best way to seal duct system

[2old2rock]

Don't overlook the adjustable elbows. Whatever method you chose, (tape, mastic), elbows can leak, especially when stressed, so look at those areas also. And get the dust/dirt off of the area first. Personally, I think both mastic and foil tape look like crap. Aluminum shade silicone caulk can work in some areas, and kinda blends in if you're concerned about those things.
When using mastic, you can apply duct tape to give a mask edge, then remove the duct tape. Leaves a clean edge.

[air2spare]

don't think I've ever read anything that said silicone was an approved sealant for duct

[hvacrmedic]

AF-100 is not mastic tape

Mastic tape works great on metal, wont stick to ductboard very long at all

That's correct. The SF-685 is mastic tape, the AF-100 isn't. Both are approved for their advertised purposes. Check with the local AHJ just in case.

[dash]

What about Aeroseal:
http://www.aeroseal.com/

Does this work?
Seems like it would really, really, really depend on the tech doing it.
Anyone with experience where this was used?
thanks,
howard

Interesting that you asked,I was just going to post it.

Excellent process tried and proven.We have been doing it for over 5 years.

It is time consuming to seal ductboard ,so a little pricey,but definately works and you have true before and after seal leakage cfms.

Plus it seals from the inside out,so we can seal ducts in spaces that no one can even get to.With hand seaing leaks are often or always under the insulation,at the metal or flex liner,hard toget to,Aeroseal seals there with no problem.

[contactor]

Duct mastic.

[howard33]

Interesting that you asked,I was just going to post it.

Excellent process tried and proven.We have been doing it for over 5 years.

It is time consuming to seal ductboard ,so a little pricey,but definately works and you have true before and after seal leakage cfms.

Plus it seals from the inside out,so we can seal ducts in spaces that no one can even get to.With hand seaing leaks are often or always under the insulation,at the metal or flex liner,hard toget to,Aeroseal seals there with no problem.

how pricey is pricey?

[dash]

Prices aen't allowed ,see the rules.

What we see is hand sealing guys chare as much as 75% less ,but no testing so you don't know what they accomplished for the $ spent.Duct leakage not sealed will cost you as long as you live there!!

[Mr Bill]

I agree!

[dash]

Glad to hear you endorse Aeroseal,have you look into using he process?

[printmanjackson]

ok, so I have to ask about this hand sealing process....

Sealing the main square trunk is pretty straight forward but the round piping coming off the main trunk has insulation on the outside. Is it nessessary to remove the insulation and check/seal all the seams then re-install the insulation?

From what I remember this insulation is held with a special staple too.

[dash]

ok, so I have to ask about this hand sealing process....

Sealing the main square trunk is pretty straight forward but the round piping coming off the main trunk has insulation on the outside. Is it nessessary to remove the insulation and check/seal all the seams then re-install the insulation?

From what I remember this insulation is held with a special staple too.

You are correct.

[adrianf]

Before you go to all the trouble to seal the ducts you should make sure they're the right size or the results you get may not be what you had in mind.

[dash]

Before you go to all the trouble to seal the ducts you should make sure they're the right size or the results you get may not be what you had in mind.

Very good point,sealing leaks will increase the static of the duct system at least a little,sometimes a lot,depends on size and location of the leaks.