If you want to evaluate air movement and ventilation in your calf barn, there’s an easy way to do it – fill it with smoke.
That smoke should not come from a fire, mind you, but from handy tools that allow you to visually evaluate where the air moves in your calf barn, and how quickly it is exchanged with fresh air from the outside.
Courtney Hallbach, MBA, researcher with the University of Wisconsin’s Dairyland Initiative, shared at the most recent AABP Recent Graduate Conference that good ventilation is critical for removing warm, humid, contaminated air from calf barns. In the summer, this helps with heat abatement; in the winter, it protects respiratory health.
She said “smoking” or “fogging” barns is a low-cost, highly visual way to observe how air is distributed in a calf barn and identify any dead spots. In barns with positive-pressure ventilation tubes, smoke can be forced through the tube from the outside, while an observer inside watches how air exits the discharge holes, and how long it takes for the smoke to leave the building entirely. Any leaks or loose connections in the ventilation tubes can also be identified.
There are several options for tools used to perform smoke testing:
- Non-toxic smoke sticks or bombs commonly used by HVAC professionals
- Bug foggers loaded with water or mineral oil;
- Electronic fog machines commonly used in theaters and fire training
This video shows a team of professionals from Cornell University Extension using smoke sticks to evaluate a New York calf barn without a positive-pressure ventilation tube.
Dr. Ryan Leiterman, veterinarian and agricultural engineer with Crystal Creek Natural, Spooner, Wis., regularly uses the method to diagnose ventilation issues in existing barns, and fine-tune the systems when he is helping clients install ventilation systems in new barn construction.
In an advisory bulletin he offered as guidance to producers building new facilities, he noted, “after fogging over 75 barns, I consistently notice fresh air from the positive pressure duct being directed to the calf level, only to be warmed and rise back up to the top of the barn.”
He said it is a myth that calves don’t produce enough body heat to influence thermal buoyancy. In truth, they absolutely do. That warm air they create needs an escape route, which he advised should be a ceiling ridge vent. “Ridge vents can and should be covered, but the covering needs to be elevated to provide space for warm air to escape,” he stated.
The clearly visible air flow patterns observed from smoking barns can also identify dead zones of stagnant air, where smoke lingers instead of clearing. Fast-moving smoke at the calf level might be fine in the summer, but indicate a cold draft on calves in the winter.
Sometimes, short-circuiting of airflow is also observed, when smoke is pulled directly from inlets to exhaust without circulating through the room. In that case, the mechanical ventilation system may be running, but not actually refreshing the air around the calves.
Leiterman records the time it takes for the smoke to completely dissipate in the building, which is an indication of air exchange speed. He explains the simple calculation in this video of fogging a calf barn addition under construction in Wisconsin. If it takes 15 minutes for the smoke to clear, that’s 4 exchanges per hour. Clearance in 6 minutes means 10 exchanges per hour. He advises at least 4 air exchanges per hour in all seasons, with possibly greater frequency in warm weather.
Remedying identified issues may be as simple as adjusting curtained sidewalls on calf barns; increasing or decreasing fan speeds; or changing the volume of air through positive-pressure ventilation tubes. In other cases, it may take more involved efforts, like cutting in roof ridge ventilation or a central chimney to allow warm air to escape, or installing a positive-pressure ventilation system.
Work with your veterinarian, design engineer, or building professional to put the power of smoke to work for your calves and the environment you want to create for them.
