Ventilation System for Dairy Barn

Where Cows Face Out O N the opposite page is shown an illustration of a cross section of a dairy barn, arranged to accommodate two rows of cattle facing out. With this arrangement, the best way to ventilate the dairy barn is to have the large out-take flues or foul air shafts arranged as indicated. These out-take flues should be built so they extend as nearly straight up to the roof line as possible in order to keep friction or resistance at the lowest point. These out-take flues should be spaced, if possible, so no point of the barn will be more than 30 feet distant. Practical tests have shown that this is the greatest distance at which these flues can be depended upon to draw efficiently. You will note that these out-takes are located either in line with the cattle or back of them, if possible, so that at no time does the foul air have to travel in front of the cattle to make its escape. The out-takes should start from twelve to eighteen inches from the floor so the damp, heavy, foul air, moisture and gasses will be drawn out rather than warm air. This gives the fresh air entering the barn an opportunity of becoming moderated through contact with the warm air nearer the ceiling before it reaches the cattle. The illustration brings out clearly the fact that the fresh air should enter the intake E from three to four feet lower than from the point where it flows into the barn F. This arrange-ment guarantees the flow of fresh air into the barn rather than a tendency for the warm air to leave through the intakes. The intakes should be evenly distributed around the building to force general distribution of the fresh air as it enters the barn so that all the animals share alike in its benefits. Note from the illustration that the intakes E release the fresh air in front of the cattle and at the ceiling F so that the pressure has a tendency to force the foul air and gasses back toward the foul air out-takes. Size and Number of Intakes The fresh air intakes should be a trifle over one-half square foot in area. Arrange for two for every five cows. To be exact, figure thirty-two square inches of intakes for each cow and forty square inches for each horse. These intakes should be distributed about the barn not more than ten to twelve feet apart. to get the best results. Keep in mind that the combined area of the intakes should exceed the combined area of the out-takes by from five to ten per cent. This gives a pressure from the outside slightly greater than the capacity of the out-takes, which tends to increase the velocity of the up-draft. Details of construction of both in-takes and outlets are given on the pages which follow. Page One Hundred Sixty-three