26 Oct '11, 5pm

Green Building Q&A: OK to install blown-in cellulose over fiberglas batts in an attic?

You can install cellulose over fiberglass batts, and as a contractor I would not remove insulation to add more. This would cost you more money and honestly is not needed unless you have water damage or rodent problems in your attic (they tend to use fiberglass as a rest room!!) Here is the thing, when you read about cellulose you will see that it draft blocks pretty well (top plates in your attic) BUT you should never insulate (with any type of insulation except spary foam) without air sealing your top plates first. Some blow and go companies will tell you that you do not need it....you do and it can save you 5% off your utilities or more, plus the safety and indoor air quality perks you receive from air sealing. When there are fiberglass batts in your attic the cellulose will not draft block the top plates. It will however fill in all the gaps that fiberglass batts leave ...

Full article: http://www.greenbuildingadvisor.com/community/forum/gener...

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