Fiberglass Isn't Decompressing to Full Thickness


Old 08-09-14, 07:18 PM
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Join Date: Jan 2012
Location: USA
Posts: 255
Fiberglass Isn't Decompressing to Full Thickness

I'm playing with some Certainteed brand R-30 that I bought from Menards. It's labeled as 16" x 10" x 48" batts. When I cut the package it blows up pretty big, but I'm not getting 10" thick batts at all. My best efforts and fluffing it up gets me to maybe 8". So I'm 20% low.

I'm used to R-13 and R-19 fiberglass plumping to it's intended size (or bigger) and I have to press it down to make it fit. This is the opposite. The manufacture date is May 2013, 15 months ago.

I wanted to build a 15" high wall out of the fiberglass to hold back the 15" of cellulose I plan to blow into my attic. The plan was to stack one piece of R-30 on top of another half-piece. I'm getting around 11".

Was it squashed in the package for too long? Should I give it time? Try to manually fluff it up more?
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Old 08-10-14, 07:56 AM
Join Date: Jan 2014
Location: usa
Posts: 466
Typical fluffing procedure is to grab the end of the batt and shake it 3 times to achieve full loft.

I have had cases where it did not attain full loft and material was taken back by factory but I would give it a few days first. We have used all manufacturers of batt material, "Knauf" seems to be the most consistent but I'm sure they all have their issues at times.

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