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Insulation question

Post in 'DIY and General non-hearth advice' started by swagler85, Nov 28, 2012.

  1. swagler85

    swagler85 Minister of Fire

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    Has anyone insulated a firred out wall in a basement? We have a finished basement and realized there is no insulation on the walls were there is block, which is about half the basement wall. They just put in 2x2's and drywall over it.The other half is framed in as part of the walkout and is insulated.. Thinking I should use foam and spray it in there. Any other ideas?

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  2. Deadeye

    Deadeye New Member

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    When you say spray foam I assume you mean the small cans? I'm not sure that will go well. That stuff is messy and could possible push the wall away from the blocks. You could take the drywall down and put up fiberglass but thats a big and project. You could have blown fiberglass put in. They will have to cut 3" holes between each stud. I don't see any quick and simple fixes here.
  3. kingquad

    kingquad Minister of Fire

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    Tear it out and do rigid foam(XPS). Then fir or stud it out and do more foam between the studs. Tape all the seems with building wrap tape. Then use moisture resistant drywall. Not the cheapest or easiest option, but do it once, do it right. Plenty of info on this stuff over on the Fine Home Building/GBA/Building Science sites.

    Bruce Harley's book "Insulate and Weatherize" is a one stop shop for all this sort of info. I just picked up the second edition. It should be on every home owners bookshelf IMO.
    Backwoods Savage likes this.
  4. DaveGunter

    DaveGunter Member

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    This is where I got all the information I needed when I added insulation to mt basement.

    http://www.homeconstructionimprovement.com/how-to-insulate-basement-walls/

    Good solid construction info all over that site
  5. woodgeek

    woodgeek Minister of Fire

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    I have a similar problem, but only a 1" cavity filled with shims. There are no good solutions short of ripping it out and going the XPS route.
  6. swagler85

    swagler85 Minister of Fire

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    How well would blow in insulation go into that small of a space? Really don't want to tear out the walls
  7. ironpony

    ironpony Minister of Fire

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    2x2 are actually 1.5 inches, I would hardly put any effort into insulating that size cavity, bite the bullet and go all the way or leave it be.
  8. woodgeek

    woodgeek Minister of Fire

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    I've got a couple hundred square feet of drywall like this in a nicely finished basement....based on IR measurements I estimate the wall is R-3 or so at best. Makes those room cold, and as I tighten up and insulate the rest of the structure, those nice finished rooms keep getting colder.

    Makes me crazy!

    As a test in one section, I cut a horizontal band out of the drywall about 8" high at waist height, and then slipped two thickness of 1/2" polyiso into the cavity through the band. Sounded like a good idea cus the furring was on 16" centers and nice and parallel. Turned into a PITA cus the cavity was filled with shims of various lengths, at random locations, that didn't show up on a stud sensor. I worked the polyiso in, but had to cut big chunks out until they looked like big jigsaw pieces that I could sneak around the shims. And then you have to patch in the drywall (took a while, but came out perfect) and repaint. After doing 50 sq ft this way, I figure I am saving $20/yr on heating!

    Not my finest DIY moment.

    Tiger foam would probably work in this app, but is super pricey making the payback lousy, and might pop the wall off, sending you back to square one.

    The job is too small to get a foam installer interested, I think.

    For DIY, one option is to get perlite insulation and pour it into the cavity. Might go from R-3 to R-6?? The prices online look cheap, but the shipping is crazy. You would need to local source.
  9. jharkin

    jharkin Minister of Fire

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    Using foam you could get R12 or so in 1.5" A huge improvement over R0 and it meets code for a below grade basement wall.
  10. woodgeek

    woodgeek Minister of Fire

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    IMO You and iron are both right. I think the foam-in foams are closer to R-6 per inch, so maybe R-9 in a 1.5" cavity. With thermal bridging by the furring, prob closer to R-6 or R-7 increase.
  11. jharkin

    jharkin Minister of Fire

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    I thought rigid icynene panels were close to R8, hence my guess above.
  12. semipro

    semipro Minister of Fire

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    I guess no matter what can do as far as adding thermal insulation I'd still worry about rot at the interface between the masonry and firring strips. I don't think building codes even allow any contact between untreated wood and masonry anymore.

    I'd be concerned that adding insulation between the masonry and drywall might somehow result in more chance of rot somehow.

    I'd suggest you yank the walls and do it right. You can even reuse the firring if you like. You'd also want to go back with mold resistant drywall and latex paint (no wallpaper of oil based paint).

    I'm in the process of doing this now so I know what I'm suggesting.
  13. woodgeek

    woodgeek Minister of Fire

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    Agreed, from a proper building science perspective, all solutions short of a total rebuild (with permeable, mold-resistant insulation such as XPS) are dodgy. And from a performance perspective, they are all kinda lame.

    On the foam in place idea, very few foams are 'rated' for cavity fill, and most of those are not happy below grade and have the right permeance and none of those I found had high R-value per inch.

    I keep coming back to the perlite idea (which is still pretty wacky) as the product is treated to be hydrophobic, and its granular/pourable. Prob v high permeance and non-molding (good). And a whopping R-2.5 per inch. And (maybe) cheap.

    If I wanted R-value and energy savings, I would rip out (and have to pay $$$ to have it done). The perlite would be DIY and cheap, but would get me from R-3 now to R-6 or so. I'd still losing plenty of heat, but comfort would prob be improved significantly by a 50% reduction in heat loss. But it would be a mess to demo later.
  14. Ehouse

    Ehouse Minister of Fire

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    I think with the perlite, if you used a small concrete vibrator (rent one to go on a cordless drill) or pad sander (minus the sand paper) against the wall. it would work quite well. If you remove the sheet rock, a trick with ridged foam is to cut the sheets for a loose fit and fill around them with low expansion foam for a tight fit.

    Ehouse
  15. ScotO

    ScotO Guest

    Have you considered framing 2x4 walls the whole way around the room against the block, and you could get up to an R15 Roxul in that space. You could frame it on 24" centers as there wouldn't be any load on the walls (to save on 2x4's) and you really wouldnt' be losing much space (a total of 8" of loss across a room counting the thickness of drywall). IMO, that would be the most cost-effective route and pay a bigger return in the end.......

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