# Will this work? Insulating a garage ceiling



## joefrompa (Aug 12, 2011)

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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## joefrompa (Aug 12, 2011)

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?


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## joefrompa (Aug 12, 2011)

http://building.dow.com/na/en/products/insulation/thermaxhd.htm

This is the type of product I'd use as a ceiling by the way - it's rated for ceiling use in wood-framed building, since fire rating was a concern of course.


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## begreen (Aug 12, 2011)

Works for me, but I am not a specialist.


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## jimbom (Aug 12, 2011)

joefrompa said:
			
		

> ...
> Is this doable? Any downsides?
> 
> 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.



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.


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## smokinj (Aug 12, 2011)

Why not just blown insulation?


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## joefrompa (Aug 12, 2011)

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.


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## Backwoods Savage (Aug 12, 2011)

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.


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## Don2222 (Aug 13, 2011)

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:

    3Â½" thick batts with R-value ratings of R14 and R15 (US only) for use in 2 x 4 exterior wall applications.
    5Â½" thick batts with R-value ratings of R22 and R23 (US only) for insulating attics and 2 x 6 framed exterior walls.
    7Â¼" 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. 1177Â°C (2150Â°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


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## fbelec (Aug 13, 2011)

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


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## joefrompa (Aug 13, 2011)

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.


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## Don2222 (Aug 13, 2011)

Hello

I know Mike do it right Luvs Spay Foam but contractors do like a quick BuckerRue!!

Be careful because sometimes a spray foam job can go wrong and there may not be a fix.

See below -- Off Gases that do not go away!
http://www.greenbuildingadvisor.com...9/odor-problem-attic-after-spray-foam-applied

That is why I like Roxul or the Pink Panther Stuff!!


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## jimbom (Aug 13, 2011)

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.


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## fbelec (Aug 13, 2011)

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.


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## smokinj (Aug 13, 2011)

joefrompa said:
			
		

> 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.
> 
> ...



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!


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## joefrompa (Aug 15, 2011)

What do you mean 50r blown-in?


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## ironpony (Aug 15, 2011)

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


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## joefrompa (Aug 15, 2011)

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.


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## smokinj (Aug 15, 2011)

joefrompa said:
			
		

> 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.



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


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## joefrompa (Aug 15, 2011)

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)?


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## smokinj (Aug 15, 2011)

joefrompa said:
			
		

> 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)?



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.


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## joefrompa (Aug 15, 2011)

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...


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## smokinj (Aug 15, 2011)

joefrompa said:
			
		

> 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...




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.


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## fbelec (Aug 16, 2011)

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


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## ironpony (Aug 16, 2011)

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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## gpcollen1 (Aug 16, 2011)

Just saw the Roxul in Lowes after looking at the website.  Why would anyone NOT use that stuff?  I hope I can take some of my R19 back and use this stuff.  I am certain to use it in the garage when I finish that this fall...

i cannot wait for the energy savings this winter with the pellet stove and 2 wood stoves fully operational, refurbished old addition with R50 ceiling and garage ceiling [LR & Kitchen above] redone...

Any down side to the Roxul?


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## joefrompa (Aug 16, 2011)

Got an airloss audit done last ~July. Home was modestly leaky and had 4 main points of air penetration. I finished 3 of them and since then have also had the house re-sided with foam and taped tyvek. I'm guessing the house is now borderline too tight - I'm expecting to have small draft issues with my stove this winter and already considering where I'd want to introduce some fresh cold air from (i.e. crack a window near the stove?)

I really want to consider it, but I'm going to price out batts + 1" of foam insulation over the walls first. I can't see spray foam being done for under $800 (a sales call to provide a quote + someone coming out and doing it over 4 hours or so + materials).

If I'm still doing batts on top of that, we're not talking a whole lot of savings in labor and cost vs. putting batts in myself and then 1" of foam on top of the studs (reducing thermal bridging).


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## Bspring (Aug 18, 2011)

Foam is great but has a very long breakeven period compared to the pink stuff. I could not justify it. I looked into it when I was building my house. Half of the year I am heading with wood and the other half cooling with a heat pump so I had to double my payback due to no utility cost with the heat. The same was the case with the tankless water heater. With only 2 people in my house there was no justification for it.


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## Bspring (Aug 18, 2011)

Foam is great but has a very long breakeven period compared to the pink stuff. I could not justify it. I looked into it when I was building my house. Half of the year I am heading with wood and the other half cooling with a heat pump so I had to double my payback due to no utility cost with the heat. The same was the case with the tankless water heater. With only 2 people in my house there was no justification for it.


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## lukem (Aug 18, 2011)

Just put a sheet of 1/2" right on top of the existing drywall, then blow in additional cellulose or fiberglass right on top of the existing insulation.  No need to tear it down, and foam panels will not save much heat and cost a lot of money.

EDIT:  didn't see that a room was above it.  Disregard.  Tear it down and do it right.  You won't regret it.  I was thinking this was open attic above the ceiling.


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## smokinj (Aug 18, 2011)

lukem said:
			
		

> Just put a sheet of 1/2" right on top of the existing drywall, then blow in additional cellulose or fiberglass right on top of the existing insulation.  No need to tear it down, and foam panels will not save much heat and cost a lot of money.



I believe to be bedrooms on top of the garage. Yea a couple of feet of blown in would be Cheap.


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