Summer Ventilation 101Summer Ventilation 101One of the main adaptations to hot weather, especially as barn temperature rises above 30 C, is that a bird will start to pant. With every breath, the bird draws air across the moist linings of her respiratory tract and water evaporates from her lungs and air sacs. As the moisture evaporates, a very large amount of heat is absorbed from the bird’s body core and trapped inside the water molecules that are exhaled. This evaporative cooling is the most powerful tool used by chickens and turkeys to keep cool during hot weather. By panting, the birds draw more air across the linings of their respiratory tracts and increase the amount of evaporation. The birds also drink more water to help keep these linings moist and aid the evaporation process. Because body heat is trapped inside the moisture exhaled by the bird, it cools of the bird without heating of the barn or raising barn air temperature.
A mist cooling system has water lines with nozzles either suspended from the ceiling or on the side wall. The nozzles spray a mist that evaporates and cools the barn. The physics at work is the same as when the chicken uses evaporative cooling when it pants.
As the mist evaporates it soaks up heat and drops the air temperature. The drop in temperature lowers the heat load on the birds. Their need to pant to loose body heat is decreased.
This effect is different from when the outside weather is humid. A rise in outside humidity never helps the birds during hot weather. It does not drop temperature in the barn but hurts the birds’ ability to lose heat by panting. Their internal cooling capacity is reduced because they will not evaporate as much water from their airways when they breath in humid air.
Misting systems help the birds because the misters lower the temperature in the barn. The finer the mist, the more evaporation and the greater the temperature drop. Very low pressure sprinkler systems produce a very course droplet and little evaporation. Their benefit is mostly to increase bird activity and drinking. Higher pressure systems have a finer mist with a higher rate of evaporation and more cooling of barn air. Cooling with any system is greatest on hot, dry afternoons because more of the mist produced will evaporate.
| Type of System | Operating Pressure | Percent Evaporation | Cooling Potential | Maintentance |
|---|---|---|---|---|
| Sprinklers | 40 p.s.i. | 5% | 0C to 1C | Maintenace requirement is low. Special filters are not needed. Plugging is rare. |
| Low Pressure | 100 p.s.i | 23% | 1C to 2C | Filters are needed at booster pump. Nozzles are prone to plugging because of small nozzle opening. Due to pressure change as water leaves nozzles, minerals from water may be deposited if the water is hard. Nozzles may need to be cleaned each flock. |
| Medium Pressure | 250 p.s.i. | 37% | 2C to 3C | |
| High Pressure | 500 p.s.i. to over 1,000 p.s.i. | 80% | 4C to 9C |
Main points to remember:
The high heat of vaporation sucks heat out of the birds and barn.
On very hot days, your fans cannot create wind chill on their own. You need mist coolers to produce beneficial wind chill.
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Nine out of ten chickens recommend mist cooling.