i've recently moved into an old rental home (circa 40s-50s) that has an attached garage (interior is identical to this and this) i'd like to turn into an office/mancave. i'm starting to research how to insulate it and have realized that there are no ridge vents or soffit vents with which to aerate the vaulted ceiling with baffles, only a simple gable vent. i was initially planning on just throwing up some faced r-30 batts but i'm learning it's a little more complicated than that. the landlord has OK'd this improvement to the garage and has literally told me he hopes the property burns down, so he's not too concerned about it. should i be?
the next option would be installing a drywall ceiling, a task slightly beyond a simple diy project for me, someone who's closest experience to diy has been driving the car to jiffy lube, though that's looking like a safer method than stuffing the ceiling with faced r-30 batts without ventilation.
i've purchased faced r-19 batts and canned foam to do the walls but this aspect of the roof has me at a pause. how quickly will the roof deteriorate without proper ventilation? should i just forget insulating the roof directly, buy a drill, a six pack and inform my best friend we're installing our first drywall ceiling? the final product doesn't need to be pretty, just comfortable. i'll settle with some slatwalls or unmudded drywall at the end of the project.
unvented usually means spray foam. greenbuildingadvisor.com has a good blog on (something like) "how to insulate a cathedral ceiling". search here and there; loads of info. moisture on boards could rot them out in a few years or so; depends on where you are.