Helpful? 0

Is it OK to rake cellulose insulation in attic after fresh blowing?

Hi. This is a follow-up to my question posted here:

http://www.greenbuildingadvisor.com/community/forum/gba-pro-help/26311/s...

I'm looking for some hard evidence or resources that can guide me in the right direction. From what I have been told in prior research is that it is NOT OK to walk/rake over freshly blown cellulose insulation so that it can be raked out. The installer wants to do this, and I do not.

Can someone set the record straight for me? Thanks!

Asked by Rocky Pembroke
Posted Fri, 01/04/2013 - 09:29
Edited Fri, 01/04/2013 - 16:04

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2 Answers

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1.
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Raking yes-, not only can you, you NEED to in order to end up with even R-values over the whole area, without performance-robbing low spots. It's standard practice in the industry (amongst better-class installers anyway, not so much with hacks.)

Walking is fine, but only if you rake your footprints level with the rest. Compressing the cellulose by walking on it makes it denser, giving a somewhat higher R/inch at the footprints after you've raked it level again, not that it'll be measurable in the performance over such a tiny fraction of the area. Leaving it compressed but not leveled out gives it a much lower R due to the much diminished thickness.

Where did you EVER hear/read that it wasn't OK?

Answered by Dana Dorsett
Posted Fri, 01/04/2013 - 15:24

2.
Helpful? 0

The guys that do my work don't rake it, they don't need to. They install rulers all over the place then blow it in to AT LEAST the specified depth. I would say the tolerance is -0/+2" and for the most part it's nice and flat. Their machine is not the biggest, so maybe the manageable flow rate is their secret, but for the most part I think it's experience and practice.

Answered by David Meiland
Posted Sat, 01/05/2013 - 20:25

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