The benefits of a roof-mounted swamp cooler include direct access to the attic for connecting the cool air to a duct system. Duct systems work best for larger homes that have multiple bedrooms off a hallway. Other benefits are similar to those of horizontal-flow swamp coolers.
The cooling process used by swamp coolers requires less energy than that of a standard air conditioning system. Swamp coolers require one electric motor to turn the blower and a smaller motor to operate the pump. They use cooling from the evaporation of water to lower the air temperature. The process lowers the temperature of the air they pull into the home by 15 to 40 degrees in areas where the humidity is low. Swamp coolers create pressure that forces stale air from inside the home out the windows.
In arid regions, swamp coolers provide additional humidity that protects the furnishings of a home from drying and cracking. However, in areas where the humidity is already high, the additional humidity causes rooms to feel muggy and encourages the growth of mold.
While most swamp coolers are roof mounted, many experts prefer ground-level horizontal-flow units because they are easier to access for maintenance. Installing the swamp cooler on the roof also increases the chances of leaks. Horizontal units are most effective in smaller homes with open areas.