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.

"what is often the biggest leak of the ductwork-- between the ductboot and drywall/floor"


I was discussing this with a co-worker, and I disagreed with this being considered duct leakage.  As a HVAC designer I see the duct system independent to the building envelope when it comes to duct leakage.  I tend to think the leakage from register connection within boot is small (if correctly sized), and that the connection from the register/boot to the drywall is more an application to air sealing.  Do you have any referenced studies or documents that makes your quote for supported? I want to know if my co-worker and yourself are correct in this assumption of duct leakage.


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?  

Good points Chris,

I like how your thinking about register/ grille performance.  But, I want to add that the once a duct is pressurized using a normal Air Handler Unit, you can expect a higher magnitude for velocity and a more precise flow direction (Bernoulli eqn or pressure, velocities in a tube).  Air infiltration and Ex-filtration act under Turbulent flow conditions, I don't know if it's correct to say natural air functions like forced air.  

So what I getting at is once the air reaches the boot it comes into contact with the register, and under goes a pressure drop (small if register has a lot of fee area, and large if register has small free area- Wood registers).  The air should being forced out at a speed range (200-700 FPM), I usually design to 500FPM when doing Manual T designs.  This speed and a high free area implies to me that there is no duct leakage.       

Edit: Would Aeroseal have a good application for sealing my boot/ register connections?


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.

That's right, I didn't comment about duct blasting testing as it relates to duct leakage calculations.  Good point, in that case, there is completely no free area and the boot/register becomes a completely pressurized and can be seen as a leakage point.  


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.


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