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rebelranger 12-05-2012 04:41 PM

What would you do...Garage ceiling?
Ok after looking here I can't find the answer, so I'm going to ask.

I have three bedrooms and two baths over my two car garage. The garage ceiling is sheetrocked and finished but does not have any insulation, thus the rooms get chilly versus the basement ceiling which has roxul sound insulation then drop ceiling. So what to do? Oh one bath subfloor was water damage so when all the subfloor was removed to lay tile I used R30 unfaced fiberglass pink insulation (I didn't know better then) installed then OBS subfloor then ceramic tile...this floor stay a nice temp compared to the hardwoods and other bath with ceramic tile.

1) Remove drywall (reuse?) install R30 faced (facing towards conditioned side) insulation then re-install old drywall. -->I've never re-used drywall, but if possible this is the very cheapest method.

2) One I want to use but highest price. Demo ceiling drywall. Fix floor creaks but screwing OBS subfloor to hardwood from below. Have 2" closed foam spray insulation installed. Then R13 faced insulation. Then drywall.

3) Possible easiest fix but largest risk and problematic. Cut holes and use fill with loose fill insulation. Then seal any holes. --> In a way I love this idea because it is so simple but (1) leaves creaky hardwoods above, (2) causes problems if I need to access HVAC runs that are covered by drywall, and (3) chance the drywall won't hold the weight [I don't know drywall's true age].

So what do you think? #2 is the best choice because it completely seals the garage thus preventing any CO2 from escaping into the living quarters, has the highest R value, and best soundproofing. But will cost about over $8 a sqft and I don't plan to stay here more than two years...but could be here up to four.

I'm at a loss...give me some guidance. Anyone who has had these problem and did something let me know. Thank you!

joecaption 12-05-2012 04:53 PM

Not sure why you would have used unfaced insulation.
There should have been a vaper barrier toward the conditioned surface.
No way are you going to be able to reuse the drywall, it needs to also be 5/8 fire rock. And also air seal any holes where wiring and plumbing was run with fire proof caulking.

rebelranger 12-05-2012 05:10 PM

@joe - Thanks for the info. I used unfaced because it was my first insulation install and I didn't know better. Now I know better.

To reuse the drwall I was going to run a magnet along the joists to find the screws then remove.
Definitely will airseal with the can foam for any holes if I don't get spray foam.

5/8 Fire rock, like

joecaption 12-05-2012 05:20 PM

That's the sheetrock. Not worth the time trying to remove the screws and reusing.
Rent or borrow a drywall lift to reinstall it.
DO not use reguler foam or caulking it needs to be fire rated.

gregzoll 12-05-2012 05:23 PM

You would be better to have someone come in and spray foam the floor above the garage, along with sill & rim joist areas in the basement.

It will quickly pay itself back within two years.

rebelranger 12-05-2012 06:17 PM

@gregzoll - I've inquired into spray foam for the garage and it's $1 per sqft per in of foam for closed cell and .78 per sqft per inch for open cell.

-I've used 2" XPS with can spray for the sill and rim joists in the basement... didn't really notice a change but per heat loss/gain but it tightened up my house for air leakage.
-What do you base the "pay itself back within two years" off? I just don't know if I'll recoup $1k plus in heating/cooling savings over two years. Please enlighten me how I will.

gregzoll 12-05-2012 07:15 PM

Raises the value of the home, along with saving you money on cooling and heating costs. It is a no brainer, and a no loss situation. I personally would not use XPS and caulk and spray foam for something that can be done cheaper and easier.

rebelranger 12-05-2012 07:44 PM

A 4'x8' board of XPS cost me $22 and it covered 32 sqft. Two cans of spray foam cost me $6 and change so for $28 I did all my Rim and Sill joist areas. I would of cost me $400 for all spray foam, such a small job, for a company to do it. I took the cheaper route.

As for the garage ceiling, I'm seriously considering the 2" of spray foam route. What do I do if I need HVAC access? Just cut the foam?

gregzoll 12-05-2012 08:24 PM

You are forgetting the time consumed, and the time spent laid up when you fall off the ladder. Besides, using XPS is not going to solve the problem, and even with the drywall up there, heat can still cause the XPS to start giving off fumes, if there is ever a fire in the garage space.

Gary in WA 12-05-2012 09:18 PM

"Figure 7: Cavity Insulation with Vapor Barrier—Adding impermeable foil faced insulating sheathing over fiberglass cavity insulation is a hybrid approach that uses the best qualities of both materials. Note that the optimum location for the airspace is above the cavity insulation. Are you folks paying attention at the EPA ENERGY STARŪ Program? Makes for warmer floors—this is the same detail that should be used under bedrooms over garages." Underline is mine, from;

PS. Of course cover it with 5/8" Type-X drywall for fire-rating per Fire Marshall/Building Codes.

rebelranger 12-05-2012 09:41 PM

@GBR - I was hoping you would comment. I have read that before when you posted it but it puzzles me again. Please tell me which it says (1) install fiberglass insulation with vapor barrier towards the upstairs living area and the unfaced insulation facing down then drywall, or (2) unfaced insulation installed then closed foam board then drywall, or (3) faced V.B. towards upstairs living area then foam board then drywall?

Figure 3 says don't install unfaced insulation without cover the bottom part.
Figure 4 says don't install V.B. faced insulation with uncovered insulation exposed. (wood moisture issues)
Figure 6 says no insulation just foam board across bottom of ceiling joists.
Figure 7 says (a) air pocket, (b) V.B. faced insulation facing ceiling [up], (c) foam board across bottom of joists.
- The rest says Spray foam closed cell.

Am I reading that wrong? Can I just install the V.B. insulation facing the rooms above and then drywall?

rebelranger 12-05-2012 09:44 PM

I really can't/don't think I can lower the ceiling height even a 1/2" because the ceiling is already just over 7' (1960s house) and the two garage doors already just barely clear the ceiling...not to much the garage door openers actually touch the ceiling. Thus asking MUST I install the foam board before drywall?

Just based on everyones comments the Drywall is coming down so blown in loose fill it out.

Gary in WA 12-07-2012 07:34 PM

I don't understand your questions. Fig.3 is showing radiation coupled- warmed cavity f.g, with cold bottom surface to cold dirt w. plastic. Fig.4 is vinyl flooring (vapor barrier) on the wrong side of the sheathing. Fig.5 is warming the joists= no moisture drive there. Fig.6 is foil-faced PIC on the bottom of the joists- (Vapor barrier and reflective surface) = no cavity insulation required if the f.b. meets your local energy code for R-value in cavity.

That is the best way if you have the clearance for it. Just drywall with 5/8" Type X for fire-stopping to meet your local code.


rebelranger 12-07-2012 10:16 PM

@GBR - thank you, that cleared it up a ton. I pulled down a corner section and think i can get 1/2" PIC in there which is only R3 so I'm going to stuff in some R13 as well, then 5/8. I'm trying to find someone who will just flash inside the joists for air sealing on the cheap but because such a small job most companies basically right off the bat say no thanks. Sigh.

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