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Discussion Starter · #1 ·
Does anybody know what IRC code is for insulation in attic over garage?
I am fighting with a home inspector hired by buyer saying it needs to be R-30.
 

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Thom
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If the garage is unheated and the space above the garage is unheated, there is no requirement.

If the garage is unheated but the space above is heated, the insulation is really floor insulation, not ceiling insulation. Look at the required minimums for that in your area.
 

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Discussion Starter · #3 ·
That is what I thought, no insulation required, I am checking with local building inspector but wanted to get feedback here as well.
 

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The insulation requirement for ceilings in your area is R-38 (Table N1102.1).

Code relative to ceilings and insulation as it pertains to IRC code is as follows, check your local codes also as these may differ from the model codes:

N1102.1.2 Ceilings.
The required "Ceiling R-value" in table N1102.1 assumes standard truss or rafter construction and shall apply to all roof/ceiling portions of the building thermal envelope, including cathedral ceilings. Where the construction technique allows the required R-value of ceiling insulation to be obtained over the wall top plate, R-30 shall be permitted to be used where R-38 is required and R-38 shall be permitted to be used where R-49 is required.

N1101.1 Scope.
This chapter sets forth energy-efficiency-related requirements for the design and construction of buildings regulated by this code.

Exception: Provided that they are separated by building envelope assemblies from the remainder of the building, portions of the building that do not enclose conditioned space shall be exempt from the building envelope provisions, but shall comply with provisions for building mechanical and service water heating systems.
 

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could you refer me to where you got that info, I dont understand all of it. I know code is r-30 over conditioned areas.
International Residential Code for one and two family dwellings. This is the model code for most jurisdictions. Your state, counties, and cities may or may not have adapted it in it's entirety. You can find it and other material at www.bnibooks.com or by searching international code council.

The R-value came from the table listed in the IRC code book and is based on climate zones. All climate zones listed in your area required R-38 for ceilings except as noted in the previous post. Your locality may or may not have adopted all or parts of the model code so their may be variances. As far as I am aware though, the majority if not all of the states have adopted IRC code as the model code to which the state codes are based off. You should be able to download or purchase your state specific codes from your state building regulatory department. Additionally different localities may impose even more strict codes then the state and/or model code(s).
 
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