Restoring your ductwork with CMC

Restoring your ductwork with CMC

The ductwork at your home or business provides many benefits. But what happens when that ductwork begins leaking or showing other signs of wear and tear? Today’s blog will show that restoring your ductwork can be quite simple and effective with Countryman Coatings.

Ductwork 101

In its most basic definition, ductwork is responsible for circulating air around your home or business. Properly installed ductwork reduces strain on your HVAC equipment and saves you money in energy costs. Sufficient ductwork also reduces hot and cold spots in your home or business by delivering consistent, even temperatures.

Ductwork serves small single-family and other systems, including the larger rooftop air-conditioning units. These rooftop AC units, which are popular on flat roof systems, typically connect directly to a ductwork system that distributes the conditioned air through a building and returns it to the rooftop unit. These rooftop units are constantly exposed to the weather, and that can result in problems.

A Call for Help

Larry lives in southern California. His AC unit and ducting are atop his roof, exposed to the harsh sun and occasional rain, and his ducting includes 12 roof penetrations. That system has brought him problems for two decades.

“For 20 years I have lived here seeing leaks inside coming from the ceiling vents during the annual rain. On the roof I was seeing cracked and peeling vent seal, which did not last but a year or two each time it was ‘repaired by professionals’ who never properly sealed them,” he said.

He needed help. He found it with CMC Heavy-Duty Silicone.

A Solution

Our Heavy-Duty Silicone is an extra-thick silicone that can seal abnormal or difficult roof features with ease. It has the consistency of butter and can be applied on vertical surfaces or the underside of horizontal surfaces without dripping or sagging.

Larry purchased our Heavy-Duty Silicone and was pleased with the application process. “I applied the coating with a 2-inch brush on a 75-degree day. The thick, goopy silicone was very easy to work with. I could easily apply it very thick in places, working it into the cracks to ensure a proper seal, and also spread it out rather thin in certain places where appropriate. I was working with the material upside down some of the time, to seal the bottom side of the ducts, and the thick silicone didn’t drip nor run, staying just where I needed it.”

The real test for our silicone came after a recent rain. While rains in the past had resulted in leaks, Larry found no issues after using Heavy-Duty Silicone. “I was pleased as I saw beads of water on the newly sealed ducting,” he said. He noted as well that the gray color he selected – Heavy-Duty Silicone is available in white, gray, translucent, and black – looks good on his ducts. “The ducting is visible from one side of my property so aesthetics matter,” he said.


Aging and cracked ductwork can result in many problems, including leaks and increased strain on your AC unit that can shorten its life and drive up your energy costs. Heavy-Duty Silicone is easy to apply and can offer more protection for your home. Thanks for reading. Please reach out to us here if you have any questions.