Insulation

[hescores]

Hey guys it's been a while since I've been on here, but I'm in some need of some help and thought I'd see if anyone here could help.

I'm currently gutting one of our bedrooms to make it into a nursery for our first (and last). The house was built in 1962 and I've discovered that the one outside wall is just brick on the outside and some sort of concrete block on the inside. It then has 3/4" furring strips attatched which then held the drywall. From what I've gathered, this is actually normal building practice for that time period.

The other outside wall insulation was economy 1 1/2" which I about flipped when I seen, but that's another story.

Anyhow, my options appear to be:
1. leave as is and just put up the drywall
2. create a new wall out of 2x4 fill as normal with insulation and drywall
3. put up a foam board and drywall.

I've pretty much narrowed it down to either leave as is or put up foam board. I'd like to insulate as much as possible, so I'd like to do foam board, but now I'm reading that by putting up the foam board, I could create moisture issues.

I'm in the Chicago suburbs so our climate is rather all over the place and I'm just not sure what the best course of action may be.

Thoughts? Opinions? Gotchas to watch out for?

[triplefreak]

I'd frame a new stud wall & insulate the cavities. It will make the room 4" smaller, but the insulation will more than make up for a little space loss.

[rrich]

Building out the wall and insulating is the only thing to do. The warmth that the insulating creates is beneficial to the whole house. While the wall is open you may want to add outlets, etc.

While I don't have the temperature extremes that you do, putting insulation in my shop was probably the smartest thing that I've ever done. It really makes a difference in both the house and shop.

BTW - I had a home in Phoenix that was built in a similar manner. Concrete block, furring strips and wall board. But the wall board was foil backed.

When you put your wall board back up, cover the furring strips or 2x4 studs with Reynolds Wrap like wall paper under the wall board. The $40 or $50 spent on the aluminum foil will pay off in less than a year. I did this on a basement in Pennsylvania and actually made the finished room warm and there was no insulation other than wall board and paneling.

[TDHofstetter]

What I did on my Summer Vacation...

This house was terribly insulated when we got here. We stripped all the existing insulation out of the exterior walls, then refilled with fiberglass (in your case, it'd be worth doing to build out the wall to accept more insulation).

THEN... I bought a bunch of 1-3/8" polyisocyanurate foam board, the kind with the foil face. At the same time, I also bought several sheets of 3/4" and 5/8" plywood. I ripped the plywood into strips about 2" wide.

I furred the wall sideways with the 3/4", then followed that with the 5/8" to make a total furring thickness of 1-3/8" (same thickness as the foam board). I started at the bottom, then fit a sheet (2'x8') of foam board horizontally on top of that, then furred, then foamboarded, till I reached the ceiling.

Next, I taped. Every joint between furring & foamboard, and every joint in the foamboard, got taped. I used the aluminum tape, the stuff that's supposed to develop a stronger & stronger bond over time.

Last, I furred again - this time with 3/4" furring strips, standing vertically, pretending to be studs. I spaced 'em evenly so the joints in my drywall would work out. They provide, among other things, that ALL-IMPORTANT 3/4" gap between the foil and the drywall (the foil insulation doesn't work without that gap).

The wall's double-insulated to something like R-40, with no risk of trapping moisture inside the wall. It's got a built-in vapor/moisture barrier on the heated side. The "studs" are evenly spaced so it's easy to find 'em through the drywall. The whole house is MARVELOUSLY quiet now, compared to how it was, and far easier to heat.

It's worth doing, if you're gonna' stay in that house for a while.

[hescores]

Thanks for the advice fellas. I think putting up a new wall would be the best option, but 4 inches in a small room is rather noticable and is ultimately losing about 4 sq. ft. If I was losing it the other way it wouldn't have been as bad.

Of course I'm still undecided as to what I will do. Thankfully I have a few days to stew about it before I have to make a final decision.

[imahic]

If it is only one wall you are doing, could you not furr it out another 3/4 inch and then have it blown with the foam insulation? Would that create a vapor barrier problem? It is more expensive but they say it is really effective and you don't need it as thick as fiberglass or cellulose insulation. Friend of mine did his whole house when he built it and I think he said it cost him about 5 grand for the whole house IIRC. So one small wall might not be real bad I wouldn't think.

[hescores]

Not sure if the foam would create any problems, but I did check into it a little and the foam was the price of the entire budget of the project. With baby on the way, there's no way I can double the budget, nor would I recover the cost through energy savings.

[Stretch]

If did add an extra 3/4" to the furring strips you'll have room for two layers of foam board insulation. That would bring you up to R10 which isn't too bad for a wall, especially when you're moving up from nothing. Then you'll only lose 2" from the end of the room by the time you add new drywall.

[hescores]

Actually Mark, that's not a bad idea. I had drywall and 1/4" panelling up there prior so I'd actually only be losing 1/2" on the wall if I add the the extra 3/4" furring strip.

I seen some info on thermal sheething. It shows an R value of 4.5 @ 3/4". I think between this and the layers of brick/cinder that it should bring my R value up to around 11 if my calculations are correct. I'm thinking this would be at the very least satisfactory.

However, I haven't found anything about moisture issues with this product.

Thoughts?

[TDHofstetter]

If it's not porous (styrofoam), it'll trap moisture between the foam & the cinderblocks. If there's any wood in there, it'll rot right out. If the foam's porous, though, it'll wick the moisture through to the inside surface of the sheetrock where it may give you mold problems.

I'd say your best bet, since you've got masonry on the outside, would be to foam on the inside but don't use anything but PT for furring. Funny spot, that.

[imahic]

I didn't know the foam would be that high. Maybe they shot you a high price because the job is smaller than what they want to deal with. I know contractors who do that. If they don't want to do it they bid it really high. I wonder if the spray foam you get in the can would work? You can get it in expanding and non expanding foam. Might be a thought.

[Stretch]

May 21, 2010 13:50:39 GMT -6 TDHofstetter said:

If it's not porous (styrofoam), it'll trap moisture between the foam & the cinderblocks. If there's any wood in there, it'll rot right out. If the foam's porous, though, it'll wick the moisture through to the inside surface of the sheetrock where it may give you mold problems.

I'd say your best bet, since you've got masonry on the outside, would be to foam on the inside but don't use anything but PT for furring. Funny spot, that.

What if he used Drylock paint to seal the cinder blocks? That would keep any moisture from coming to the inside of the wall. Then he could use construction adhesive to stick on 1.5" furring strips and then do the foam.

[TDHofstetter]

I've read some Consumer Reports reviews on DryLock and similar paints... they make the 'crete act a little less like a sieve, but not a lot less. They're far from waterproof.

Roofing tar, that I'd trust pretty well, provided the cinderblock wall is fully exposed to free air on the outside. Be a booger to get construction adhesive to stick to tar, though.

[woodmannie]

Hey, just a thought, but why not foam fill the block. We do it all the time here. They drill a hole at the bottom, one at the top in each core, then fill till it comes out the top. Great r value.
The reason they didn't add insulation was that the dead air space (meaning the air trapped in the block cores) acts as an insulator. It's also has dead air between the block and brick. This practice is still in use today.

Tom

[hescores]

A bit of an update - the block is actually solid. I'd say approx 3X8X4, then a slight gap, then a couple rows of brick.

HD ticked me off. I went to purchase a bunch of my supplies and for the one section of wall I got R-21 on sale for $15. For the other wall I got R-15, but then promptly returned it when I seen they wanted $47.47 for it. Every other fiberglass insulation is anywhere between $9 and $20 and is roughly $.20 sq. ft. The R-15 is $.70 sq. ft. Unbelievable.

[woodmannie]

wow, trip brick with 3" backers? wow. Kinda unusual. usually it's one on one, or just the trip brick.
Guess the foam fill is out.

Tom

[TDHofstetter]

We could hollow 'em with a hammer drill & some cordite...