Stapled to the submitted letter was a cover warning.

“NOTE TO EDITOR,” read the first three typed words (all capitalized), “Please feel free to edit as is necessary. I am an HVACR contractor, not an English major.”

As I’ve said here many times, readers of The News produce some great Feedback letters. Steve Johnston, of Johnston Sheet Metal and Air-Conditioning, is no exception. The contractor from Hot Springs, AR, sent the above “warning note,” which was stapled to what I consider to be a most-informative letter.

“It’s time to take a new look at a growing problem in the HVACR industry,” wrote Johnston. “Moisture and mold problems in the crawl space or basement mechanical room are being blamed on the heat and air unit. To the homeowner, during the peak summer months, the sweating duct lines and equipment cases appear to be the source of his moisture and mold problem. This misunderstanding increases the litigation liability to the HVACR contractor who installed the system.”

It is Johnston’s belief that unless the contractor can explain the obvious moisture dripping from the ductwork, he will possibly have a problem.

“The HVACR contractor should explain this phenomenon and offer a solution,” he wrote.


Johnston also provided a sample text for a competent contractor to give to a doubting customer:

Mr. Homeowner, you are observing one of the principles of air conditioning. Moisture will collect on a cold surface. Inside the air handler, the return air is being forced through the evaporator coil during the cooling cycle. The evaporator coil is cold and collects the moisture from the return air, which came from inside your house.

As the moisture increases on the coil surface, gravity pulls it down the fins and into the drain pan. From there it runs out the condensate drain line. The moisture we see on the ductwork is collected because the ductwork is cooler than ambient air and other parts of the crawl. As more moisture collects, it drips to the ground.

The installation we use on the ductwork is rated R-6. This is the requirement of the State of Arkansas. But R-6 is not as efficient as, say, R-19 or R-30. Some of the cool escapes through the insulation and allows it to be cooler than anything else. So, of course, like the evaporative coil, the moisture collects here.

If we could somehow use insulation with a rating of R-30, I doubt you would see these dripping lines. This is an option.

Although it appears the unit and ductwork are creating the problem, if the system is properly balanced and the ductwork is free of leaks, the actual cause is from another source. Moisture in the crawl space comes from the soil or opening in the foundation walls. I recommend installing plastic sheeting for the soil vapor barrier. Repair any holes that allow outside water to enter the crawl space. Repair or extend any French drain that isn’t removing standing water on the footer or along crawl space walls.

Now that we have those repairs taken care of, let’s talk about mold.

Mr. Homeowner, most forms of mold begin to thrive on moisture levels of 60% and up. Even with the repairs you have made, there is still a moisture level within this range. I recommend we install a freestanding dehumidifier at a low point in the crawl space.

It is best to operate the unit continuously for the first few days, depending on the amount of moisture. Then, we’ll set the humidistat to maintain a low moisture level, one that won’t allow the ductwork to sweat.

Mr. Homeowner, by making those repairs and installing the dehumidifier, you have virtually eliminated the moisture and mold problem that was growing in your crawl space.


Johnston added that the dehumidifier drain can sometimes be tapped back into the unit condensate line or an existing French drain. A check of local and state codes will give you some ideas, he noted.

“Remind the homeowner that mold and moisture are not a problem with units installed in the attic due to a lack of constant moisture,” he wrote. “The dehumidifier only has to run during the summer months and occasionally during the winter.”

He noted that it is time for professionals in the HVACR industry “to step up and solve these moisture and mold problems before litigation fever spreads throughout the customer base.

“The thermal dynamics of a basic air conditioning principle shouldn’t be the downfall of any HVACR contractor.”

Mark Skaer is editor-in-chief. He can be reached at 248-244-6446; 248-362-0317 (fax); (e-mail).

Publication date: 10/14/2002