Through reverse engineering air handlers, David Monson of Armstrong Duct, Vent, Hearth and Home has developed a tried-and-true process for restoring everything from small to large air handlers. He also has friends in the HVAC business, which is vital for developing this skillset. 

While ductwork insulation is held to high standards with Sheet Metal and Air Conditioning Contractors' National Association (SMACNA) requiring 90% coverage for adhesives, in addition to pins, air handler units from manufacturers are not held to the same standard, Monson said.

“There are no recognized professional protocols on how to do it, and there is no authority you can appeal to come and inspect your work and say ‘this passes,’” he said. “You and your customer are really on your own when you enter into air handling unit restoration.”

With no guidance on materials to use or methods to follow, how do you proceed? Here is Monson’s advice. 

The Process for Air Handler Restoration

Before you can begin, you and your customer must be on the same page regarding the job. Lay out all the information including what’s falling apart, the possibilities and risks related to the job. 

“If you go down this path, do a lot of research and choose your materials wisely. For example, we do a lot of work with ripping out fiberglass duct liner, replace it with elastomeric foam. But as an example, you would never want to use that insulation in the heat exchanger compartment on a rooftop unit. It's not intended to take the radiant heat that comes off the tubes of that unit,” he said. 

To see what’s going on in the air handling units, Monson suggested removing any cover that can be removed to get a better look inside. Once you know what the issue is, it’s time to get to work. 

“There’s no secrets to this. It’s manual labor,” he said, noting you should scrape and pull the insulation off and get a clean surface before attaching new insulation.

“One little trick if you're doing insulation removal from an air handling unit: you don't care what condition the insulation is that you're ripping out,” he said. “Spray the insulation with a mist of water. It keeps the dust down like you wouldn't believe and makes the whole project a whole lot less difficult to bear.”

Lift the top off one of the units to scrape the insulation off and once you’ve completed the rough rip-out stage, you’re going to focus on getting all the hairs out of the adhesive. It doesn’t matter if the adhesive stays behind, but the hairs have to be gone. 

“If you leave the hairs there, the new insulation is going to stick to the hairs and they’ll tear off, and it will peel off,” Monson said.

If you’re nervous about this process, Monson suggested making friends with an HVAC contractor. 

“The beautiful thing about knowing an HVAC contractor is for one, they replace a lot of HVAC units and throw the old units out,” he said. You can call that HVAC contractor and ask for one of those discarded units to practice your job. This way you can experiment and make mistakes before working on the actual unit. 

“My rule with our employees is always: never take something further apart than you’re sure you know you can put back together,” Monson concluded. “That’s a good rule of thumb.”