I need to insulate my garage attic. Which one do I go with. Celulose is $5.80 a bag the Fiberglass is $38 a bag?

Cellulose will settle a lot and fiberglass will settle very little. As insulation settles, you lose R value. At the current cost of energy, a little extra for the fiberglass now might mean bigger savings for years to come.

The cellulose also weights more.
I put that in the garage in our first house and you could see that the sheet rock was bowing from the weight. Especially if it gets wet from snow blowing in or condensate it will hold the moisture.
I put 15" of fiberglass up in my Main garage and also in the shop as well on the new house. Much better R value and easier to install as well.

Along with what is mentioned above the $5 -vs- the $38 is not for like coverage. Fiberglass is more expensive but not that much. I can't remember what the cellulose bag covers -vs- the fiberglass but it is not the same. The biggest thing for me is the clean up, cellulose blows dust EVERYWHERE including where you are spraying it and where you are loading it. The fiberglass is much much easier to clean up.

i work with a guy that has been blowing insulation in houses for the a quite a few years now and he told me a while back he would never put fiberglass in an attic. heres what he told me.

you are right that cellulose packs more. but insulation works with on how air moves, or doesnt move through it. the less the air moves through it the better the insulation value is. one thing is you will probably need to go twice as deep with the fiberglass as opposed to the cellulose. we put 14 to inches of insulation for a i think an R 50. from what i know about chopped fiberglass you would need more.

ever thought about just rolling out some fiberglass in the rolls between the trusses, then rolling out more at 90 degrees to the bottom layer.

If you don't have the ceiling rocked then use the fiberglass bats. Two layers run perpendicular.

I might consider blown glass in a wall cavity but because of the air movement I'd go with cellulose in the attic. Having said that I've blown cellulose in more attics and walls then I care to remember. Protect your lungs and a good mask respirator with spare cartridges. The mess isn't bad unless you plug the hose. Keep the feed down, that'll ensure you won't plug and it'll give more loft to the cellulose. Rolling bats would be tough if you have a 4/12 trusses, although crawling in to put in chutes isn't fun either.

I already put upt the chutes before I sheetrocked. Celulose is suppose to be way better when it comes to fires plus it is a recycled product. That is why I was leaning. I have 5/8" rock so I would think that should hold it up just fine. I think I need 15" of cellulose vs 20" of the fiberglass. The price difference was 490 vs 820 quite a jump. I guess it is a ford chevy thing. Thanks for the input.

Make sure you put in the chutes and the windwash barrier. Chutes do not meet current code by themselves any longer.