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Thoughts on insulating duct work before building soffit?

Thoughts on insulating duct work before building soffit?

Old 09-03-14, 06:39 PM
Thread Starter
Join Date: Sep 2008
Location: MA
Posts: 591
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Question Thoughts on insulating duct work before building soffit?

So I was wondering what peoples thoughts were on insulating the duct work before I go ahead and start putting up the soffit ladders.

The thing that made me think to do this in the first place isn't for the R value but more so sound vibration dampening. I figure it would absorb some of the vibration to 2x4 soffits & drywall created from the above floor to duct work.

It would also be nice to be able to but the soffits snug to the duct work with the insulation between instead of having to mount my soffits an inch out.
Old 09-04-14, 05:51 AM
Join Date: Oct 2008
Location: New England
Posts: 10,524
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New building requirements, especially in MA, require leakage testing and very well air sealed ducts. It may just be for new construction, I didn't read through them. But 5 years from now who knows what they will require. In any case, while it is open, air sealing is a good thing. Where the ducts are inside the conditioned space the energy penalty is less, but leakage into wall and ceiling cavities can force air in or out in unexpected places.

As for the insulation, Roxul makes a "safe and sound" version of their insulation. I'm not familiar with it, but I believe it is basically their standard insulation packaged a bit thinner. Also, in the hvac departments they have fiberglass blankets specifically for duct insulation. Again, not my specialty.


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