I am getting mixed info on spray foam insulation
fenn
| Posted in Building Code Questions on
I am in Louisiana. I have gas heaters and water heater in the attic. Should I insulate the ceiling of the house (attic floor) or the rafter in the attic (attic ceiling) ?
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Replies
From an overall system and house efficiency point of view an unvented sealed & insulated attic is by far the better way to go when the mechanical systems are in the attic, but it's not as simple as that. If the gas-burners aren't power vented/direct vented there are make-up air issues that may be difficult to meet.
Since the gas burners represent an ignition source, any foam insulation installed up there (whether at the attic floor or the roof deck), needs to have a thermal barrier against ignition, such as half-inch wallboard or half-inch plywood or OSB.
If it's a simple roof design and the make up air issues become non-issues, it may be simpler, cheaper & better to install rigid foam polyiso insulation above the roof deck, and rock wool batts between the rafters, sealing up all venting.