To preface my post i am not saying one is better then the other both have their place. but it makes me wonder what really is green?
Cellulose is said to be green because it uses 85% recycled news paper the other 15% is natural harmless fire retarder borates. That sound wow! I like the stuff because it is itch free! Now after doing research on cellulose and it good stuff. I found it really is not as green as I thought it was that 85% recycled paper is 3.2 million tons of paper permently taken out of the loop never to be reused again annually. or 175,392 trees were just cut down and made in to pulp chips to replace the paper that could have been recycled over and over again. it takes o get with the new energy code were I live now R-49 15.25 inches to have R-49 with That if you are insulating a 1,000 squar foot attic is 85.6 bag of cellulose or 1,581 pounds of paper sitting over your head. Now even when cellulose settles it will still keep its R value. How ever manufactures say to install 25% more then called for sounds like a way to sell more.
Now Fiberglass yuck! it itches it scartches it make me break out in bumps.
it will melt at high temps un like cellulose that smolders at 500 degrees. with no flame spread. Now the recycle content of FG is around depends on who makes it any were from 45 - 60 percent post consumer glass. does not sound all that great compaired to cellulose. Now for the reality of those numbers that is equal to 2.2 Billion tons of glass not tossed in to the lad fill each year. that is very green. to do blown FG to get to R-49 I have to use my numbers were I live ok.
I will need 26 Bags of fiber glass lose fill to do the same 1,000 square foot attic.
to get the 16.20 inches for a R-49 value the weight of that is 735 pounds and a settling rate of 0.01 inches. that is less material less cost more renewable and sustainable recources then cellulose. in my opinon both are very green both have their advatages and disavantages. but I feel that FG is greener in the long run.