Common Commercial Air Duct Problems

ByMarc Silberberg


Commercial buildings that host expensive HVAC systems have a noticeably different type of ductwork than that of a residential home. The ducts and vents are made up of highly durable steel trunks with little to no flex ducts. This is to air condition an enormously large area, sometimes in the tens of thousands or hundreds of thousands, in cubic square feet. Each facility will have its specific heating and cooling requirements that determines the amount of steel trunks needed for the ductwork to keep the space cool during the days of summer and warm during the days of winter. 

Besides commercial spaces like warehouses and distribution centers, there are many office buildings that require a robust HVAC system to circulate the conditioned air. The steel duct trunks can sometimes be visible while other times neatly concealed by a drop ceiling. These metal ducts are the arteries for the heating and cooling system to perform properly and keep occupants in the building comfortable. Commercial HVAC systems host multiple compressors and air handlers, and are very expensive to run. Leaky ducts in such complicated heating and cooling systems can hinder their performance and increase energy bills without anyone even knowing. But how can one possibly maintain such a robust system and attend to the variety of commercial air duct problems? 

Air Leakage In Commercial Air Ducts 

When air leaks in a commercial HVAC system it can greatly hamper its overall performance. Even though these trunks are made from steel, they can still get perforated by sharp items like tools and screws. A facility may need an electrical repair and the professional might need to get into a tight area only to poke a hole in the air duct with pliers. It sounds far-fetched but it can happen quite easily. Over the course of time the conditioned air will escape this hole and cause the system to work harder to cool or heat the facility.

But more often than not, it’s not the holes that are the issue but its the trunks and elbows that are not tightly fitted which allows air to escape. Where the vents join together there are fasteners that are supposed to give an airtight seal. However where it’s situated can present a problem to how well they are sealed. The vents usually hang from the ceiling as is the custom in many warehouses. But there is always a point where the duct meets a tight spot and the installer can’t completely access the tight spot (now you know why these ducts are exposed in gyms and other commercial spaces) and can’t get the tight seal at that specific joint. Then the conditioned air escapes and does not make it to the building envelope to where the air ducts were supposed to take it to. If it were a single air leak, chances are that the deficiency would go unnoticed. However, when there are multiple air leaks throughout the air ducts and the conditioned area is a fulfilment center that can span many football fields, the negative effects will be noticed on your energy bill. If the duct leakage is very bad then the people who occupy the commercial space will begin to notice the discomfort.

How To Check a Commercial HVAC System For Duct Leakage?

For every problem there is always a solution and if one does suspect that their facility has leaky air ducts then they should schedule a duct leakage test. A certified duct leakage expert will measure with software and equipment how many CFM (cubic feet per a minute) are escaping the HVAC system. In order to gain a Certificate of Occupancy (CCO), no more than 8 CFM are allowed to escape. The system gets measured by creating a tight seal on all vents and blowing in negative pressure that will allow the software to sense air leakage in the ducts. The challenge is to find the places where the air escaped and to get them sealed up. There will be a visual inspection done by the technician who will use spray foam or mastic to seal those spots. But since the ductwork is so big it’s sometimes impossible to find the air leaks.

Vaporizing Sealant For Air Ducts 

In order to tackle the issue of not being able to spot the air leaks, a vaporized sealant can be sprayed into the air ducts that will fill any hole or opening 15 mil or less. As the aerosol travels throughout the duct work it will build up in the spot that is allowing the conditioned air to escape. After a complete treatment the liquid hardens into a foam and air will no longer be able to escape and remain on track to the designated conditioned space to where it’s supposed to reach. It’s a good solution for treating ducts where you know there is an issue but you’re not exactly sure where it is.

But one should not be complacent thinking that spraying a solution in the form of a vapor will be a quick fix to your problem. The mere fact that an aerosol can seal a 15 mil hole won’t help you when there is a bigger puncture or gap in the duct. For such a scenario you’re going to have to have a professional crew come down and identify where the air leak is. Sometimes duct leak professionals won’t be able to access the area where the duct is and will have to use a scope with a camera at the head to do a thorough inspection. This will only be done if the duct leakage test is showing a significant air leakage of more than 8 CFM. The objective is to find and repair the air leaks that will have a positive impact on how your HVAC system performs.

Identifying The Issue In Commercial Air Ducts

Unlike residential air ducts, commercial air ducts tend to be more exposed in case there is an issue. At the same time, warehouses and facilities are not really so concerned about the look of a commercial ceiling and will install the vents in the most economical way. This puts commercial facilities at an advantage when trying to identify where the air is leaking from as all the steel venting is exposed. In most cases it’s not a puncture but rather a loose elbow vent that was not sealed or not fitted properly. If that’s the case, mastic can be used to cover over that gap to make an airtight seal that will not allow for any air to escape. Thereafter, another duct leakage test will be performed until the number of CFM improves.

Once the problem is solved the facility will be able to see significant savings on their electric bill as the HVAC system will be running more efficiently. It goes without saying, but the larger the facility the greater the savings. Unfortunately, many facility managers won’t ever think of how their HVAC system performs but stay focused on if it’s working or not. But yearly savings can be in the thousands or sometimes tens of thousands depending on the size of your facility and how bad the duct leakage is.

Air Leaks Stemming From A Commercial Air Duct Cleaning Job

Not all air duct cleaning companies have experience in duct leakage and can sometimes create another problem in the process of a commercial air duct cleaning. While on site, multiple things can go wrong with an air duct cleaning job without anyone knowing. There are two ways to clean air ducts, the right way and the wrong way. The right way is to seal all the vents and to create negative air pressure that will send a burst of air through the vents that will loosen all debris and send it out of the facility to a large waste bag. Sometimes the air duct cleaning company will make use of soft non-abrasive brushes to loosen the debris. The wrong way is to use a ShopVac and hope that all the venting is sealed properly. If the specialist can’t reach certain areas they will make a hole in the vent to be able to access that particular steel trunk. After they are done cleaning that specific area they will take a circular plate and affix it to the vent. The problem is that even when vent is fixed tightly with screws there may be a gap left that will cause air to escape.

Pipes of HVAC system (heating ventilation and air conditioning).

The bigger commercial air duct cleaning job the more opportunities for circular steel plate covers to be used which can create multiple air leaks all throughout the venting. The correct way to cover a hole would be to make sure the plate covers a significant area beyond the hole and seal it with mastic. Thereafter, the professional should inspect for any leaks once the system is turned back on.

Final Words

Commercial air ducts can cover a vast area of square footage depending on the size of the facility. It’s important to know that vents are the arteries of your HVAC system and in order for them to be functioning properly there needs to be healthy air flow. Dust and debris can negatively impact how your system performs and lower the air quality in the conditioned spaces. For that a commercial air duct cleaning can solve that problem but sometimes leave over other issues like leaky air ducts that can hamper your HVAC’s systems performance. That’s why it’s important to hire a licensed commercial air duct cleaning company that has expertise in both duct cleaning and duct leakage. With the knowledge of both you will have clean ducts and healthy air flow that will not only have your HVAC system running efficiently but cost effective as well.

All Blog Articles

Get Free Estimate

Give us some info and we'll get right back to you with a quote


    How can we help?


    At NJ AIR QUALITY, we get excited every time the phone rings or another contact form is filled out. That’s because we LOVE what we do. And we look forward to doing it for YOU!