I had a call from a customer asking me if we sealed ducts.  He was watching This Old House on TV and the contractors were using equipment that sealed the ducts from the inside.  They stated that this procedure kept duct leakage to 5% or less.  Has anyone ever heard of, seen, or used this procedure. Just curious, I'll stick to mastic, but I always like to keep up with the latest.



Tags: Duct, HVAC, Sealing

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He's probably talking about Aeroseal http://www.aeroseal.com/

I have no experience with it. One of my customers is definitely a candidate for this.

I would find out what was being sprayed on the inside of the ducts...
The air being blown through the house goes through those ducts...
The homeowner will get to breathe the sprayed on sealant for quite a while.. You want to make sure it's not harmful.
Ira Eisenstein
Keep in mind they were using this on "This Old House" so they probably aren't going to use something dangerous or toxic or harmful to the system. Never heard of anyone using it here in the south.
You also want to make sure there are no motorized duct dampers (for zoning)...
You don't want to "seal" them into one position.
Ira Eisenstein


  • Seal ducts that are inaccessible
  • Seal joist spaces that are used as duct runs to hopefully improve air quality


  • Forget about having the ducts cleaned after they are sealed from the inside.
This product typically can only seal small holes 1/4 inch or less. For the overall cost, your better off buying a bucket of mastic and mesh tape and doing it the old fashioned way. This might be an option for brand new systems but many older ones will have larger holes that this cannot fix.
Thanks for the info.  It may be useful in situations were all the ducts are run through bulk heads in the basement.













We just completed an Energy Upgrade on a home that had the FAU replaced with a 90% sealed combustion unit. The HVAC Contractor who sold our client the FAU the year before, told them their ducts were fine, and he'd just seal them.  We tested the duct leakage at 25%, and the photos reflect the condition of the ducts.  For clients that ask for a sealing option, make sure they know the true condition of their ducts. 

If the product is effective I would think many would benefit from its use- What's the point

of renting conditioned air.Question, can the application process show before and after pix?

Confirmation of the products proper application would be of interest,                                                                   - not just to me but for any customer.

Invented here at LBNL.

More info at this link: http://epb.lbl.gov/aerosol/



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