What types of evaporative coolers are there to choose from?
Direct evaporative coolers add moisture to the air while increasing the relative humidity. Direct systems require a building’s exhaust system to match the rate at which the conditioned air is introduced to the space without circulating the same air. (Central air conditioning systems sometimes work similarly to direct evaporative coolers.) Indirect evaporative coolers lower the temperature without adding moisture to the air. However, this type is more expensive than the direct type. Keep in mind that indirect systems provide the same energy efficient alternative as a direct cooler, in situations where the direct type may not be practical or useful.
