What is best insulation material?

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The wildfires in Southern California left my house standing but the attic insulation was covered with soot and ashes.
They pulled out the fiberglass-batten insulation that was between the 2x6 rafters. I need to put in new insulation. This is a single story ranch, about 3200 sqft. My old insulation is R-19, but Code requires an upgrade to R-22 min.
What is the state of the art with regard to insulation? Fiberglass in rolls or battens, or cellulose, blown in, or what?? I heard that cellulose has a tendency to pack down and lose its value over the years??
Thanks for all input.
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Walter
www.rationality.net
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State of the art is blown foam. Very expensive tho.
Cellulose still has a tendancy to pack down, and does bad things if it gets wet. Fiberglass much less so. Rockwool (eg: Roxul) essentially doesn't at all, and costs about the same as fiberglass but availability is spotty in the US. It's also a lot more fire resistant than either cellulose or fiberglass.
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Chris Lewis,

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Chris Lewis wrote:

Also known as "spray foam". It goes on liquid, then expands and hardens. Also doubles as vapour barrier and blocks airflow.

Roxul is great (used it in my utility room for noise control), but around here in Canada it commands a 20-30% premium over fiberglass batts, and more than that over blown-in fiberglass.
When I did my garage attic, it was cheaper to contract out for blown-in fiberglass than to buy the fiberglass batts and do the labour myself.
Chris
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wrote:

Especially in California you are restricted to what you can use. The best insulator is a vacuum. I prefer the non-itch fiberglass batts. In S.CA, you don't need much insulation, but I'd get the highest R-value I could find unless I plan to move soon.
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closed cell foam is over R6 per inch, pricey but effective
cuts noise transmission and air infiltration, self vapor barrier. all positives except price
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5.5" of fiberglass seems apropriate for your area for fire and Zone, foam and celulose burns quicker. What is your Zone,
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Good cellulose insulation won't burn at all.
steve

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Steve Barker wrote:

It only doesn't burn because it's been treated with flame retardants.
From what I've read, there are some doubts as to the durability of the flame retardants, and no test exists to verify how long they last.
Chris
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Why would they go away?
s

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Evaporation, sublimation, etc. etc. etc.
They are only retardants. They generally _aren't_ fire proofing.
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Well at least it doesn't burn like fiberglass, and support combustion in a big way like the foam does.
s

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Except for the binders, fiberglass can't burn - silica isn't combustable, and the amount of binder is relatively small. Whereas, depending on the cellulose formulation, virtually _all_ of it will burn sooner or later.
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i guess burn was the wrong word. it melts away and then the fire (heat) can get to the next level or structural member. You can melt fiberglass insulation away with a match. Just as you can melt steel wool away with a match.
s

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Of course, his house would have burned down with foam insulation, but no problem
Bob
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Blown in, stabilized cellulose is the only way to do an attic. It's cheap, fire retardant, and insulates better than fiberglass.
check out www.centralfiber.com for more info on just one brand.
s

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Hogwash.
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Cellulose is paper, it degrades to dust, a roof leak ruins it, it settles alot.
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1. I've just let out a few cubic yards of it that were put in in 1958. None was degraded. 2. Why would you let your roof leak? 3. stabilized cellulose does not settle.
you people are only hurting yourselves by keeping your head in the sand. I'll keep using the cellulose, spend less money, have better insulation.
thanks for your input
steve

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oh really? what part? of the three items i mentioned, what is not correct?
s

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'Blown in, stabilized cellulose is the only way to do an attic."
Bob

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