09/08/2026
Just published our latest Poultry Housing Tip - "Basic Tunnel Fan Selection Criteria". Here is an excerpt:
"Selecting tunnel fans is one of the most important decisions to be made when designing or upgrading a tunnel-ventilated poultry house. A house’s tunnel fans will determine a producer’s ability to keep birds comfortable during hot weather as well as have a major effect on a farm’s electricity bills throughout the year. Purchasing an “inexpensive” tunnel fan can prove to be a costly mistake if it moves less air, uses more power, or loses a large percentage of its capacity as static pressure increases as the pads become more and more clogged with minerals and dirt over the years.
The first question when comparing tunnel fans should be how much air the fan will move at the static pressure at which it will actually operate on a hot summer day. Knowing a fan’s air-moving capacity at a 0.00" static pressure has little value because tunnel fans never operate at a 0.00" static pressure. Tunnel fans must work hard to pull air through cooling pads, into the cross-sectional area of the house, down the length of the house, and then push it through shutters and screens. Each component creates resistance to airflow, or in other words, pressure that the fans must work against.
A tunnel ventilation system’s design static pressure is primarily determined by the desired maximum air speed. The higher the target air speed, the higher the static pressure tends to be. For instance, a house with a tunnel velocity of 500 ft/min when all fans are running will typically operate between 0.09" and 0.12" static pressure. At 600 ft/min, the static pressure will generally range from 0.12" to 0.15"; at 700 ft/min, between 0.15" and 0.18"; and at 800 ft/min, from 0.18" to 0.21". Therefore, if we want to determine the number of fans for a tunnel house with 700 ft/min air speed, the number of tunnel fans required should be based on their air-moving capacity at a static pressure of at least 0.15", ideally 0.20" so a grower will be assured that the fans will be able to generate the desired level of cooling as the static pressure increases as pads age.
Shutter type and location can significantly affect fan performance. Traditional exterior panel shutters tend to be the most restrictive because they interfere with the rotating air exiting a fan. Simply moving the shutter to the intake side of a fan can increase the air moving capacity of the fan 5% to 10%. Exterior butterfly shutters tend to be even less restrictive because they interfere less with discharge air and the fan does not have to pull them open against gravity. Because of this, butterfly-shutter fans will often move 5% to 10% more air than similar interior-shutter fans. Furthermore, dust on conventional shutters can reduce airflow by 10% to 20%, whereas dust has far less effect on butterfly shutters.
Butterfly shutters do have disadvantages. They can slam shut, scaring the birds, admit more light, causing birds to migrate out of the tunnel fan area of a house, and are more prone to condensation problems during cold weather. When warm, moist house air comes in contact with cold fan surfaces, condensation will tend to form on those surfaces. Since moisture, dust, and ammonia promote rust, butterfly-shutter fans installed in cooler climates should preferably have plastic or fiberglass housings.
A discharge cone is another feature worth considering. It provides a transition area that allows rapidly moving exhaust air to slow before contacting the relatively still outside air, reducing turbulence and back pressure. A properly designed cone will typically increase fan capacity by 5% to 10% without increasing power usage.
Fan energy efficiency should be compared using cfm/watt, not motor horsepower or total wattage. Depending on motor efficiency, loading, and service factor, fans with nominal one-horsepower motors can use between 700 and 1,300 watts of power. What matters is how much air is moved per watt consumed. At 0.10", approximately 19 cfm/watt should be considered a minimum, 20.8 cfm/watt good, and 22 cfm/watt or higher ideal. As a general rule, increasing a fan’s energy efficiency rating by 1 cfm/watt will reduce the average tunnel fan’s operating cost by between $20 and $25 per year (average tunnel fan operating hours = 2,500, power cost = $0.15 per Kw*hr)...."
This Poultry Housing Tip as well as over 300 others can be found at poultryventilation.com then click on the resources tab :)
