BARNS MAY LACK VENTILATION IN WARM WINTER WEATHER

Good ventilation system management calls for ventilation openings to be reduced in winter—adjusting a slot inlet in a mechanically-ventilated warm barn or placing fabric over an open sidewall in a naturally-ventilated cold barn. But, even though the calendar says it is winter, our recent weather has not been winter weather. And a major reason for air quality problems, especially in cold barns, is adjusting ventilation for the worst case—severe winter weather—and not readjusting to allow increased ventilation when the severe weather passes and milder winter weather appears.

Winter ventilation management is important in a naturally-ventilated barn with open ridge and eaves plus open sidewalls and endwalls as well. We invite real trouble when we adjust for winter ventilation during the first cold period in the fall (say the middle of November) and leave it there when, later on, we experience warmer days. If we don't open something for additional air movement, moisture buildup in the air will occur and the result is a cold, damp environment. Not much is worse, especially for baby calves, in terms of the environment. The situation is made even worse when warmer weather (35-50F) is accompanied by rain. Unfortunately, when people experience a cold, damp barn, their tendency may be to close it up even more—in response to feeling cold and damp—when the real answer is to provide more ventilation to flush out built-up moisture.

Changes in weather during fall, winter and spring often give rise to respiratory problems in animals, especially in calves when wide fluctuations in temperature occur. Remember that ventilation is truly a process of dilution. Air moved through a barn actually serves to dilute the inside air and, very importantly, to dilute all of its components. Dilution reduces concentrations of moisture and heat. Dilution reduces concentrations of airborne disease organisms, harmful gases and dust, and undesirable odors as well.

In winter, air movement through a cold barn should be sufficient to maintain inside temperature within 5-10F of outside temperature. Hang a thermometer inside the barn. If the temperature inside is more than 5-10F above outside temperature, more ventilation is necessary. Also, persistent condensation or odor indicates that additional ventilation must be provided.

Bill Bickert