DIY Home Improvement Forum banner

Insulate finished garage ceiling or condition garage?

9K views 19 replies 5 participants last post by  pasichnyk 
#1 ·
I have a drive in garage (basement level) with slab cement floor and walls (top few feet of walls are wood framed with brick exterior). My living room sits directly over the garage (about the same size too) with hardwood floors. The living room floors are noticably cold, due to the unheated garage and uninsulated floor cavity. Our forced air furnace can keep up just fine, but this room is always colder than the rest, due to the floors mostly. Air could be warm (even too warm), but you "feel cold" from the floors. I'd like to even this out and just get a overall warmer feeling to the room.

Hardwood Floor to garage ceiling are like this:

OAK FLOORING
SUBFLOOR
FLOOR JOISTS (~10") - Currently air space
SUBFLOOR material (yeah, again...)
1/2" drywall
1/2" plaster (in a metal mesh lathe)


I see that I have a few options here:
  1. Insulate the floor cavity
    1. Seeing as the cavity would need access holes drilled to blow in insulation, I believe I'm stuck with either cellulose or fiberglass? Suggestions on which would be more cost effective/insulating effective?
    2. Anyone have a acceptable price range for this? Just to keep the estimators in check. :)
  2. Condition the garage (as much as possible)
    1. Garage door insulation kit
    2. insulate walls with something (sprayfoam, rigid foam, ...)
    3. better seals on the bottom of the garage door, etc
  3. Both
    1. Not sure if it would be overkill (is there ROI?) but I could start off with one of the above, and then do the second to help in the future, but I think there are other areas of the house which could use the attention/money first...
I'm in Seattle, so usually in the 30-40's in the winter, +/- depending on the day.... Slab walls are mostly underground, maybe 1.5ft or so above the dirt.

I was thinking that it would probably be most effective to get someone to come bore some access holes in the ceiling and spray in the cavities, but just wanted some opinions on the best approach from an ROI point of view.

Thanks,
Jesse
 
See less See more
#2 ·
After doing a lot of reading on greenbuildingadvisor.com and buildingscience.com about this, I would be inclined to condition the basement, esp since you would have to retro-insulate the floor. Mineral wool is apparently good against basement walls, if you air seal well. Look up ADA (airtight drywall approach). Or, rigid foam w/ spray foam at the edges to fill gaps. No vapor barrier. Your statement "even too hot" typifies what happens in your situation, as warm air (forced air heat) will rise like a banchi and leave the floor cold.
 
#3 ·
So you think I would get more insulation for my money/effort with conditioning the basement alone? I didn't aim to fully finish the garage anytime soon, so if I went this route id probably just glue/seal foam boards to the walls (at least the top section) and insulate the door. However I would still be left with an uninsulated area on the exterior wall in the 10" floor cavity which I'm assuming would leak a lot into my "conditioned" space. The only way i could insulate that section would be to cut access holes in each floor joist section and try to can spray foam each section. do you think this is necessary?

My exterior walls are wood framed with a single layer of brick face, and the cavity is uninsulated currently, but I don't want to blow in insulation until i can pull out and replace all the old knob and tube wiring.

Anyway, I understand this is going to be an incremental process and I'm just looking to do peices of it that will all add up to a good finished product.
 
#4 ·
I'm going to insulate my garage fully
Planning on insulation under the slab, insulated garage doors
I may never heat the garage, but I do have a kerosene heater I could use out there
Or a few electric heaters if I needed to work out there
Insulating the garage ceiling would have a noticeable effect on keeping the room above warmer
Make sure that the drywall is 5/8" when it goes back up to meet code

My garage is not insulated yet, but its a lot warmer then outside
 
#5 ·
It's hard to define anything w/ out being there, and you have your own criteria to meet, too; we all do. So, insulating the ceiling will sure help, but can be problematic. Conditioning the crawl space is apparently the best way to minimize problems w/ vapor. If you can't finish, it may be best to wait till the money and time are all there and do it as best you can, once. That'll have to be your call.
 
#6 ·
In my case the slab is poured on dirt, so there is no crawl space to condition. However its a drive in to garage below grade, so the slab is actually about six feet below ground, so I wouldn't expect huge loss there as compared to the walls near or above the surface, or the door itself.

Money is not as much of a concern as doing the project correctly, bug at the same time I'm not going to throw it away on a solution that is way more expensive but doesn't really get me anything extra. ROI is important...

If I start off by conditioning the walls and door of the garage, is gluing and selling foam board to the walls A good approach if I don't plan on framing in the walls, or so I need to frame (adding unfaced batts) and drywall on top of the foam to be up to code?
 
#8 ·
Is there any pretreatement of the concrete walls that should be done prior to glueing the foam board to the walls, such as sealing paint, etc? The walls appear to be fairly (if not totally) dry...

Is there a certain type of foam board that would be best? What about glue and tape?
 
#9 ·
Generally, you don't want a concrete wall sealed on the interior, since it can';t breathe to the outside. It could not breathe at all, then. If painted for aesthetics, they should be painted w/ a latex paint that is vapor open. I do not have the goo name off the top of my head, but there are specific ones for each kind of plastic. I think EPS (white, "bead board") is probably OK to use, and it is more permeable than XPS. No foil faced. Since your walls appear dry, I THINK you'll be fine w/ EPS. I used to think it was XPS only, but that seems debatable now. Apparently EPS only absorbs about 0.2% of its weight in water. Myself, I'd stick w/ XPS unless someone more knowledgeable says EPS.
 
#14 ·
Does the metal door itself not act as a vapor barrier? Is the point for more permeable insulation here to let anythign condensing on the metal itself to escape? You know, the kits that i have see are all white board, so maybe that is the way to go anyway. I just wanted to get the extra R value if i could, but seems maybe too much risk.

That said, you mentiond earlier that the blue/pink board is what you'd use against the poured concrete wall. That still stand?
 
#16 ·
IMHO I believe your money would be better spent on updating the electric in

the ceiling and then properly insulating the ceiling rather than trying to

upgrade the garage side walls.

Foam needs to be covered with rock , so now your building a stud wall besides.

If your not heating the garage ,the walls are actually helping to heat it in the cold of the winter.

Huh What !! Think about it , the walls ( opposite the earth ) below the

frost line ( 18" ) are around a constant55-57f and you outside temps are 30-40f .

The only heating source is your warm engine block when you pull in.

You may get a 10 to 15 degree rise ( for a while ), the walls aren't hurting

you in this respect.

Nothing wrong about insulating the garage in the future if you want to

heat it and work out there ect just don't see it helping your floors much .
 
#17 ·
I installed some foam board (EPS) on the garage door today, which is already making a huge difference in the ambient temp of the garage, which is nice for my projects (I don't currently park in it, too much misc stuff laying around).

I hear what you are saying about covering the foam, and wasn't sure if that was required or not in a garage. I also understand the comment about the earth actually warming the garage, and took that into consideration. I was only planning on putting up any insulation on the top 2 feet of both long walls, as well as the vertical (~2ft wide) strips on the side of the door, as these are the places that are either exposed to or near air.

There is only one circuit runnign in the ceiling there, and its easily accesssible, so it's on my list of things to do already. Once thats done i could blow in insulation if needed to the 10" air cavity.

Still not sure if i want/need to put up insulation on the top 2' of the wall, but we'll see what diff the garage door makes to the upstairs and go from there. If i decide to do it, is it ok to simply glue the XPS to the wall, and then glue drywall on top of it to protect from fire? Or does it need to be framed out? There are some heavy duty shelves on the walls of the garage that I was hoping to not touch anytime soon (really bolted into the concrete, and very handy as well). If i framed out, i'd have to take those down and figure out some new shelving arrangement post framing.

Anyway, thanks much for the feedback. Very helpful to hear peoples opinions.

Thanks,
Jesse
 
#18 ·
#20 ·
Gary, so you recommend xps on the slab wall as well? Cover it with just standard drywall, or would you recommend some special stuff for a WA garage? Ok to glue to the foam, or so I need to shim it out a little so it doesn't make contact with the drywall paper? If i need to shim, how much is optimal?

Thanks,
Jesse
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top