Any real benefit of R-21 vs. R-19?

Beetle-Kill Posted By Beetle-Kill, Dec 28, 2012 at 7:55 PM

  1. Beetle-Kill

    Beetle-Kill
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    I have 3 weeks to kill before my new flooring shows up, so looking to tackle the front room.
    It's framed with rough sawn 2x4's, so I plan on furring it out to accomadate at least R-19 (current is R-11 with no vapor barrier. Like living in a barn.)
    Lineal footage is 57' along the walls and an 8' ceiling. Plus, huge old dbl. pane windows I won't be able to replace for a while. The attic space above it will get an additional R-38 of blown in after this is finished, as will the rest of the attic space (40 bags)
    So, is the R-21 worth it?
    thanks, JB
    EDIT- Sorry, should have asked if the cost difference between R-19 and R-21 is worth it.
    For my situation, I don't think so, but that's why I'm asking.
    R-19 is about $0.51 per sq./ft
    R-21 is about $0.74 per sq/ft.
    The diff. is about $100.
     
  2. Highbeam

    Highbeam
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    I wish I had R-11. Most of my wall area is R-5 fiberglass batts with a funky aluminum type facing. R-5 is only 1.5" thick, it's pretty silly but in 1963 that's what they used. R-19, stick with standard.
     
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  3. coaly

    coaly
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    It's better than putting it in the stock market.

    I ripped 2 X 4's down to 2 X 2 and cut 1/2" foam board in 1 1/2" strips. Held the strip on the existing 2 X 4 and screwed the 2 X 2 through the foam board to the 2 X 4 with 3 inch drywall screws. It's also the same thickness as a 2 X 6. This gave me a thermo break in the wall so the studs do not conduct cold to the inner wall. I got a deal on R-22 that was a special order high density Owens Corning product at the time for the entire house. Then doubled it in the ceiling, crossed over the joists.
    I got the idea from going into customers homes with unvented gas heaters with white cathedral ceilings. You could see the dark stripes from dust sticking to the roof rafters from the condensing moisture on the cooler ceiling surface over the solid wood. Counting all the solid studs and rafters in a home will equal something like 10% of the total surface area that is actually uninsulated and conducts heat and cold.
    Do everything you can while you have the wall open. $100 isn't much when you factor in what the cost of fuel will be in 20 years.
     
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  4. woodgeek

    woodgeek
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    I got those too...in 1960. Called 'econo-batts' they are to thin to really do much good, and thick enough to eff up a lot of cavity fill options. Grrr.
     
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  5. jharkin

    jharkin
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    We have at least one wall with that useless stuff also. Even worse than the 1950s vintage kimsul cellulose batts in the attic.... At least those disintigrated enough to blow cellulose in ;)

    I think the OP won't be able to calculate any measurable ROI from the extra R2, but for only a hundred bucks why not?
     
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  6. Beetle-Kill

    Beetle-Kill
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    I don't think I'll even notice the R-19 much, not with these windows.
    I am probably going for the R-21, and I like Coaly's idea of running the foam strips between the existing studs and ripped 2x's.
    I'll only do it once, so may as well go for it and hope for the best.
     

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