Iowa Farmer Today
10-20-07
Producers use breezes to keep pigs comfortable
By Jeff DeYoung, Iowa Farmer Today
NEWELL -- Some Northwest Iowans harness the wind with a turbine.
Tom Olsen uses a double-curtained hog building.
Olsen, who farms with his father, Marvel, and son Mark near here in Buena Vista
County, uses double-curtained buildings in his finishing operation. For the better
part of the year, Olsen uses the wind to keep his pigs cool.
“Our goal is to cool down the pigs, and the double-curtained, naturally ventilated
buildings work very well,” says Olsen, who also works full-time as an
Extension farm management specialist for Iowa State University.
Hogs come into the operation at about 40 pounds, he says. Olsen and his son
use a 150-day production plan in their operation. Each day, they record daily high
and low temperatures.
Ventilation settings are determined ahead of time and programmed into the
automated control system.
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“I really think you need to have to set up a plan and stick to it to make natural
ventilation work,” Olsen says.
At this time of the year, he says there is also a financial savings when it comes to
double-curtained buildings. His utility bill is about $100 per month, compared to
about $500 per month for a mechanically ventilated building.
“We believe pig performance is similar with both styles of buildings,” Olsen says.
“Recently, the cost of electricity in this area has gone up significantly compared
to the cost of propane, so we really have to pay attention to that.”
Curtained buildings are a hybrid, notes Larry Jacobsen, Extension ag engineer
with the University of Minnesota.
He says natural ventilation is used in the summer, then the building is switched to
mechanical ventilation in the winter.
A true naturally ventilated building would have an open ridge at the top,
Jacobsen explains, but most buildings have flat ceilings that depend on the wind.
“The wind is really a dominant force, and it blows most of the time in the
Midwest,” he says.
“If you are in an area that has little wind, it would be problematic to have a
naturally ventilated building. If you are in the right location, a curtained barn
works very well.”
Jacobsen says any ventilation system also must control moisture inside a
building. Buildings must include an insulated shell to help reduce condensation in
the winter and keep surface temperatures down in the summer, he adds.
Inlets are a crucial part of any building designed, Jacobsen says.
In a naturally ventilated building, air should flow upward into an open ridge, or
across the building.
“You want these inlets evenly distributed down the length of a barn,” he says.
An automated control system is also a necessity, he says.
“You have to be able to rely on that system to keep moving the curtains,”
Jacobsen says. “It needs to have regular maintenance along with the rest of the
ventilation system.”
Most buildings run east and west, he says, allowing the prevailing summer winds
to flow through a building. In some areas, a north-south building could work as
well.
Jacobsen says exhaust fans provide very little benefit in a naturally ventilated
building.
“Circulation fans can provide some benefit in naturally ventilated systems by
being hung inside the barn and creating air movement over the animals in the
summer.”
He says producers must look at economics, too, before putting up a naturally
ventilated building.
“There is more labor and more management involved with a curtained barn,”
Jacobsen says.
“There is also very little wind from 2 to 5 a.m., so it won’t take pigs long to get
uncomfortable. You may see less feed efficiency as well, so you have to decide if
it’s worth the extra days it may take to get a pig ready for market.”
Olsen believes if a producer keeps detailed records for the building, a naturally
ventilated system can work very well.
“It does require maintenance and management, and you will have to replace the
curtains periodically because of the mice and bird issues,” he says.
“But, we believe if you have a good plan and you can stick to that plan, naturally
ventilated buildings can work very well in a grow/finish operation. If we were
going to put up another finisher, it would be a double-curtained building.”