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Rim Joist Sealing and Insulation

Post in 'The Green Room' started by velvetfoot, Dec 18, 2008.

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  1. mainstation

    mainstation Feeling the Heat

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    We had our rim board and cellar walls professionally foamed , and man what a difference. It has already paid for itself with this extra cold winter.
    My question is,
    Is it ok to put fibreglass insulation in your floor joists, my kitchen floor is always cold--it is farthest from the corn stove. If yes can I put up vapour barrier also.?

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  2. velvetfoot

    velvetfoot Minister of Fire

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    I don't see why you can't put up insulation, but I don't think you would actually need a vapor barrier if your basement walls are insulated.
    My house came with fiberglass insulated floors and I am insulating the basement walls to make the basement a little warmer.
    The insulation that I have are thick batts with paper on the first floor side. They are just wedged in there.
    I'm not too crazy about the stuff hanging there, so I'm going to cover with something or other.

    I'm not so sure how much it would help though since you already have foam on the basement walls. I might help some but maybe not a super lot.
  3. ihookem

    ihookem Minister of Fire

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    I just took out my fiberglass insulation between my rim joists and I won't ever do that again. My home is four years old and the wood id turning black and has frost between the joists and the fiberglass. I think spray foam is the only way to go because it sticks tight to the wood and plugs every hole and leak. I am getting spray foam this time. I have heard a home looses a lot of heat this way. Foam sheets may be ok but might leave an air gap and leave room for a leak and a leak means frost. No reason you can't fiberglass your floor joists in your basement and vapor is better cause it keeps fiber particles in place .
  4. velvetfoot

    velvetfoot Minister of Fire

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    I'm still at it. I'm about a third done on the third wall which is one with a lot of bays.
    I'm doing about one bay a night, but on this wall I'm doing five layers, covering the top of the concrete and meeting the wall foam.
    I think I'm getting it pretty tight, caulking between each layer.
    I've noticed a lot less condensation when it's warmer. Today's bay didn't have much.

    But man, this is so tedious.
    I have plenty of detail work to do on the wall foam too.
  5. velvetfoot

    velvetfoot Minister of Fire

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    I probably should have made more use of the Great Stuff.
    I'm going to foam those spaces below.
    Another void is pretty deep so I might try that straw trick.

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  6. j00fek

    j00fek Feeling the Heat

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    velvetfoot, are you just sealing above the concrete walls?

    im still planning mine out and have 4ft of brick, then 5ft of concrete (which is 2in out from the brick above) i plan to cover the brick with the 4x8 sheets of rigid foam i got. then ill have a mainly flush wall after. thing im stuck at is getting the foam on the brick...(liquid nails...or drilling into the brick and using plastic anchors.

    ill try to get some pics tonight....
  7. velvetfoot

    velvetfoot Minister of Fire

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    I started with the walls but then thought that I should do the rim joist area which is taking a long time.
    I'm not sure about brick. You have to make sure you're not getting any water in.
    You have to cover the foam that I'm using with 1/2" of sheet rock (or something else of equal fire retarding capability).
    Then you still have the concrete to insulate.
    Maybe you could put another 2" of foam on the whole wall and put a stud wall in front of it and put insulation and sheet rock on that.
    Then you wouldn't have to drill holes.
    They seem to be saying to put a layer foam on the inside wall so water vapor doesn't condense on the concrete.

    I was thinking a little about the cost of this method of rim joist insulation while I was cutting up the stuff yesterday.
    I think it's pretty high. The stuff isn't cheap.
    I'd get a quote on a contractor spray job if I was considering this again.
  8. d.n.f.

    d.n.f. New Member

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    Can't remember how you said you are cutting the foam but Fine Homebuilding just had a tip that you sharpen the edges of a putty knife or a 3 or 4" drywall knife (application tool). Slices through like butter along a straight edge and no positively charged bits clinging to everything.
  9. velvetfoot

    velvetfoot Minister of Fire

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    I've seen that tip about a sharpened putty knife but I've been using a snap-off knife by Stanley.
  10. velvetfoot

    velvetfoot Minister of Fire

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    Well, I finished today.
    I told you I was stubborn.
    Now I move on to finishing the wall insulation.
  11. precaud

    precaud Minister of Fire

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    Good on ya, velvet. Perserverence furthers.
  12. Cutter

    Cutter New Member

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    Howdy all. I just got through reading this thread and I realize that it might be too late, but here are a few things to consider.
    1. My favorite insulation tool is cheap and works on batts and ridgid foam. I take an old 12" Saw-zall blade with course teeth. Duct tape the tang end for a handle and then sharpen both top and bottom edges with a file or grinder. This gives you a knifes edge for cutting through thick batts and a saw for fine fitting of foam.
    2. buy 4-6" length of tubbing the same size as the little tube that comes with cans of Great Stuff. Stick it on your can and then you have better dexterity in getting your foam where you need it. Of course you need to do all of your other work first. You can go through several cans of foam with the tube. Then throw it away.
    3. You can use Great stuff as a glue to stick your foam board to just about anything. A little goes a long way. Small globs on the back, let it expand a little while and then press into place. You do have to go back to make sure that it hasn't expanded more and pushed your board away from sub-strate.
    4. Be careful with vapor barriers. One is good and two are generally bad. If moisture happens to get in between barriors resulting unseen rotting can have devestating effects. Both structural decay and groth of molds.
    Brad
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