Proper Ducting for Swamp Coolers

Evaporative coolers are also known as "swamp coolers," a system for homes and buildings which emits moisture to keep the air cool. This method of cooling is popular in the dry climate of the Southwestern United States. Existing ducts for conventional heating, ventilation and air conditioning may work for swamp coolers depending on the size of the premises. For efficiency, you may need to enlarge the ducts or reduce them to a window opening depending on the cubic feet of the area and size of the cooling unit.

Cooling system on exterior of building
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Installing a cooling system on the roof could result in leaks.

Size

Swamp coolers need more volume of air flow than a conventional air conditioner because swamp coolers produce warmer air supply. The ducting system should handle the increased volume of air blown into the house. First you need to determine the right cooler. Divide the cubic feet of space you want to cool by two for the required cubic feet per minute of air blown into your home to determine the right cooler. The formula for a 1,500 square foot home with ceilings 8 feet high calculates as 1,500 x 8 = 12,000 cubic feet and then 12,000/2 = 6,000 cfm. You will need a swamp cooler with 6,000 cfm. For coolers 4500 cfm or smaller, use 18" ducts, 20" for up to 5500 cfm and 24" for 6500 cfm.

Installation

Homes with hallways and multiple bedrooms require duct installation for swamp coolers. Installers commonly used down-flow swamp coolers on roofs to flow through ducts. Flowing air through ducts from ground-mounted horizontal units makes maintenance easier with less risk of leaks on the roof.

Security

Opening or closing windows regulates the temperature and humidity. Installing up-ducts in the ceiling will properly duct the area where opening windows could present a security issue. Up-ducts release warm air into the attic and allows the cool air from the swamp cooler in. You may need additional attic ventilation for this method of duct installation.

Small Units

Swamp coolers depend on dry, outside air. During hot and muggy weather, the coolers blow in hot, humid air which can emit a musty odor through the duct work into the house. Small premises have the advantage of installing a small unit in a window to blow cooled air directly into a room. Compact houses might not require ducts and can keep cool with central-location installations.