I wrote this up and took photos last fall of 2008 as I worked on finishing off a single car garage bay here at my shop to be used for working on bikes in the frigid winters here in Ohio. I hope this is of use to those of you who are trying to work in garages so cold your feet turn into blocks of ice and you can't close your hands, I empathize. With a bit of money for the materials and some labor, and perhaps some help from a friend, you can quickly insulate your shop and make it a much more comfortable work space.
I am working on transforming an unused bay in my shop into my winter workshop, as my main garage isn't heated and has big non-insulated bay doors on both sides and would be tough to insulate properly. I figured it might be helpful to someone to post some photos of the work I am doing to get it ready for winter.
Here is the bay in question, approx. 8' x 19', with a bay door at one end and a man door at the other. It is sandwiched by insulated, heated bays which are my office and shop.
The first step was insulating the cheap steel 7' garage door. I used 1.5" thick sheets of rigid foam insulation, it has an R7 rating. Cut it to size and fit it into the panels pretty easily.
Next, I used a roll of vapor barrier, a 2' x 20' roll was around $20, it is 5/16" bubble wrap with aluminum coating on both sides, it cost about $20. It has an R3 rating and will help cover the pink foam, which is flammable. I cut that and tucked it in where possible, and where there wasn't a lip to tuck it into I used foil tape to secure it, found by the duct work at your local hardware store.
A bit of weatherstripping between the door panels and edges and it is 100x better than it was, and for a total cost of around $65. Next I will be insulating and finishing the ceiling, installing more lights, putting a stud wall on the exterior wall by the man door, running 220 for my welder, running black pipe and installing natural gas wall heater, building a work bench, etc etc. I will have a bike lift in here as well. It will be a bit crowded but nice and toasty, no more wrenching in a 0 degree garage.
Cased around the doors, these are interior doors leading into my shop.
Resized the attic access and put drop down stairs, great storage for my hoarding of motorcycle parts. The stud wall is in on the one exterior wall.
Picked up the insulation for the ceiling, as well as baffles. Baffles are available in plastic or styrofoam, either is fine. These get stapled to the inside of the roof, slide them down til they just about butt up to the gables (the underneath overhang of the roof). They allow for air to keep flowing up into the attic to ventilate, if you stuffed insulation all the way to the gables it would block air flow and the insulation could get wet. They are available in 16" or 24" widths depending on the centers of your joists.
Installing the insulation is easy, just stick it up there and staple the flaps of the vapor barrier (brown kraft paper) to the ceiling joists. OR even easier if you aren't going to have finished attic space above (ie a floor) you can just put up whatever you are using for your ceiling (wood, drywall), leaving an access panel, then go up there and simply roll the insulation out, or fill it with loose fill insualtion. The insulation should just extend onto the top of the exterior walls, don't cram it into the gables. A tip, douse yourself with baby powder before installing the insulation, it keeps the fibers from sticking to your sweat.
Trickiest part was making the garage door supports look clean, it turned out real nice.