Horse barns need air exchange to remove moisture, prevent condensation and provide fresh air.
Naturally-ventilated systems are less costly, but have limited control of air flow and distribution.
Mechanically-ventilated barns are designed for year round conditions.
Well spread out air inlets eliminate air spaces in mechanically ventilated barns.
Insulation keeps buildings warmer in the winter, cooler in the summer and prevents moisture build up.
Why do horse barns need air exchange?
Air exchange in horse barns is key to:
Controlling and removing moisture
Preventing condensation on surfaces
Maintaining good air quality
Removes dust, pathogens, ammonia, fumes and other compounds in the air
Removing heat and keeping barns cool during the warm conditions
How do you accomplish air exchange?
Buoyancy (hot air rises) and wind forces drive natural (non-mechanical) systems.
Open front sheds facing south are the simplest of the natural ventilation systems. These sheds protect horses from the elements and allow for fresh air. Lean-tos are adequate for horses that are well fed and acclimated to current weather conditions.
An enclosed naturally-ventilated barn must have inlets (e.g. sidewall vents or eave openings) and outlets (e.g. a ridge or roof chimney openings). Usually the temperatures in these facilities are at or slightly above outside temperatures year round. This draft-free system combined with dry bedding can provide a comfortable environment for mature and healthy horses.
These barns should have heated water lines and tanks to prevent freezing during cold conditions.
Natural systems are less costly, but have limited control of air flow and distribution.
Mechanically-ventilated barns are designed for year round conditions. They provide air exchange by using inlets and electrical exhaust fans.
Cold weather ventilation
During cold weather, the barn needs little ventilation to remove moisture. The rate of ventilation should be 25 cubic feet of air per minute (cfm) per 1,000 pounds of horse. Continuously running sidewall exhaust fans provides the best cold air exchange.
Mild weather ventilation
The barn will need a second fan(s) during mild weather. This fan(s) should deliver another 100 cfm per 1,000 pounds of horse (total of 125 cfm per 1,000 pounds of horse) with indoor temperatures set to about 50 F.
Hot weather ventilation
The barn will need another exhaust fan(s) during hot temperatures. This fan(s) should deliver another 200 cfm per 1,000 pounds of horse (total of 325 cfm per 1,000 of horse). These fans and a separate controller set to activate at about 60 F can help keep the temperature from rising.
Keys to air exchange
Well spread out air inlets eliminate air spaces in mechanically-ventilated barns. Exhaust fan(s) location has little to no impact on the barn’s air distribution. Properly designed and operating mechanically ventilated barns will have a slight negative pressure. Fresh air will then enter the barn through the inlets and provide fresh air to the horses. For boxstalls you can obtain good air quality by making sure there’s at least one air inlet near the boxstall.
Supplemental heat in the winter can prevent indoor temperatures from falling and water lines from freezing. A small gas-fired or electric space heater can maintain the minimum desired temperature. Size your heater to roughly 4,000 BTU per hour (gas) or 1 kW (electric) per horse. Space heaters are the number one cause of fires. Always take safety precautions when using them.
All horse housing must be well constructed and have insulated walls and ceiling. Mechanical ventilation systems require the building to be as air tight as possible. Insulation does the following:
Keeps the building cooler in the summer
Prevents moisture condensation
Keeps the building warmer in the winter
We recommend using a roof insulation with an R-value between 2 and 4 for open-sided and enclosed naturally-ventilated barns. This will prevent condensation from forming on the underside of the roof in winter. It will also reduce heat load in summer.
Mechanically-ventilated barns require the following insulation R-values.
Walls: R-value in the mid-teens, 15
Ceiling: R-value in the mid-twenties, 25
A vapor barrier or retarder (sheet of plastic) placed on the warm side of the insulation (walls and ceiling) will keep moisture from moving through it. This will protect and prevent the building materials from deteriorating.
Keep mechanically-ventilated barns closed in the summer. Operate the exhaust fans and inlets to keep the temperature from rising. Fans inside the barn can increase airflow but don’t provide as much air exchange as sidewall exhaust fans. Only use these fans to help keep the animals cool.
In some cases, cooling systems such as sprinklers or air inlet evaporative pads in the walls have been put in horse barns.
If a mechanical ventilation barn has less than or equal to 125 cfm per 1,000 pounds of horse, open the building and use natural ventilation in the summer. Once large doors or windows are open, exhaust fans no longer benefit air exchange. You should turn them off. Use circulation or mixing fans to move air over your horses. Air exchange will solely depend on wind forces.
Reviewed in 2021