Home insulation experts chime in

[Howard]

There's a room in my house directly above the garage which gets very cold in the winter. As you may have guessed, the "roof" of the garage is not insulated.

What's the proper way to insulate it? Obviously I need some type of insulation, but is moisture/vapor barrier necessary? How do I fasten the insulation to the... uh, I don't know if it's subfloor above the garage; I'd have to check.

 

[drnickriviera]

So is it an unfinished attic space? no drywall on the roof rafters? any decking or plywood on the floor? is it conditioned space (heated/cooled)?

 

[Howard]

Originally posted by: drnickriviera
So is it an unfinished attic space? no drywall on the roof rafters? any decking or plywood on the floor? is it conditioned space (heated/cooled)?

No, the room is a bedroom so there is at least subfloor plywood. It is both heated and cooled, but too much energy is lost through to the garage.

 

[Rastus]

Blowing cellulose into the rafters (if you have them) is what is done mostly.

 

[drnickriviera]

Yep you need a vapor barrier. I think the easiest way is to remove the flooring and put in some kraft faced fiberglass. Some will say you don't need a barrier with blown cellulose, but i'd rather have one.

 

[RU482]

Originally posted by: Rastus
Blowing cellulose into the rafters (if you have them) is what is done mostly.

if there isn't already some insulation there, I've always heard that batt fiberglass>blown fiberglass>celulose

 

[biggestmuff]

Although it may seem like a good idea asking The Collective (ATOT) for advice, call a home insulation expert. I'd wait until early fall to get the quote and work done. People don't like working with insulation in hot spaces.

 

[Squisher]

A better option is sprayed foam insulation, more R value and no vaper barrier needed.

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[Greenman]

If I understand what you're saying, the space you want to insulate is the floor system of the room over the garage. It should be drywalled on the garage side, as it's supposed to be a fire rated assembly. Blown insulation might or might not work, it all depends on how it's framed. I'd just pull down the drywall and insulate it, probably 15 sheets of board.

 

[Greenman]

Originally posted by: biggestmuff
Although it may seem like a good idea asking The Collective (ATOT) for advice, call a home insulation expert.

Some of us are experts.

 

[Howard]

Ah, I'll take some pictures tomorrow. That would be the best way to explain it.

All the advice is well-appreciated, by the way.

 

[amdskip]

Originally posted by: Greenman
If I understand what you're saying, the space you want to insulate is the floor system of the room over the garage. It should be drywalled on the garage side, as it's supposed to be a fire rated assembly. Blown insulation might or might not work, it all depends on how it's framed. I'd just pull down the drywall and insulate it, probably 15 sheets of board.

I'll second this. No sense ripping up the floor, much easier to insulate it from below.

 

[desy]

Vapour barrier goes on the warm side then the insulation. It keeps the warm moist air from inside the house from condensing and creating mold.
The spray foam is a good idea and the best way of doing it but not a DIY deal so probably more $ although I've never quoted it out

 

[Greenman]

Originally posted by: desy
Vapour barrier goes on the warm side then the insulation. It keeps the warm moist air from inside the house from condensing and creating mold.
The spray foam is a good idea and the best way of doing it but not a DIY deal so probably more $ although I've never quoted it out

Spray foam is very expensive.

 

[Howard]

Well, I can't get a camera until tonight. The garage ceiling is drywall, though.

 

[Strk]

Is it a finished garage or can you see the joists? If the latter, just get the thickest insulation you can get in there.

 

[Howard]

No, the joists are covered by drywall, unfortunately. What are my options now?

 

[desy]

You rip down the drywall get some 6 mil poly and acoustic seal , seal and staple that to the bottom of the floor fill the joist void with fiberglass bat insulation.
Drywall the ceiling again

 

[bctbct]

Vapor barrier, nice to install in new construction...not feasible for remodel

Just call an insulation company to come out and see if they can blow either fiberglass or cellulose into the void. Much cheaper and easier than pulling down the drywall. There is also a expandable foam but I think its pretty pricey.

 

[RGN]

Originally posted by: desy
You rip down the drywall get some 6 mil poly and acoustic seal , seal and staple that to the bottom of the floor fill the joist void with fiberglass bat insulation.
Drywall the ceiling again

+1, its not that hard and won't cost that much.

 

[Analog]

Vapor barriers are generally not done on ceilings, because the roof above the insulation is vented. Vapor barriers are for walls, which are not ventilated...

The ceiling of the garage should use 5/8" firestop sheetrock. The 5/8 firestop should also be between the living area and the garage.

I would then blow insulation over the garage area.

Edit: since it sounds like the room is directly over the garage, and there is no roof area as I originally thought, then a vapor barrier would be ideal.

 

[flamingelephant]

uhhh, one who doesn't use vapor barrier between a garage filled with carbon monoxide and their living space is an idiot!

 

[flamingelephant]

and you do put a vapor barrier over any ceiling even if the attic is vented... otherwise the warm moist air from the living space seeps through the ceiling, hits the cold insulation in the attic during the winter, condenses, turns into water, then leaks back into the house, or starts to mold, rot the framing in the attic etc....

 

[Pepsi90919]

5 stars

 

[Greenman]

Originally posted by: flamingelephant
and you do put a vapor barrier over any ceiling even if the attic is vented... otherwise the warm moist air from the living space seeps through the ceiling, hits the cold insulation in the attic during the winter, condenses, turns into water, then leaks back into the house, or starts to mold, rot the framing in the attic etc....

Both of your posts are incorrect. A garage should never be full of carbon monoxide. The idiot would be the person who runs his car in the garage with the door down.
A vapor barrier isn't always required, it depends on what climate zone you're in. Here in the Bay Area we don't use them at all.