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scott moss Posted: Jul 28, 2009 07:46 PM	covering duct work in attic looking to spray underside of roof deck with oc foam. my big problem is there is duct work inbetween rafters and I'm not going to be able to get proper depth with foam. any suggestions
mason Posted: Jul 29, 2009 08:00 AM	The ICC building codes allow sprayfoam to be applied over ductwork in attics in residential construction (but not in commercial buildings, long story but just one of those political issues that happens at code hearings). So, I would cover the ducts with the foam and install a code approved ignition barrier over it. Is there room above the ducts for some foam to be sprayed? Note: in situations where there is not enough space to fully insulate to the underside of the attic, the building codes allow a lessor amount of insulation to be installed so long as it does not exceed 500 sq ft of the attic area or more than 20% of the attic area whichever is less. For example, you can install R 30 in a ceiling where R 38 is required or R 38 where R 49 is required. (IRC, SEction N1102.2.1 & N1102.2.2)
scott moss Posted: Jul 29, 2009 07:43 PM	so in the situation that I have duct work running in between the rafters of cathedral ceiling I can just spray as much as i can and then use a barrier as codes demands
mason Posted: Jul 30, 2009 07:56 AM	Yes, I believe the codes would allow that, but as always before application contact your local building official to obtain their OK on the proposed application. Nothing is worse than having the job completed and the code official disallowing your work. For example, if your code official is working with the 2006 ICC code book, it does not allow sprayfoam over ducts. But it is in the 2009 code book

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Comments

scott moss

Posted: Jul 28, 2009 07:46 PM

covering duct work in attic

looking to spray underside of roof deck with oc foam. my big problem is there is duct work inbetween rafters and I'm not going to be able to get proper depth with foam. any suggestions

mason

Posted: Jul 29, 2009 08:00 AM

The ICC building codes allow sprayfoam to be applied over ductwork in attics in residential construction (but not in commercial buildings, long story but just one of those political issues that happens at code hearings). So, I would cover the ducts with the foam and install a code approved ignition barrier over it. Is there room above the ducts for some foam to be sprayed?

Note: in situations where there is not enough space to fully insulate to the underside of the attic, the building codes allow a lessor amount of insulation to be installed so long as it does not exceed 500 sq ft of the attic area or more than 20% of the attic area whichever is less.

For example, you can install R 30 in a ceiling where R 38 is required or R 38 where R 49 is required. (IRC, SEction N1102.2.1 & N1102.2.2)

scott moss

Posted: Jul 29, 2009 07:43 PM

so in the situation that I have duct work running in between the rafters of cathedral ceiling I can just spray as much as i can and then use a barrier as codes demands

mason

Posted: Jul 30, 2009 07:56 AM

Yes, I believe the codes would allow that, but as always before application contact your local building official to obtain their OK on the proposed application. Nothing is worse than having the job completed and the code official disallowing your work. For example, if your code official is working with the 2006 ICC code book, it does not allow sprayfoam over ducts. But it is in the 2009 code book

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