential will be increased over that which would normally result without mechanical circulation of the air. It would be difficult from present available information to establish rules for determining the temperature difference to use in all cases. However, for residences and other structures having ceiling heights under 10 ft, the comparatively small temperature differential between the breathing level and ceiling may generally be neglected without serious error. For higher ceilings where specific test data are not available, an allowance of approximately 1 per cent per foot of height above the - breathing level may be made for ceiling heights up to 15 ft and approxi mately 1/10 of 1 deg per foot of height above this level. The values in ' Table 3 are calculated on this basis. For direct radiation and gravity warm air systems, the allowance should be increased from 50 pier cent to 100 per cent over those given in Table 3. These rules should, however, be used with considerable discretion. Temperature at Floor Level: According to the University of Illinois Research Residence tests*, the temperature at the floor level ranged from about 2J4 to 6 deg below that at the breathing level, or somewhat greater than the difference between the breathing level and ceiling temperatures. Tests at the University of Wisconsin* indicated a some- ^University. of Illinois Engineering Experiment. Station Bulletin No. 318--Investigation of Oil-Fired rorced Air Furnace Systems in the Research Residence, by A. P. Kratz and S. Konzo. w .!.'S-H.V.E. Research Report No. 1011--Tests of Three Heating Systems in an Industrial Type of Building, by G. L. Larson, D. W. Nelson, and John Jama (A.S.H.V.E. Transactions, Vol. 41,1936, p. 185).