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Jan. 22, 2020
Residential construction practices allow sheet rock dust and other construction detritus to come to rest in HVAC ductwork.

A widespread practice during residential new construction is for sheetrock and paint subcontractors to operate the HVAC system during construction. Recently, a friend of mine had problems with the HVAC system in his new home. His installing HVAC contractor arrived, removed the blower door and found a bucket full of sheet-rock dust and gunk in the system. Let’s take a look at what happened, the solution, and the response from the builder.

What Happened?
During the construction process, the installing HVAC contractor roughed-in the HVAC system after the framing stage. The indoor equipment was installed, and the utilities connected to it. Their work was finished until it was time to set the thermostat, registers, and grilles.

Meanwhile, general construction proceeded. In our story, a few bad boys showed up on the job, hotwired the heating system, and warmed up the house they were working in. Judging by the volume of contaminants in the system, the fan apparently was run non-stop throughout most of the project.

The first culprit was the sheet rock contractor. With the heating system blasting, the workers cut, installed, taped, sanded, mudded, sanded, and finished the sheetrock. This accounted for most of the thick white dust throughout the duct and HVAC system.

 Since dust dirt, paint, and sawdust are airborne during construction, you should seal duct inlets and outlets with heavy plastic when you install boots and cans. This is inexpensive, and you can easily remove the plastic before installing registers and grilles        

The second troublemaker was the trim contractor. He kept humming away with his table and chop saws – two big dust-makers. He also used sanders that spewed dust throughout the house. Sure, sawdust will be present during construction. But the HVAC system doesn’t need to circulate and store it.

The third villain was the painter. She used an airless paint system that fills the air with paint particles. Can you imagine the long-term impact on efficiency losses caused by a fresh coat of paint on the heat exchanger and cooling coil?

 What Happened to the HVAC System?
Throughout construction, the hotwired HVAC system assured pollutants remained airborne and loaded up the duct system and equipment with contaminants. In addition to the duct system, other components including the blower, motors, controls, circuit boards, temperature sensors, burners, and the heat exchanger were covered.

Of course, another result was the system now had a plugged cooling coil. Not only did the dust plug the coil, as soon as cooling season arrived, but condensate also added water to the coil which turns sheetrock dust into mud. Can this coil ever be cleaned and restored to its original performance?

We haven’t measured the system performance, yet, but no one will be surprised if system capacity is reduced by 30%, decreasing the home’s comfort increasing utility bills, and leading to premature equipment failure.

Once the home was finished, the new owner began using the system and discovered a constant coating of construction material, contaminants drifting onto the carpet and furniture. Oh, and the occupants breathed all that good stuff in, too.

The Solution
The bottom line, using the home’s heating and cooling while a home is under heavy construction is a BAD idea. Construction contaminants fill the system reducing its capacity, efficiency, and life span. The problem is hidden from view but continues to carry a significant liability to the homeowner for years to come.

Ideally, during the build, the home’s HVAC system should not be used. One way to assure the system remains clean is to not connect it to power until overall construction is complete. Without power, the fan will not operate and bring contaminants into the system.

Since dust dirt, paint, and sawdust are airborne during construction, you should seal duct inlets and outlets with heavy plastic when you install boots and cans. This is inexpensive, and you can easily remove the plastic before installing registers and grilles.

Use portable construction heaters to maintain minimum temperatures during general construction. These heaters recirculate heated air though the rooms leaving the duct system mostly uncontaminated.

Some contractors use sanding vacuum control systems during construction to reduce the amount of dust entering the duct system by as much as 95%. This protects the workforce as well as the HVAC system.

If job specifications and weather conditions require using the HVAC system during construction, you should install dense external air filters over return air inlets. This may capture most of the contaminants. But be aware that doing so may also cause the blower motor and other system components to operate outside of published specifications causing long term damage.

Response of the Builder
My friend contacted his national homebuilder and described what he found. He even included a video showing evidence of his contaminated HVAC system. He requested the problem be addressed.

Round one ended with the builder attempting to dismiss the complaint. They accepted no responsibility for the matter or made any attempt to solve the issue. No valid excuse was offered. There was no inspection of the HVAC system or interest in pursuing a solution.

The bell is almost ready to sound for round two, this should be interesting.

What to Do?
New construction HVAC contractors agree the system should not be used during dirty construction. Installing covers to seal boots and cans during construction is one step. Not connecting power to the system is another way to assure the system remains uncontaminated.

Few construction contracts mention using the HVAC system during construction. If contracts required the HVAC system to be used during construction without providing for system cleanliness, the builder is exposed to significant long-term liability.

Should the builders, the sheetrock, paint, and trim subcontractors be held responsible for the damage to the HVAC system?

The purpose of this article is to bring awareness to this long-standing new construction problem. Like many defects that deteriorate HVAC system performance, this one is hidden from view. Your assignment is to consider your exposure to this preventable system defect and decide how you’ll handle it in the future to eliminate your potential liability.

When you service a system filled with construction dust and contaminants, use caution. Do not get dragged into a legal matter. You may choose to perform the clean-up work but do so offering a reasonable outcome and with disclosures keeping you free from a potential court case.

When you service a system filled with construction dust and contaminants, use caution. Do not get dragged into a legal matter. You may choose to perform the clean-up work but do so offering a reasonable outcome and with disclosures keeping you free from a potential court case.

Granted, many systems are not as mucked up like my friend’s. His HVAC system is admittedly one of the worst scenarios I’ve heard about. It is doubtful it can be restored to like-new operating condition.

Looking forward, should this issue call for a company meeting to plan for this situation in the future? If you’re a new construction HVAC contractor, of course, this is a bigger issue and requires you to be well-prepared with a solution before sitting down with your builders.

If you’re a service company, discuss and decide your approach to this problem when called in to diagnose and resolve it. Your initial response can either cause you to be hauled into the middle of a battle or keep you unstained from any legal action. Decide your position and make it the topic for your next service tech and installers training session.

Depending on the response of the national home builder, there may be more to report on this story.

Rob “Doc” Falke serves the industry as president of National Comfort Institute, Inc., an HVAC-based training company and membership organization. Contact Doc at [email protected] or call him at 800-633-7058. Go to NCI’s website at nationalcomfortinstitute.com for free information, articles, and downloads.

About the Author

Rob 'Doc' Falke | President

Rob “Doc” Falke serves the industry as president of National Comfort Institute an HVAC-based training company and membership organization. If you're an HVAC contractor or technician  interested in a building pressure measurement procedure, contact Doc at [email protected]  or call him at 800-633-7058. Go to NCI’s website at NationalComfortInstitute.com for free information, articles and downloads.