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edselsouth1 04-18-2012 11:09 PM

Insulation requirements for addition/ garage.
I'm trying to go forward and complete an addition begun by the property's previous owner, and have a few questions concerning insulation of spaces.
First question: The upper floor exterior walls are of 2x4 construction, 7/16 OSB sheathing, and 1/2" green foamboard (shiplap) caulked at each joint and around the perimeter. Foamboard seams are staggered. What insulation should be used on the interior of these exterior wall, R-19 faced or unfaced, and 1/2" drywall?
Second question: The second floor has 3/4" OSB over 12" i-joist construction on 16" centers. Nothing else at present time. What insulation under the 3/4" OSB to get maximum protection. I would like to spray foam, but #1 -cost is prohibitive at this time, and #2-the insulators here are not willing to come and do a "small" job (approximately 500 sq. ft.). The project is about 25 miles from the nearest insulator.
Thanks for your responses and advise. David.

nealtw 04-19-2012 12:22 AM

The foam board is a vapour barrier so you don,t use insulation with facing. Safe and Sound has a fire quality. The cieling in the garage should have 5/8 drywall and should be taped and filled to stop off gasses from autos.

edselsouth1 04-19-2012 02:24 AM

Insulation requirements...
nealtw.... Thanks for your response. The i-joists are 12" depth. Where should a vapor barrier be placed when using such as Roxul Safe & Sound? The garage will be a finished, non-conditioned space. The exterior walls of the garage are 2 x 6 PT construction on 16" centers, 7/16" OSB with 1/2" green foamboard also, so no facing on the insulation. Thanks, David.

nealtw 04-19-2012 07:16 AM

They never put a vapour barrier in the floor and you always want airflow under the insulation like under a house but they seem always to forgo that in a garage. I don't know the rules on it, but I never see anything but insulation and 5/8 drywall. on the ceiling.

edselsouth1 04-19-2012 04:18 PM

Insulation requirements...
nealtw..... Thanks. I believe that will answer my questions for now. Time to get back on the project. I appreciate your time and knowledge. David.

AndyGump 04-19-2012 10:40 PM

Use R-13 in the 2 x 4 walls.


edselsouth1 04-20-2012 12:03 AM

Insulation requirements...
AndyGump.... R-13. Thank you! David

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