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Duane Sears Posted: Feb 27, 2014 03:09 PM	Garage Ceiling / Bonus Room I am planning on spray foaming my garage ceiling in the near future. I have two rooms above my 2.5 car garage. I have talked to various spray foam contractors and each vary on the depth of install. I have been told 2", 4", and 6" of open cell would be suitable. I live in Kentucky, so we can get extremes of heat and cold. What would be the best depth for my install? obviously, the more the merrier, but I don't want to overspend. Thanks, mike
mason Posted: Feb 28, 2014 03:44 PM	I would go with more insulation. Building codes call for R 38 in the attic in your area. 1/2 lb density foam has an R value of around 3.8 per inch, so to be code compliant you would need 10 inches of open cell. Based on attic simulator tests conducted at Oak National labs, 5.5 inches of open cell foam performed about 10 to 15% better than R 38 of blown in fiberglass installed to the floor of the attic. So, the 6 inches is not out of a question. I would agree that 6 inches of open cell would give you equal performance or slightly better than of R 38 of fiberglass. But, If I were you, I would add a couple of inches more. Be sure to get written approval from the local code official before installing less amounts of foam than the building code requires. If you have to sell, they would want to have confirmation that the application has been approved.

Author

Comments

Duane Sears

Posted: Feb 27, 2014 03:09 PM

Garage Ceiling / Bonus Room

I am planning on spray foaming my garage ceiling in the near future. I have two rooms above my 2.5 car garage. I have talked to various spray foam contractors and each vary on the depth of install. I have been told 2", 4", and 6" of open cell would be suitable. I live in Kentucky, so we can get extremes of heat and cold.

What would be the best depth for my install? obviously, the more the merrier, but I don't want to overspend.

Thanks,
mike

mason

Posted: Feb 28, 2014 03:44 PM

I would go with more insulation. Building codes call for R 38 in the attic in your area. 1/2 lb density foam has an R value of around 3.8 per inch, so to be code compliant you would need 10 inches of open cell.

Based on attic simulator tests conducted at Oak National labs, 5.5 inches of open cell foam performed about 10 to 15% better than R 38 of blown in fiberglass installed to the floor of the attic. So, the 6 inches is not out of a question. I would agree that 6 inches of open cell would give you equal performance or slightly better than of R 38 of fiberglass.

But, If I were you, I would add a couple of inches more.

Be sure to get written approval from the local code official before installing less amounts of foam than the building code requires. If you have to sell, they would want to have confirmation that the application has been approved.

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