Insulating old forced air ductwork in basement?


Old 07-28-16, 09:51 AM
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Insulating old forced air ductwork in basement?

Hi all

One of the next projects I want to do is to insulate the ductwork in my freezer... I mean basement

I have been told to use bubble wrap and mastic. I have been on a youtube marathon looking for how to do this. Doesnt seem extraordinarily difficult, but all the examples I have found show them insulating ducts on the floor--mine are in the air.

Here is the photo I shared on previous thread (please ignore the arrows/text)

Sounds like process is:
  1. Dust the duct off--especially the top
  2. Mastic all the joints (or tape??)
  3. wrap duct
  4. tape seams
  5. mastic taped seams

Wrapping the duct seems like it will be challenging... Straight runs should be ok... but off shoots like the one on the pic (to the left) will be tricky. Also, what is the approach when I encounter duct hangers? Slit the wrap then tape it/mastic when done?

Trying to figure out the difficulty of this job. Thanks for any advice
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Old 07-28-16, 11:10 PM
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Using mastic or metal foil tape on the joints and connections is a good start.

The problem with insulating the ductwork in a damp area is that if you don't insulate the ductwork from the air 100% any air that gets behind the insulation will condense and cause more problems.

There is a company called Armacell that has a product called AP/Armaflex that offers excellent duct insulation and sealing properties but it's very expensive.
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