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under floor insulation

Herman D'Elena
Herman D'Elena Member Posts: 3
in THE MAIN WALL
I have a single story house heated by hydronic baseboard, unheated full basement, 3/4" oak floor over 3/4" pine subfloor, no insulation. I would like to insulate below the floor and have been reading about the foil on plastic bubble type of insulation which states an R value of 16.89 for under floor installation. This seems high for such a thin material. Is it true? Is it just as good as fiber glass with foil?

Comments

  • Constantin
    Constantin Member Posts: 3,796
    No way, IMHO

    The test reports I have seen do not support claims of R16 for something that is 5/16th of an inch thick, unless it's an aerogel-filled vaccuum-insulated-panel. Those panels can be found on spacecraft and in luxury yachts, but not at Home Despot. If you like, look at the stuff from Glacier Bay.

    To reduce infiltration, I'd seal all the holes in the ceiling with closed-cell polyurethane (Good Stuff, et al), then consider your fiberglass options. However, your best bet is to review the material at Building Science to see if insulating the basement walls doesn't make more sense than insulating the basement ceiling.
  • Wayco Wayne_2
    Wayco Wayne_2 Member Posts: 2,479
    Herman

    I'm not clear where you want to insulate. Are you going to heat the basement or the floor in between the basement and the 1st floor? The foil stuff is widely mis-represented and must be used in specific ways to perform anywhere close to claims. Be careful. Better yet find a good insulation contractor who knows his stuff. Good insulation pays better than a good mutual fund. IMHO. WW

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  • Herman D'Elena
    Herman D'Elena Member Posts: 3
    floor insulation

    Thanks for the replies.
    My objective is to reduce heat loss from the living space to the unheated basement. I do not want to heat or finish the basement. The basement stays 57-59 deg.F during the heating season. Is it worth it to insulate under the floor, and if so what is the best way to do it?
  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542
    Good ol'

    fiberglass insulation. R-19 ought to do you well. Nothing like DEAD AIR to make for good R value IMHO... No smoke and "mirrors", just DEAD AIR...

    ME
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