It is a type of “air conditioner” that is much more efficient than refrigeration systems. If you grew up in the Midwest, or in a humid place like Florida, chances are you’ve never heard of a swamp cooler, and your local air conditioning contractor definitely wouldn’t have offered them.
The technical name is an evaporative cooler. During the summer in most states, you want humidity stripped from the air, as the hot, sticky summer weather is uncomfortable. However, in some desert climates, the summer air is actually low on humidity. In these climates, homes can be cooled using a swamp cooler, which evaporates water into dry outside air, and blows this into the home.
During the 1920’s in the Arizona desert region, people would sleep outside in screened-in porches on hot summer nights. Blankets or sheets soaked with water would be hung on the screens, and large electric fans would pull the night air through the moist blankets to cool the room. These were evaporative coolers in primitive form – way less technology to deal with as an air conditioning contractor back then!
Swamp coolers rely on evaporation to cool the air in your home. A motor pumps water into a mesh pad type filter within the cooler. Then another fan motor draws hot, dry air from outside, and forces it through the soaked pads. The evaporation that occurs actually uses heat energy (known as enthalpy of vaporization) which is why the air becomes cooler. In arid climates, a swamp cooler can cool the air by as much as 30 degrees.
If the air is humid, these coolers are not effective. With 50% humidity and the outside air in the 90’s, a swamp cooler may get you down to high 70’s inside. However if the humidity is at only 10%, the inside temperature could drop to the high 60’s.
A normal system installed by your air conditioning contractor uses refrigeration to cool an area. In a basic sense, this is taking the heat energy from one location, and moving it to another. The output of air conditioners is rated with British Thermal Units (BTUs). Evaporative coolers are rated by CFMs, which stands for “cubic feet per minute”, and relates to the air flow moved through your home.
To calculate the CFMs needed for your living space, divide the cubic feet you want to cool by two. This will give you the CFM rating you’ll need. Example:
A 2000 square foot home with 10-foot ceilings: 2000 x 10 = 20,000 % 2 = 10,000 CFM needed.
Evaporative coolers can use as much as 75 percent less energy than a normal air conditioner. For hot desert climates, this can mean substantial savings.
An evaporative cooler also costs about half as much as an air conditioner needed to cool the same sized area. Some utility companies such as California PG&E offer rebates for homeowners who install whole-house evaporative systems. Ask your air conditioning contractor about possible utility incentives in your area.
Additionally, normal A/C systems work best with all of the windows shut because this technology works by removing heat energy from inside air, and moving that heat energy outside. Swamp coolers work by the evaporating water into dry air from outside, which guarantees a constant flow of fresh air into the home. Air doesn’t become stale and polluted with VOCs and other contaminants that can be introduced due to the sealed house of typical split systems.
Even the dry, Mediterranean climate of California still has summer months where rain can happen, increasing the humidity in the air, and rendering a swamp cooler useless. These coolers also require from 3-15 gallons of water each day to work, which can be an issue for some areas. Swamp coolers also will not work with small ducting in a large home, as more airflow is needed than with a traditional system.
Newer, 2-stage versions are available that cool the air some before it hits the pads, and they boast the same ability as normal air conditioning systems, however the cost on this equipment goes up a bit.
Read more at the California Consumer Energy Center.
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