An evaporative air cooler cools a workshop by drawing hot outside air through wet pads. The water evaporates and absorbs heat, so the air leaving the unit comes out cooler than the air that went in. In a hot, dry climate that drop is real: 5–12°C in most conditions, and up to 10–15°C where the air is very dry. The payoff shows up on the energy bill, too. Direct evaporative coolers can run on less than 20% of the electricity a standard air conditioner uses, when the climate suits them.
This guide covers how to size one, what to compare between models, and the cases where evaporative cooling is the wrong tool.
How It Works, and Why the Energy Bill Is Different
Air is pulled through constantly wetted cellulose or synthetic pads. Evaporation lowers the air temperature toward the wet-bulb temperature, which depends on humidity as much as on the dry-bulb reading on a thermometer. No compressor is doing the heavy lifting. A fan and a small water pump are the main power consumers, so most of the running cost is fan power.
That is the fundamental difference from refrigerated air conditioning. An evaporative cooler trades a little water for a lot of electricity.
When Evaporative Cooling Works, and When It Does Not
Evaporative cooling is a dry-climate technology. As a rule of thumb, it works well below about 60% relative humidity. Above 70%, the air is already close to saturation and the cooling effect falls sharply.
It has a second benefit in a factory: the air is drawn in fresh and pushed through, so the cooler also ventilates the space. That flushes out heat, fumes, dust and stale air instead of recirculating them. In an open, high-heat workshop, that is often worth as much as the temperature drop itself.
It is not the right tool in humid coastal areas, or for a process that needs a tight temperature and humidity range. For those, a refrigerated system, or a sealed cold room, is the correct choice.
Size It by Air Changes
The standard way to size workshop cooling is by air changes per hour:
Total airflow (m³/h) = room volume (m³) × air changes per hour
Industrial workshops usually need 20–40 air changes per hour. Machine shops and assembly areas often land around 25–30. Processes with ovens, molding, or other concentrated heat go higher.
A 20m × 30m × 3.5m workshop has a volume of 2,100m³. At 30 air changes per hour, the total airflow needed is 63,000m³/h.
Ballpark coverage numbers, assuming a normal factory ceiling height:
- 12,000m³/h ≈ 80–100m²
- 16,000–18,000m³/h ≈ 100–130m²
Several smaller units usually beat one giant one. They spread the air more evenly, add redundancy, and let you stage cooling by shift.
What to Compare Between Units
- Airflow in m³/h, and static pressure if the air is ducted
- Cooling efficiency and the expected temperature drop in your climate
- Water tank size and consumption; a 12,000m³/h unit can use around 10–12L/h
- Noise, around 70dB(A) on larger units, if people work close by
- Power draw in kW and the supply it needs: single-phase or three-phase
- Controls: variable speed, timer, remote monitoring
Installation and Maintenance
Place the units on the cooler, shaded side of the building and give the air a clear path both in and out. Without exhaust openings or roof ventilators, the room pressurizes and airflow drops.
Plan for water supply, drainage, and a way to flush the tank. Maintenance comes down to a few items: clean or replace the pads, flush the tank and change the water regularly, keep the pump and water distribution clear, and check fan guards and belts. Stagnant water becomes scale and algae, and hard water shortens pad life.
Evaporative Cooler vs Refrigerated Air Conditioning
Choose an evaporative cooler when the workshop is open, the climate is dry, and the goal is whole-space comfort plus ventilation at low running cost. It will not hold a precise temperature.
Choose refrigerated air conditioning for sealed or clean spaces, humid climates, or a room that must hold a set temperature. The energy cost is higher, and the compressor and condensing unit do the work.
The two are often paired: evaporative cooling for the main workshop, refrigerated cooling for a small QC room, lab, or office.
Information Needed for a Quote
- Workshop floor area and ceiling height, and whether the space is open or partitioned
- Local summer temperature and humidity
- Number of workers and the main heat sources, such as ovens or machines
- The goal: general comfort, or a specific setpoint
- Available water supply and drainage
- Power supply: voltage and phase
- Ducted cooling or spot cooling
Frequently Asked Questions
How much can it cool?
It depends on humidity. Expect 5–12°C in most dry-climate conditions, and more where the air is very dry.
Does it add humidity?
Yes. Evaporative cooling raises indoor humidity, which is exactly why it works best in dry climates.
Can it replace air conditioning?
For comfort cooling in an open workshop in a dry climate, yes. For a space that must hold a precise temperature or humidity, no.
How many units do I need?
Work it out from air changes: room volume × air changes per hour, then divide by the airflow of one unit.
Need an Evaporative Air Cooler for Your Workshop?
BesCool supplies industrial evaporative air coolers for workshops, warehouses, and factory floors. Send us your floor area, ceiling height, local climate, and power supply, and we will come back with a sizing and a quotation.
Contact BesCool for an evaporative air cooler quotation.
Sources and Further Reading
- International Institute of Refrigeration (IIR): The energy and comfort performance of evaporative coolers
- Honeywell Air Comfort: Evaporative air cooler humidity guidance
- Workspace Cooling: Evaporative cooling sizing by air changes
