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VETERINARY VIEWS
CLEAN AIR RECOMMENDATIONS
Ridding a barn of ammonia relies on good ventilation and practical hygienic strategies. Ventilation is best achieved by providing air flow to flush stale air out and allow fresh air to enter the barn. A stable with appropriate ventilation has openings that are open year-round. Moisture condensation stains and degrades a building structure while
high levels of humidity cause a barn to feel chill, dank and stuffy. Allowing a stable
to “breathe” reduces ammonia, odors, and humidity to keep a barn fresh and dry even in the coldest weather.
The best recommendation for horse stables in winter is to change air turnover 4-8 times each hour but because air changes are virtually impossible to measure, ventilation recommendations are based on proven general rules: Permanent openings that provide at least 1-square-foot of opening per horse work best as a long slot rather than
a square. For example, a one-inch wide, permanently open slot at the eaves along
the entire 12-foot length of the stall allows for air exchange. Placement of this slot inlet high up at the eaves allows fresh, cold air to
enter in a thin air stream that mixes quickly with the still, slightly warmer stall air to move stale air outward. Openings larger than 1-square-foot maintain good air quality year-round and can be fitted with adjustable openings for warmer weather.
It helps to take advantage of thermal buoyancy – warm air rising. Moist air is less dense and rises to high openings, especially if warm. As it rises to the high openings, a mild ‘siphoning’ or stack effect allows fresh, outside air to enter the stable through lower openings. Thermal buoyancy is one of two “natural ventilation” driving forces; the other is wind, which is much more effective than thermal buoyancy in ventilating a horse stable.
Of similar importance is to locate at least two sets of openings on different parts of the building; one ventilation opening alone isn’t effective at improving air quality throughout the stable. Include eave openings along both long sidewalls or at the eaves (low) and ridge (high) of the roofline. Cupolas with openings can replace ridge vents by providing an outlet for warm, moist odorous air at the top of the stable roof that allows wind to move air into and out of the stable.
Allowing a stable to “breathe” reduces ammonia, odors, and humidity to keep a barn fresh and dry even in the coldest weather.
Well-ventilated stalls can be optimized for air flow by using open partitions between stalls. Doors with mesh or sturdy screening to both the outside and stall interior enable crossflow breezes throughout the stable when housing horses inside on hot days.
FANS
Fan-driven ventilation relies on fresh air inlets, fans and controls that allows precise air exchange rates. A heavily insulated barn implies that “supplemental” heat is planned; therefore, provide mechanical-fan ventilation when heat is supplied during cold weather. Poor interior air quality results from using horse body heat to warm a barn. Insulation does nothing to directly improve air flow – in residential homes, it only reduces heat loss through the structure’s surfaces whereas in a horse stable, heat is mostly lost through the ventilation system, yet ventilation is needed to maintain good air quality. To reduce condensation in a heated barn, it works best if the interior wall temperature approximates stable air temperature. In an unheated and well-ventilated barn, air temperature tends to remain within 5 to 10o F of the outdoors.
Fan-driven ventilation relies on fresh air inlets, fans and controls that allows precise air exchange rates.
70 SPEEDHORSE July 2021