Are you a subscriber but don’t have an online account?

Register for full online access.

 
 
 
 
+ Reply to Thread
Page 1 of 2 12 LastLast
Results 1 to 15 of 20
  1. #1
    Join Date
    Jun 2004
    Location
    Lancaster County, PA
    Posts
    653

    Default Insulating below raised floor

    I have a fire damage restoration job coming up, so the homeowners want to take advantage of the house being gutted to improve some areas.

    One area is a sunroom on the back of the house. It was apparently a concrete slab on frost footer that the previous homeowner had enclosed. The slab is approximately 3" below FFE. To get heat into the room, they cut floor diffusers in along what was the exterior wall and also made a half attempt to direct the air towards the room. To say the least, heating in that room sucks.

    One option that the HVAC contractor and I have discussed is laying sleepers & lining up the floors. That way he can run ducts to the outside wall and I can insulate the floor, even if it is only 2". My question is what would be the best insulation method? I was thinking closed cell spray foam for R value and to dampen the echo of the new hollow floor. Would a loose fill cellulose work just as well? The room is a little over 300sf so I could get away with a 400bf foam kit to get ~2" of foam under the floor. I'm sure cellulose would be half the price, but is it ok to use cellulose in this application? Any other ideas?

    Here are my 3 options as I see them:

    1. spray foam
    2. cellulose or other loose fill
    3. cut foam board to fit between sleepers and foam edges
    Contact us for all you mailbox post installation needs!

  2. #2
    Join Date
    Jan 2007
    Location
    Billerica MA
    Posts
    208

    Default Re: Insulating below raised floor

    I just did my 180sf porch with 3 layers if 1 3/8 and foam. My closed cell sub would be about 3x the cost of this. It took me and 1 guy about 2.5 hour with a table saw.
    Attached Images Attached Images

  3. #3
    Join Date
    Jun 2004
    Location
    Greenville,S.C.
    Posts
    377

    Default Re: Insulating below raised floor

    I would lay 1" extruded polystyrene on the slab and Tapcon 2x sleepers on top, then rip 1&1/2" foam between the sleepers. With 3/4" T&G plywood on top you'd be @ 3&1/4 " above slab. The 1" base layer would be a moisture and thermal break.

  4. #4
    Join Date
    Jun 2004
    Location
    Lancaster County, PA
    Posts
    653

    Default Re: Insulating below raised floor

    I guess I was overthinking it a little. I like Norm's approach, and I've done it a few times before. For some reason I wasn't thinking clearly...must be the turkey.
    Contact us for all you mailbox post installation needs!

  5. #5
    Join Date
    Jan 2007
    Location
    Billerica MA
    Posts
    208

    Default Re: Insulating below raised floor

    Have you guys done a floor on top of rigid? I would be concerned of it breaking down over time. I like the thermal break but seems like over the years the sleepers would wear into the foam. I have been curious about this approach, but afraid of the call backs.

    Joe

  6. #6
    Join Date
    Jan 2005
    Posts
    9,252

    Default Re: Insulating below raised floor

    Joe - that is interesting.

    I suspect with a high PSI foam and the floor system - much of the weight would be evenly distributed through out, not causing a lot of force on the sleeper; but I am curious to long term stability of such a set up...

    99.9% of the time the floor has only a few pounds of loading. Might make special considerations if there was a lot of heavy furniture...
    “Racism is man's gravest threat to man - the maximum of hatred for a minimum of reason.”
    Abraham J. Heschel (Jewish theologian and philosopher, 1907-1972)

  7. #7
    Join Date
    Jun 2004
    Location
    Greenville,S.C.
    Posts
    377

    Default Re: Insulating below raised floor

    The plywood is supported not only by the sleepers (which is supported by foam) but by solid foam all the way to the slab. No problem in my opinion. Of course it all depends on the compressive strength of the foam. I think in most residential applications it would be difficult, or impossible to overload it. The use of foam for support has been around for a long time. I have seen pictures of building up railroad overpasses in the Scandanavian countries with foam so as to act as a frost protected foundation for the tracks and train to bear on.

  8. #8
    Join Date
    Jan 2005
    Posts
    9,252

    Default Re: Insulating below raised floor

    Norm - I agree with your thoughts. Something I have not though of before regarding floors and foam.. I can get 60 PSI foam here and that stuff is really hard...
    “Racism is man's gravest threat to man - the maximum of hatred for a minimum of reason.”
    Abraham J. Heschel (Jewish theologian and philosopher, 1907-1972)

  9. #9
    Join Date
    Nov 2004
    Location
    Boston, MA
    Posts
    4,828

    Default Re: Insulating below raised floor

    Is that PSI or PSF?
    "First we finish the game, then we’ll deal with the Armada!"

    Sir Frances Drake

  10. #10
    Join Date
    Jun 2004
    Location
    Greenville,S.C.
    Posts
    377

    Default Re: Insulating below raised floor

    A look at Dow's website revealed the following. The standard blue edge board is 25 psi @ 10% compression. They also have 40#,60# & 100# "Hardfoam" that has a 5% compressive rating. With the 25psi the psf is 4100#. I have built many commercial buildings, church's, schools, retail, where the soil compaction spec reqts. were 3000psf. With 3/4" plywood on top to distribute any concentrared loads I can't see that it could ever be a problem. The 10% compressive factor may make the floor more comfortable to walk on than a regular slab..

  11. #11
    Join Date
    Jun 2004
    Location
    St Louis, Mo for the past 25 years
    Posts
    7,570

    Default Re: Insulating below raised floor

    another thing to learn. I just always figured foam was foam, had no idea about different strenghts of the stuff. Not sure I will ever be able to use this information but if I do I now know about it.

  12. #12
    Join Date
    Jan 2005
    Posts
    9,252

    Default Re: Insulating below raised floor

    Quote Originally Posted by Ted S. View Post
    Is that PSI or PSF?
    PSI - we can get up to 60 here, from our local manufacturer.

    http://www.insulfoam.com/index.php?o...=60&Itemid=154

    I agree Norm - with higher PSI and even distribution of the subfloor and flooring this would not keep me up at night either.

    And now if Mark needs to do this, he'll know to ask for denser foam.. :)
    “Racism is man's gravest threat to man - the maximum of hatred for a minimum of reason.”
    Abraham J. Heschel (Jewish theologian and philosopher, 1907-1972)

  13. #13
    Join Date
    Nov 2004
    Location
    Boston, MA
    Posts
    4,828

    Default Re: Insulating below raised floor

    Quote Originally Posted by davenorthup View Post
    PSI - we can get up to 60 here, from our local manufacturer.

    http://www.insulfoam.com/index.php?o...=60&Itemid=154
    This is a strange one, I remember the Dow Highload insulation was something like 40, 60 and 100 PSI, but then after doing the research I was mistaken and it was PSF. That was a long time ago, then CDServices made that same statement, we all thought it was PSF.

    So now it looks like the Highload is 40, 60 or 100 PSI...as I just googled it.

    I guess my confusion is if I have a 1" x 1" square punch and I load 100 lobs on it, I can't believe it won't punch through the insulation? I find that hard to believe, even if I load it with 60 lbs, it for sure will deform the board, what am I missing?
    "First we finish the game, then we’ll deal with the Armada!"

    Sir Frances Drake

  14. #14
    Join Date
    Nov 2004
    Location
    Boston, MA
    Posts
    4,828

    Default Re: Insulating below raised floor

    I'm determined to figure this out, according to the Dow data sheet, the test protocol is :

    "Compressive Strength(1), ASTM D1621, psi, min."

    The standard cost $40- How could I load 100lbs on a 1" x 1" square and not have it go though the foam? I swear it used to say 100 PSF...
    "First we finish the game, then we’ll deal with the Armada!"

    Sir Frances Drake

  15. #15
    Join Date
    Jan 2005
    Posts
    9,252

    Default Re: Insulating below raised floor

    Ted - you are more into this than I but could the PSI test assume that the foam is against something like the ground etc?

    Just a thought - good luck...

    FWIW our foam is pretty tough... :)
    “Racism is man's gravest threat to man - the maximum of hatred for a minimum of reason.”
    Abraham J. Heschel (Jewish theologian and philosopher, 1907-1972)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts