GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

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!

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.

Replies

  1. GBA Editor
    Martin Holladay | | #1

    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."

    1. qilei | | #2

      Thank you so much Martin for your advice. That's very helpful!

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |