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Home foam insulation - floor joists?

Discussion in 'Off-Topic' started by rep308, Feb 11, 2019.

  1. rep308

    rep308 NES Member

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    My daughter is having a home built now and it's tight to the weather. It is 2x6 construction and they plan to use 2" foam in the walls and 4" fiberglass. I have a general question about where they foam, I am new to the process. The house is a two story colonial with a unfinished basement that they plan to finish at a later time.

    Do they or should they foam the floor joists in the unfinished basement? Should they foam the floor joists between the 1st and 2nd? Do they foam the ceiling on the 2nd floor?

    Any info on the foam process or links would be appreciated. I'm trying learn more as the building progresses
     
  2. Super99Z

    Super99Z NES Member

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    Close cell spray as much as possible. In between floors isn't neccessary. It pays for itself in the long run. Don't skimp on insulation, it's the 1 thing that is extremely difficult to replace later. Just about Anything else in a house can be upgraded without tearing into the walls..
     
  3. rep308

    rep308 NES Member

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    Thank you for the quick response. I was thinking that doing the basement floor joist would help with heat and noise when they finish the basement at a later time. Any other tips or questions that we should ask of the foam insulation company?
     
  4. evalance

    evalance NES Member

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    Is the basement floor insulated ? Spray floor joist basement and r30 Kraft rest or spray it all.

    Spraying all floor joist is common and I'm not sure with what you mean spray the 2nd floor they would spray the roof deck.
     
  5. alpineboard

    alpineboard

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    I did foam in walls via 2 x 8 foot/ 2 inch foam panels = R10, then fiberglass, had a panel saw, then can of spray foam to seal the small edge openings/cracks, weld it right in there. Works great and saved a pile of cash. that spray foam is good, but very pricey.
     
  6. evalance

    evalance NES Member

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    The joist itself will provide minimum noise reduction you would have to use a barrier for the remaining space a r30 Kraft or say rockwool
     
  7. evalance

    evalance NES Member

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    Insulating a house starts on the outside and before they pour the slab
     
  8. Fritz the Cat

    Fritz the Cat NES Member

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    I wouldn't foam the floors between conditioned spaces. Use a product meant for sound control like recycled denim or rockwool. Do use closed cell foam on the rim joist of the entire basement.
    A couple of thoughts
    1) why not foam the entire exterior wall cavity? I have found that trying to get fiberglass into the wall after foam to be very labor intensive. The foam is not often uniform.
    2)consider a hybrid wall assembly. It is what I would do. It is what I do do. Nerdy reading about insulation applied to the real world
     
    vicorjh likes this.
  9. NHCraigT

    NHCraigT NES Member

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  10. Spanz

    Spanz NES Member

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    as it is a floor, and not an outside wall, you probably will not have condensation issues, so open cell foam would be ok.
    I would have them paint the exposed surface with the fire code paint, or sheet rock it, in case there is ever a fire.
     
  11. Dennis in MA

    Dennis in MA NES Member

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    Why would you do only 2" of foam and then fiberglass??? I was under the impression foam was far more efficient.

    One thing that I saw on TOH this season, and I'm not sure it'd make THAT much of a difference, is using 2x6 bays but going 24" on center. It allows less wood to reduce your overall insulation #. I found that fascinating. Of course, this being TOH and this being a Net Zero house that will see break-even sometime after 2222, they then "wrapped" the entire house in that closed-cell-foam-on-OSB stuff. It was crazy the lengths they went to insulate. Each window bay has to be 8=10" deep. For Jamestown, RI. Cooler than most places in Summer, warmer than most places in Winter. ?????
     
  12. bfm

    bfm NES Member

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    Assuming you mean the floor joists for the first floor, meaning the basement ceiling.

    I would not, as mentioned above if the basement is going to be considered indoor space. I did it in my house and regret it. It made my basement colder and damper and I had to do some extra HVAC work later to correct something that was never really a problem in the first place. This was an existing house I had been in for a few years at the time, so I can tell you the effect was 80% negative. the only upside is that it did make things a bit quieter, but from a temperature and moisture stand point, all negative.
     

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