Page 1 of 2 12 LastLast
Results 1 to 13 of 17
  1. #1
    Join Date
    Jun 2002
    Posts
    460
    I'm in the process of having to clean up after some sloppy installation work by my builder's HVAC subcontractor.

    Basically, they left gaps between the supply and return boots and the surrounding construction, which is allowing some crawlspace/attic air to leak into the returns and supply air to leak into the crawlspace/attic.

    Downstairs, all the supplies are in the floor, so I had some gaps open to the crawlspace. I sealed between the boot and the wood or tile with metal tape which would stick to both surfaces pretty well and seemed to work OK.

    Upstairs, though, all the openings are in the ceiling drywall, which means I'm sucking some air into the returns from the attic and/or blowing some supply air up there also.

    Tape isn't going to stick to the drywall too well. What should I use here? I was hoping there would be some sort of expandable-foam insulation type product that woudn't be too hard, but I'll use whatever you guys recommend.

  2. #2
    Join Date
    Jul 2004
    Posts
    322
    I just used Alex-plus siliconized latex caulk. About $2 a tube. Soap and water clean-up. Did it from inside the house by removing the registers. I hate that spray foam.

  3. #3
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Bob's right that is the best way.Let it dry before reinstalling the grilles,so they'll come down when it's time to paint.



  4. #4
    Join Date
    Jun 2002
    Posts
    460
    Originally posted by fat bob
    I just used Alex-plus siliconized latex caulk. About $2 a tube. Soap and water clean-up. Did it from inside the house by removing the registers. I hate that spray foam.
    OK, thanks! I just didn't want to have to bet in there with a putty knife and mastic or something like that.

  5. #5
    Join Date
    Jul 2005
    Posts
    171
    Joe, we do this all the time. If the gaps are small, caulk will work. HOWEVER, be aware that silicone of any kind will contaminate the surface and subsequent paint will fail.
    If the gaps are too large for caulk, and if you have access to the back side of the drywall, you can use expanding foam. The latex foam is much easier to use than the urethane and cleans up nicely. It is not as good, however. No free lunch.

  6. #6
    Join Date
    Jun 2002
    Posts
    460
    Well, it turned out that once I started removing some grills that I had gaps that are too large for calk (like 1/4" or maybe even more).

    So, I went over to the local HVAC supply house and got a tub of duct mastic. Can I fill gaps this big with the mastic or is this asking for trouble?

    (I could go the foam route, but the stuff I saw required acetone clean-up while the mastic is water-based.)

  7. #7
    Join Date
    Jul 2004
    Posts
    322
    1/4-inch backer rod and caulk?

  8. #8
    Join Date
    May 2004
    Location
    Rapid City, SD
    Posts
    7,415
    Mastic (aka Pookey) will fill that size gap pretty easy. If you need a lil something to help it fill the hole, use some of the tape the drywall guys use or something similar.

    Slap it on thick though and it'll fill some pretty good size gaps.

  9. #9
    Join Date
    Dec 2002
    Location
    in a house, Appomattox, Va.
    Posts
    3,436
    You can goop the mastic on the backside of boot?

    May want to watch for the drywallers forcing the boot out of position. If you have metal plaster frames they'll slam up the sheetrock and push the boot 1/2" up and create gap between the boot and back of drywall. Them you have to cut the drywall to get everything back into place so it can ve sealed.

    Did they seal the duct? air handler?(not the doors) you'll loose lots of air if they didn't.
    Col 3:23


    questions asked, answers received, ignorance abated

  10. #10
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,981
    I know its messy, but that expanding foam is the way to go. Shoot it into the gap and let it do its thing. Leave the job for the day and go back later to trim the excess foam and you are done with it.

    That foam is also great for leveling condenser/heat pump pads. Just level the pad with rocks, pieces of wood or whatever is availble and shoot that foam between the ground and the pad all the way around. Let it set for the night and trim the foam with a knife to conform to the side of the pad.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  11. #11
    Join Date
    Jun 2002
    Posts
    460
    Originally posted by RoBoTeq
    I know its messy, but that expanding foam is the way to go. Shoot it into the gap and let it do its thing. Leave the job for the day and go back later to trim the excess foam and you are done with it.
    So, are you on board with the latex/water based foam or should I use the oil-based stuff?


  12. #12
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,981
    I have not heard of water based latex foam. Sounds like the better way to go. That oil based stuff is a real pain to clean off of anything it gets onto before it has cured.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  13. #13
    Join Date
    Jul 2001
    Posts
    3,112
    RoBoTeq, DAPtex is the brand of latex foam I use. Comes in a blue can. A lot better than GreatStuff, in the red can. It is really good stuff. I buy it at Lowes but I'm sure other places also sell it. I like the fact that this stuff won't overexpand like the polyurethane foams. It only expands until it meets resistance. It won't buckle or warp objects it comes in contact with. One can can seal around all of the boots in a new home.

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event