using insulation baord against a concrete wall

[radstorm]

Hi again; A new question.

My house is made of concrete block. I want to drywall the interior walls, but would like to insulate them as well.

Some say considering it is concrete and pretty much air tight anyways..insulating is overkill..heh

Anyhow I have some of that insulating board, 4x8 sheets that is brown in color. It may have a different name..not sure

Can I attach that directly to the wall, then place the drywall over it. If so..should I also use a foil or maybe plastic sheeting first for moisture protection?

If so..which side do I place it, against the exterior wall or against the drywall?

Thanks

PS: this is an old house, and I am not as much interested in "pretty" as I am just staying warm

[HayZee518]

if your blocks are hollow get some insulation called VERMICULITE. this product is a mined product real close to MICA. just pour it into the hollow spaces. now about the insulation board. you can just glue it on the blocks with a construction adhesive. fastening the sheetrock is another story. this also you can glue to the insul-board but I'd feel much, much safer if its screwed to a framing member. 2x3s laid sideways and fastened to the concrete block makes more sense. for outlets in the wall you can use shallow boxes for this.

[pushkins]

I'm assuming your referring to above ground application. It would be very unwise to attach anything directly to the block wall as this will help allow moisture to wick in and eventually cause you a great deal of problems. The foam board your refering to has a very low R value so using it is almost pointless, you really need to build internal stud walls and install insulation between the studs then drywall over, if the insulation is"faced" then there is no need for any plastic or foil on the block side, if your insulation is not faced then vis-queen or foil should be added to the block side of the studs.
If you do still want to attach to the blocks then you must use all treated material and attach with Tapcons.

[radstorm]

Yes thanks. That was my concern..the walls "sweating" so to speak.

So then I guess putting in interior wall studs is the plan.

Considering the walls are pretty much airtight..would perhaps furring strip be ok, instead of 2x4?

Its a very small room as it is..don't want to shrink it too much more

[pushkins]

A furring strip would work for attaching drywall, the only problem you have is that code everywhere dictates R13 as the minimum wall insulation and that only just fits in a 2x4 stud cavity, it may not be a problem for you but if you try to sell the house it will become a problem fast. Now if it was just a garage then that's a different story.
Also remember that the insulation shouldn't touch the block wall or it will act like a big sponge even on walls you think are dry.
If it were me and a "living space" I'd give up the 4" on each wall and install studs with R13.

[HayZee518]

how's he gonna fasten outlets? boxes are a minimum of 2 1/2 " deep?

[pushkins]

I don't know, I kinda assumed that it's a house of sorts, therefore it has outlets already attached to the block walls (steel boxes etc...).

[radstorm]

ok then..so would I put the foil side to the wall to keep the moisture at bay getting into the insulation.. 2x4 is no problem I guess..also what would I use to attach studs to the walls..just screws. glue??

This is a little cottage of sorts with 7 foot ceilings, it's old and so am I,,lol,,and I am stuck with it for life..so no plans to resell it.

[pushkins]

If your going to build a stud wall then there is no need to physically attach it to the wall, you would build it as a wall freestanding with maybe a 1/2" gap between the stud wall and the block wall. ANY wood that will touch concrete/block MUST be treated material, so in a conventional stud wall the bottom plate will be treated if built on a slab. If you intend to screw to the wall the studs should be treated.
If you want to attach it to the wall with studs turned on their sides then then you need to use Tapcons (little blue masonry screws available at Lowe's/HD), between the stud and the block wall make sure you install a layer of tar paper/roofing felt this will stop physical touching of wood to block and moisture transference, then install your insulation boards in the stud cavities.
Like I mentioned before your foam board is going to offer very little insulation with an R value of around 2 or 3 compared to R13 standard wall insulation, so while it might "help" with the cold room, it's not going to retain heat or AC very well at all.
Using R13 will also get you a tax credit, (I think they just extended the credit as well) The credits can differ state to state, where I am it's up to $1500 and at $9 a roll (R13) you won't come anywhere near that amount for your room. One roll (11 pieces) will do a 15' long wall @8'.

[radstorm]

thanks push, that sounds like the way to go..I can do that considering I have wood floors and of course the ceiling joist are wood too..that is better then actually attaching the studs to the concrete

but what about the insulation..do I put the foil side to to the concrete to keep it from sponging?

[pushkins]

If your going to use the foam board then the foil goes towards the heated side of the dwelling...which naturally is the interior side, the foam board won't absorb moisture BUT if possible add nylon straps (ducting strapping is ideal) to the rear side of the new wall, to stop the boards from falling backwards. If your going to use fiberglass insulation the the paper side faces the heated side (interior).

[radstorm]

thanks again everyone for the help..doing it right the first time will mean less future grief I am sure