CCPIA Articles - Certified Commercial Property Inspectors Association

An evaporative cooling system is different from an air conditioning system in that an air conditioning system relies on refrigerant gases and a chemical process to cool the air, whereas an evaporative cooling system uses water to cool the air.

(Here, we discuss evaporative coolers, also called swamp coolers, that utilize direct evaporative cooling technology. Read “Evaporative Cooling at Commercial Buildings” to learn more about the different types of evaporative cooling.)

Put simply, direct evaporative coolers cool the air by evaporating water. This process increases the moisture content of the air and is thus a system best used in hot and dry regions.

Types of Evaporative Coolers/Swamp Coolers

When looking at evaporative cooling, there are two basic methods: portable and permanently-installed systems. Both rely on similar methods for producing cool air in buildings.

Portable Evaporative Coolers

Commercial property inspectors are only required to assess permanently installed or built-in components and equipment. Since portable evaporative coolers are not permanently installed, they are beyond the scope of an inspection performed in adherence to the ComSOP.


  • Cost-effective
  • No installation
  • Sizes up to 500,000 cubic feet of space


  • Consumes water; will need topping off
  • Needs good natural ventilation
  • Is trying to cool very warm air
  • Performance depends on ambient humidity
  • Noisy

Suited to:

  • Small industrial or commercial spaces
  • Applications that are:
    • well ventilated
    • not sensitive to noise
    • not troubled by airflow

Permanently-Installed Evaporative Coolers

Unlike a portable evaporative cooler, a permanently-installed evaporative cooler is a type of permanently installed HVAC equipment, and thus should be assessed during an inspection.

The cooler can be installed to blow air directly into a central location, or the cooler can be connected to ductwork in different rooms. These systems are typically installed on the outside of a building. Down-flow systems, which are mounted on the roof and connected to a duct system, are the most common type. However, inspectors may also come across ground- and wall-mounted units. Use CCPIA’s Inspection Checklist for Evaporative Coolers/Swamp Coolers to assess exterior direct evaporative coolers.

This unit is a wall-mounted evaporative cooler/swamp cooler.

The presence of a water fill line and label indicates the unit is an evaporative cooler/swamp cooler.


  • Cost-effective
  • Cools outside air (which is already cooler than indoor air)
  • Cool air is ducted to where it’s needed inside
  • Warm air is displaced to the exterior
  • Cool air supplies up to 2,130,000 cubic feet of space

Compared to mobile units:

  • More efficient cooling
  • Less noise (fan is outside)
  • Permanently connected to a water supply
  • Out-of-sight, out-of-mind cooling

Suited to:

  • Large industrial and commercial buildings
    • Manufacturing
    • Warehouses, distribution centers, food-processing facilities
  • Special-use buildings
    • Sports arenas
    • Greenhouses
    • Schools
    • Medical labs
    • Data centers

How Evaporative Coolers/Swamp Coolers Work

Evaporative coolers/swamp coolers are a fairly simple device consisting of a box-like housing. The cooling system works by pulling in the outside air through pads that are thoroughly wet by water that is sprayed or dripped on them. This process creates a feeling of latent heat of evaporation. The resulting fresh, cool, humidified air is blown into the building, where the pattern of airflow (and how the cool air is delivered) is determined by the location and number of openings in the conditioned envelope, such as windows or special dedicated ducts.

Typical parts of an evaporative cooler/swamp cooler:

  • Blower fan: This high-volume fan circulates the outside air through the pad and into the building.
  • Motor: This is the power source for turning the fan.
  • V-belt: This is attached to the motor to turn the fan by the motor and blower pulleys.
  • Water trough: This is the reservoir at the bottom where the water collects. Water is drawn from this reservoir by the pump.
  • Float valve: The float valve refills the water trough and shuts it off when it gets to the proper level. This adjustment is similar to that of the toilet flush valve.
  • Pump: The pump pulls water from the trough at the bottom and pumps it to the top of the pads, where it distributes it through a drip, spray bar, or nozzles for moistening.
  • Pads: The pads get moistened from the pump discharging water onto the top. As the water soaks down, it moistens the entire pad.

Common Concerns of Evaporative Cooler/Swamp Cooler

It is a 100% outside-air system, so it is important that careful attention be paid to the location of any exhaust vents or anything else that could introduce odors or pollutants into the building. Similarly, issues can occur if stale water is not properly drained or gets contaminated. Some units may be equipped with automatic draining systems.

Additionally, evaporative cooling systems require a continuous water supply, thus it is susceptible to salt build-up in the unit, which can lead to rust, corrosion, clogged parts, or contaminated water and air. For additional information about inspecting evaporative coolers/swamp coolers, review CCPIA’s Evaporative Cooling/Swamp Cooler Inspection Checklist.

Takeaway for Commercial Property Inspectors

Commercial property inspectors are required to inspect permanently installed evaporative coolers, also referred to as swamp coolers, whereas they are not required to inspect portable evaporative coolers. Evaporative coolers cool the air using evaporation, consequently increasing the moisture content of the air blown into a building. Commercial property inspectors should assess the various readily accessible elements of the unit and make sure the unit is free of damage and clogs.

Article Written by: Rob Claus, CMI® and Maggie Aey

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