Roof-mounted Evaporative Cooler Recommendations

Cost

• Compared with house air conditioning units, roof-mounted evaporative coolers are cheaper to install and operate. As of 2011, the cost of purchasing and installing an evaporative cooler is about 25 to 30 percent of the cost of buying and installing an air conditioning system. An evaporative cooler uses 20 to 30 percent as much electricity as an air conditioner, and this reduced usage results in a lower electricity bill. Often the homeowner can complete much or all of the annual maintenance and repairs for an evaporative cooler.

Design

• Evaporative coolers mount on the roof or in a window. It is often less expensive to install an evaporative cooler on the roof than in a window, and the unit is out of the way when on the roof. An evaporative cooler for a residence usually has a metal housing, electric motor, blower, water pump, water reservoir, float value and water lines. Pads made of aspen wood fibers or other materials are installed inside the housing. The unit plugs into a standard wall plug. The size of the evaporative cooler largely depends on the size of the house it cools.

Evaporative Cooler Size

• Roof-mounted evaporative coolers range in capacity from 3,000 to 25,000 cubic feet per minute. To estimate the required size, find the square feet in the house. Multiply this number by the ceiling height and divide by 2. For example, to find the evaporative cooler size for a 1,200-square-foot house with an 8-foot ceiling, multiply 1,200 by 8 and divide by 2. The result is 4,800. Find an evaporative cooler model close to 4,800 cfm.

Requirements

• Depending on the model and the climate, evaporative coolers use 3.5 to 10 gallons of water per hour. It is recommended that the cooler be checked monthly. The belt and the water level are adjusted and the water from the reservoir is drained to remove mineral buildup. Replace the pads as they fill with mineral deposits. This maintenance may be more difficult when the cooler is mounted on the roof.

Problems

• If the evaporative cooler isn’t used for a few days, drain the water reservoir or add a commercial product to reduce bacterial growth in the water. When operating, a roof-mounted evaporative cooler requires 1 to 2 square feet of open window space per 1,000 cfm of cooling capacity. Sometimes an open window is a security problem and vents rather than an open window are required. Some models of roof-mounted evaporative coolers are noisy when running. Without proper installation, the roof may leak around the evaporative cooler.