On Tuesday, February 18, 2014 9:11:22 AM UTC-5, wrote:
I am wanting to convert my flex duct in my crawl space to metal duct. However, the duct at Lowes seems flimsy. I also am having in the summer condensation on my ductwork. I want to eliminate this.



Can I use the expanding spray can foam sealant or rubberized undercoating like you use on a car to spray the duct before installation, then wrap it with the duct wrap insulation to maximize the insulation value of the duct and to give the duct rigidity?


I don't know how you'd control the expanding foam so as to not have
a gigantic mess. And the rubberized stuff sounds like a big pain in
the ass for little gain. I wouldn't re-invent the wheel. The Lowes
material properly supported is probably fine. If you want heavier gauge,
go to an HVAC supply and they should have it.

This might be a project where if it has to be done, hiring pros might
be a better idea. I've done a little DIY duct work, but I wouldn't take
on this myself. Having the right tools, equipment, shop to make up
any necessary pieces, etc and the experience and this goes fast and
you get a pro job. DIY for a typical redo of a whole crawlspace duct
system, I would think is going to be a real pain in the ass and the
finished product, not so good.





One last thing, can a person buy the professional spray insulation material and spray it themselves at home in the attic etc? I have a large air compressor and several spray guns? I would like to add some insulation myself, especially in the attic.



I really appreciate it!

AFAIK, no. They have a truck with pumps, the material comes in 55 drums,
I think it gets heated, run through a special gun that mixes it, etc.