Ventilation System for Dairy Barn

Where Cows Face In THE illustration opposite shows a cross section of a dairy barn arranged to accommodate two rows of cattle facing each other. 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 that they extend straight up to the roof line and follow it to the cupola or ventilator. They should be spaced so that no point of the barn will be more than 30 feet distant, as practical tests have shown that this is the greatest distance where these flues can be depended upon to draw efficiently. Out-take flues should start from 12 to 18 in. from the floor so that the damp, heavy, foul air, moisture and gasses will be drawn out rather than the warmer air. This gives the fresh air entering the barn an opportunity of becoming moderated through contact with the warmer air, nearer the ceiling, before it reaches the cattle. The illustration brings out clearly the fact that the fresh air should enter the intakes from three to four feet lower than the point where it flows into the barn. This arrangement guarantees the flow of air into the barn rather than a tendency for the warm air to leave through the fresh air 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 of the animals may share alike in its benefits. Note from the illustration that the fresh air intakes must be extended to the center of the barn so that the fresh air is released in front of the cattle and 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 outlets by from five to ten per cent. This gives a pressure from the outside slightly greater than the capacity of the outlets, which tends to increase the velocity of the up-draft. Details of the construction of both intakes and outlets are given on pages which follow. Pave Mlle hundred Sixty-one