In the blown-in category: does it matter what’s on top of what?
Brian Lengel| Posted inGeneral Questionson
In the blown-in category: does it matter what’s on top of what? I.e., can you blow cellulose into an attic on top of fiberglass? Does it matter if cellulose is on top of fiberglass?
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Replies
Brian,
For best performance, it's always best if cellulose is on top of fiberglass rather than the other way around.
Blown-in fiberglass doesn't perform as well as cellulose in an attic, because blown-in fiberglass does a poorer job of reducing air leakage and is more subject to convective looping than cellulose. Capping poorly performing fiberglass with a top layer of cellulose is a standard approach to improving attic insulation performance.
-- Martin Holladay