Styrofoam insulation -- foil in or out?

Discussion in 'Home Repair' started by BetaB4, Apr 27, 2009.

  1. BetaB4

    BetaB4 Guest

    I have two exterior cinder block walls in an apartment that are being redone
    on the inside. The furring strips are in place and the walls will be
    getting sheetrocked. I have 1-inch styrofoam insulation that will be going
    in the spaces between the furring strips. The styrofoam insulation has foil
    on one side.

    Which side should I keep the foil on? -- the inside facing the room, or the
    outside facing the cinder block wall?

    I'm thinking the inside since that's the "warm" side, but I don't know.
     
    BetaB4, Apr 27, 2009
    #1
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  2. BetaB4

    RicodJour Guest

    On Apr 27, 9:08 am, "BetaB4" <> wrote:
    > I have two exterior cinder block walls in an apartment that are being redone
    > on the inside.  The furring strips are in place and the walls will be
    > getting sheetrocked.  I have 1-inch styrofoam insulation that will be going
    > in the spaces between the furring strips.  The styrofoam insulation hasfoil
    > on one side.
    >
    > Which side should I keep the foil on? -- the inside facing the room, or the
    > outside facing the cinder block wall?
    >
    > I'm thinking the inside since that's the "warm" side, but I don't know.


    An excerpt from
    http://www.toolbase.org/Technology-Inventory/Interior-Partitions-Ceilings/radiant-barriers
    says this:
    "All radiant barriers have at least one reflective (or low emissivity)
    surface, usually a sheet or coating of aluminum. Some radiant barriers
    have a reflective surface on both sides. Both types work about equally
    well, but if a one-sided radiant barrier is used, the reflective
    surface must face the open air space. For example, if a one-sided
    radiant barrier is laid on top of the insulation with the reflective
    side facing down and touching the insulation, the radiant barrier will
    lose most of its effectiveness in reducing heating and cooling loads."

    The foil radiant barrier requires an air space - it's not supposed to
    touch anything. If it is touching the back of the wall covering it
    loses some of its effectiveness.

    The foil also acts as a vapor barrier, which may or may not be
    necessary depending on what type of rigid foam insulation it's on.

    R
     
    RicodJour, Apr 27, 2009
    #2
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  3. BetaB4

    ransley Guest

    On Apr 27, 8:08 am, "BetaB4" <> wrote:
    > I have two exterior cinder block walls in an apartment that are being redone
    > on the inside.  The furring strips are in place and the walls will be
    > getting sheetrocked.  I have 1-inch styrofoam insulation that will be going
    > in the spaces between the furring strips.  The styrofoam insulation hasfoil
    > on one side.
    >
    > Which side should I keep the foil on? -- the inside facing the room, or the
    > outside facing the cinder block wall?
    >
    > I'm thinking the inside since that's the "warm" side, but I don't know.


    I bet both sides have foil but one side is painted as my Celotex board
    was, try alcohol or laquer thinner or some paint remover to see. One
    inch is only R 7.2". 2" is still substandard in most zones for R
    value, I used 2-4.
     
    ransley, Apr 27, 2009
    #3
  4. BetaB4

    BetaB4 Guest

    Thanks. I checked out the link and read the article, and I appreciate you
    providing the key excerpt. I had tried doing some Internet searches before
    posting my question but didn't seem to get to any sites that had the
    information I wanted.

    The bottom line is that the styrofoam is going up with the foil facing the
    inside of the house and with the insulation slightly back so it creates a
    space between the foil covering and the inside of the sheetrock.

    RicodJour wrote:
    > On Apr 27, 9:08 am, "BetaB4" <> wrote:
    >> I have two exterior cinder block walls in an apartment that are
    >> being redone on the inside. The furring strips are in place and the
    >> walls will be getting sheetrocked. I have 1-inch styrofoam
    >> insulation that will be going in the spaces between the furring
    >> strips. The styrofoam insulation has foil on one side.
    >>
    >> Which side should I keep the foil on? -- the inside facing the room,
    >> or the outside facing the cinder block wall?
    >>
    >> I'm thinking the inside since that's the "warm" side, but I don't
    >> know.

    >
    > An excerpt from
    > http://www.toolbase.org/Technology-Inventory/Interior-Partitions-Ceilings/radiant-barriers
    > says this:
    > "All radiant barriers have at least one reflective (or low emissivity)
    > surface, usually a sheet or coating of aluminum. Some radiant barriers
    > have a reflective surface on both sides. Both types work about equally
    > well, but if a one-sided radiant barrier is used, the reflective
    > surface must face the open air space. For example, if a one-sided
    > radiant barrier is laid on top of the insulation with the reflective
    > side facing down and touching the insulation, the radiant barrier will
    > lose most of its effectiveness in reducing heating and cooling loads."
    >
    > The foil radiant barrier requires an air space - it's not supposed to
    > touch anything. If it is touching the back of the wall covering it
    > loses some of its effectiveness.
    >
    > The foil also acts as a vapor barrier, which may or may not be
    > necessary depending on what type of rigid foam insulation it's on.
    >
    > R
     
    BetaB4, Apr 27, 2009
    #4
  5. BetaB4

    RicodJour Guest

    On Apr 27, 12:46 pm, "BetaB4" <> wrote:
    > Thanks. I checked out the link and read the article, and I appreciate you
    > providing the key excerpt.  I had tried doing some Internet searches before
    > posting my question but didn't seem to get to any sites that had the
    > information I wanted.
    >
    > The bottom line is that the styrofoam is going up with the foil facing the
    > inside of the house and with the insulation slightly back so it creates a
    > space between the foil covering and the inside of the sheetrock.


    What color is the foam? I'm curious as I haven't seen rigid foam
    insulation with foil on one side.

    R
     
    RicodJour, Apr 27, 2009
    #5
  6. BetaB4

    BetaB4 Guest

    It's white styrofoam with foil on one side. I'm going to the property now
    and will check out what brand it is, etc., and will post that info back here
    later today.

    RicodJour wrote:
    > On Apr 27, 12:46 pm, "BetaB4" <> wrote:
    >> Thanks. I checked out the link and read the article, and I
    >> appreciate you providing the key excerpt. I had tried doing some
    >> Internet searches before posting my question but didn't seem to get
    >> to any sites that had the information I wanted.
    >>
    >> The bottom line is that the styrofoam is going up with the foil
    >> facing the inside of the house and with the insulation slightly back
    >> so it creates a space between the foil covering and the inside of
    >> the sheetrock.

    >
    > What color is the foam? I'm curious as I haven't seen rigid foam
    > insulation with foil on one side.
    >
    > R
     
    BetaB4, Apr 27, 2009
    #6
  7. BetaB4

    RicodJour Guest

    On Apr 27, 1:04 pm, "BetaB4" <> wrote:
    > It's white styrofoam with foil on one side.  I'm going to the property now
    > and will check out what brand it is, etc., and will post that info back here
    > later today.


    White foam is polystyrene. The typical expanded polystyrene stuff
    (Styrofoam being the biggie in brand names) is made up from little
    beads of polystyrene bonded together and used in everything from
    packaging to coffee cups. It has one of the lower insulation values
    of the rigid foam insulations - something around R3 or R4 per inch.

    More info at:
    http://www.energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11620

    R
     
    RicodJour, Apr 27, 2009
    #7
  8. BetaB4

    BetaB4 Guest

    RicodJour wrote:
    > On Apr 27, 1:04 pm, "BetaB4" <> wrote:
    >> It's white styrofoam with foil on one side. I'm going to the
    >> property now and will check out what brand it is, etc., and will
    >> post that info back here later today.

    >
    > White foam is polystyrene. The typical expanded polystyrene stuff
    > (Styrofoam being the biggie in brand names) is made up from little
    > beads of polystyrene bonded together and used in everything from
    > packaging to coffee cups. It has one of the lower insulation values
    > of the rigid foam insulations - something around R3 or R4 per inch.
    >
    > More info at:
    > http://www.energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11620
    >
    > R


    It definitely looks like white "coffee-cup-like" polystyrene, with foil on
    one side. I'll get the exact brand name etc. and post it.
     
    BetaB4, Apr 27, 2009
    #8
  9. BetaB4

    BetaB4 Guest

    RicodJour wrote:
    >
    > What color is the foam? I'm curious as I haven't seen rigid foam
    > insulation with foil on one side.
    >


    Here's what it says on the 4x8 sheets of insulation:

    "Polyshield"
    Sheathing/Underlayment

    ICC ESR-1820

    Cellofoam North America, Inc.
    Conyers, GA

    Here's their website:

    http://www.cellofoam.com/cellofoam-building.htm
     
    BetaB4, Apr 27, 2009
    #9
  10. BetaB4

    ransley Guest

    On Apr 27, 4:01 pm, "BetaB4" <> wrote:
    > RicodJour wrote:
    >
    > > What color is the foam?  I'm curious as I haven't seen rigid foam
    > > insulation with foil on one side.

    >
    > Here's what it says on the 4x8 sheets of insulation:
    >
    > "Polyshield"
    > Sheathing/Underlayment
    >
    > ICC ESR-1820
    >
    > Cellofoam North America, Inc.
    > Conyers, GA
    >
    > Here's their website:
    >
    > http://www.cellofoam.com/cellofoam-building.htm


    That site crashes my IE. Polystyrene is white and only maybe R5 new
    4.6 settled. Polyisocyanurate is white, [not as bright] and is R7.2
    new and settles to R 6.8 or so, it is superior in R value for spaces
    with little depth. 1" or even R 10 is not much on an exterior wall,
    unless area is moderate temperature.
     
    ransley, Apr 27, 2009
    #10
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