Cooling system enhances tunnel ventilation: Utilizing a stanchion barn feature – tunnel ventilation – helps Grotegut Dairy enhance ventilation in its freestall barn.

With Lake Michigan’s shore just a few miles from their dairy, Dave and Doug Grotegut, Newton, Wis., strive to take advantage of natural air patterns.
   Predominant easterly breezes cool Grotegut Dairy’s 1,780 cows. To enhance this natural cooling, Groteguts installed tunnel ventilation in their freestall barns.
   While tunnel ventilation is more commonplace in stanchion barns, Groteguts wanted to capitalize on this system’s highly thought of ventilation capabilities. A well-designed ventilation system ultimately enhances herd health.
   “It seemed like the only dairies that didn’t drop milk production during summers’ heat waves were those that had tunnel ventilation in stanchion barns,” Dave Grotegut commented.
   Stanchion barns weren’t an option for the Groteguts, so they asked, “Why not put tunnel ventilation in freestall barns?” That’s just what they did.

3 criteria
   Three important criteria impact tunnel ventilation’s effectiveness. First, the correct number and size of fans are needed to create 400 to 600 feet per minute during full ventilation. An end wall provides the best location for fans. Place them as low as possible to the floor. Fans should exhaust opposite prevailing summer winds.
   Second, the entire volume of air entering the facility needs to enter the facility at the farthest point opposite the exhaust fans. The air mass needs to be spread out across as much of the building’s width as possible. Regulate the opening area to create negative static pressure to match the optimal operating efficiency for the type of fan used.
   And third, fans must exchange air about every 45 seconds to one minute during full ventilation. While several variables impact air exchange, the building’s cubic area and length are the main factors.

Insulate above
   To prevent sun’s thermal rays from penetrating the roof and ceiling, Groteguts insulated the steel structure’s roof and ceiling. They open the ventilated ridge only on the east end.
   “From a cooling perspective, tunnel ventilation is the best option,” stated Bob Wagner of AEI Environmental Inc. And to make the best even better, Groteguts worked with AEI to install a new mister system.
   “Despite tunnel ventilation, our summer milk production drops still exceeded our goals,” said Grotegut. “We sought ways to minimize milk losses and improve reproductive performance.”

Oscillating fans
   In the summer of 2000, Groteguts put six oscillating fans with high-pressure misting rings in their holding area. Air moves south to north across the cows. Positioned at a 45-degree angle, fewer fans are required if they oscillate, compared to stationary fans.
   The holding area is 24 feet wide by 84 feet long. It can accommodate up to 160 cows. When in use, the Groteguts set cooling to start at 74 degrees Fahrenheit, with maximum relative humidity set at 80%. Fans kick in when the temperature reaches 62 degrees Fahrenheit.

Extending the system
   The Groteguts were so satisfied with the fan/mister cooling system that they installed a complimentary system in their freestall barn last summer. “It cools cows no matter where they are,” Grotegut commented. “If misters are placed above the headlocks, cows only get cooled when they’re eating.”
   A series of stainless steel tubing with nozzles deliver mist at 1,000 psi into the air. Each droplet is only 15 microns. Average human hair is 85 microns wide.
   The steel tubing is mounted on every other vertical post in the freestall barn. Spaced 36 feet apart, the nozzle sticks are 20 feet long and have 12 nozzles each. Nozzles are 18 inches apart. The nozzle sticks run perpendicular to the feed alley – from the headlock area to the curtain sidewalls. Also, they are mounted parallel with the sidewall for the first 40 feet on the east end of the barn. The 9-foot curtain sidewall is lowered in this area.
   With a 640-cow capacity, the cooltech-equipped freestall barn is 108-122 feet wide by 424 feet long. (The barn is 122 feet wide for 200 feet of the barn’s length, where the lead alley goes to the holding pen. It narrows to 108 feet wide, because the remaining length does not have this lead alley.)
   The six-row barn has four pens. Beds are 18 inches high. The freestall barn’s set point for cooling is 72 degrees Fahrenheit. Maximum relative humidity is set at 75%. Thirty-six 48-inch belt drive fans complement the cooltech system. There are 14 fans on each sidewall at the west end and eight fans on the west end wall. With 20,000 cfm per fan, the total cfm is 720,000.

Consistent cooling
   Bob Wagner of AEI explained, “The main purpose of this cooling system is to keep cooling consistent throughout the barn.” A probe mounted inside monitors airflow, moisture and temperature.
   Grotegut noted that not all of the nozzles are used. As you move west through the barn, some nozzles are capped off. Moisture builds up as you go west, so not as many nozzles are necessary on the west end. “It took some trial and error to figure out how many nozzles we needed in various locations,” he said.
   At first, the system only dropped the barn’s internal temperature 7 to 8 degrees Fahrenheit. “With some tweaking as the summer went along, we eventually got the barn 15 degrees cooler than the outside temperature,” Grotegut noted.
   “Our milk production didn’t drop this year as much as other summers,” the east central Wisconsin dairy producer noted. (Wisconsin experienced one of its worst hot spells during 2001.) At summer’s sultry peak, cows were off 10-11 pounds per day.

Helps with reproduction
   Besides curbing milk production losses, Groteguts installed the cooling system to get more cows pregnant. “We had good herd checks in the fall, which means our summer breedings were fairly successful,” Grotegut added.
   Technicians took temperature and humidity readings to determine where nozzles needed to be capped off and the system’s run time. Admitting that it’s somewhat subjective, Grotegut said the system delivered the cooling they wanted.
   A control unit operates the cooling system in both the holding area and freestall barn. They installed a probe outside that monitors approaching weather. According to Wagner, if rain is coming the cooling system will shut down before rain comes. “There’s a direct correlation with what’s happening outside to what’s happening inside,” he noted. The internal and external probes communicate with one another.

Tackling problems
   Besides fine-tuning the nozzle sticks, Groteguts experienced water pressure problems after installing the cooltech system. “The first system was tough on water pressure,” Grotegut noted. “So, the new system has reservoir tanks. This keeps pressure consistent throughout the dairy.”
   While cooling is important during warm weather, it’s not needed several months of the year. To winterize the system, they blow out the steel tubing and put RV anti-freeze throughout the entire system before winter weather arrives.
   Wagner noted that filters play a key role in achieving success with the cooling system. “Evaluate your water, because you need good quality water for pumps and nozzles to operate correctly,” he said.