At this time of year, it’s tempting to try to keep your horses snug and warm by closing up your barn. Yet for the health of your horses, it’s important to keep fresh air circulating. Photo by Betsy Lynch.

Poor barn ventilation is among the leading causes of decreased performance, illness, and possibly death in today’s horse population. It’s also a commonly unaddressed issue for most horse owners.

How does poor barn ventilation really hurt your horse’s health? After all, it’s common for horse barns to smell like ammonia. By discussing everything from pathogens to porches, Brad Cumper, DVM, and Lorri Hayward of Hayward Design will help you understand how your barn’s polluted air can make your horse sick, and how to design your barn for proper horse barn ventilation—whether you’re updating the old or building a brand new barn for your horse.

“Poor barn ventilation can ultimately kill your horse,” affirms Dr. Brad Cumper of Saginaw Valley Equine Clinic in Freeland, Michigan. Such a decree may sound excessive at first, but as Dr. Cumper explains, the long-term effects of poor ventilation create a wide variety of respiratory disorders, some of which are fatal under the right conditions.

From the rancid smell of ammonia from degrading urine, to the build-up of dusts, molds and other pathogens from insufficient ventilation, your barn may be the reason for your horse’s respiratory difficulty.

Basic Physiology
First, let’s understand the basic physiology of a horse’s respiratory defense system and how it becomes susceptible to disease.

“The primary defense mechanism of the equine respiratory tract is the trapping ability of mucus,” Dr. Cumper explains. “Mucus is then expelled by the cilia which line the airways of the lungs and trachea. Billions of microscopic hairs (cilia) fan or wave mucus out of the lungs, up the trachea, and expel the overflow of mucus which catches and contains the irritants and pathogens.”

This is seen as a nasal discharge (or snotty nose).

The secondary defense mechanism is the immune system, composed of cells that consume infectious agents and other antigens, such as hay dust. This second arm of defense invokes an immune response—which protects the respiratory tract from infection. However, constant aggravation of the respiratory tract’s immune system can cause it to overreact (such as occurs with a severe allergic reaction), which can cause loss of airway function and death in minutes to hours.

So the basic physical responses can be associated with different types of pollutants.

“There are three categories of airborne irritants that adversely affect horses: contact irritants, airborne allergens and infectious agents,” Dr. Cumper explains.

“Contact irritants aggravate airway linings, and if constant aggravation occurs, the primary defense mechanism of the respiratory tract is activated to clear this aggravation,” he cites. Examples of contact irritants are vaporized chemicals such as ammonia and gasoline. There are also dust particles from dirt that physically hit the airway, create clogs and need to be cleared with a snort or a cough.

“Contact irritants are not truly harmful by themselves and invoke a mild inflammatory response without an immune response,” notes Dr. Cumper. They become the trigger for the overproduction of mucus and constrict the lower airways.

“Once the noxious irritant is removed, airways quickly return to normal function,” he explains “If irritants persist, the primary defense mechanism is weakened, exposing a vulnerable respiratory tract.”

Airborne allergens—molds, pollens and proteins derived from plants, such as hay dust—invoke a mild to severe immune response. This may show up as periods of labored breathing, a chronic cough, and severe nasal discharge.

“Infectious agents—bacteria, fungi and viruses—invoke a severe immune response and can diminish the horse’s ability to defend itself by eroding the airways of its defense mechanisms,” Dr. Cumper explains.

The invading infection is often defended effectively in a well-vaccinated horse. If infection overwhelms the immune system, the horse may become lethargic, have no appetite, become feverish, and display nasal discharge and/or a cough.

A commonly diagnosed respiratory illness is equine reactive airway disease (ERAD). ERAD is a low-grade, chronic disease that stems from constant irritation and immune responses to contact irritants and airborne allergens. This disease progresses as the horse ages. Symptoms include coughing, labored breathing, and excessive, viscous nasal discharge. Irritants continuously trigger the immune response, and your horse may have what resembles an asthma attack.

ERAD, asthma, and other respiratory diseases often result from constant exposure to concentrated irritants such as ammonia, allergens and infections agents. An easy way to help prevent these diseases is to remove the high concentrations of irritants.

So now that you know how the air in your barn may adversely affect your horse, here’s how to make it better.

A Healthy Design
Lorri Hayward of Hayward Design of Lafayette, Georgia, has been planning, designing and constructing equestrian facilities of all types and sizes for 20 years. To remedy poor ventilation, the most

important factor is also the most unsophisticated. Noting that hot air rises and cool air falls, she says, “The basic principle when trying to move and remove air is that you want to pull fresh cool air in from below and pull hot air out from above.”

That means replacing the stale, moist air from inside the barn with fresh, outside air. Air circulation is important, but if you’re recirculating the noxious gasses within the barn, you’re not providing any ventilation to the area.

Whether you’re building a new barn or renovating an existing one, Hayward insists that facilitating proper ventilation throughout your barn can be easily accomplished.

You’ve Got to Move It
When the temperature rises, many horse owners put box fans on their horses to keep them cool, but as Hayward asks, “Are you just blowing air on top of them or are you pulling in fresh air? If the barn is set up properly, you shouldn’t need a box fan. You want fresh air, not stale, old, hot air.”

While box fans may keep the flies off your horse, it’s not assisting proper ventilation. Put the box fans away.

From the Inside Out
A monumental issue for Hayward is the misconception that a breezy aisle-way means the whole structure is properly ventilated. While the aisle may have cool, fresh air blowing through it, the stalls may be cut off from that nice breeze. In essence, the cool, outside air may be blowing right by your horse and never touching him. Ceiling fans combined with cupolas on both ends of the barn can be an easy solution to this common problem.

Ceiling fans should be installed in three areas inside your barn: over the horse stalls, over the stall partitions, and down the center aisle. Hayward explains that positioning the fan blades to pull air up from horse stalls is an effective way to remove hot, stale air from the barn.

Ceiling fans are a great idea, but they won’t do any good if the warm moist air doesn’t have an exit. “You need vented cupolas,” Hayward explains.

Vented cupolas are basically air vents in the roof. They are a great way to foster ventilation, and they’re relatively inexpensive and easy to install. Even without ceiling fans, the warm, moist air that naturally rises off your horse will have an exit through a vented cupola.

Ventilated cupolas are equipped with an electric fan that pulls air out of the barn. “Ventilated cupolas cost more money (as opposed to just a vented cupola), but in the long run, it’s a critical feature,” she says. “You don’t have to do anything fancy to have a ventilated cupola and good airflow.”

No matter what the season or where you’re located, you can easily maintain healthy airflow with a thermostatically controlled cupola or an air exchanger. The thermostatically controlled cupola works like the ventilated cupola, with the addition of a thermostat like the one in your home. When your barn reaches a certain temperature, the cupola fan turns on.

Air exchangers replace stale, polluted air inside a structure with clean, outside air that is filtered to remove pollens. The filter also removes moisture from the air, which can carry pollutants and cause mold and mildew. It truly exchanges the air. Hayward notes, “It’s a big expense, but it’s worth it.”

There are a few other design elements that are straightforward and fairly inexpensive when building or renovating a barn with ventilation in mind. If possible, leave open spaces in the pitch of the roof, especially over the stall areas. Hayward explains, “You want a volume of air above the horse. Don’t put ceilings over the horses. Instead, put a ceiling over the wash rack or tack stall and have vaulted ceilings over the horses.”

Remember, hot air rises. So a ceiling over the stalls means the warm, moist air remains closer to the horses.

Interior stall vents at the bottom of the stall front increase ventilation and air flow at the floor level and within the stalls, where air is typically still.

“There’s actually a vent you can install low on the stall front that you can open and close, which is a nice feature, but it can be expensive,” she says. “Doors that I recommend on the interior either have grill or mesh on the bottom half of the stall, with a bedding guard on the bottom. It helps ventilation and airflow—opening up the lower area helps promote cross-ventilation.”

Since the grill or mesh stall fronts can be pricey and unattractive, Hayward notes, “Some stall companies advocate the full mesh or grill stall—this is where I balance cost and aesthetics. Plus, it can feel like the horses are in a zoo or something.”

More Than Just Curb Appeal
Landscaping and porches—they may seem like extras for the horse owner with deep pockets. But Hayward utilizes landscaping and porches around barns for more than aesthetic purposes.

“They help shade and cool the air before it comes into the barn. Have you ever walked off the blacktop and onto the grass on a hot summer day? You probably noticed a huge change in temperature,” she explains.

Surrounding your horse barn with shade trees, shrubs and grasses, as opposed to blacktop or gravel, will greatly reduce air temperatures around the barn, hence, the airflow into the barn will be cooler. “An 8-, 10- or 12-foot porch can easily be added to your barn,” she says. This element alone can cool your barn several degrees by providing shade areas which naturally cool the air.

The picturesque Dutch door is more than just pretty. It allows outside airflow in. If direct turnouts aren’t an option because of limited acreage, boarding arrangements or other situations, Hayward recommends Dutch doors that open to the outside, noting, “If at all possible, have stalls with outside airflow.”

If your horse does have a turnout door, a full-sized, durable screen door with a bedding guard on the bottom is also a great way to foster fresh air circulation when inclement weather keeps your horse inside.

You are now armed with the knowledge to prevent that winter cough and keep fresh, cool air flowing during the sizzling summer. Swear off the fall and winter build-up of ammonia gases and the subsequent cough syrup in the spring. Properly ventilate your barn—old or new—and you and your horse will reap the benefits.