Blown Insulation Specific Weight

[RFreund]

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

http://www.HowToEngineer.com

 

[JAE]

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

 

[Ron]

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.

 

[RFreund]

Thanks guys.

EIT

http://www.HowToEngineer.com

 

[MiketheEngineer]

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.....

 

[msquared48]

.3 psf per inch of thickness is what I use.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[MiketheEngineer]

Call the mfg

 

[MikeHalloran]

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

 

[msquared48]

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

 

[MikeHalloran]

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