Adding attic batt insulation – plywood sheathing
qilei
| Posted in General Questions on
hi,
My fiberglass batt insulated attic is covered with OSB sheathing in quite an area. I guess those were left from the original construction 20 years ago.
Now, I’m thinking adding another layer of R30 batt to bump up my R-value to over 60. My question is: should I remove those sheathings for my project? In essence, does the current sheathing offer help or harm to be placed in middle of two layers of batt? If leaving them at where they are today, should I put on top “faced” or “unfaced” batt?
Thanks a lot for your advice!
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Replies
QiLei,
If you leave the OSB in place, it will do no harm. (That said, this type of OSB subflooring in an attic can be useful -- it allows maintenance workers to have somewhere to stand. Once you cover the OSB, it will be harder to navigate the attic. If you want, you can elevate the OSB with 2-by framing, or build a higher catwalk before you add insulation.)
If you want to buy batts, buy unfaced batts. But you might consider blowing cellulose instead of adding batts -- the cellulose does a better job of reducing the rate of air leakage, and does a better job of filling nooks and crannies. More information here: "Borrowing a Cellulose Blower From a Big Box Store."
Thank you so much Martin for your advice. That's very helpful!