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Question DetailsAsked on 10/1/2015

how can you tell if your ac duct work is leaking air?

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5 Answers


You can almost guarantee the duct system is leaking air! I'm an HVAC contractor,and supervised the install of the ducts in our home,15 years later maybe from day one, they were found to be leaking about 15% on each system.

We have done over a thousand "tests" and they all leak! Over half leaked over 10% of the conditioned air from the system. All leaked over 5%.

We have been using the Aeroseal process for 13 years and it will seal better then any other method! Plus a 10 year guarantee.

The issue with trying to hand seal ntheleaks is that you can't find all of them,some are very tiny holes.

Take a few minutes and review their website,

You can check on the website for the nearest Dealer.

I watch this site regularly, so post any questions you may have.


Answered 4 years ago by BayAreaAC


You can inspect all the ductwork visually and by feeling around the joints with the fan running, but the simplest way is to hire a contractor that does this type of work. They have the equipment to accomplish a duct leakage test and this method is the most accurate. Be aware that duct work repair, if necessary, may not be a part of any estimate.

Just be sure to check them out with your state license board and try to get reviews on their work. You may find a contractor on Angie's List.

Another way that works is to have a test done on each register to calculate the total CFM of air flow. The contractor can then consult with the equipment manufacturer's representative; or the equipment specifications; to estimate the expected air fow in CFM. This works if the static pressure is known, the fan is operating properly, the fan scrolls are clean, no restrictions in the ducting, and the filter and cooling coil are clean (these conditions will apply no matter the method). (The contractor should be able to estimate the static pressure using his ductolator) This method is only semi-accurate but will present an estimate in the 90% range, if done right.

I have used the latter and found it to give a reasonable estimation. Get three quotes before you sign anything and check out the contractor.

Source: Poppy Ross

Answered 4 years ago by PoppyRoss


(The contractor should be able to estimate the static pressure using his ductolator)

A ductolator has no relationship to statc pressure, it is the friction Rate. Manual D, uses the static pressure the equipment can produce, along withe design of the duct system , to determine the friction rate ,to be used on the ductolator, to size the ducts, to get the predicted static pressure.

Determining the airflow of the system,does not determine the duct leakage, a duct blaster test or the Aeroseal method ,will determine the leakage.


Answered 4 years ago by BayAreaAC


Bay Area is correct.

Do note that not all HVAC contractors have the equipment to test the actual duct leakage.

Also, Aeroseal is indeed the best method Ive seen in my 27 years of HVAC experience, to seal entire ductwork.

Answered 4 years ago by Guest_93399141


As BayAreaAC said, basically all ducts leak - the issue is whether it is enough to be a problem, and if the leaks are into areas where the heat is wasted, or ending up heating the same area you are trying to heat anyway. For instance, many in-floor duct leaks end up heating the same floor the air is headed to, so as long as you are getting enough airflow from the registers to distribute air in that room evenly you might not notice that some of your heat is coming from the floor rathaer than the registers. Of course, leaks like that can cause other issues particularly if running A/C through the same ducts so you are chilling your floors or walls.

Another, and probably the most detailed way to check ducts which includes those you cannot reach to test by hand (wet hand works much better) or better yet a smoke pencil, is to use thermal infrared scanning. Some HVAC contractors have thermal IR cameras, you can rent them for under $100/day at some Home Depot stores, some auto parts stores, and most tool rental places, and many Energy Auditors, Insulators, and some Home Inspectors have them. Many tablets and smart phones also have (Apple) or can download apps that allow you to finetune the camera sensitivity so it gives a "false IR" reading which will show major temperature differences, but not anywhere near as accurate as a thermal IR camera. Thermal IR works especially well in detecting thermal differences in walls and ceilings/floors, be they from overheating wiring, leaking pipes, or leaking ductwork - and also show areas with poor insulation.

If looking at having a thermal IR scan done professionally, you might consider if you want the contractor to do a full-house scan while he is there for a fairly nominal additional amount, and make sure if you do that he is set up to give you a DVD or thumb drive that you can view directly as a movie on your computer, so you can show it to insulation or repair contractors who you hire to do repairs or upgrades. Also is a useful reference for where ducts and piping and studs and headers and such are in the walls, because if they are flowing during the scan they will normally show up too.

Answered 4 years ago by LCD

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