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Is closed-cell foam the way to go?

user-1001576 | Posted in Energy Efficiency and Durability on

My two & half story, frame house, built in 1907 in climate Zone 2A, Gainesville,FL, has NO Insulation..

The entire house is built with 2 1/2 In. T&G long-leaf heart pine except for the novelty siding; a shiplap clapboard. The floor, interior walls and roof sheathing are all the same T&G wood.

In the 70’s, 3/8″ drywall was applied to the walls. There is no subfloor or sheathing on the exterior walls and the joist and stud spacing ranges between 18 and 21 inches on center.

The one big insulating company here was totally baffled as how to best handle this type on construction.

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  1. jklingel | | #1

    I'm missing something here; maybe it's just me. Your exterior walls are 2 1/2" T&G, you have studs inside the exterior T&G, and there is no insulation between the studs. Yes? You have no sub-floor; slab on grade?

  2. GBA Editor
    Martin Holladay | | #2

    Assuming you have empty stud bays, they can be filled with dense-packed cellulose.

    [Later edit: I just re-read your question, and I noticed that your house has no wall sheathing. I assume that means you have 2 1/2-inch thick boards on the interior of your studs, covered with drywall, and nothing but siding on the exterior. If that's so, then dense-packed cellulose might not be ideal. Your wall really needs some wall sheathing.]

    The roof can be insulated from above with rigid foam, followed by new roofing.

  3. user-1001576 | | #3

    John & Martin,
    Thanks for your replies. Let me clarify; the interior of the exterior walls are 2 1/2" T&G pine nailed to the studs. On the outside, the only attachment is the novelty siding, no bldg. felt, nothing. The house is set on piers approx. 3' above grade with the flooring consisting of only the same T & G pine nailed to 2X10 joists.
    Martin, I also thought of the cellulose until I realized there was nothing to isolated it from water intrusion.
    As for the roof, a new standing seam metal roof was applied three years ago.
    As the ceilings are also the same T&G pine, when the local insulating company saw that he was hesitant to
    recommend foam be used between the rafters.
    I hope this info helps .

  4. GBA Editor
    Martin Holladay | | #4

    It sounds like you will probably need to remove the siding, install insulation and new sheathing, and then reinstall the siding.

    I'm sorry to hear that you installed new standing-seam metal roofing on an uninsulated roof assembly without developing an insulation strategy. That was certainly a missed opportunity!

  5. user-869687 | | #5

    Someone should point out that you don't need insulation if you don't try to maintain a delta-T. That is, if you don't condition the space. I'm guessing this is how the house worked for the first several decades of its use. When it's hot outside, that doesn't cost energy if you don't run air conditioning.

    I agree with Martin that it was a missed opportunity not to insulate above the roof structure, and now it's too late because there's a durable new roof. Now if you insulate below the structure, that's going to take away from the architectural character, and lower the ceiling. The choice is between that and toughing out the heat.

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