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Community and Q&A

Insulate basement ceiling?

gi4ever | Posted in Energy Efficiency and Durability on

Good morning everyone. Contractor is suggesting dense pack cellulose in conditioned basement (basement finishing job). Walls are insulated with cellulose/sprayfoam on concrete. Is this advisable? I’ve read not to insulate basement ceilings. Will it make it warmer in the winter? I’m in zone 6. This will obviously also help with sound dampening. Alternatives?

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  1. GBA Editor
    Martin Holladay | | #1

    Most conditioned basements have wall insulation but no ceiling insulation. Insulating a basement ceiling is unnecessary (especially if the basement walls are insulated).

    If you are interested in sound control, you would want to design a ceiling assembly specifically aimed at reducing sound transmission -- which would require details other than dense-packed cellulose (although the cellulose would, indeed, help reduce sound transmission).

    The alternative to your contractor's suggestion is to leave the ceiling uninsulated.

  2. Expert Member
    Dana Dorsett | | #2

    If the foundation walls are going to be well insulated and air tight, you'll get more return on investment out of 2-3" of EPS (R8-R12) under the slab in US climate zone 6 than dense packed cellulose in the floor joists. If the slab isn't poured yet, that's the way to go.

    But even if the slab has been poured with nothing under it, there's no ROI for dense packing between the joists. From a soundproofing performance perspective, low-density cellulose will outperform dense pack.

  3. gi4ever | | #3

    Thank you gentlemen. You just saved me $2000.

  4. GBA Editor
    Martin Holladay | | #4

    Not everyone who visits GBA is a subscriber -- but even if you subscribe, your investment can save you money. Especially if GBA saves you $2,000.

  5. gi4ever | | #5

    Good point. I'll take a look; thanks again!

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