What the Heck is a Swamp Cooler, Anyway?

If you’re asking this question, partner, you’re not from around these parts!

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“Swamp Coolers”

A swamp cooler, also known as an evaporator, desert cooler or evaporative cooler, cools air through the evaporation of water. The mechanism was first patented in the US in 1906 but the concept was pioneered by the ancient Persians and Egyptians for cooling buildings in the desert passively by directing dry hot air into “windcatchers” then over a pool of water.

Evaporative cooling is especially popular and well suited for climates worldwide where the climate is hot and humidity is low. A swamp cooler will work well in very dry climates in all but the hottest most humid weather. The evaporative unit consists of a pump that sits in the bottom of a big box which pushes water up to the top of each of its sides to drip down excelsior (aspen wood wool) pads. The pads absorb water which a pump drips over them while a fan pulls hot exterior air through them causing evaporation and cooling of the air and distributes cooled air. Evaporation and the combination of moisture and a steady air movement, will drop the temperature by as much as 30⁰F. The dryer the exterior air is, the more effective is the process of evaporation and subsequent cooling results.

The cooled space must be vented to allow the continuous supply of cooled air to blow through unrestricted to the outside. These systems force about 15 air exchanges per hour, a relatively high rate which may be beneficial in industrial and commercial kitchens, factories laundries and dry cleaners where exhausting fumes as well as heat is critical. Evaporative coolers are available in portable, window, roof or ground mounted options.

How do Swamp Coolers Compare to Air Conditioning?

Swamp coolers cool outside air as it enters the building whereas air conditioning continuously cools and re-cools the same recirculated interior air allowing temperature to get much colder than evaporative cooling.

Evaporative cooling is much cheaper than air conditioning, and despite some drawbacks, it is still widely used in desert communities. Installation and operating cost of evaporative cooling is much lower than air conditioning by about 80% or so. All cooling equipment including swamp coolers and air conditioners require regular maintenance. The swamp cooler will need seasonal cleaning, and replacement of pads, tubing, pumps and fans. Many simple units can be maintained by the homeowner assuming it is located in an accessible location while air conditioners generally need professional attention.

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Swamp coolers differ from typical air conditioning systems which use refrigerant-compression which use more energy and more complex equipment. In hot arid climates such as Southern Arizona, evaporative cooling offers a cost effective alternative for certain applications by reducing energy consumption, maintenance and total equipment costs for cooling and conditioning air as compared to air conditioners. Evaporative cooling is widely used in industrial plants, factories, warehouses, loading docks, construction sites, athletic events, and in dairy, hog, and poultry farming. While many people cool their homes using evaporative cooling, the low cost of running a swamp cooler makes cooling a garage, workshop, semi-enclosed patio, cabana, animal habitats, kennel, greenhouses or atriums affordable.

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Even in mostly arid regions, short periods of relatively high humidity may prevent evaporative cooling from being an effective cooling strategy, for example southern Arizona’s monsoon season in July and August. Swamp coolers significantly increase interior humidity whereas air conditioning removes humidity. Increased humidity may be considered desirable for some applications and a problem for others. High humidity tends to make people feel hotter in warm weather and colder at chillier temperatures but also rehydrates skin and sinuses. When cost and comfort are important, but swamp cooling is too “swampy” and typical air conditioning is too expensive, you might consider a highly efficient ductless mini-heat pump (also known as a mini-split- see our blog for more on mini-splits).

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