Yes. you will need to hang the sheetrock before you insulate the attic space.

I would try to get the blown in in the cathedral cieling also. The effective Rvalue is better.

another question, do i need to have a vapor barrier between the drywall and the insulation... and if i do this in the cathedral, i assume there is a mesh or plastic to hold the blown in in place, won't that sag before i get the drywall on? This seems silly and didn't really think about it until i decided i wanted blown in cellulose not batts.

Check your code as far as whether you need the vapor barrier in the cieling. Some locations mandate it. Yes, you will need to "mesh" the cieling of the vault or use a reinforced vapor barrier. Or, you could hang the vaulted cieling to within a few feet of the top, and only mesh that portion, provided there is enough room to adequatly blow down the rafter cavity.None of these should be a problem with your insulator.

Thank you so much for your information, the "insulator" is us, we are doing everything ourselves.....very slowly.. lol

If you will be doing it yourself your options are greatly limited. I would comment on the possibilities but I don't really understand your description well enough.

I will try to be clearer, we are paying to have one inch of spray foam installed on exterior walls and 3 inches on cathedral ceilings. We will likely to filling the remaining wall cavity with blown in cellulose. I thought my only option for the remaining space in cathedral was batt, Rolie just wrote i have other options for that. In the areas of the house that will have 'attic' type space, is where is am questioning, that gets blown in after the ceiling drywall is in? and when do i do this? walls are done, before? Told you it was a silly question.

What is not clear to me is whether the cellulose will be applied dry or wet, whether it will be normal or high density (dense pack) and whether any of it will be stablaized.

Not all of these techniques are suitable for DIY.

If you want to get the most R value I would recommend a professional installer.

I'm also doing most of the work on my house, just went thru the insulation part. Here is what I did, just for comparison. (this is a 2100 SF house)

Insulated the 2x6 walls myself with standard R19 batts

For the vaulted ceiling, spray foam.
Walls around this ceiling, that back toward attic: spray foam
Area under floored attic (approx 250 more SF): spray foam.
Rest of attic: blown fiberglass 12 inches. I am going to roll out more fiberglass on top of this myself.
Garage: 6 inches blown fiberglass.

I've forgotten the exact footage of all that I had sprayed/blown, but the spray bill was $1400, and the blown $875. I think the wall insulation total was around $700, I may spend another $400 or so on attic blankets. So thats about $3400 all together, with me doing alot of the labor.

The foam is expensive, but when you see it go in, you realize how good it is. When you have areas like the ceiling, and under attic floor where you've only got 6 inches to work with, I felt I had to spring for the stuff to get a good r-value.

If you go with a "professional installer", make sure they are experienced and reputable to your area. Check them out thourougly or you'll end up straightening out their work if you know what you're looking at concerning a proper install. Insulation is a behind the scenes install that you dont see, (with the exception of attic, basement, or crawl space applications), when covered up, so it needs to be installed correctly to gain it's full benefit. While our insulators were great, I straightened out some of their batts work in two small attic spaces concerning blocked venting. They did a professional install other than that but being meticulous or anal with insulation installs isn't a bad thing!

It would help in this discussion if spray foam was identified as low or high density since there is a substantial difference in the R value and the installation equipment used. Many would assume it is always low density foam because it is cheaper but I find assumptions about building design issues can lead to misunderstands and misunderstanding can lead to pain and trouble.

Low and high density spray foam can also be differentiated as open cell and closed cell. This is important to recognize not only because of the difference in R value but because of the difference in moisture movement through the assembly. It is always important to describe the entire assembly in order for others to participate in the discussion. If that makes it seem like such design issues are complex, it's because they are.