Document 8RgGgLMQ0DK9kqm6q6D2zkZyk

176 CHAPTER 9 1949 Guide; the wind, in splashing therefrom, will create a suction. The additional height also increases the effect of temperature difference to cooperate with the wind. 11. The intensity of suction or the vacuum produced by the jump of the wind is greatest just back of the building face. The area of suction does not vary with the wind velocity, but the flow due to suction is directly proportional to wind velocity. 12. Openings milch larger than the calculated areas are sometimes desirable, espe cially when changes in occupancy are possible, or to provide for extremely hot days. In the former case, free openings should be located at the level of occupancy for psy chological reasons. 13. In single story industrial buildings, particularly those covering large areas natural ventilation must.be accomplished by taking air in and out of the roof open ings. Openings in the pressure zones can be used for inflow and openings in the suc tion zone, or openings in zones of less pressure, can be used for outflow. The ventila tion is accomplished by the manipulation of openings to get air flow through the zones to be ventilated. DAIRY BARN VENTILATION* A successful bam 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 production. Milk producing stock should be kept in a bam temperature between 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 mater nity 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 hr. 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 hr. To set a standard of permissible relative humidity for cow bams is difficult. For 45 F an average relative humidity of 80 per cent is satis factory, with 85 per cent as a limit. Where the bam 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 open ings hear 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 hr, and if a bam for the cow has 600 cu ft of air space with 130: sq ft of building ex posure, 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 tem perature zone, vary between 0.043 and 0.066 Btu per (hr) (cu ft of bam space), and 0.197 to 0.305 Btu per (hr) (sq ft of bam exposure). GARAGE VENTILATION Because of hazards resulting from carbon monoxide and other physi ologically harmful or combustible gases pr 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 -'Ha6talvi*|ltaati?n 177 cause t)ie doors and windows are kept' open; - As (Sold weather sets in; k5 and more of the ventilation openings are closed and consequently on extremely cold days the'carbon monoxide concentration runs high. Many garages can be satisfactorily ventilated by natural means, pari i,,riv during the mild weather when doors and windows can be kept' en 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 nossible in at least two outside walls, and that the total area'of such open ings shall be equivalent to at least 5 per cent of the floor area. The code further states that where it is impracticable to operate such a system of natural ventilation, a mechanical system shall be used which shall provide for either the supply of .l 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 . Cooperative research on garage ventilation, undertaken by the A.S.H.V.E. Committee on Research at Washington University, St. Louis, Mo., and at the University of Kansas, Lawrence, Kans., and tests conducted at the A.S.H.V.E. Research Laboratory, have 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 car- bon monoxide in the occupied portion of a garage than that obtained with 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 and 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 SO 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 mon oxide concentration down to one part in 10,000 partB of air. REFERENCES 1 Predetermining Airation of Industrial Buildings, by W. C. Randall and E. W. Conover (A.S.H.Vl. Transactions, Vol. 37, 1931, p. 605). * Neutral Zone in Ventilation, by J. E. Emswiler (A.S.H.V.E. Transactions, Vol. 32,1926, p. 59). Dairy Barn Ventilation, by F. L. Fairbanks (A.S.H.V.E. Transactions, Vol. 34, 1928, p. 181). Cow Barn Ventilation, by Alfred J. Offner (A.S.H.V.E. Trans actions, 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