Ventilation: Go With the Flow

Barn and arena ventilation is critical for the health of horses and their caretakers.

Have you ever walked into a stuffy or uncomfortable-feeling barn? How about an indoor arena where you were dripped on, even though it wasn't raining outside? What a miserable experience for you and your horse. What went wrong in those facilities? Someone was not paying enough attention to the importance of ventilation in the facility prior to construction. In fact, many horse people and builders alike agree that the most common mistake in barn construction is failure to provide adequate ventilation.

Natural Ventilation

Lucky for us, nature provides a means to naturally cool and freshen the air, even in a barn or indoor arena. We just need to effectively tap into it.

Air naturally stratifies (separates into layers) with temperature and moisture. The old adage "hot air rises" is true. When it comes to the design of a barn or arena, it is up to us to take advantage of this phenomenon and tap into natural airflow to keep our equine buildings comfortable. The two goals in ventilation are to exchange air--replacing stale air with fresh--and to properly distribute the fresh air throughout the facility.

Todd Gralla of GH2 Equestrian Architects out of Norman, Okla., specializes in using design to maximize airflow. "Environmental control needs vary depending upon geography in terms of what we need to achieve for people and horses," Gralla says. "In most cases excellent ventilation can be achieved through natural means in the design of the building."

Barns are very different environments than houses. Horses naturally produce a large amount of moisture through respiration, sweat, urination, and defecation, to name a few, and sometimes we bathe them in the barn. This makes the environment very humid. High humidity can increase odor problems, pathogens can thrive and grow in such conditions, mold can flourish on wood, rust can form on fixtures, and horses can develop respiratory illnesses when kept in enclosed high-humidity conditions.

For these reasons, humidity is not a good thing in a barn, and barns and arenas need an increased air exchange rate to keep the animals comfortable. While agricultural engineers have recommended four to eight air exchanges per hour, Gralla says his baseline is 10 air exchanges per hour. Residential builders often do not realize this because the average home requires far fewer exchanges per hour.

The primary design elements, which aid natural ventilation, are the roof, side walls, doors, windows, and stall design. All of these elements work in concert to take advantage of nature's ability to move air. Air naturally stratifies and moves around a space even when there is no wind. Warm air is less dense and tends to rise. The Ontario Ministry of Agriculture in its Horse Farm Ventilation Fact Sheet ( points out that with every 10°C increase in temperature, the moisture-holding capacity of the air approximately doubles. Hence, warm air rises, carrying moisture with it.

Roof and Vents

The roof is a key element in any ventilation dynamic. Especially in barns and arenas, the moist warm air needs an effective means of escape. This can be accomplished in a variety of ways. Some barns have a running vent along the entire roof peak, called ridge caps. This design allows for even airflow with a cap vent, keeping out the elements while allowing air exchange. Other designs have vents spaced along the roof. These are viable designs, but you must make sure your vent space is adequate for the square footage you are trying to ventilate.

Large cupolas can very effectively move air out of your barn or arena, but they must be well-vented and of sufficient size to have any effect. As with ridge caps, the number and size of cupolas needed depends on the square footage of the interior of the building and the amount of air that needs to be circulated. Unfortunately, many barn architects use small cupolas as accents rather than functioning units.

Another effective design element that can offer the added benefit of natural lighting is a long row of operable windows near the roof peak, called a clerestory. These windows can move a tremendous amount of air, according to Gralla. The functionality of being able to open them to increase airflow or shut them to shelter from a storm makes this type of design very effective for a barn or arena. A roof can also be built with overhangs that provide a passive solar element by shading the exterior walls as well as the shed row.

Roof materials are also a big contributor to the inside air quality of a barn or indoor arena. "One of the biggest mistakes I see is that people fail to insulate their roofs," says Gralla. "Proper insulation is important. Most roofing materials are temperature conductors, particularly metallic materials. Insulation helps to reduce this conduction and prevents condensation, which is magnified by the interior temperature stratification discussed earlier. It is crucial in arenas with metal roofing."

Gralla recommends insulating the roof with a rigid type of insulation, or you can use any of a variety of insulation types if you have an interior liner for it (so insulation pieces don't come loose and fall). Insulation also has the added benefit of sound dampening, a plus in large arenas.

Exterior Walls

The exterior walls of barns and arenas often have a gap between the top of the wall and the roof to promote natural ventilation, yet protect the facility from the elements. This design can offer an equal distribution of air, and the gap's location allows the internal and external air to mix before it hits the horse, lessening the draft potential. You might consider installing wire mesh at the opening to discourage birds from roosting and nesting. Gralla urges builders to insulate wood or metal walls. Block buildings can go without insulation, as they provide their own insulating properties. "Insulation has a huge impact on maintaining environmental controls," says Gralla.

Doors and Windows

Seasonal openings are very important, as they allow you to take advantage of cross-ventilation, which captures natural breezes that ventilate your facility. End doors that can be opened fully and windows in each stall are very important for effective ventilation. Eileen Fabian Wheeler, an associate professor of agricultural and biological engineering at Pennsylvania State University, prepared a publication on horse farm ventilation available as a PDF online ( She recommends windows be 5-10% of the floor area in size in order to be effective. Louvers on the windows allow you to control airflow during variable weather conditions.

Use of the barn is another factor to consider when making plans for windows. For example, in foaling barns, side vents lower down help bring fresh air to the foal.


Historically, stalls would have three tall side walls and a front door, perhaps with a metal grille at the top. This traditional style, while popular, is very ineffective for ventilation. The stall design healthiest for horses is to make the space as open and ventilated as possible.

Horses thrive in environments that most closely simulate the outdoors. High, open ceilings, open grillwork in walls between stalls, and full-view stall doors with bedding guards are ideal. This type of design minimizes obstacles to airflow, allows for lots of natural light, and allows horses--which are naturally herd animals--to interact with other horses while in the barn.

No matter the design of your barn, it is important to ensure that there is adequate airflow to the stalls. Most of the moisture in the barn is generated in the stalls, and this is where your animals typically spend most of their time while indoors.

Miscellaneous Dos and Don'ts

Avoid using screens to keep out insects because the moisture inherent to the barn environment will quickly clog screens to the point where they will restrict airflow.

Within the barn, try to remove moisture and any airflow restrictions that you can.

Barns also tend to be dusty from hay, feed, grooming, etc. Periodically wetting the floors, mucking out stalls regularly, and not storing hay and feed above the horses will help improve indoor air quality. You and your horse will appreciate this, especially if either of you have allergies!

Mechanical Aids

Extreme climates, such as the cold in Minnesota or the heat of Texas, might mean adding mechanical aids to increase air exchange. In some conditions it is helpful to add additional cooling or heating mechanisms. "The drawbacks to mechanical aids include initial installation cost, energy cost, long-term maintenance issues, and noise," says Gralla.

When Gralla's team members need to add mechanical ventilation devices, they prefer the newer wide-bore, low-speed, high-volume fans. "We put them in every arena we build because they are energy efficient, low maintenance, and incredibly cost-effective," says Gralla.

Adam Hatton, agriculture market and development specialist for Big Ass Fans company, agrees. While it is optimal to include fans in a barn's or arena's initial design, it is often an option to add high- volume, low-speed fans to existing structures in order to increase the exchange rate of air and create more circulation to break up moisture barriers.

"It is a mistake to build to human comfort standards in a barn," Hatton explains. "You will have healthier horses when they are kept to the most natural standards. The ideal is to use big fans that move a lot of air with a gentle breeze."

This type of airflow is natural to horses, he explains. High-speed air movement is unnatural and, more importantly, becomes ineffective when it's moving faster than roughly 8 mph. For example, when winds become gusty, you'll notice that pasture horses will turn their backs. Slower breezes aid in the evaporative cooling process for livestock. Large high-volume, low-speed fans are excellent for use in arenas, as they move large columns of air down and out as the natural buoyancy of hotter air diffuses it up and around the building's interior. The same holds true for barns, especially if they have high roof peaks.

Heating might be necessary in extremely cold climates, although horses are comfortable at lower temperatures than humans. Generally, a horse's comfort zone is 45-75°F. In places where the weather gets extremely cold, Gralla opts for user-controlled radiant heat. The company has installed in-floor radiant heat in the aisles, creating a heat sink in the floor. In task areas (such as wash stalls) they choose overhead radiant heat.

"Our goal with barn heating is to temper the barn. We shoot for 40-50 degrees," says Gralla. He suggests avoiding forced air, as it is inefficient for barns. It can also be noisy and less safe (due to all of the flammable items in barns, such as feedstuffs and bedding).

Take-Home Message

Ventilating your equine facilities is critically important for your horses' and your own health and well-being. Taking advantage of natural ventilation is the best way to design your facility for long-term comfort. Make sure your architect and/or builder is familiar with the unique ventilation needs of animals. While human comfort is important, animal comfort reigns supreme in the barn. Remember the unique character of a barn environment means you will need to exchange air much more often that you might in your house to keep your horses comfortable and healthy.

Further Reading

About the Author

Liza Holland



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