Cross ventilated barns provide air conditioning for cows

Dairymen may want to consider using cross ventilation to provide a cooler environment for the cows.

“By using cross ventilation, we’re trying to air condition the barns and we’re going to evaporate water to do that by using evaporative pads,” stated John Smith, extension dairy specialist at Kansas State University, during an educational seminar held at the World Dairy Expo.

“There are some limitations to doing that, we have to realize high humidity limits our ability to evaporate water to cool the air,” the dairy specialist said. “Temperature and humidity are inversely related.”

Smith discussed a cross ventilated dairy barn that is 210 feet wide and 420 feet long which provides housing for 800 cows. “The barn includes baffles, which forces the air flow down to the cow level,” he added. “The barn is divided into four pens with 200 cows per pen.”

One thing that Smith really likes about the barns is the light. “They are very comfortable to work in,” he added.

“It is important to insulate the roof and the spray-on insulation is the preferred type,” the dairy specialist said. “We’re trying to provide an air conditioned environment, but we’re also trying to provide a warm environment in the winter.”

Smith discussed some of the issues that are associated with cross ventilated barns. “One issue is the air exchange rate,” he stated. “At the low rate, we’re getting air exchange about every 200 seconds, at the medium rate every 104 seconds and at the high rate every 70 seconds,” he reported.

Air velocity will change throughout the barn, depending on where the baffles are placed. “We put the baffles on the row of stalls closest to the feedline,” the speaker told those at the meeting. “We use white metal to get the reflection of the light and they are eight feet above the alley which is actually six feet six inches above the beds where the cows lay.”

Static pressure is the resistance encountered by the fans as they try to pull air across the building. “There are a number of things that can impact static pressure, including the building width, the inlets and the air speed,” the extension specialist said. “The static pressure across the baffles is additive so the number of baffles, the baffle height and the distance between the baffles all have an impact.”

During the winter, the challenge is dealing with high humidities. “You’re always going to be compromising between air quality and temperature,” Smith explained. “Because if you shut the ventilation rates down too low, you’ll change the temperature in the barns, but it’s probably not the right thing to do for the cows – we can’t sacrifice air quality.”

In order to manage heat stress, the dairy specialist said, “it’s all about stabilizing the core body temperature, we want to eliminate the fluctuation of body temperatures.”

In comparing two different barns, Smith said, in a naturally ventilated barn with soakers and fans, the cows’ body temperatures remained under 102 degrees. “However the cross ventilated barns had much more consistent cow body temperatures,” he added. “Because the cows that are comfortable in a free stall will not get up until their body temperature starts to go up.”

So if the cow has a more consistent body temperature, Smith said, “then there is better dry matter intake, more milk production, better reproduction, less lameness and it goes on and on.”

When constructing cross ventilation barns, dairymen don’t have to worry about orientation. “If I have an existing dairy, where I really don’t have a good place to put a naturally-ventilated barn, that’s not an issue with cross ventilated barns,” the speaker said. “So these barns have a lot of potential for retrofit dairies.”

Other advantages of cross ventilated barns include providing a consistent environment during both the summer and winter for the cows and it may be possible to put the dairy under one roof which can help to control runoff.

“Cross ventilated barns reduce the distance you have to pull air and that increases the number of air exchanges per hour,” Smith said. “And air can be baffled down to the cow level.”

In addition, these barns provide dairymen with the flexibility to cook the air, cool the cow or cool both. “You can use the evaporative pads to cool the air, or you can use feedline soakers to cool the cow or you can do both,” the dairy specialist explained. “And the fans are down where you can work on them.”

Another advantage is the ability to put the cows closer to the parlor, which will reduce the walking distance for the animals. “But that means you may have less time to scrap the barn,” the speaker added.

Smith also identified disadvantages to cross ventilated barns. “For those in dry lot country, the cross ventilated barns can’t compete on cost,” he concluded. “And you are tied to mechanical ventilation 365 days a year and you will have a greater need for generators.”

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Cross ventilated barns provide air conditioning for cows