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Low profile cans /speakers below closed cell in a flash and batt roof.

BullOak | Posted in Energy Efficiency and Durability on

I have a retrofit (zone 4, Humid SE) where we’re doing an unvented roof with 4″ closed cell SPF and an R-13 unfaced batt.

Contractor and client have been asking to use low profile speakers and can lights below the SPF layer. Generally I have been hesitant to do that as I’m unsure to what extent those penetrations in the G.W.B. will pose issues thermally and hygroscopically But if the foam is very solidly our air/moisture barrier, do I need to worry about those penetrations?

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  1. GBA Editor
    Martin Holladay | | #1

    In Zone 4, the building code calls for roofs to be insulated to a minimum of R-49. You are planning to install about R-26 of spray foam, plus R-13 of fiberglass, for a total of about R-39.

    So it's worth pointing out that you haven't planned enough insulation to meet minimum code requirements.

    If you penetrate the drywall with speakers and recessed lights, you won't have any moisture problems. But you will be reducing the R-value of your roof assembly from R-39 to R-26 in those areas.

  2. BullOak | | #2

    Martin - Thanks.

    In North Carolina we haven't updated to 2012 base codes yet, so the requirement is still R-38. I would love to put rigid foam above the sheathing, but it's a historic house by a semi-famous architect. Even R-26 would be a massive improvement on what was there...

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