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674 CHAPTER 46 I960 Guide Table 3 .... Water Usage for Water-Cooled Equipment Summer Wiriif Temperature, Norma/ Extreme* F Gafloot Per (Hoar] (Too) Summer Water Temperafwe, Normat Extreme* F GoOon* Per (Hour) (Ion] 55 34 75 58 60 39 80 70 65 44 85 88 70 50 continuous fan operation the number of hours of compressor operation should be subtracted from the number of hours in the cooling season to obtain the extra hours of fan opera tion. This value may then be used with the appropriate value of power consumption and power cost for the fan motor only, to find the added power cost for continuous fan operation and the result should then be added to the power cost during compressor operation. For water-cooled condenser applications the water cost, as determined from the operating hours, water rate, and manu facturer's data on equipment water usage, is added to the power cost to obtain the estimated total operating cost. Another method hag been developed "ring cooling degree days above 70 F as a criterion but tabulated values of cooling degree days for various localities are not available.' Approxi mate values can be obtained from degree-day maps."- n The daily range of temperatures for various localities is also required with this method." It is important that the method 'used in estimating operating cost be consistent with the method used in calculating the heat gain of the structure. EFFECTS ON FUTURE HOUSE DESIGN Air conditioning, like automatic heating, has brought about improved practice in residential construction, particularly in those regions where cooling is of primary importance. Al though it is true that construction practices which reduce the heating load also reduce the cooling load, there are certain considerations that are unique in their effect upon the cooling load. Special attention should be paid to window orientation and shading. South windows may be shaded by awnings or roof overhangs, but it is not practicable to shade large win dow areas having an east or west orientation except by ex terior solar screening of some type. The use of insulation in the walls and ceiling of the residence will reduce the cooling load appreciably. In addition, attention should be paid to adequate ventilation of the attic. Double-glazed and weather- stripped windows, heat-absorbing glass, planned shade tree locations, and light-colored' exterior wall and roof surfaces, also help to reduce the cooling load. REFERENCES *T. N. Willcox, C. T. Ocrgel, S. G. Reque, C. M. toeLeer, and W. R. Brisken: Analogue computer analysis of residential cooling loads (ASHVE Transactions, Vol. 0, 1954, p. 505). * Application Engineering Standard for Year-Round Resi dential Air Conditioning (Air Conditioning and Refrigeration Institute, 610-56. * Summer Air Conditioning (National Warm Air Heating and Air Conditioning Association, Manual No. 11, 1955). 4 Cooling Load Calculation Guide No. C-30 (Institute of Boiler ana Radiator Manufactures). *M. E. Childs, R. W. Rooee, H. T. Gilkey, and S. Konzo: Comparative Performances of Two Warm Air Perimeter Sys tems and Three Convection Systems (University of Illinois, Engineering Experiment Station Bulletin 403, 1942). 'A. P. Kratf, M. K. Fahnestock, and S. Konzo: Investiga tion of Summer Cooling in the Warm Air Heating Research Residence (University of Illinois, Engineering Experiment Sta tion Bulletin 290, 1930). 'R. A. Gonzalez: How power usage varies for summer air conditioning of identical residences (Refrigerating Engineering, January 1957, p. 35). *T. N. Willcox: Annual utility cost operating residential cooling system (Fuel Oil News, June 1954). S. F. Gilman, L. A. Hall, and E. P. Palmatier: The oper ating cost of residential cooling equipment (ASHVE Transac tions, Vol. 60, 1954, p. 525). n "S. S. Visher: Relative cooling requirements for American homes (The Scientific Monthly, November 1945, p. 211). . u E. N. Kemler and S. Oglesby: Heat Pump Applications (McGraw-Hill Book Co., New York, 1950, 1st ed., p. 246). "Summer Weather Data (The Martey Co., Kansas City, Kansas, 1939, Chapter VI). . BIBLIOGRAPHY H. T. Gilkey, D. R. Bahnfleth, and R. W. Rooee: Cooling a small residence with a two-horsepower mechanical condensing unit (ASHVE Transactions, Vol. 60,1954, p. 271). Continuous Air Circulation (National Warm Air Heating and Air Conditioning Association, Manual No. 6, 1955). D. R. Bahnfleth, C. F. Chen, and H. T. Gilkey: Cooling a small residence using a perimeter-loop duct system (ASHVE Transactions, Vol. 59,1953, p. 283). H. E. Straub and S. F. Gilman: Room air distribution research for year-round air conditioning. Part II--Supply out lets at three floor locations (ASHVE Transactions, Vol. 60, 1954, p. 249). R. A. Gonzales: How and where to install air cooled condens ers (Heating and Air Conditioning Contractor, May 1956, p. 44). Residential Air Conditioning--a Summary Report of the Austin Village Project (National Association of Home Builders, May 1956). CHAPTER 47 SCHOOL SYSTEMS General Considerations, Criteria for Design, Design Considerations, Preliminary Design, Mechanical Plaid Design, Types of Ventilating Systems, Types of Heating and Cooling Systems, Automatic Control, Operation, Maintenance HE purpose of this chapter is to outline the factors af A.lsn have different and varying ventilation temperature Tfecting the selection of heating, ventilating, and air- requirements. Many schools include multipurpose rooms conditioning systems for schools. The components of these serving as auditoriums, gymnasiums, and community centers. systems are the same as used for other types of buildings. The normal periods of operation are five days per week Their combination in school systems, in some cases, will be for nine months per year, with complete shutdown during the same as for other buildings, but may differ considerably week-ends and vacation periods. Where schools are not op in others in order to provide optimum conditions for effec erated during the summer months school boards may not tive school work and to comply with local regulations. find complete air conditioning justified except in southern GENERAL CONSIDERATIONS climates. Systems for administration areas, gymnasiums, auditoriums, and multipurpose rooms, suitable for commu The proper criteria for heating, ventilating, and in many nity activities, will often be operated at times when the sys instflm*>R air conditioning, of school buildings, particularly tems for classrooms and other general educational areas may classrooms, are often not recognized fully. not be in operation. Many designers and school administrators approach the Automatic control of temperature and system equipment problem as one of heating, whereas analysis may show is a necessity if comfortable conditions are to be obtained. that cooling, rather than heating, is required during periods Proper application of controls may return the cost of in of occupancy throughout most of the year. Ventilation vestment by savings in labor and fuel within a year or two. systems are frequently designed to supply, .air at 72 F for Frequently, insufficient consideration is given to provi ventilation. Generally, they should be designed to supply air sions for access and maintenance with the idea that the at 55 F to GO F to provide all cooling possible during occu mechanical system is a fixed part of the structure and should pancy. last as long as the structure, without attention. With regard to ventilation, code requirements vary from School boards are often criticized by their constituents for acceptance of natural ventilation, such as obtained by spending large sums of money for so-called luxury items, with opening of windows, to a requirement of mechanical supply the result that economy in construction and design becomes of a specified quantity of air, which sometimes is as high a paramount factor. This often tends to limit the mechani as 30 cfm of outdoor air per occupant. The variations in cal equipment selected below that required to maintain a quantity of outdoor air specified usually are due to the lack proper indoor atmospheric environment. However, many of a uniform understanding of the reason for ventilation. Re schools in areas having warm spring and fall climates are now search has established that ventilation air is required, not being designed to include air conditioning, at least in spaces to replace oxygen for breathing, but to dilute body odors, of densest occupancy and greatest use. which become intensified in densely occupied spaces. A dis cussion of air requirements trill be found in Chapter 6. CRITERIA FOR DESIGN When planning for introduction of ventilation air into Comfort, cleanliness, reduction of odors, maintenance of rooms, careful consideration should be given to air dis alertness, compliance with codes, installation cost, ease and tribution and circulation within the occupied space, as well cost of upkeep, cost of operation, and adaptability to con as the natural convection and temperature effects. trol in relation to periods of use as related to outdoor con Elementary schools of recent design are generally single ditions are the chief criteria by which a design for main story buildings, often placed at considerable distance from tenance of indoor environment for learning may be judged. each other. Windows 7 ft or more in height and extending Comfort, which may be defined as freedom from strain in the full length of one or more classroom walls, .often raise accommodating to the environment, is a necessity. Uniform great problems in maintenance of an optimum indoor at ity of air movement and temperature within the space is re mospheric environment and in prevention of eye strain. quired to provide a comfortable environment. Fundamentals Secondary or high schools are more often two- and three- in this respect are discussed in Chapter 6, Physiological story structures but present problems only slightly less Principles, and Chapter 20, Air Distribution. Intermittent severe than grade schools. Separation of school buddings currents of air or air movement at varying velocities may results in increased cost of the mechanical systems. result in discomfort. Similarly, variations in temperature A further characteristic of school buildings is a wide may contribute more to discomfort than uniform main variation in use and occupancy. Classrooms (the largest tenance of slightly higher or lower temperatures. single group of occupancies), lecture rooms, assembly rooms, Odors, while they may not be deleterious to health, are auditoriums, and other similar areas have uniformly dense disagreeable and distracting, even to the point of being nau occupancies. Gymnasiums, cafeterias, laboratories, shops, seating. Natural odors present in occupied spaces are body and similar functional spaces have lighter occupancies and odors. Odors should not be perceptible in schoolrooms. 675