Evaporative coolers, also called swamp coolers because of their air-moistening abilities, work by drawing warm air from the outside through a water-wetted pad. This produces cooler (up to 35°F cooler), moist air, which is then circulated throughout the building. Warmer inside air is then forced out of the building through windows or vents. To see how it works, check out The Consumer Energy Center's animated illustration.
How to install an evaporative coolerThe first step in obtaining an evaporative cooler is to choose one that will work for you. When purchasing a new evaporative cooler, consider these factors:
- Location: Because swamp coolers must draw outside air in, they have to be installed outside of a home. They come as portable units and can be mounted in windows for room-specific cooling, or installed on roofs, in attics, or at ground-level using dedicated ducts in a whole-building system. Evaporative coolers also require water, so you'll need to choose a location close to a water source.
- Types of coolers: Direct coolers come in two varieties: fiber pad and rigid pad coolers. Fiber pad coolers are the most common. They employ 1- to 2-inch thick plastic-netted wood- or synthetic-fiber pads. Rigid-sheet pad coolers, on the other hand, require stacked corrugated sheet material that is 8 to 12 inches thick and can handle higher velocities than fiber pad coolers. Indirect evaporative coolers are also called two-stage coolers because they use the basic direct cooler method as well as a secondary heat exchange, which prevents humidity from being added to the air stream. These chillers are pricier but will cool a room as effectively as an air conditioner.
- Water exchange: In order to prevent water from becoming brackish, some recommend installing a bleed-off system to infuse the cooler with fresh water. This will reduce the maintenance required to keep your cooler running, but will require about 5 additional gallons of water per hour.
- Size: Swamp coolers are rated by the cubic feet per minute (CFM) of air they can circulate. You can figure out how large your system needs to be by using this formula: Room square footage x height of ceilings, divided by two). For example, if you're room is 1,100 square feet with 9 foot ceilings, the formula will look like this: 1,100 x 9 = 9,900. Then 9,900/2 = 4,950. You'll therefore need a machine that has a minimum of 4,950 CFM capacity. Sizes range from 3,000 to 25,000 CFM.
- Features: Look for a unit with multiple fan speeds and a vent-only option so that you can vary the operation based on the weather. You may also want to find one with an air filter system to keep dust and pollen out.
Find it! Evaporative coolers
Before you buyThere are a few drawbacks to evaporative coolers that should be considered before purchasing one. Evaporative coolers work best with dry air, and aren't really suited for humid areas, so you'll need to live in a dry climate to consider one. Evaporative coolers are also water-intensive — they can use up to 15 gallons of water per day (more if it has a bleed-off system) or 19,000 gallons per household per year. When installed on the roof, an evaporative cooler can cause damage to roofing materials (as they leak water) and can be difficult to maintain.
Evaporative coolers also need regular cleaning and maintenance, unlike other cooling devices, so make sure you can keep up with yours before buying one. To keep your swamp cooler in good working order, you'll need to:
- Drain and clean the cooler: If sediment and minerals build up in your cooler, its efficiency will drop dramatically. To prevent this, be sure to adopt a monthly cleaning/draining schedule. Inspect the pads, filters, reservoir, and pump and give them a good scrubbing when needed.
- Replace pads: Follow the manufacturer's recommendations about replacing the pads to ensure your machine is at its best.
Installing an evaporative cooler helps you go green because
- They use much less energy to cool your space than an air conditioner.
- They're chlorofluorocarbon (CFC)- and hydrochlorofluorocarbon (HCFC)-free, which means they won't damage the earth's ozone layer.
- Air quality in your home is improved with infusions of fresh air.
Operating without the use of CFCs and HCFCs, evaporative coolers do not pose the same ozone-depleting threat as conventional air conditioners. However, since evaporative coolers work best in dry climates, higher humidity locales cannot benefit from these systems.
Tax breaks and subsidiesSome electric companies provide rebates for those purchasing evaporative coolers:
- PNM (New Mexico) offers rebates up to $400 for residential electricity customers who install evaporative cooling systems.
- Southern California Edison gives rebates between $300-600 per unit for ducted evaporative cooling system installations.
- xcel Energy (Colorado) provides rebates for residential electricity customers installing energy-efficient evaporative cooling equipment.
- Alliance to Save Energy: Offers an index of energy efficiency programs by state.
- Database of State Incentives for Renewables & Efficiency: Provides information on state and federal incentives.
Related health issuesBy filtering dust and pollen from the air and pumping it indoors, evaporative coolers can improve a building's air quality, reducing allergies, asthma attacks, chemical sensitivities and more.
- chloroflourocarbon (CFC): A haloalkane compound containing chlorine, primarily used as a refrigerant. When this gaseous compound reaches the stratosphere, UV light liberates the chlorine from the molecule and it is then capable of breaking down up to 100,000 ozone molecules (O3) into O + O2. Freon is a trademarked term referring to CFCs used in refrigeration and cooling systems.
- hydrochlorofluorocarbon (HCFC): A similar haloalkane compound where not all the hydrogen atoms are replaced by a halogen atom. These are typically used to substitute for CFCs, as the ozone-depleting capacity of these compounds is 10 percent less than that of CFCs.
- ozone layer: Part of the earth's atmosphere, the ozone layer contains relatively high concentrations of ozone (O3). Ozone acts like a blanket that protects the earth from damaging UV radiation, which has been linked to cancer.
- Consumer Energy Center - Evaporative Cooling
- Home Energy - Installing and Maintaining Evaporative Coolers
- Oikos Green Building Source - Evaporative Coolers: An energy-saving way to beat the heat
- The Green Guide - The Cutting Edge of Cool: Evaporative Coolers
- ToolBase Services - Evaporative Coolers: Summary
- ToolBase Services - Evaporative Coolers: Operational Cost
- US Department of Energy - Evaporative Coolers
- The Green Guide - Keep Your Cool with Less AC: Pump Up the Cool
- Consumer Energy Center - Evaporative Cooling: How an Evaporative Cooler Works
- Home Energy online - Installing and Maintaining Evaporative Coolers: Cooler Performance
- Do It Yourself.com - A Guide to Evaporative Coolers
- US Environmental Protection Agency - Ozone Depleting Substances
- ScienceDaily - Ozone layer
- US Environmental Protection Agency - What You Should Know about Refrigerants When Purchasing or Repairing a Residential A/C System or Heat Pump (see bottom of page)