Compared to our homes, stables have much more moisture, odor, mold, and dust being added to the air, not to mention manure being deposited within the facility. Ventilation is needed to remove heat from the stable in hot weather. It is beneficial to provide a cooling breeze over the horse, which is more comfortable than hot, still air. During warm weather the stable doors and windows are usually open to aid in moving air through the stable. During cold weather, the stable is often managed with closed windows and doors to keep chilling winter winds off the horse. In winter, the ventilation goal changes from heat removal to controlling moisture, odor, and ammonia that have built up in the more closed environment of the stable. Moisture comes from horse respiration and other stable activities such as horse bathing and facility cleaning. With moisture buildup, comes increased risk of condensation, intense odor, more ammonia release, and pathogen viability, which contributes to respiratory infection.
Natural ventilation is often expressed in “air changes per hour.” An air change per hour (ACH) means that the total volume of air in the stable is replaced in an hour’s time. Six air changes per hour means a complete air change every 10 minutes. Provide 4 to 8 air changes per hour to reduce mold spore contamination, minimize condensation, and reduce moisture, odor, and ammonia accumulation. For comparison, the modern home has 1/2 air changes per hour from infiltration through various cracks, such as around doors and windows. This recommendation for stable ventilation is substantially more than the average residential air exchange rate to maintain fresh air conditions and good air quality in the more challenging stable environment.
Natural ventilation uses openings located along the sidewall and ridge (roof peak) to accommodate these air movement forces. The sidewall openings are more important than the ridge openings if stable design cannot accommodate both sets of openings. The stable ventilation system will work better when both ridge and sidewall openings are provided. The ridge opening allows warm and moist air, which accumulates near the roof peak, to escape. The ridge opening is also a very effective mechanism for wind-driven air exchange since wind moves faster higher off the ground.
Circulation fans may be used in stables for temporary relief to disrupt warm, stale areas or to provide a cooling breeze over the horse’s body. These fans move air already in the stable so they do not provide more fresh air to the horse. A properly designed stable ventilation system should virtually eliminate the need for circulation fans.