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Open-cell or closed-cell spray insulation in hot humid Bahamas roof?

caz999 | Posted in Energy Efficiency and Durability on

We will spray insulate the underside of the plywood roof deck with at least R-20 foam. The attic encloses the A/C unit and ducts. The roof is reflective white shingles on Ice/Water membrane. One local installer says I should use an Open Cell (Icynene brand) insulation another says Closed Cell.

I will leave the insulation exposed in the attic apace.

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  1. GBA Editor
    Martin Holladay | | #1

    Either type of insulation will work. I would ask both installers how many inches (or centimeters) of insulation they plan to install. Open-cell foam has an R-value of about R-3.7 per inch, while closed-cell foam has an R-value of about R-6.0 or R-6.5 per inch. Choose the insulation with the highest R-value.

    I don't know anything about building codes in the Bahamas, but in the U.S., exposed spray foam is considered a fire hazard. I would strongly suggest that you consider an application method that allows you to cover the cured foam with a layer of gypsum drywall.

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