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American Society of Heating and Ventilating Engineers Guide, 1937 supplied through or near the ceiling. It is better to have the exhaust openings near the floor as larger volumes of warm air are then held in the I bam and there is better temperature control with less likelihood of sudden change in barn temperature. If a cow weighs 1000 lb and produces 3000 Btu of heat per hour, and if a bam for the cow has 600 cu ft of air space with 130 sq ft of, building; exposure, one cow will require 2600 to 3550 cfh of ventilation, depending on the temperature zone in which the bam is located. The permissible heat losses through the structure, based on one cow and depending on the temperature zone, vary between 0.043 and 0.066 Btu per hour per cu ft of barn space, and 0.197 to 0.305 Btu per hour per sq ft of barn exposure. GARAGE VENTILATION8 On account of the hazards resulting from carbon monoxide and other physiologically harmful or combustible gases or vapors in garages, the importance of proper ventilation of these buildings cannot be over emphasized. During the warm months of the year, garages are usually ventilated adequately because the doors and windows are kept open. As cold weather sets in, more and more of the ventilation openings are closed and consequently on extremely cold days the carbon monoxide concentra tion runs high. Many garages can be satisfactorily ventilated by natural means par ticularly during the mild weather when doors and windows can be kept open. However, the A.S.H.V.E. Code for Heating and Ventilating Garages, adopted in 1929 and revised in 1935, states that natural venti lation may be employed for the ventilation- of storage sections where it is practical to maintain open windows, or other openings at all times. The code specifies that such openings shall be distributed as uniformly as pos sible in at least two outside walls, and that the total area of such openings shall be equivalent to at least 5 per cent of the floor area. The code further states that where it is impractical to operate such a system of natural ventilation, a mechanical system shall be used which shall provide for either the supply of 1 cu ft of air per minute from out-of-doors for each square foot of floor area, or for removing the same amount and discharging it to the outside as a means of flushing the garage. Research Research on garage ventilation undertaken by the A.S.H.V.E. Com mittee on Research at Washington University, St. Louis, Mo., and at the Code for Heating and Ventilating Garages (A.S.H.V.E. Transactions, Vol. 35, 1929), (A.S.H.V.E. Reprint, January, 1935). Airation Study of Garages, by W. C. Randall and L. W. Leonhard (A.S.H.V.E. Transactions, Vol. 36, 1930). Carbon Monoxide Concentration in Garages, by A. S. Langsdorf and R. R. Tucker (A.S.H.V.E. Trans actions, Vol. 36, 1930). Carbon Monoxide Distribution in Relation to the Ventilation of an Underground Ramp Garage, by F. C. Houghten and Paul McDermott (A.S.H.V.E. Transactions, Vol. 38. 1932). Carbon Monoxide Distribution in Relation to the Ventilation of a One-Floor Garage, by F. C. Houghten and Paul McDermott (A.S.H.V.E. Transactions, Vol. 38, 1932). Carbon Monoxide Distribution in Relation to the Heating and Ventilation of a One-Floor Garage, by F. C. Houghten and Paul McDermott (A.S.H.V.E. Transactions. Vol. 39, 1933). Carbon Monoxide Surveys of Two Garages, by A. H. Sluss, E. K. Campbell and Louis M. Farber (A.S.H.V.E. Transactions, Vol. 40. 1934). 96 . Chapter 4--Natural Ventilation . nf Kansas, Lawrence, Kans., in cooperation with the A.S.H. v'p^Research Laboratory, and at the A.S.H.V.E. Research Laboratory has resulted in authoritative papers on the subject. Some of the conclusions from work at the Laboratory are listed below: n ward ventilation results in a lower concentration of carbon monoxide at the V,- line and a lower temperature above the breathing line than does downward breathing i same rate of carbon monoxide production, air change and the same temperature at the 30-in. level. 2 A lower rate of air change and a smaller, heating load are required with upward than with downward ventilation. ,, . e average case upward ventilation results in a lower concentration of carbon d vide in the occupied portion of a garage than is had with complete mixing of the ""h^st eases and the air supplied. However, the variations in concentration from . a.ur; "oint together with the possible failure of the advantages of upward ventilation toacerue suggest the basing of garage ventilation on complete mixing and an air change sufficient'to 2fjute the exhaust gases to the allowable concentration of carbon monoxide. 4 The rate of carbon monoxide production by an idling car is shown to vary from 25 to 50 cfh, with an average rate of 35 cfh. 5 An air change of 350,000 cfh per idling car is required to keep the carbon monoxide concentration down to one part in 10,000 parts of air. PROBLEMS IN PRACTICE 1 What factors may make the adoption of a system of ventilation depending upon wind movement inadvisable in new construction? a. Variation in direction of wind. b. Variation in wind velocity. c. Inability to clean incoming air. d. Inability to control location, size and shape of buildings on adjacent property. e. Unsatisfactory warming of incoming air during cold weather. 2 9 a. What factors are important in the location and control of ventilating openings? b. What types of ventilating openings are best suited to a proper distribu tion of the air supplied? a. The proper distribution of air as required by the occupants,-and the best utilization of natural ventilating forces. The general rules on page 93 apply particularly to these factors. b. Windows with swinging sash and openings with deflectors may be used to direct air to the points desired. 3 9 a. What is the best location for ventilating openings? b. How are the sizes of ventilating openings determined for proper air supply? . Inlet openings should be low and facing the prevailing winds where possible. Outlet openings should be high and on the side opposite the prevailing winds. . For simple openings use Formula 1: Q = EA V and for stacks use Formula 2: Q = 9.4 A V H (t - to) ~ The use of these formulae is illustrated in Example 1 of the text of this chapter. Inlet and outlet areas should be approximately the same for best results. 97