How do evaporative coolers work in horse facilities and when are they most effective?

Evaporative coolers — sometimes called swamp coolers — are mechanical units that draw hot outdoor air through water-saturated pads, causing the water to evaporate and absorb heat from the air before that cooled air is distributed into the building. They are an energy-efficient alternative to refrigerative air conditioning for facilities in appropriate climates, and they can maintain significantly lower temperatures in barns and arenas during hot weather. The fundamental operating principle — evaporation absorbing heat — means that these systems are most effective in hot, dry climates where low relative humidity allows rapid evaporation from the pads. In arid regions, evaporative coolers can produce significant temperature drops while consuming a fraction of the energy that refrigerative cooling would require for the same effect. In humid climates where the air is already carrying significant moisture, the evaporation rate from the cooling pads is reduced and the cooling effect is correspondingly diminished. Horse facilities that use evaporative coolers benefit from ensuring adequate air movement through the building so that the cooled air is distributed throughout rather than concentrated near the unit. Open doors, windows, or vents on the side of the building opposite the cooler allow hot air to escape as cooled air is introduced. A sealed building with an evaporative cooler simply adds humidity without adequate cooling because the humid air has nowhere to go. Maintenance includes regular cleaning of the water pads to prevent mineral buildup and biological growth, checking the water distribution system for even saturation across the pads, and winterizing the water system in climates where freezing temperatures occur.