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Will this work? Insulating a garage ceiling

Post in 'DIY and General non-hearth advice' started by joefrompa, Aug 12, 2011.

  1. joefrompa

    joefrompa New Member

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    Hi all,

    My garage drywall is all torn up - tons of holes in it, tape lines, blah blah, blah. But the ceiling is relatively level and functional.

    The vertical walls are torn up with big cracks in the drywall/seperations at seams, holes, etc.

    I'm planning on ripping down all the VERTICAL wall drywall in the garage, sealing, vapor barrier, and re-insulating it and then re-drywalling.

    But since the ceiling is such a huge PITA, and the drywall is level, I had this idea:

    Could I nail/screw 1" thick foam panels to the entire ceilingto provide an air barrier and an R-4 to R-6 gain vs. what is in the ceiling right now. Then put 1/2" (Not 5/8") drywall screwed into the foam, taped, etc.

    I'd lose 1.5" of drywall ceiling height, gain r-4.5-6.5 (depending on foam, and including .5 r-value for drywall)

    But I wouldn't create an absolute disaster area, I'd gain alot of sound insulation from the garage, and it'll be far easier to accomplish.

    Is this doable? Any downsides?

    Joe


    P.s. I figure my attaching drywall straight to a 1" foam backer, I can get away with thinner drywall (like .5", maybe thinner?) by screwing it into the foam more frequently.

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  2. joefrompa

    joefrompa New Member

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    Actually, I just realized it might be a good idea to use a similar on the interior-facing walls of the garage. They are already insulated with r-9 or r-11 fiberglass batts, and the sound & vibration insulation between those walls and the garage would be really welcome.

    I could rip down the existing 1/2" drywall, slap up a 1/2" to 3/4" foam panel, and then 1/2" soundboard or drywall.

    One more weird question for ya'll - do I have to slap up drywall? Could I simply put up foam, caulk seams with a color-matched caulk, and call it a day?

    :)
  3. joefrompa

    joefrompa New Member

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  4. begreen

    begreen Mooderator Staff Member

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    Works for me, but I am not a specialist.
  5. jimbom

    jimbom Combustion Analyzer

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    If the garage is not attached to a home, anything may go. If it is attached, many safety issues to consider.
    http://www.gypsum.org/#
    As as a minimum, you might consider fire resistant construction.
  6. smokinj

    smokinj Minister of Fire

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    Why not just blown insulation?
  7. joefrompa

    joefrompa New Member

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    The drywall surface is really screwed up. I either want to cover it over or rip it down, not just put insulation on top of it (which there is fiberglass under there).

    The ceiling is such a PITA that I think I just want to cover it over and air-seal it. It goes up to a bedroom, and that bedroom is like 50 degrees when the house is 65. I need to address that.

    The sidewalls are insulated with r9 or r11 fiberglass batts. They are also messed up, so I want to redo them.

    I'm thinking that this point that for the sidewalls I'm going to ripdown the existing drywall and inspect the existing batts and inside walls. I'll then add a vapor/radiant barrier against the inside drywall and either put up new batts or reinstall the old ones. I'll then put a sheet of foam over the wall for sound insulation, thermal bridging, and r-value. Then I might do something like fire-rated OSB - I'd like to be able to nail/screw anywhere into the wall and have good anchoring capabilities.

    For the ceiling, I'm undecided. I might just do regular foam and then drywall - it'll be cheap and give me a nice spike in ceiling r-value and air sealing.
  8. Backwoods Savage

    Backwoods Savage Minister of Fire

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    Joe, the foam idea sounds good to me. You could even put up firring stips to fasten it too and that would give you a small air space between the foam and the existing. If you do go with drywall you could also go with thinner stuff which is much easier to put up and it would still serve your purpose.
  9. Don2222

    Don2222 Minister of Fire

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    Hello

    I have the same problem with my garage ceiling, but I think you are wasting your time if you Do Not rip down the ceiling and insulate it properly! My garage ceiling is very poorly insulated with a very thin strip of R7 fiberglass. As Mike "Do it Right" Holmes on Homes would say "Drop that ceiling!!!"

    I want to drop mine and put in Roxul sound and fire rated. That I can do myself.

    http://www.roxul.com/residential/save energy with comfortbatt
    What is R-value of Roxul?
    R-value is the measurement of an insulation's ability to prevent heat flow. The higher the R-value, the more insulating power it provides. Roxul ComfortBatt delivers top performance for all thermal applications around the home. It is available in the following sizes:

    3½" thick batts with R-value ratings of R14 and R15 (US only) for use in 2 x 4 exterior wall applications.
    5½" thick batts with R-value ratings of R22 and R23 (US only) for insulating attics and 2 x 6 framed exterior walls.
    7¼" think batts with R-value rating of R28 and R30 (US only) for insulating attics and 2 x 8 framed exterior walls.

    Equally important, the R-value of Roxul insulation is not affected by water. Roxul ComfortBattâ„¢ does not store or transfer moisture, and it's completely resistant to mold, mildew, rot and bacterial growth.

    http://www.roxul.com/residential/products/roxul+safe'n'soundâ„¢

    Properties:

    Non-combustible stone wool insulation with melting point of approx. 1177°C (2150°F)
    Easily cut
    Excellent sound absorbency
    Fire resistant due to its high melting temperature
    Water and moisture resistant; does not absorb moisture to maintain insulating value
    Chemically inert
    Does not rot, promote mildew, fungi, or bacteria, or sustain vermin
    CFC- and HCFC- free product and process
    Made from Natural and Recycled materials
  10. fbelec

    fbelec Minister of Fire

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    just a thought and i'm not trying to spend your money. get a quote from a spray foam insulator. with a 10 degree difference in temp from the rest of the house to that room, with a little insulation you got, you might be doing a lot of work for a little difference. if you have someone spray it with foam then all you have to do is board it and it's done, and done the best way you could for most likely 2 x 6 joists. spray foam would be something like having 12 inches of insulation up there and it would seal everything up like a big wad of caulking.

    frank
  11. joefrompa

    joefrompa New Member

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    Thanks guys - keep sharing stuff.

    I've read the expense of spray foam insulation and I've lost my desire to use it, compared to rigid board foam.
  12. Don2222

    Don2222 Minister of Fire

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  13. jimbom

    jimbom Combustion Analyzer

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    What Don222222 said. He is spot on. Demo of drywall takes almost no time. Get er down. Put up some fire resistant insulation and hang some firecore. Who ever is sleeping in that bedroom can rest in peace. If fire resistant insulation is hard to find in your area, at least do the fire resistant drywall. The cost is almost the same as regular drywall.
  14. fbelec

    fbelec Minister of Fire

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    i'd still get the price. nothing to lose. find out what product he uses and look it up. a good friend across town had his attic rafters sprayed. he's got a old farm house from the 1850's the day before the spray it was in august mid 90's and humid outside. in the attic of course it was in the mid 100's. next day the same weather. 2 pm 78 degrees in the attic. amazing stuff. no odor at all. hand full of jobs i have been on in the past year and a half done by the same guy. no problems. no odor after 2 hours.
  15. smokinj

    smokinj Minister of Fire

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    Rip it all down at one time.......You will save money and can put 50r blown in. You will have less time in it too! ;-) oh and cheaper!
  16. joefrompa

    joefrompa New Member

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    What do you mean 50r blown-in?
  17. ironpony

    ironpony Minister of Fire

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    if I am reading correctly there are bedrooms above it???

    it has to be built to fire rated

    minimun 5/8/drywall possibly 2 layers on ceiling

    check your local codes

    I would not leave foam exposed it is highly flammable

    do it right safety first
  18. joefrompa

    joefrompa New Member

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    One bedroom above it. Currently the ceiling is fiberglass batts with one sheet of 5/8" drywall.

    Thinking it through, I'm leaning towards ripping it all down and starts from the subfloor down. New vapor barrier, sealed. New fiberglass batts. Maybe do some foamboard. Then fire-rated drywall using a drywall lift.
  19. smokinj

    smokinj Minister of Fire

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    If there bedroom over head......It worth every penny to rip it out.....I would check into spray foam!
  20. joefrompa

    joefrompa New Member

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    I get that spray foam has benefits. But let me ask: it's massively expensive for me because I'd have to hire for it, plus it's just expensive. I can achieve the same air-sealing and the same r-value simply by using fiberglass batts and then maybe 1" rigid foam on top of the studs, with caulked seams.

    So what's the benefit to me of using spray in foam when I can achieve the same effect for far less (albeit DIY)?
  21. smokinj

    smokinj Minister of Fire

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    If its bedrooms above you will still have air getting through....Seen this with lots of homes with living space over the garage. Needs to be air-tight that cant be done with bats and plastic....Bats would be cheaper but its not apples to apples.
  22. joefrompa

    joefrompa New Member

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    Ok, I'm curious how air is getting through an inch of foam with caulked seams - but I do know it's rated to .5 permeability (essentially impermeable, but recognizing some airflow does occur). So I recognize the airflow might be different. I need to assess a bit more I guess...
  23. smokinj

    smokinj Minister of Fire

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    Yea its worth looking at hard.....I really dont know how air get though there I have seen some Very Good home builders do an above avaerage job knowing its bedroom going in above it. Home owner will still complain about the rooms being cold. A spray in foam job and you still use the bats no issues.
  24. fbelec

    fbelec Minister of Fire

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    with the spray foam guy it would save you hours of time. and do a way better job because you get closed cell foam and in about .5 to 1 hour he's done and you can board. if anything you can have him cut the cost by giving you 2 inches of foam which would be better than 4 inch fiberglass so that you could get the room sealed off from the garage then throw in fiberglass from there. his price will depend on how thick he sprays. i'm not trying to force you just throw the idea out there. it is very good.
    but i do hear you about money. doing alot lately my self because i'm so poor right now.

    frank
  25. ironpony

    ironpony Minister of Fire

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    just my thought,
    depending on how tight the rest of the building is
    or if you plan on making it tighter,
    spay foam in the middle of a "hole" probably is not going to do much

    another words if the whole house is leaky
    sealing the floor is not going to help

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