Good Air In, Bad Air Out

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The cool breeze you feel standing in your barn aisle on a hot day is wonderful. But it not only feels good, it’s important for a horse’s health. That breeze, which is a form of natural ventilation, moves heavy, stale air out and brings in fresh, cool air. Of course, when the temperatures turn colder, we humans want to close up the barn to keep it toasty warm. But while you don’t want cold winds blowing through, your barn should be breathable, even in winter, to keep respiratory problems in check.

Ventilation can be as simple as open barn doors or as complex as a system of fans and duct work. There are a variety of factors to consider, so get out there and check out your stable or, if you are constructing a new facility, make certain you take proper ventilation into consideration.

Why Ventilation?

“You need holes in the building to get air in,” says Eileen Fabian Wheeler, associate professor of agricultural and biological engineering at Penn State University. Horses are susceptible to respiratory illnesses caused by an accumulation of moisture, foul air and dust. But it’s not just the horses; the barn itself deteriorates because of condensation. Therefore, the goal of a good ventilation system is to provide a dry, clear environment for horses while decreasing building problems.

When the horses are inside during the bitterly cold temperatures, proper air flow pushes out the winter moisture produced by respiration and doesn’t allow for condensation. Keeping the humidity level at 70 percent or below is best. Horses are comfortable around 55 degrees, which is chillier than what we humans prefer. And while we might feel the barn is cold, “a well ventilated barn is 5 to 10 degrees warmer than the outside temperature,” says Wheeler. For human comfort, supplemental heat can be located in an office or tack room, or radiant heat lamps can be placed in a wash stall or grooming area.

In contrast, the main goal in the summer is to remove the excess heat and keep the air flowing.

Older, Existing Barn

Are there steps you can take with an existing barn? Sure. First of all, Wheeler points out that older barns already have lots of holes. Old board siding has little gaps and cracks for breathable walls, and you can also cut in windows and doors. The traditional Eastern bank barn is more difficult to ventilate because it is built into the side of a hill. One solution:?cut holes in the ceiling to the hay area, with grills placed over them for safety and support. Another option is a duct with holes that runs across the back wall with a fan to blow air through (see following page).

From Top to Bottom

As well as the air might move down the aisle, if the stalls are closed in, the horses will not benefit. Windows on the outside walls are helpful. They should be at least four square feet and located six feet above the floor. Some barns are designed with stall doors on both sides of the building. If that is the case, full mesh or Dutch doors allow for good cross ventilation. If possible, use open grillwork on the top part of the front and side stall partitions.

Of course, don’t forget about ground level, particularly if horses eat off the floor. The best way to check is to get your nose down there and breathe. If you can smell ammonia or inhale a lot of dust, you can bet your horse will do the same. One-inch gaps between wood boards in the lower half of stalls allows for even more air movement. In addition, removing dust, cleaning cobwebs (when the horses are outside), using low-dust bedding and cleaning stalls daily will definitely improve the stall environment.

It is best to have the interior open to the roof peak, which means no overhead storage. If that is not possible, the next best option is to make the ceilings at least 12 feet high and to place overhead storage only over the aisles, not the stalls. This allows for decreased dust and allergens. Storing hay in a separate building not only helps the horse’s respiratory system, it significantly decreases the fire hazard as well.

Natural Ventilation

In the cold months, enough air needs to flow through the barn to control moisture without creating a chilling wind. This can be accomplished with either continuous or evenly spaced 3-inch to 4-inch eave openings at the top side of the walls. Being placed up high gives the air time to mix and warm slightly before coming down to the horse. In the summer, these same openings allow for summer breezes. Large doors located at both ends of every aisle allow for more air movement. Of course, all doors and windows need to be managed to keep out wind and rain during storms.

Cupolas are popular and attractive additions to the roof, but they also provide a practical purpose. When fitted with louvers, they can be used as openings. On long buildings, one cupola should be placed every 50 feet.

Mechanical Ventilation

If you don’t want to rely solely on Mother Nature, mechanical methods utilizing fans, ducts and inlets give you more control. Circulation fans (such as those hung in the stalls) provide a cooling breeze, but they are only moving the existing air.

According to Harry Huffman of the Ministry of Agriculture, Food and Rural Affairs in Ontario, Canada, the recommended ventilation per horse is at least 20 cubic feet/minute (CFM) in the winter to at least 200 CFM in summer. There should be at least two air changes per hour—that is, the total volume of air should be replaced twice in an hour’s time. To aid the fans, exhaust fans with either two speeds or variable speeds can be used to make the air exchange. To maintain the desired conditions, fans can be controlled automatically via a temperature sensor. Some newer barns are built with an air duct system, which uniformly distributes fresh air throughout the barn. “With this system and a tight barn, the fresh air is allowed in one end of the barn through motorized shutters or other openings, mixed with some barn air and distributed along the length of the barn through an air duct with holes spaced along one or both sides of the duct,” says Huffman.

For More Information

No matter whether you choose natural or mechanical ventilation or a combination of both, consistent air movement will create a more pleasant environment for both you and your horses. Wheeler prepared an extensive publication on horse barn ventilation that can be found at www.horsestable.psu.edu. She is also author of “Horse Stable and Riding Arena Design,” published in January 2006.