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Blown Insulation Specific Weight

Blown Insulation Specific Weight

Blown Insulation Specific Weight

(OP)
Most attics around here (Midwest USA) are insulated with blown cellulose (I believe) insulation. Has anyone come across an average density or average thickness/weight used in homes?
Or how about the insulation that has a 'paper' side and the other-side has the fiberglass insulation.

Thanks!

EIT
www.HowToEngineer.com

RE: Blown Insulation Specific Weight

Pretty light - I'd only use 2 psf or so. That might be heavy.

RE: Blown Insulation Specific Weight

JAE is right. It is about 0.1 to 0.2 psf per inch of thickness, as long as it hasn't compressed with time.

Fiberglass batt insulation is about 1/2 those values.

RE: Blown Insulation Specific Weight

I usually just ignore it IF I spec 10 psf for ceiling load which would include drywall, insulation, lights, etc. That is typical around here.....

RE: Blown Insulation Specific Weight

Call the mfg

RE: Blown Insulation Specific Weight

Blown cellulose, layered at least as deep as the rafters as is usual in SoFla, gets pretty heavy when it gets wet, like after a hurricane has peeled away your shingles. Fiberglass doesn't absorb and hold water to the same extent.

Maybe that's not a legitimate design condition, but it does happen.



Mike Halloran
Pembroke Pines, FL, USA

RE: Blown Insulation Specific Weight

I think you guys in Florida need to design airtight houses so that just before a Hurricane hits, you can suck all the air out and keep the shingles tight to the roof membrane. Just a thought...

Mike McCann
MMC Engineering
http://mmcengineering.tripod.com

RE: Blown Insulation Specific Weight

As part of an ad-hoc repair team after Andrew, I inspected a condo's roof where the membrane had been lifted, mostly intact, a couple of feet above its plywood support, and settled down, mostly intact but with a few leaky wrinkles.

After Wilma, I intend to ride out future hurricanes in some other state, say Idaho.

Mike Halloran
Pembroke Pines, FL, USA

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