Evaporative Cooling Make-Up Air Unit
Cooling tens of thousands of CFM of outdoor air with mechanical refrigeration drives your power bill up fast. In a dry climate, an evaporative cooling make-up air unit cools the same supply air for a fraction of that energy, using water and an evaporative media instead of a compressor.
We spec evaporative cooling make-up air units across multiple manufacturer lines and match each unit to your airflow, climate, and water supply. Every unit is US-made and backed by strong manufacturer warranties.
RWA Ventilation Solutions is an authorized representative/distributor for the leading American manufacturers of makeup air equipment.
These manufacturers have selected us to represent them because of the skills of our sales engineers as well as our company mantra:
“Our knowledge is your knowledge”
Key Takeaways
How Evaporative Cooling Make-Up Air Units Work
An evaporative make-up air unit pulls warm outdoor air through a wetted media, where evaporating water absorbs heat and drops the air temperature before it reaches your space.
Direct evaporative cooling adds that moisture straight to the supply air, while indirect cooling drops the temperature through a heat exchanger without raising humidity. Wet-bulb temperature sets the floor in either case, so the drier your outdoor air, the deeper the cooling.
When your application cannot tolerate any added moisture, a chilled water make-up air unit handles the load without humidity gain.
Evaporative Cooling MUA Specifications and Configurations
Sizing an evaporative unit starts with your design entering conditions, target leaving temperature, and required airflow, then works back to media depth and water treatment.
Run your numbers through our make-up air sizing calculator to scope airflow and cooling load before you spec. The ranges below cover most commercial and industrial cooled make-up air configurations.
| Parameter | Typical Range |
|---|---|
| Airflow (CFM) | 800 to 64,000+ |
| Saturation efficiency, direct | 85 to 90% |
| Saturation efficiency, indirect | ~75% |
| Evaporative media | Rigid cellulose, glass fiber, or synthetic polymer, 6 to 12 in depth |
| Face velocity | 400 to 600 FPM |
| Dry-bulb temperature drop (dry climate) | 20 to 28°F |
| Approach temperature | 2 to 4°F |
| Water consumption | ~0.25 to 0.35 gal/hr per 1,000 CFM |
| Construction | Indoor or outdoor-rated cabinet, UL900 media |
Advantages and Disadvantages of Evaporative Cooling
Evaporative cooling wins on operating cost and simplicity, but the same physics that makes it cheap also sets its limits. Whether it fits your facility comes down to two questions: how dry is your climate, and how much added humidity can your space tolerate. The breakdown below weighs both sides so you can match the technology to your application before you spec.
Advantages
The savings come from what the unit does not have. With no compressor and no refrigerant circuit, an evaporative unit cools high-volume supply air on a fraction of the energy a mechanical system needs.
| Advantage | What It Means for You |
|---|---|
| Fan and pump power only, no compressor | Cooling energy runs a fraction of a comparable DX unit |
| Zero refrigerant | No EPA Section 608 compliance, no charge, no leak risk |
| No compressors or condensers | Fewer parts to service and lower long-term maintenance |
| High-volume cooling economics | Cools large CFM at a cost mechanical cooling cannot match |
Disadvantages
The limits trace back to the same evaporation that drives the cooling. Every degree of temperature drop comes from adding water to the air, which constrains where and how the technology performs.
| Disadvantage | What It Means for You |
|---|---|
| Adds moisture in direct configurations | Supply humidity rises, which some spaces cannot tolerate |
| Performance tracks outdoor humidity | Cooling drops off as wet-bulb climbs in humid climates |
| No dehumidification | Moisture-sensitive spaces need a downstream cooling stage |
| Requires water and treatment | You need a reliable water supply and a treatment program |
Standard Features
Most evaporative make-up air units share a common set of water, control, and motor components regardless of manufacturer.
- Submersible recirculation pump with float-operated makeup valve and open sump drain
- Adjustable bleed-off or conductivity-based blowdown control for scale management
- UV sterilization or biocide injection options for biological control
- Blower motor available with VFD for part-load and static pressure reset
- Control sequence with pump interlock, high-limit cutoff, and low-ambient lockout
Where Evaporative Cooling Make-Up Air Works Best
Climate decides the fit before anything else. Evaporative cooling delivers its full temperature drop where the outdoor air is hot and dry, with a wide gap between dry-bulb and wet-bulb.
In arid and semi-arid regions, a unit can pull supply air down 20 to 28°F on water alone. As outdoor humidity climbs, that drop shrinks, so humid coastal climates see far less benefit and often need a mechanical stage instead.
The technology earns its place in facilities that move large volumes of air and can accept some added humidity.
High-exhaust operations are the strongest fit, where evaporative supply air replaces what the process pulls out at a fraction of the cooling cost.
- Warehousing and distribution centers with high dock and forklift exhaust
- Manufacturing plants in metal fabrication, automotive, and food processing
- Pharmaceutical facilities, using indirect configurations where humidity must stay flat
- High-exhaust process environments with welding, coating, or fume hood exhaust
For spaces that need cooling without any humidity gain, our make-up air unit lineup covers tempered and mechanically cooled options across the full range of configurations.
Why Engineers Spec Evaporative Cooling MUA With Us
Specifying evaporative cooling is a climate and application decision before it is a product decision. Because we carry multiple manufacturer lines, we size the unit to your entering conditions, target leaving temperature, and water supply without steering you toward one brand. You get the configuration your application calls for, whether that points to direct, indirect, or a mechanical stage instead.
Every unit we spec is US-made and backed by strong manufacturer warranties.
If a warranty issue ever comes up, we handle it with the manufacturer directly, so you are never left working that out alone. Call us at 847-262-3457 ext. 23 to review your specs and size the right unit for your facility.
Frequently Asked Questions
Does an evaporative make-up air unit work in my climate?
It depends on how dry your outdoor air runs during cooling season. Hot, dry climates get the full 20 to 28°F temperature drop, while humid regions see much less. Tell us your location and design conditions and we will tell you straight whether evaporative makes sense or whether a mechanically cooled unit is the better call.
What CFM range can you supply?
We spec evaporative make-up air units from around 800 CFM for smaller commercial spaces up to 64,000 CFM and beyond for large industrial and high-exhaust facilities. Send us your required airflow and external static pressure and we will match the unit to your load.
Why buy through a distributor instead of going straight to a manufacturer?
A single manufacturer sells you what they build. We carry multiple lines, so we spec the unit your application actually needs and stay neutral on the brand. You get one point of contact for sizing, selection, and any warranty issue down the road.
How do I get a quote?
Call us at 847-262-3457 ext. 23 with your airflow, design entering conditions, and target leaving temperature. We will size the right configuration and get you a quote on US-made equipment backed by strong manufacturer warranties.
