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182 CHAPTER 9 1946 Guide DAIRY BARN VENTILATION8 A successful barn ventilating system is one which continuously supplies the proper amount of air required by the stock, with proper distribution . and without drafts, and one which removes the excessive heat, moisture, and odors, and maintains the air at a proper temperature, relative humidity, and degree of cleanliness. Bam temperatures below freezing and above 80 F affect milk produc tion. Milk producing stock should be kept in a bam temperature be tween 45 and 50 F. Dry stock, at reduced feeding, may be kept in a bam . 5 to' 10 deg higher. Calf bams are generally kept at 60 F, while hospital and maternity bams usually have a temperature of 60 F or somewhat higher. The heat produced, by a cow of an average weight of 1000 lb may be taken as 3000 Btu per hour. The. average rate of moisture production by a cow giving 20 lb of milk per day is 15 lb of water per day, or 4375 grains per hour. To set a standard of permissible relative humidity for cow barns is difficult. For 45 F an average relative humidity of 80 per cent is satisfactory, with 85 per cent as a fimit. Where the barn volume and construction permit adequate heating by the stabled animals, the air supply need not be heated. The air should be 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 bam and there is better temperature control with less likelihood of sudden, change in bam 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 cu ft per hour of ventilation, depending on the temperature zone in which the barn 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) (cubic foot of barn space), and 0.197 to 0.305 Btu per (hour) (square foot of barn exposure). GARAGE VENTILATION 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 of Minimum Requirements for Heating and Ventilating Garages, adopted in 1935, states that natural ventilation 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 possible 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 Natural Ventilation______________ '______________ /__________ _________ - 8 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 garage4:- . 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 University of Kansas, Lawrence, Kans., in cooperation with, the A.S.H.V.E. 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 in the following statements: 1. Upward ventilation results in a lower concentration of carbon monoxide at the breathing line and a lower temperature above the breathing line than does downward ventilation, for the 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. 3. In the average case upward ventilation results in a lower concentration of carbon monoxide in the occupied portion of a garage than is had with complete mixing of the exhaust gases and the air supplied. However, the variations in concentration from point to point, together with the possible failure of the advantages of upward ventilation to accrue, suggest the basing of garage ventilation on complete mixing arid an air change sufficient to dilute 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 cu ft per hour, with an average rate of 35 cu ft per hour. 5. An air change of 350,000 cu ft per hour per idling car is required to keep the carbon monoxide concentration down to one part in 10,000 parts of air. REFERENCES 1--Predetermining Airation of Industrial Buildings, by W. C. Randall and E. W.- Conover (A.S.H.V^E.' Transactions, VoL 37, 1931, p. 605). . 2--Neutral Zone in Ventilation, by J. E. Emswiler (A.S.H.V.E. Transactions, VoL 32,1926, p. 59). ' 3--Dairy Barn Ventilation, by F. L. Fairbanks (A.S.H.V.E. Transactions. Vol. 34.1928, p. 181). Cow: Bam Ventilation, by Alfred J. Offner (A.S.H.V.E. Transactions, Vol. 39, 1933, p. 149). For additional information on this subject refer to Technical Bulletin, U. 'S. Department of Agriculture (1930), by M. A.` R.'Kelley: Also see Air Conditioning of Farm Buildings, by F; L. Fairbanks (Agricultural Engineering* November, 1937, p. 485). ` t. ^ 4--Code of Minimum Requirements for Heating and .Ventilating Garages (A.S.H-.V.E.' Transactions," Vol. 41, 1935, p. 30). Airation Study of Garages by W. C. Randall and L. W. Leonhard (A.S.H.V.E. Transactions. Vol. 36. 1930, p. 233). .... A.S.H.V.E. Research Report No. 874^--Carbon Monoxide Concentration'in Garages, by A. S. Langs-dorf and R. R. Tucker (A.S.H.V.E. Transactions, Vol. 36, 1930, p. 511). A.S.H.V.E. Research.Report No. 935--Carbon Monoxide Distribution in Relation to the Ventilation of an Underground Ramp Garage, by F. C. Houghten and Paxil McDermott (A.S.H.V.E. Transactions, Vol. 38, 1932. p. 439). * . , A.S.H.V.E. Research Report No. 934--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. p. 424).. . A.S.H.V.E. Research Report No. 967--Carbon Monoxide Distribution in Relation to the-Hating and Ventilation of a One-Floor Garage,- by F. C. Houghten and Paul McDermott (A.S.H.V.E. Trans-- actions, Vol. 39, 1933, p. 395). ' 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, p. 263).