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Old 02-02-2013, 04:14 PM
 
Location: Queen Creek, AZ
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Our house uses cellulose insulation for the exterior walls (R13, with a total R-value of R19 for the entire walls), but still uses the pink fiberglass insulation (R30) for the attic/ceiling. From what I heard, this is a very common practice by many builders.

So, I was wondering, what makes cellulose insulation less desirable for attics/ceilings?
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Old 02-02-2013, 06:54 PM
 
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It weighs about 3 times as much for equivalent R-value.
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Old 02-02-2013, 08:42 PM
 
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Cellulose also packs down over time, IME.
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Old 02-03-2013, 12:32 AM
 
Location: Not far from Fairbanks, AK
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Cellulose and fiberglass are the most common materials for attic insulation:
Insulation Materials | Department of Energy
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Old 02-03-2013, 12:48 AM
 
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When a builder is using cellulose in walls of new construction they are likely using a high velocity blower that results in a denser packing for a higher R-value. Most attic / rafter / eave spaces don't afford as easy access and achieving as good an application is hard to achieve. Fiberglass batts install much faster in such applications.

If you have "blown fiberglass" above your ceiling it too suffers from "packing down over time" as well as being prone to being to dislodged by air circulation. Many experts recommend. A combination approach of blown cellulose layered with blown fiberglass but few builders like such a multi-step approach. It is probably a cost effective homeowner upgrade and certsinly more affordable than sprayed in foam ( though foam offers superior resistance to air movement and is far more effective as moisture barrier...)
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Old 02-03-2013, 10:17 AM
 
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Makes sense for ceiling, but what about exterior basement walls (the kind that are above grade). Do people typically use blown in for insulation?
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Old 02-03-2013, 12:28 PM
 
Location: Not far from Fairbanks, AK
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Quote:
Originally Posted by blazerj View Post
Makes sense for ceiling, but what about exterior basement walls (the kind that are above grade). Do people typically use blown in for insulation?
If you use this kind of foundation, you don't have to worry about insulation there. It's very common in cold regions these days. The cement mix (concrete) is poured into the forms, so there is about 2" of insulation outside the house, and 2" inside:

Foam Foundation Begins - YouTube
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Old 02-03-2013, 10:47 PM
 
Location: Lost in Montana *recalculating*...
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I'm getting ready to blow in eco-fiber into the space over my garage (about 1,000 sq ft). At. R-60 is within tolerance of my truss system and I'm okay with that. Just add 2-3" over the recommended fill height to account for settling.
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Old 02-04-2013, 12:41 PM
 
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I would not put blown in insulation in my home, especially in the attic. Anytime you have to open up a ceiling the stuff would be everywhere.
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Old 02-04-2013, 11:01 PM
 
Location: Lost in Montana *recalculating*...
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It wouldn't be that much more to clean than the drywall dust that will be laid down. You'd have to put some batt insulation on the drywall you are reinstalling to cover the loss of insulation or simply go up and fluff the area with an extra amount of loose fill insulation.

Over my garage is a no brainer- I will not be using the attic over that for any storage whatsoever. I will insulate, then seal the opening shut and forget about it.
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