I would like to insulate my 2 car garage. I use the the ceiling to store wood so I want to leave the ceiling open. . . . . . I'm in Denver, Colorado so the temps can range from 0-100 degrees. . . . .
I don't like to dampen your enthusiasm, but looking at the big picture makes me wonder:
1. Spending winter in a Denver garage (doing woodwork) with no ceiling is not logical. Numb fingers or having to wear gloves will hinder precise woodworking, and any temporary heat will quickly float upwards into the attic area (but it will keep your stored wood toasty).
2. Why not sheetrock the ceiling, lay in some heavy (R31) batts above the sheetrock, and keep the supplemental heat in the work space?
3. Beneath the ceiling, you can build a few innovative lumber racks in locations that aren't being used (above the garage door comes to mind, or where the hood of your vehicles are when parked). Suspend the verticals from the trusses' panel points before rocking, connected to both top and bottom chords. If you're going to put hundreds of pounds on any one rack, consider tying each vertical to adjacent trusses on either side, using horizontal 2 x 4 spreaders. If you want to go heavier yet, have an engineer design some bottom chord flitch plates for you, glued and screwed to each loaded truss, in addition to the spreaders.
4. I've built at least a half dozen such racks in garages, and every one has worked extremely well. Just know their limitations, and keep in mind they are not to be used for hoisting engines.
5. You really need to install some venting at or near the ridge, in an effort to move attic air. Soffit vents by themselves are next to worthless, especially in the summer.
