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Thread: Insulating a remodel

  1. #1

    Default Insulating a remodel

    I've got a 45 -50 yr old cinder block home, over a 3ft vented crawlspace in North Central Florida.

    1) The exterior block is not painted, though I may end up doing this.
    2) There are no moisture issues presently in the house (there was, but it was due to some grading issues that have been addressed), it's a dry house.
    3) The crawlspace has no vapor barrier down, though this may change, the floor is likewise not insulated (this also may change).

    The tear-out of the utility, mudroom, laundry area is about half done. I found the following about the old construction:

    1) The joists and subfloor are in very good condition and very clean, though there is about a 1 inch continuous gap between the end of the sub-floor, and the cinder block exterior wall....you can see down to the ground below.

    2) There was no insulation in the walls at all, I expected this, very typical of the time.

    3) The interior walls were made up of: furring strips under small (maybe 2'*3'-4') sheets of heavy drywall-like material, hung horizontally. The exterior side of this material was covered in an aluminum-type backing (I'm thinking this might have been an early type of vapor barrier, I can't figure they were thinking about radiant barriers back then). On top of the small drywall pieces was plaster.

    4) This all resulted in a small, vertically running air gap that runs from the crawlspace into the attic space.

    My questions are these:
    1) What can I do to insulate this when I re-construct?

    2)Am I O.K. sealing this entire airgap leading from the crawlspace on up? If I seal it too well, can I end up causing myself new problems (moisture)?

    3) Should I consider any type of vapor barrier, or should I just insulate and let it breath as it has.


    I've already got some thoughts, but would like as much input as I can get.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Well, you'll get lots of opinions...here's mine. You need a vapor barrier on the ground of the crawlspace. You didn't have a problem since it is well ventilated. WHen you add insulation, you will be stopping that airflow. I'd consider a spray-in foam for insulation in the walls. This would also add a vapor barrier if it was a closed cell foam.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3

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    I forgot to include that I've re-framed part of it with 6* to contain the new wet wall for the washer set up. This is the exterior wall.

    Of course nobody seems to be having any input........c'mon, I'm just looking for opinions!

  4. #4
    Homeowner geniescience's Avatar
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    Quote Originally Posted by Alex47
    .... 1 inch continuous gap between the end of the sub-floor, and the cinder block exterior wall....you can see down to the ground below.
    ....
    covered in an aluminum-type backing
    ....
    air gap that runs from the crawlspace into the attic space...
    yes this was a radiant barrier at that time; "they" did know about the physics of heat transfer at that time.

    My guess is that the gaps (both the gaps you described) were left by the builders as a way of being cautious. Like insurance. Now that you know the house is dry, you can be more certain. I would probably close off the continuous air gap in the wall. In order for a radiant barrier to work, it must touch air, not solid material. Use foam.

    About the floor, I have no clear idea what to do.

    David

  5. #5

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    Thanks for your advice.

    Quote Originally Posted by geniescience
    yes this was a radiant barrier at that time; "they" did know about the physics of heat transfer at that time.
    David
    Why the quotes around "they"? I just meant the standard of the day.

    I agree with you, I'd like to use foam. The room being only about 8.5 * 10, and just under half the wallspace being exterior wall, I thought I might have a hard time getting somebody out to spray. I guess I could add in the interior walls to muffle sound into the rest of the house, might not even really add to the price.

    I might look into one of those DIY foam kits, but they look a little expensive.

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