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Community and Q&A

Barrel vault insulation

xb4LpMN3q7 | Posted in Energy Efficiency and Durability on

I live at the border between zone 4a and zone 5a in Kansas City. My home has a barrel vault (see photos) with sheetrock following the curve on the inside, 6 in rafters withR-19 fiberglass bats, unvented, and then the decking and roof.

We are planning to replace the roof, likely with standing-seam metal. Is there any insulation that we could put on the deck under the metal, or any other ideas to improve efficiency when we replace the roof?

Thanks for your suggestions.

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  1. Foamer | | #1


    What a great looking house you have. Congrats on daring to break the mold.

    The simplest but still significant improvement you can make is to strip the roof sheathing, remove the fiberglass and insulate the bays with closed cell spray foam. You will get R-30+ and a complete vapor barrier, which is important. Unvented spaces over fiberglass can lead to trapped moisture with potential for structural damage.

  2. GBA Editor
    Martin Holladay | | #2

    Your insulation system -- "6 inch rafters with R-19 fiberglass bats, unvented" -- violates current building codes. But your probably already know that.

    Depending on the curvature of the roof, you should be able to install rigid polyisocyanurate insulation on top of your existing roof sheathing. Install several layers, with staggered seams, until you achieve the R-value you need. Then install soffit-to-ridge 2x4s, either 16" or 24" on center, for ventilation channels, followed by plywood and new roofing.

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