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468 CHAPTER 25 1965 Guide*And Data Boole n F. C. Houghton and Margaret Ingels:ASHVE Research Repoet No. 786--Infiltration tirough plastered and unplastered brick walls (ASHVE Transactions, VoL 33; 1927, p. 377).'G:'L. Larson, D. W. Nelson, and C. Braatz: 'ASHVE Research Re port No. 826--Air infiltration through various types of-.brick wall construction (ASHVE Transactio.ns,Vo1. 35,1929, p. 183). Q. L. Larson, D. W. Nelson, and C. Braats: ASHVEReseabch Report No. 851--Air infiltration through various-types of brick wall construction (ASHVE Transactions, VoL 36, 1930, p. 99). G. L. Larson, D. W. Nelson and C. Braatz: ASHVE Research Report No. 868--Air infiltration through various types of wood frame construction (ASHVE Transactions, VoL 36, 1930, p. 397). - V*. M A. M. Simpson and K.-B. Atkinson: The infiltration problem of multiple entrances (ASHVE' Journal Section, Heating, Piping and Air Conditioning, June 1936, p. 345). A. M. Simpson: Infiltration' characteristics' of entrance doors (Retrigeraitno Engineering, June 1936). w W.1 H. Carrier,- R. E. Cherne' and W. A. Grant: Modem Air Conditioning, .Heating and Ventilating (Pitman Publishing Corporation, - 2nd - Edition, 1950, p. 57). American1 Architect -Time Saver Standrds Series, No. 66: Heat transmission and.in filtration through doors, windows and glass masonry (American Architect and Architecture. VoL 149, No. 2651, Nov. 1936. p. 163). " L. F. Schutrum, N. Ozisik, C. M. Humphrey, and J. T. Baker: Air Infiltration Through Revolving Doors (AsHRAE Trans actions, VoL 67, 1961, p. 488). * < 17 T. C. Min: Engineering Concept and.Design of Controlling Infiltration, and Traffic Through Entrances in .Tall Commercial Buildings (International Conference on H*t.inp Ventilating and' Air Conditioning, London, September 27-October 4, 1961): . . u State Building Construction Code Applicable. to One- and Two-Family Dwellings (New York State Building Code Com mission). M W. C. Randall and'EL W. Conover:. Predetermining aira- tion of industrial buildings (ASHVE Transactions,- VoL 37 1931, p. 605). BIBLIOGRAPHY J. B. Dick: Experimental Studies in Natural Ventilation of Houses - (Department of Scientific and. Industrial Research, Building: Research Station Note No. 180, Gareton, Watford, jTb7 Dick: of ventilation using tracer gas- technique (ASHVE Journal Section, Heating, Piping and Air Conditioning, May 1950, p. 131). . J. B. Dick and D. A. Thomas: Ventilation Research in Occupied ' Houses {Journal of the Institution of Heating and Ventilating Engineers, October. 1951; p.306) \ > C. W.Coblent* and P.- R. Achenbach: Design and per*, formance of a portable infiltration meter (ASHA FI Transac tions, VoL 63, 1957, p. 477). . - ' F. C. Houghton, J. L. Blackshaw; 'and Cori Gutberlet: ASHVE Research Report No. 994--Wind velocities near a building and their, effect on heat loss (ASHVE Transactions, VoL 40, 1934, p. 387). CHAPTER 26 HEATING LOAD General Procecfirre, Design Outdoor Weather Conditions, Indoor Temperatures, Attic Temperatures, Temperatures in Un heated Spaces, Ground Temperatures, Basement Temperatures and Heat Less, Heat Losses from Floor Slabs, Transmission Heat Loss, Infiltration Heat Loss, Selection of Wind Speeds, Auxiliary Heat Sources, Intermittently Heated Buildings, Residence Heat Loss Problems PRIOR to designing a heating system, an estimate must equals or exceeds the amount of natural infiltration that would be made of the maximum probable heat loss of each occur without ventilation, the natural infiltration may be neg lected. room or space to be heated, based on maintaining a selected 9. Tbe sum of the beat losses due to transmission (Item 6) indoor air temperature during periods of design outdoor through the outside walls and glass, as well as through any cold weather conditions. The heat losses may be divided into two groups: (1) the transmission losses or heat transmitted through the confining walls, floor, ceiling, glass, or other surfaces, and (2) the infiltration losses or heat required to floors, ceilings, or roof, plus the heat equivalent (Item 7) of the cold air entering by infiltration, or required to replace mechani cal exhaust, represents the total heat loss equivalent for any building. 10. In buildings that have a reasonably steady internal heat warm outdoor air which leaks in through cracks and crevices,' around .doors and windows, or through open doors and windows, or heat required to warm outdoor air used for venti lation. release of appreciable magnitude from sources other thr the beating system, a computation of this heat release under design conditions should be made for deduction from the total of the heat loses computed in Items 1-9. This is especially important for heating systems of high initial cost or those for which a de mand charge is based on installed capacity. GENERAL PROCEDURE The general procedure for calculating heat losses of a DESIGN OUTDOOR WEATHER CONDITIONS structure is: The ideal solution to the basic problem which confronts the 1. Select the design outdoor weather conditions: tempera ture, wind direction, and wind speed. The data on climatic con designer of a beating system is to design a plant that has a capacity at maximum output just equal to the heating load ditions given in Table 1 will be helpful, but should be used with which develops when the most severe weather conditions for judgment as suggested in the section Design Outdoor Weather Conditions. . 2. Select the indoor air temperature that is to be m.int*nAH - the locality occur. In most cases, economics interferes with the attainment of in each room during the coldest weather. (See Table 2.) this ideal. Studies of weather records show that the most 3. Estimate temperatures in adjacent unheated spaces the attic. (See section, Attic Temperatures.) The attic tempera ture need not be estimated if the combined roof and ceiling co efficient is used. 4. Select or compute the beat transmission coefficients for outside walls and glass, *nd for inside walls, floors, or topfloor ceilings, if these are next to unheated space; include roof if next to heated space. (See Chapter 24. If the design wind speed ifl appreciably different from 15 mph, the appropriate change in the heat transmission coefficients in Tables 5 to 15 of Chapter 24 ' can be found in Table 20 of that chapter.) 5. Determine net area of outside wall, glass, and roof next to heated spaces, as well as any cold walls, floors, or eeilinga next to unhealed space. Such measurements are made from building plans, or from the actual building, ing inside dimensions. severe weather conditions do not repeat themselves every year. If heating systems were designed with adequate capacity for the maximum weather conditions on record, there would be considerable excess capacity during most of the operating life of the system. Recommended design temperatures, together with the range of wind velocities associated with severe cold, are presented in Table 1. All the data are based on detailed records from official weather stations of the U. S. Weather Bureau, U. S. Air Force, U. S. Navy, and Canadian Department of Trans port.1-* With few exceptions, the data were from airport stations, 6. Compute the heat transmission losses for each kind of wall, glass, floor, ceiling, and roof in the building by multiplying thi ht transmission coefficient in each case by tbe area ot the surface in square feet, and the temperature difference between the umIoot and outdoor air. (See Items 1, 2, and 3.) where hourly observations have been made by trained ob servers for a sufficient period of years to permit reasonably accurate definition of the climatic range for each station. Three temperature levels are offered for each station. The Ji un*t values and compute the heat equivalent of tbe infiltration of cold air taking place around outside doors and wmdows. These unit values depend on the kind or width of ?*** wind speed, and the temperature difference between the mdoor and outdoor air; the result expresses the heat required to Median of Extremes is the middle value of the coldest tem perature recorded each year for periods up to 25 or 30 years, and is approximately equal numerically to the Average Annual Minimum published in some previous editions. In the Chapter^)* "*e budding per hour. (See Canadian table, the Average Annual Minimum is the value 8. When positive ventilation using outdoor air is provided hy an air-heating or an air-conditioning unit (see Table 1 of Chapter 7, Table 2 of Chapter 27), theneat required to warm listed. The 99 and 97} percent values represent the tempera tures which equalled or exceeded these proportions of the total hours (2160) in December, January, and February. In ^Jbdoor air to room temperature must be provided by the unit. If mechanical exhaust from the room is provided, in an equal to the outdoor air drawn in by th* unit, the natural infiltration loses must also be provided for.by the unit. u no mechanical exhaust is used, anti the outdoor air supply a normal winter there would be approximately 22 hr at or below the 99 percent value, and approximately 54 hr at or below the 97} percent design value.. The wind data shown'in Column 6 pertain specifically to ,, wpwwbUltr for this ehopter is uncaed to TC 2.1, Load velocities which occur .coincident with periods of extreme Data and Proeodaics; and TORS, Weather -Data and be*i*n- - ' {Text continued on p. 477) 469