Has anyone had experience with the Aeroseal duct sealing product? I am aware of how it works, but I wanted to see if there are any pros and cons regarding this method of duct sealing.



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The stuff is amazing.  Test in, repair, and test out all in one.  

But hard to sell. People don't realize the comfort and energy penalty caused by not delivering conditioned air to where it is intended.  This is another case where tracking peoples savings would be really useful.

There are some great Aeroseal discussions at HVAC-Talk.  

I'm curious too. I was just asking my friend, a local foam insulation installer, whether he ever used it. He said he he had a sub that would do it, but his sub required cleaning the ducts first, despite Aeroseal's website's claim that pre-cleaning ducts wasn't necessary. He said that made it VERY expensive, but I'd still love to see the actual cost of a job. $$$? Could it be cheaper than what I recently had to do to meat my tax-credit-dependent duct leakage targets at a historic renovation in downtown Cincinnati? Two returns were routed without ducts through stud cavities and leakage was >500 CFM@25 . Target was ~100CFM@25. Several walls had to be opened up, properly ducted, and HVAC installers had to be monitored the whole time. They just didn't know any better.

Whatever the cost, I still see a potential oversight with this method based on their installation description-- their temporary plugs will prohibit the aerosol sealant from sealing what is often the biggest leak of the ductwork-- between the ductboot and drywall/floor. That's not a problem intrinsic to the sealing method, nevertheless, an issue that tends to get homeowners in an accusatory mood, blaming HVAC guys, drywallers, painters, general contractors. In my opinion, that's the first (low cost) way to seal most leaky ducts, but it is the task that is rarely assigned ownership in the project planning phase.

Hi Sean,

It seems like your duscussion with your co-worker is over the semantics- when does the "duct" end and the "envelope" begin? As far as a duct blaster and blower door test is concerned, it's both. Sealing it would improve both duct leakage and envelope leakage. All I've got is personal anecdotes to back me up here. Sorry- no cool white papers.

Below is a picture of the situation I see daily. The duct installer will nine times out of ten say that his ductwork job is complete and sealing this ovious leak is not in his scope. He might be right. Imagine next, the grill is screwed on to the face of the drywall and a painter is told to caulk the grill to the drywall. Then, once the duct system is pressurized (or depressurized for a leakage test) the space between the boot and the grill will certainly fall somewhere in the spectrum of pressures between that of the main zones of the home and the max/min pressure of the duct system.

Even more relavent than performance during a testing procedure would be how it behaves during actual occupancy and daily living. Let's conservatively call it a 1/8" hole and a 4" x10" boot. That would would put the leakage area at ~3.5 sq in. Does the proximity of this 3.5 sq in hole to pressurized air of the ductwork make it bahave differently than a 3.5 sq in hole on the ceilng, floor, or wall? I would guess it acts more like a 3.5 sq in hole in the trunk of the ducts than it does a hole in the wall. I could be wrong, but I think my point is that it's not as simple as either/or.

I've had the great pleasure of testing and failing many homes that are pursuing various "green programs' " duct tightness protocols. Caulking or taping this gap tends to be the first and easiest place to tighten the systems up and the evelope. It doesn't usually involve a call-back to the HVAC guy but instead the super-intendent running around caulking and cursing the name of the HVAC guy. In my opinion, the scope of work needs to be better defined at the front end of the project. You can't blame the duct guy or the painter if it's never been defined.

Nice.  That picture and your post are my light bulb of the day.  

I'm also grateful for the humor, although when you consider "the super-intendent running around caulking and cursing the name of the HVAC guy" should he be thanking him for the work instead?  Or maybe thanking the painter?  Or the guy who missed defining caulking boots when building the job specification?

Where does responsibility for this task really lie?  Who got paid to take the time to do this right, then didn't do their job?  


Where does responsibility for this task really lie?  Who got paid to take the time to do this right, then didn't do their job? 

Haha-- question of the day!



Ever try this trick with your kids? http://www.youtube.com/watch?v=V_H4g250UGQ Get the size/location of the hole wrong and it just doesn't do what you were hoping it would do for the audience. As a professional "wind chaser", I'm routinely humbled by the gap between what I think should happen and what does happen with air and pressure. When I hear you say "this speed and high free area implies there is no duct leakage," I'm wondering how you might conduct a duct blaster test that agrees with you.


There are 3 Aeroseal contractors in the Gr. Cincinnati area.  The contractors provide a pre and post total duct leakage test to the home owner. I have seen total duct leakage go from 700cfm down to 100cfm in some of their jobs.  Average (whatever average is) costs are about $2000 for a 1500-200 sqft home.  You are correctthat their system does not deal with leakage around the boot, but their system does not measure that leakage either.

Hey Jim,

Great to see you here!

That's disappointing to hear that those local compaies don't measure the duct boot leakage.

I just visited a job yesterday for some diagnostic stuff here in Cincy where the brand new "platinumy" apartment had four supply registers. Testing duct leakage to outside (with ductboots as is = NOT sealed to drywall) measured 55CFM@25. Taping that gap at all four supply grills brought the leakage (to outside) down to 14 CFM@25.

The stuff is basically aerosaulized rubber cement. If the duct is really dirty, crusty dirty, you'll probably seal the dirt rather than the duct, and when the homeowner DOES clean the duct the seal will go with the dirt instead of staying with the duct.

Taking the judgement call out of the process may be a qc decision.

I suspect tremendous efficiency having both projects done at once. Separately they might be $13-1800 and $6-800 whereas together they'd be $15-2100.

When you get into the $1500 range you can just replace the duct system if it accessible.

With Flex being so inexpensive is it really worth Aeroseal the old ductwork? If you already have a well designed metal ductwork then sealing the existing may be worth it. Odds are the ductwork wasn't installed very well to begin with and doing the corrections manually is the way to go. Poor distribution/insufficient airflow is a bigger issue than minor leakage IMHO.

Duct leaks are never "minor".  I see no reason whey they are not essentially air tight.  Plumbing is watertight, why can't ducts be similarly tight? Most existing codes require ductwork to leak no more than about 100 CFM which represents about a quarter ton of cooling. If the energy bill is $2400 per year that totals $6,000 over a 40 year life of the system. For a typically bad duct system that leaks 400 CFM that is $24,000 over its life.  How can this be ignored?  I talk to installers who get systems down to 5 CFM leakage regularly and they say it doesn't take much time once you get used to it.

It seems as if Aeroseal has an important application where ducts are built into the structure and major renos are required to get access.  Even when using Aeroseal, it stll make sense to seal the registers because flow levels directed at those registers needs to be above a certain velocity to move the rubber material to the leak otherwise it will just settle on the duct when the velocities get too low. Great for areas where velocities due to leaks are greater such as building cavity returns. 


Colin Genge

Aeroseal does make sense for difficult to access ductwork. For easy to access ductwork it makes more sense to repair it mechanically, while at the same time fixing those rooms that never seem to be cool/warm enough. If it were me building the house I'd have the equipment and ductwork all in conditioned space to begin with. That alone will add 20% to the systems capacity.


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