I have a 1909 1.5 story hip roof in Spokane, WA. We get both winter and summer here.
The upstairs is just one room; a bedroom. The north end of the room (small side of the hip, or whatever it is called) is basically attic but used as a closet. A door separates the unfinished closet from the bedroom. I'd call it semi/mostly conditioned. There is a knee wall built in this closet area that is well-sealed and has cellulose over older fiberglass on the floor. That work was done by an outfit here doing energy retrofits and was permitted, etc. and as far as I can tell they did a decent job.
We do have some (inadequate) venting in the actual ceiling portion of the upstairs but this attic/closet is unvented.
I'm getting to my question
In preparation to have some electrical work done I have cleaned out the attic/closet considerably, thrown away some old stuff, etc. The roof is 2x4 (actual 2x4) with cedar shingles layered directly over horizontal 1x6. Old style roof with several layers of composite shingles on top. A tear off and new roof is in the future, but not immediately.
Ok. Until this weekend we had R-7 foil-backed fiberglass stapled into the studs with no drywall or any other wall board. No airgap other than the sorta-gap created by the horizonal 1x6. The fiberglass was extremely dirty and in in many areas compressed or torn or both. I figured since I had the room emptied out and it isn't a very large area I would go ahead and remove the fiberglass, let the electricians do their thing, and replace. I hauled out 4 large garbage bags of the R-7, mildly compacted. So that gives you an idea of the area maybe. I haven't calculated the sq. ft.
NOW for my question: What to replace this stuff with?
I had thought I might use some of the expensive 2" foil faced foam panels to sqeeze some extra R value into a tight space and get a radiant barrier for summer but am not real keen to drywall this area because the plan is to tear off the roof and do a little bump out here in the next 2-5 years. For the same reason I don't really want to fur out the studs.
Basically I'm just looking for the best option for insulating this area that doesn't include structural changes. I don't want to leave a hack job, but don't want to put a bunch of money into a temporary solution.
Any advice? Should I just put back a new version of what I had?