Residential Insulation Reftrofit

Here is a more detailed scenario for retrofitting a house with insulation.
It's a 2000 sq ft slab on grade in texas, 8' ceilings, 5' attic at peaks, currently has 4" of fiberglass betwwen the ceiling rafters in the attic.
Was going to add cellulose for benefits: better r value than fiberglass; 30 to 40% radiant barrier; "seal" of attic (which fiberglass cannot do).
Now it looks like cellulose has these problems: invites mold; decomposes over 20 years; loses its inflamability over 20 years; makes a constant layer of dust in the house.
xxxxxxxxxxxxxxxxxxxxxxxxxx So back to the original situation, wanting to increase insulation significantly, can this be done by fiberglass and how many layers can be added in an attic? Also there is no radiant barrier, should one be added? xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
What is rock wool and would it be better than fiberglass?
Also needing to insulate a 4" airspace with 2" of insulation but cannot find anything to do it with at retail outlets, except maybe use an electric carving knife to split some 4" thick insulation but then the r value is minimal...the insulation manufacturers make a fiberglass board insulation with aluminum facing, but it cannot be purchased by the general public, only licensed contractors can buy it supposedly.
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For insulating boards there is foil faced foam it has the highest R value you can get R 7.2 per inch, available everywhere. The regular foamboard, pink or blue unfaced is R5 per inch. The white is crap R 3.5 per inch Fiberglass is apx 3.5 per inch. You dont want fiberglass boards avalaible at menards and made by Celotex it has large grain glass that gets in you arms very easily, and hurts. I threw mine away. Celotex also makes the R 7.2 board plus others. Blow in fiberglass in the attic. It wont mold or compress from roof leaks. Yes celulose is crap.
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foil faced foam board is flamabale
looking for nonflamable insulation 2" thick with high r value (15 or so or more if such exists)

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How cold does it get, check Dow, Owens Corning, and Celotex and Energy Star or other Gov sites to learn for optimum R values. Remember codes are Minimums. I use double of code and more. It is the cheapest way to lower bills. Im zone 5 and have R 100+ in attic and have the lowest bills in the area now acording to the utility co. Put in what fits it will pay back quick. The biggest part of insulating the attic is really the labor, once you are there adding 6 more inches than planned is cheap compared to comming back to redo it . Also insulation will settle 10- 15% so add what you can and more. Remember codes are only minimums so home owners dont go broke before paying the bank.
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dont worry about a radiant barrier
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The first step might be reducing air leaks. Get a blower-door test or run a window exhaust fan and feel outdoor air leaking in around other window and door frames, where pipes and wires enter the house, and so on, and fix the leaks with clear-curing siliconized latex caulk.

Haven't heard it's a radiant barrier, but cellulose is a better insulator. Fiberglas loses half its R-value by internal convection when it's very cold and loses another half when it contains as little as 2% moisture, which can easily happen with an imperfect vapor barrier.

You might talk with some ap engineers from cellulose and fiberglas makers, vs the alt.home.repair cocktail party :-) They all collect horror stories about competitive products, including the "facts" that cellulose insulation can corrode copper pipes and support snakelike tunneling fires.
Nick
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nicksanspam are you saying fiberglass batts loose 50% of their R value at very cold temps. What temps are you refering to. Also could you provide a fact link, I have never heard of a 50% cold temp loss or another 50 % loss due to moisture.
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No, I wrote that fiberglass batts lose 50% of their R value...

Very cold, as in -10 F. R19 becomes R9.

Considering your other posts, that doesn't surprise me :-) You seem to be a shoot-from-the-hip kinda guy.
You might try looking for on-line reports from the Army Cold Climate Research station in Vermont, or google something like fiberglass cold R-value. The 50% loss with 2% moisture is well-known in the fiberglass industry, but seldom talked about.
Nick
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I do and dont dought you, Nick , but that if true is a serious issue as 99.999 percent of the public in cold areas are actualy underinsulated when they need it most. An Issue that is not reflected in code, And suprisingly is not talked about by Dow, Owens Corning, Celotex, or other Gov or energy sites. Or as a way for insulation companys to sell more insulation.
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Radiant barrier is an waste of money IMO
Cellulouse is used every day and is not a problem unless the attic is improperly vented. Acutally cellulouse will lose about an R per year. Partly because it settles and partly because it gets dirty. The air trapped in the attic is the real isualator not the material. I just added 6 inches to my home this year and dropped the a/c bill dramatically. I also did and r-30 in the garage.
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