Ohio Farm News
By Roger Bender

Have you entered a livestock barn this summer and sensed a higher level of humidity than outside? Did you check out a livestock tent or building at your local county fair on a hot day? Was it stuffy?

On the farm or at the fair, did the animals appear to be uncomfortable due to heat and humidity? In many such situations, fans are used to help reduce heat stress, but often overlooked is a basic physics principle: That warm, moist air rises, a process called thermal buoyancy.

Picture a teakettle boiling on a stove as an extreme example; you should visualize the steam rising. Providing properly sized openings at the peak of a building’s roof and or gable ends of a building can contribute significantly to indoor air quality.

Of course, adequate sidewall, door or window openings are necessary for fresh air to enter farm or fair structures to replace air exhausted through higher up openings. During hot, humid conditions, the ideal livestock structure would have no walls, to allow maximum cross ventilation that might come from summer breezes. Roof and endwall openings provide additional opportunities for stale air to escape animal occupied facilities.

Sizing those “higher up” air escape pathways is relatively simple. For every 10 feet of building width, there should be a one-inch opening at the roof’s peak. For example, if a building is 60 feet wide, a six-inch open ridge vent running the entire length of the roof would provide an adequate opening for air to escape.

Some farmers have chosen to add properly sized chimneys, cupolas and gable end openings to supplement the natural ventilation process. Such designs should provide one square foot of opening for each 100 square feet of floor space.

If considered, keep in mind that those types of air exits generally will draw no more than 30 feet. So, if the building is, say, 100 feet long, you may need to install a combination of gable end openings and chimneys or cupolas to make the system work properly.

Regardless of your naturally ventilated livestock housing needs, remember that animal health and diseases are influenced by air quality, which is directly related to ventilation.

The natural flow of air through properly sized and managed ventilation openings continuously replaces contaminated air with fresh outside air.

This air exchange helps control relative humidity and reduces the concentration of pathogens, ammonia, carbon dioxide and other air pollutants.

Whether building a new structure or modifying an existing facility, note that ventilation improvements will reduce dampness and odor within the building. Proper ventilation design should also improve animal health, save bedding costs and extend the life of the building.

Without question, this article only scratches the surface on design needs for optimum natural ventilation for summer weather.

More detailed information for summer, fall, winter and spring conditions can be found from the Midwest Plan Service online at www.mwps.org or http://ohio line.osu.edu/aex-fact/0115.html

The views and opinions expressed in this column are those of the author and not necessarily those of Farm World. Readers with questions or comments for Roger Bender may write to him in care of this publication.