I've got a lot of work to do this winter in the garage and would prefer not to freeze my arse off. It's an attached 3 car garage, and I've insulated the walls, but not the roof or the garage door. Anybody know of a way to insulate the roof without actually finishing things off and sheetrocking the ceiling? I want to keep it easy to store things in the rafters, but know I need to get some insulation up there to have any chance of keeping it semi-warm. I was thinking of ripping down 1x4's and running them across the joists to hold the insulation against the roof itself.

I also want to heat it since I live in MN and it gets COLD here. I bought a cheap natural gas one from Menards, but I don't know if it will move enough air to keep it at about 55 degrees. I could add a second one which would probably do the trick, but I wonder if something like a radiant heater (like this one cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=41987&item=5927607295&rd=1 would work better? Thanks for the advice

insulate the roof and staple plastic sheets over it

Quoted: insulate the roof and staple plastic sheets over it

Won't that drip condensation when it is first warmed up ???

They make insulation for just your needs.

The comes with flaps so you can staple it to the beems.  Goto menards and ask for it.

As for heat,  get a hanging electric heating unit.  Look in the local papers, they can be had for cheap.  There's currently a 55,000 BTU hanging unit in my local paper for $150.

If it does you will be able to see it.

Check behind the insulation after you have had it up through a winter and spring.  If you are trapping water between the insulation and the roof (sheathing), the insulation backing will deteriorate and this is a good location for mold growth.
If you have trusses or ceiling rafters, laying the inslution between them (stapling to the wood or using ripped 2x's is a good idea.  This is not perfect, but will slow the heat loss (especially if you can seal any joints or openings).

Use rigid foam insulation sheets, line the interior of the garage door with them, and the ceiling line - block off the garage attic space. You'll have a smaller much-easier-to-heat space for the winter.

Build a waste oil heater that heats using used motor oil.

journeytoforever.org/biofuel_library/ethanol_motherearth/me4.html

Use the oil from you cars and whatever you can carry off from shops.. most will give it to you as they have to pay to have it disposed of.