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Should closed spray foam be used in Cathedral vented roof?

CMRICHA | Posted in General Questions on

We paid for spray foam, now the builder is saying there’s no need to spray as high in the cathedral roof, it would be more efficient to sheet rock near the HVAC and spray foam. After reading articles it says it’s best to spray un-vented cathedral roof, which will keep bad heat and air from entering at the surface, therefore the area between the HVAC and cathedral roof is cooler.

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  1. GBA Editor
    Martin Holladay | | #1

    Your question is hard to interpret.

    If you have a cathedral ceiling, the entire slope of the cathedral ceiling needs to be insulated.

    If you have a Cape-style home, it's possible to have a horizontal ceiling that intercepts two sloped ceilings. If that's the kind of house you have, then the attic above the horizontal ceiling can be insulated two ways: either (a) the attic can be insulated on the attic floor, or (b) the cathedral-style insulation can follow the roofline all the way to the peak.

    When you say "HVAC," are you talking about ducts? Or a furnace? Or an air handler? Or all of the above?

    Where is the HVAC equipment? In an attic?

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