I posted before about using tigerfoam. I used in in my addition. My garage ceiling was sheetrocked by my builder, and I'm sure he did the least he could get away with. Part of my bedroom is over the garage. I'm thinking that they didn't used to build living space over garages before. Now we all see why. If someone could figure out how to retrofit insulation onto a sheetrocked garage ceiling, that would be great. For stockrex, you don't have to fill the entire space for the Tigerfoam to be effective. Just a few inches will probably stop the air leaks. Then, you can fill the rest with the same batting that you take out, if it's clean. I think that it's best to figure out where the airleaks are coming from first. My powder room shares a wall with my garage. It was always cold before we renovated, but now it's freezing. When I had a wall mount sink installed, I decided to have an access panel behind it in the garage. Cold air was flowing in through the electric plug. I sealed that. It's better, but the walls are still very cold.

Good idea on the baffle, another friend suggested tacking up a piece of metal flashing, leaving a gap. All the baffles are in now; but there are gaps on the edges. Someone suggested using some roll insulation pieces to put in the gaps so insulation doesn't get down in the soffits; but the baffles will still allow good air flow. Haven't done air sealing yet. Been working on one area at a time. After the soffits are ready, I'll start going through sealing. I have a few electrical issues to address. Also have to raise my walkways a bit in case I need to get back in after blowing. (see above photos!) There are 2 areas, the main, and one above one bedroom. Have to climb up in a closet area above the bathtub... out of all places. In that access area, there's a attic opening with board covering. Will have to work on that opening a bit. No recessed lighting or ductwork up there. Its a slow process, I can only get up there in the early hours each morning. Wish I had had time earlier this year!

I recently spun myself in circles and delayed our renovation a bit over a similar topic (how to insulate a 1914 stucco house with a slightly leaky tile roof). I can tell you that we put most of our energy into the roofline (baffles and closed cell foam) and secondarily to the walls and gable ends we had open for the reno (furring strips, rock wool, certainteed membrain smart vapor barrier). Your situation is different, but I think you are right to think about this carefully. 1. Is your roof/attic insulated? If not, do that first, much more bang for your buck 2. I agree with putting an air gap between the outer wall and the insulation, to the extent that cement shingles are permeable (are they?). We used furring strips for that. 3. People seem to like rock wool batts. I would recommend posting your question at greenbuildingadvisor.com. Someone here gave me that pointer, and GBA gave me some great advice.

I don't see the insulation location being a bad thing unless you've had problems with ice dams or leaks. It is difficult to properly insulate and vent a cape with upstairs rooms. Ours is insulated in a similar fashion and the only negatives are icicles and shingles don't last as long. green building advisor.com has some good advice about insulation strategies for capes.