There is one aspect of the paint and coatings finishing business virtually guaranteed to give the budget director heart failure: climate control. There's no way around it – climate control systems are expensive.

Before considering a climate control system, it's important to assess whether your applications truly demand quality finishes of the highest level with guaranteed consistency. In most cases this is true of 24/7 high-volume operations, such as aerospace and OEM automotive, tier 1 production environments.

You might need climate control if:

  • Failure of the coating is not acceptable.

  • Production operations run 24/7 and you can't wait for climate conditions to be right.

  • Your coatings are particularly climatesensitive and react immediately when applied in conditions that are too hot, dry, cold or humid.

Typical problems arising from lack of climate control in the finishing application include:

  • Defects from excess humidity, including blushing, flow of coating, too slow flash-off/cure, adhesion problems.

  • If air is too dry and hot, solvents flash too quickly, coating doesn't flow out to a smooth finish, solvent pops, and orange peel effect or dry spray can occur.

Your coatings supplier should be aware of the impact of these various climate conditions on their products and can offer guidance on optimal application parameters. Also anyone quoting you a climate control system should be using this data in assembling their proposed system setup. If you are replacing an outdated system, the information in this article can also help guide you on how to budget for this expense.

In general, if your organization guarantees the finish, a flawless finish is critical, and production schedules are tight, then climate control is required.

What Affects the Cost of a Climate Control System?

Climate control system design and budgeting is one of the least understood aspects of the finishings industry and among the most complex. Each application requires a customized setup, unique to your company's equipment, coatings, usages, facility, local climate conditions and variations.

To help you understand how to budget for climate control, there are some key metrics to keep in mind:

  • Temperature: 78°F +/- 5°F (your goal temperature with acceptable variation)

  • Relative humidity (RH): 65% +/- 10% (your target RH with acceptable variation)

Air makeup units (AMU's) for wet paint applications in spray booths or the finishing system area are the industrypreferred solution. Perfectly matching your coating suppliers’ climate conditions can be a costly addition to your finishing system or facility, but when properly designed and installed, climate control systems allow consistent, top quality finishes in any climate condition 24/7.

What Codes Require the End User to Do

Codes require replacement air, for air exhausted from your booth or facility. How you do it is up to you. Filtering and heating/cooling inbound air is the accepted industry standard.

Leaving an overhead door open to pull air in is not an option for the highest quality finishes.

How Climate Control Works

Conditioned Air Supply for Finishing Systems, Spray Booths, or Powder Room Enclosures

RH too high - Air is cooled to remove the moisture, reducing the humidity in the air going to the spray booth or system. The air velocity through the AMU needs to be reduced so the moisture (water) drops into the pan and doesn't get blown down the duct. This makes the physical size of the AMU unit larger. Coils and other components increase as determined by the specifications, and units are priced accordingly.

RH too low - This can occur in either very cold or very hot climates. Very hot dry climates (for instance, Phoenix at 120°F) are too hot and too dry for some liquid coatings. Very cold and dry air (i.e., Minneapolis at -20°F for the fifth day in a row) flashes off the moisture from the coating before it can be applied to the part being painted.

The raw air is pulled into the AMU through filters, then passes over the cooling coils. The air may need to be cooled below the spray temperature required in the spray booth to remove the moisture. Then the air is reheated to bring it back up to the right temperature for spraying. To do the above, there are various methods that can add costs if the customer doesn't have the source for cooling/drying the air.

What Is a Typical/Reasonable Cost?

A common question is: What is a typical or reasonable cost for a climate control system? Of course, different organizations may have vastly different definitions of reasonable – and depending on the application, typical costs vary significantly. Some systems may not meet the specifications above but will be discussed here for comparison.

As an example, if 20,000 CFM (cubic feet per minute) is the volume of air required for a finishing application, here are the range of actual costs:

  1. No heat, filtered air: $0.50 to $1.00 per CFM = $10,000 to $20,000. This system might be sufficient in places where the climate is mild and consistent, such as southern California.

  2. Heated, filtered air: This is a typical standard AMU with gas heat (direct fired burner). 20,000 @ $0.75 to $2.00 per CFM is $15,000 to $40,000, depending on the amount of ductwork, and the particulars of the installation area, etc.

  3. AMU with direct fired burner and an evaporated cooler. $2.00 to $4.00 per CFM = $40,000 to $80,000. This is for hot, dry climates, where it generally does not dip significantly below 50°F and the majority of the time is hot and dry.

A psychometric chart can help to understand the complexities of measurement in this area and better understand terms like RH – Relative Humidity, temperature uniformity, etc.

Acronyms, Definitions and Specifications

Water piping for evaporative cooler in an AMU.


  • CFM = Cubic Feet of Air per Minute

  • AMU = Air Make Up Unit also known as MUA, air handler or heater, depending on the market and industry.

  • Other variables include the location of the unit, equipment required for installation; indoor vs. outdoor, roof or stand/ground mounted. Significant variables include: how close to the spray booths will this location be – or how close can the chiller, condenser, boiler, or humidification units be to the AMU and booth?

  • Heat source = gas, steam/hot water, electricity, or other.

  • Cooling Sources = (for drying air) mechanical (standard AC compressor), chilled water, or evaporative cooling (swamp cooler). Desiccant wheel -dryer are also used to dehumidify air.

  • Re-Humidification via gas or electric vaporizer, adding humidity to air that is too dry.

Other Costs

Common added costs include:

  • The amount of duct needed for supply or intake.

  • Piping for chilled or hot water and/or coolant gases, including how far the pipe runs from the unit to the AMU.

  • Compressor location in proximity to location of AMU.

  • Weights of equipment vs. capacity of building roof.

  • Power supply to the HVAC equipment and control wiring. (The footprint of this equipment can be as much or more square footage than the spray booths.) All the above factors must be considered and all affect the price.


  • Temperature: 78°F +/- 5°F (means 73°F to 83°F)

  • RH: 65% +/- 10% (means 55% RH to 75% RH)

This phase of the process begins to quickly multiply the cost of the system. There are ways to lower the below costs if you have chilled water, hot water or steam with enough extra capacity for the new system.

  • Simple Dehumidification: cooling to condense water from the air and then reheat to 70°F/80°F for painting. At $10 to $20 per CFM, a 20,000 CFM system costs $200,000 to $400,000 before installation.

  • Re-humidification: this adds another $10 to $20 per CFM = another $200,000 to $400,000. This is different than #3 (above) where it is hot and dry and water evaporates quickly and easily. This system addresses cold and dry air where water needs to be heated (boil it/turn to steam) and put it into the airstream properly. Too much humidity and it can cause a rain effect in your booth.

  • To summarize, if your system requires just one of the above processes the cost is $200,000 to $400,000; If you need both, it's $400,000 to $800,000.

  • There are exceptions and conditions. A smaller CFM system can cost disproportionally more because the per CFM rule is skewed and a large system has more CFM to spread out the overall cost per CFM.

There are many factors behind the cost: indirect fired burners, boilers, chillers, and re-humidification. For boilers and chillers there is piping, tanks, water treatment, freeze protection, weight of units to support on a building roof or stand, weight of water (8.64 lbs/ gal), and drainage systems. All this equipment has a fairly large foot print and may need to be located some distance from the booth it is supplying.

A note regarding freeze protection: The colder the installation climate the higher the cost of freeze protection for a chiller. This keeps the units safe from bursting pipes and coils, but it takes away capacity. You may need to upsize the unit capacity to allow for the proper amount of heating/cooling for the unit in question, also affecting the price.

Reducing Costs While Meeting Specifications

Large cost savings can be achieved by recirculating the air of the spray booth. With 20,000 CFM exhaust, recirculate 80% and exhaust 20%. Recirculation involves various requirements but the basic formula is for 20,000 CFM, exhaust 4,000 CFM and recirculate 16,000 CFM.

4,000 CFM × $40 per CFM = $160,000 instead of the worst case $800,000, which is a reduction of $640,000.

There are many variables to discuss with your supplier. However, recirculation, if allowed, can greatly reduce the system price.


Internal view of a control panel showing the programmable logic controller (PLC) and multiple variable frequency drives (VFDs).

Whichever system you choose it will require controls. This is already factored into the cost structure given above. The control system senses the temperature of the incoming air and the humidity content. It will then supply more cooling and/or heat to the system, monitor the outbound conditioned air going to the spray booth and make adjustments.

This control system typically controls and/or monitors the:

  • Spray booth air supply

  • Spray booth filter condition

  • Spray booth exhaust fans and speed

  • Cooling, chiller output, or the mechanical air conditioning system

  • Heating unit, burners or boilers

  • Plus, all safety sensors included in the system if the booth is utilizing a recirculation of exhaust air to reduce the exhaust volume.

Location, Location, Location

Every location has a climate average temperature and humidity, along with average and minimums. Relative maximums humidity also frequently changes throughout the day, as well as throughout the year, and by the location of your factory.

Finishing equipment and coatings application equipment specialists can help troubleshoot when coating defects or issues occur. Having a controlled climate in finishing systems and spray booths is the surest way to minimize or eliminate defects.

Filtering paint, using rotary atomizers, electrostatic spray guns, infrared or convection ovens are all opportunities to improve the finish. Such equipment can be dialed into the optimum range for a Class A finish. However, the wrong climate can make all those efforts ineffectual.

Interior view of a helicopter booth

The Tradeoff/ROI

For some businesses, climate control may be an option they are considering after experiencing finishing defects caused by climate conditions in their area and coating reactions to those conditions. However, some will find the cost of this equipment prohibitive. Other customers must install this equipment because in their operations there is no room for error. Those with experience in automotive production or aerospace are generally familiar with this cost and prepared for it.

Considerations In the Final Decision

Each business must decide what it is worth to the bottom line of the business:

  • How many days/shifts per year can the business afford not: to paint? (Some can manage only painting at night or during off-hours, due to climate conditions.)

  • What is your cost of rework?

  • Some products, if not done right the first time, are scrap.

  • Some aerospace finishing requires verifiably documenting the conditions when the parts are processed.

  • What is the cost of failure?

Hopefully now you feel armed with the information you need to make a sound decision on climate control and have a better understanding of the costs involved and the factors affecting those costs, which all must be assessed and calculated when obtaining a quote.

This article was written by Marty Powell, Technical Systems Expert, Carlisle Fluid Technologies (Scottsdale, AZ). For more information, visit here .