Basic types of ventilation in swine barns
What type of ventilation would be better for my production?
Technology, such as pit fans, curtains, and heaters, is being implemented into swine barns today in an effort to become more efficient at providing an optimal environment for pigs. Ventilation has seen particular developments as more and more swine barns become reliant on electronic modes and mechanics. Due to the advancement of technology, ventilation management in swine barns has become more complex noting fan stages and more precise inlets for air movement; which may lead to a lack of understanding on the science of how to ventilate a barn to the pig’s optimal health and comfort.
Ventilation can be defined as a process for controlling several environmental factors by diluting inside air with the mixing of fresh outside air (The Service, 1990). Basically, ventilation brings in oxygen and expels or dilutes harmful dusts, gases, and undesirable odors, as well as airborne organisms and moisture from the pigs. The ventilation system within a barn affects various temperature and moisture components including air temperature, moisture level, surface moisture concentration, air temperature uniformity, air speed across animals, and airborne dust and gases, which can result in decreased health performance. The ventilation system is also known to control odor and gas concentrations as well as combustion fumes from un-vented heaters inside the barn (Jones and William, 1996).
In pork production today, there are three types of known building ventilation systems; mechanical, natural, and a combination of the two. Mechanical ventilation forces air through the building with fans. Mechanical ventilation is the most popular form of ventilation and is more technologically advanced. Natural ventilation, on the other hand, is more dependent on the wind and thermal buoyancy of the weather outside of the barn. Typically, natural ventilation favors older pigs that can retain more body heat, whereas mechanically ventilated barns are typically recommended for farrowing and nursery pigs to control air temperature during winter and summer.
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Mechanically ventilating systems within swine production can either be negative pressure barns, positive pressure barns, or neutral pressure barns (The Service, 1990). Negative pressure barns force outside air away from the structure, which are typically inlets, and out through fans. Positive pressure barns force outside air into the structure with fans. Neutral pressure barns use fans to force air into and out of the buildings, typically one fan pushes outside air into the barns through a duct, while exhaust fans pull stale air out of the barn. With mechanically ventilated barns, airflow and distribution is immensely important. Proper airflow rate, which is when air is properly moved through the building, on average is 800 to 1,000 cubic feet per minute. If this is not achieved, pig behavior and comfort can be influenced which is demonstrated by changing their dung patterns and sleep locations. The barn air exchange rate depends on fan capacity, however, the inside air distribution uniformity depends on air inlet location, design, and adjustment; which directly affects where air is exhausted from of the barn.
Photo by Iowa State Extension
Naturally ventilated systems include two main types; cold and modified-environment with the option of a gable or monoslope roof. A naturally cold ventilation system is designed to maintain winter indoor temperatures within a few degrees of outdoor temperatures (The Service, 1989). These buildings do not require insulation. A modified-environment system is designed for higher winter indoor temperature with insulation for the barn. Both types rely on animal heat to warm the building and the dry, outdoor environment to remove moisture from the barn, which is preferable for older animals who are able to retain their own heat and withstand colder temperatures. Site selection for naturally ventilated systems in critical. The ideal location would be on higher ground where obstructions such as trees do not disturb airflow around or through the building.
In conclusion, ventilation systems are complex. When considering what type of ventilation may work best for your respective farm, be sure to research the various parameters, such as gas exchange, as well as temperature and humidity of outdoor conditions, in advance to make an informed decision to optimize pig health and comfort. Although natural ventilation seems to be cheaper, it may require more labor intensive management. In contrast, mechanical ventilation may be more efficient and precise in providing airflow to pigs.
Jones, Don, and William Friday. “ENVIRONMENTAL CONTROL FOR CONFINEMENT LIVESTOCK HOUSING.” || What to Expect, www.extension.purdue.edu/extmedia/AE/AE-96.html. 1996.
Heating, Cooling, and Tempering Air for Livestock Housing. First ed., Midwest Plan Service, 1990.
Mechanical Ventilating Systems for Livestock Housing. First ed., The Service, 1990.
Natural Ventilating Systems for Livestock Housing. Midwest Plan Service, 1989.