Winter Barn Ventilation

How do you know if your barn is well-ventilated, and what can you do to fix it?

What could possibly be more interesting than barn ventilation? It ranks right up there with oil changes and trimming those low-hanging tree limbs that catch every time you mow the pastures. It doesn't increase the useful space in the barn or dramatically increase the value of your property, at least in the short run. Nevertheless, it is an essential factor in maintaining a healthy environment in your barn for the welfare of the horses confined within.

Respiratory ailments associated with lack of air exchange are universally recognized as debilitating, performance-limiting, and sometimes even fatal. Dust, mold, bacteria, and ammonia can irritate, infect, and affect the airways and limit the natural defenses of the respiratory system. In addition to problems associated with breathing in air pollutants, there are a myriad of skin conditions, allergies, and eye issues that can be traced to confinement in poorly ventilated buildings.

Moisture Sources

Your barn-dwelling animals are, for purposes of this discussion, giant fountains of moisture. They ooze it from every pore, deposit it on the stall floor, dribble it from the water bucket, and add to it every time they exhale. This moisture contains more than water. It is alive with microorganisms both beneficial and harmful and a cocktail of chemicals, such as ammonia, that add to the barn's community and ambience.

Ground moisture constantly tries to return to the atmosphere through your barn floor. Rainwater leaks through every loose piece of roof metal or poorly caulked window. If the drainage around the barn is inadequate, storm water will run into the barn instead of out.

Unless there is an effective ventilation system all of this accumulating moisture--which can average gallons a day--can damage your equine charges, the items stored in the barn, and the barn itself. Barn ventilation problems tend to be most acute during the winter when doors and windows are kept closed, and the ground is less permeable than during the spring and summer months.

The Cost of Poor Ventilation

The first question is whether you are trying to keep your barn warm because you are concerned about the comfort of the horses or the comfort of the people. Horses remain comfortable in much colder temperatures than humans, particularly if kept out of direct drafts. Keeping a barn warm just to keep water buckets from freezing is a waste of energy that few can afford.

The healthiest location for your horses in all but the worst weather is outside. Provide a run-in shed to break the wind and rain, plenty of forage, and a good, reliable water source. The closer you can duplicate this environment inside your barn, the happier your horses will be.

One of the principles of modern design of public buildings is constant introduction of fresh air. This increases oxygen levels, reduces mold, and allows for the escape of toxic airborne material that might be the cause of "sick building syndrome." Typically 10% to 30% fresh air is introduced into the building using sophisticated air-handling equipment that monitors humidity and the differential between indoor and outdoor air temperature.

Keep in mind moisture is the enemy of all structures, including barns.

Wood is most affected when constantly damp. Rot sets in from the bottom up as well as every damp spot at a wall and roof leak. Termites must have a nearby source of water to perform their insidious work from the inside out. Carpenter ants and bees and other wood-boring bugs likewise need to drink to survive.

Metal corrosion takes place rapidly in a damp environment. The acid from urine in the air accelerates the process, causing deterioration of nails, bolts, hooks, and other items that support your barn.

Masonry also is affected by moisture and acid. Water expands as it freezes, so any damp spot has the potential to crack floor slabs, split masonry joints, and heave footings.

Hay needs a dry, well-ventilated storage space to cure properly and avoid mold. Few things are more depressing than discovering all of the hay you have carefully put by for the winter has molded and become too dangerous to feed horses.

What Can I Do?

Start with preventing as much moisture introduction into the barn as possible. Fix any site drainage issues. They will haunt you on a daily basis. Fix leaks and keep caulking dressed (touch it up/smooth it out) on a regular basis as part of your maintenance program.

However, even the best maintained barn will build up interior moisture. Let's review the fundamental ventilation needs required for any barn:

  • Allow moisture evacuation The amount of moisture depends on how many animals are in the barn and for how long, as well as climate and condition of the barn and site drainage. The less time horses are in the barn and the fewer leaks, the smaller the problem becomes. Nevertheless, no barn is moisture-free.
  • Allow warm air to escape in hot weather This one is obvious--more on it later.
  • Provide air movement without drafts directly on the horse when in the stall The best answer to all of these issues is to construct or retrofit your barn to take advantage of natural air convection. Warm air naturally rises, taking with it moisture in the form of water and ammonia vapors. As simple as this sounds, natural convection is a powerful force that operates 24 hours a day for free. It consumes no fossil fuels and does not require high- maintenance equipment. It does, however, require basic construction techniques that can be difficult (but never impossible) to install in an existing structure.

The basic method is this:

  1. Provide a way to allow a large volume of warm air to exit the structure at its highest point, typically the ridge.
  2. Provide a way for a large volume of cool air to enter the structure around its perimeter as low as possible without creating drafts in the stalls.
  3. Let nature do the work.

Those Pesky Details

How much is air enough? That depends on the variables discussed above. Architecturally designed breeding barns allow for as much as 12 square feet each of intake area at the eave and exhaust area at the ridge for each 12-by-12 stall. This is in addition to air that comes in barn doors and stall windows. While you might not need that much fresh air, the closer you can get to the optimum volumes, the better.

Remember the picture-perfect old red barns that used to dot the American countryside? All had huge cupolas on the roof. Our grandfathers knew the value of air movement in their barns, and this still can be an effective way to provide the ridge ventilation needed. However, modern barns, particularly pre-engineered metal barns, often add an ornamental cupola on top of a metal roof with no open space to allow the air to escape. The cupola might not even have louvers or screens and it might require modification to be functional. This modification is well worth the cost.

If cupolas aren't an option, you should install continuous ridge ventilation. It must allow a larger air space than the ridge ventilation on a house. Construct a raised ridge cap at least the height of a 2-by-4 laid on edge. Cut the existing roof deck back on each side of the ridge to allow the warm air a pathway to freedom. Cover the openings with heavy chicken or rat wire (the latter is also called hardware cloth) to discourage birds.

Rooftop turbines that spin due to the natural air movement and wind also can be mounted at regular intervals along the ridgeline. These must be the large turbines designed for barns and other large structures. The variety designed for residential use and sold at building supply houses are too small to be useful. Check with farm supply stores and agricultural building suppliers for the larger ones.

If sufficient ridge ventilation is difficult, gable wall vents up near the ridge are a slightly less effective alternative (the air can escape, but not as readily as it would with ridge vents). The biggest problem with installing gable vents is making sure you provide enough air space at a location high enough for the temperature differential to move the air in sufficient volume to be effective. Nevertheless they can help.

Never stack hay or other material so high that it blocks air movement along the roof deck all the way to the ridge, as this will defeat this entire ventilation system.

The same concept applies to the intake side of the equation. Allow the same spacing that you have at the ridge. The most common location for the intake is at the roof eaves. Remove the soffit material under the roof overhang that encloses the eave and cover with mesh used at the ridge.

Stall doors and windows are a poor substitute for intake ventilation. There is a tendency to close these when it is cold outside because of the direct drafts they create. If you are lucky enough to be using a former tobacco curing barn as your horse barn, as is common in the southeastern United States, the narrow gaps between the vertical siding boards make ideal air intakes without excessive draftiness.

If your structure will not allow for passive ventilation, mechanical devices can help. Large electrically powered low-speed exhaust fans that can be installed in exterior walls are commonly used in confinement hog and cattle operations and are available through farm supply vendors.

Take-Home Message

While not a spellbinding subject, barn ventilation is essential for the health and safety of your horses and the maintenance of your barn. A little effort up front can prevent expensive and disappointing problems later.

About the Author

David Preston

David Preston, president of Preston Construction Group, specializes in unique commercial and equine projects. A horse owner and sportsman, he has built and remodeled several barns in Kentucky and Illinois ranging from development of complete Thoroughbred farms to small horse barns.

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