Cost of ventilation.
To ventilate a house is expensive, and to ventilate a barn requires not only a certain expenditure of money but also a considerable amount of judgment. It is evidently cheaper to heat the same air in a room over and over than to be continually admitting cold fresh air, which will have to be warmed. This extra cost is, however, not excessive, when the movement of the air currents is properly controlled. The cost of warming the air necessary for ventilation for five persons should not be, at the rate of 1000 cubic feet of air to each person, more than ten cents a day in zero weather, with coal at five dollars a ton. Enough coal will have to be burned in addition to compensate for radiation, or, in other words, it requires a certain amount of coal to keep an empty room warm in winter without any question of ventilation, and in some badly built houses this amount is large.
Relation of heating to ventilation.
It does not follow because much heat is lost in this way that the ventilation is good, since the heated air may ascend to the ceiling and there escape without influencing the ventilation. In fact, one of the first principles of ventilation is that as soon as regular inlets and outlets are provided, all other openings ought to be rigidly closed. Then and then only can the warmed pure air be admitted as desired, at the points intended, and the full value of the heat utilized. Especially is this control of openings important in ventilating barns. Here each animal is a natural heater, warming the air by direct contact and by rapidly breathing in and out large volumes of air which are thereby changed to a temperature of over ninety degrees Fahrenheit. The air around their bodies being warmed rises to the ceiling and spreads out to the two sides and is there gradually cooled and at the same time mixed with fresh air which enters at the top, so that the cow is constantly supplied with freshened air. A flue is needed to carry the foul air up through the roof, and fresh-air inlets in the outer walls on both sides are required, and with these openings carefully controlled and with no others interfering, the stable may be well ventilated, as shown in Fig. 21 (after King).
Fig. 21.—Cow-barn ventilation.
In all cases where ventilation is to be practiced, the walls and ceiling should not merely be tight in themselves, but they should be double, and the strictest attention paid to limiting the amount of heat lost by radiation. All the heat used ought to be concerned in ventilation, and in that only. To secure air-tight walls and ceiling, the studding and joists should be boarded in, both on the inside and out, and the space between should be filled with shavings, straw, dry moss, or any similar fibrous substance. The outside sheathing must be well laid and must be water-tight in order that rain shall not penetrate to the inside of the wall, and the roof must be tight so that the ceiling filling does not get wet and rot.
The choice, therefore, so far as ventilation of either house or barn goes, lies between a poorly built, loose-jointed structure without artificial ventilation and with poor economy in heat, and a well-built, air-tight structure, with ample ventilating pipes, carefully and intelligently planned and built. The first is healthy so far as pure air is concerned, but drafty and uncomfortable. The second is more expensive to build, but insures lasting health and comfort. Then the choice cannot but fall on the building which is easy to warm, healthful to live in, and readily ventilated.