Livestock production is significantly influenced by animal health and comfort. Ventilation of animal housing to remove moisture and odors and replacing them with fresh air is necessary for livestock productivity. Ventilation also provides air movement that promotes cooling and improves air quality for confined animals. While good ventilation contributes to profitability, if not properly designed, the energy used by a cooling and ventilation system can significantly reduce those profits.
Passive, or natural, ventilation is the supply and removal of air through openings in a building. It is driven by natural wind flow around the building and temperature differences between the inside and outside of the building. Passive ventilation may be used alone or in combination with some type of mechanical ventilation.
In many cases natural ventilation alone is not adequate, since inside temperatures and air exchange rates fluctuate with outside changes in temperatures and wind conditions. Its use in confinement livestock production is most common in large animal housing, with air passage through sidewall and ridge openings.
Mechanical ventilation is created by fans, thermostats, and air inlets. It is used where the air temperature and movement must be controlled, such as housing for animals that are sensitive to cold, sudden changes in temperature, and drafty conditions. Mechanical ventilation is common in swine farrowing and nursery buildings, lambing sheds, warm dairy cattle barns and calf housing, and milk houses. The most common approach is to use fans to blow air out of the building, with fresh air drawn in through inlets on the opposite side. However, fans can also be placed within a barn to circulate the air and improve uniformity of conditions.
The main advantage of mechanical ventilation is that it provides improved control over temperature and airflow within the facility – even on days when the wind is not blowing.
The primary disadvantages of mechanical ventilation are initial expense and operating cost as well as loss of animal heat in the winter, which may require a supplemental heating system to keep the animals sufficiently warm.
There are two principal types of fans used for mechanical ventilation of animal housing: box type fans and large, low-speed paddle-type fans. Box fans are used in conventional tiestall barns or loose housing such as freestall barns. Large paddle-type fans, also called high-volume, low-speed fans (HVLS) are most suitable for loose housing applications.