Hi all, just finished wiring my garage for a new woodshop..... Ready to drywall now and am curious if I were to insulate just the walls (2x4 16" O.C.) and leave my rafters exposed would I accomplish any increase in comfort? Or will I still fry in summer and freeze in winter and have wasted all that cash to boot. How bout the garage door, anything I can do to insulate it, it is a cheapo aluminum door.

Insulation will only delay the inevitable. Insulation doesn't create warmth or coolness, it simply retards the passage of heat through it. Let's say you put R-11 in the walls. R-11 is equivalent to a U factor of 0.09, and that is the amount of heat in BTUs per hour per square foot that will be transmitted through the insulation. If your garage is 20x20 feet, and the walls are 8 feet high, three walls comprise 480 square feet, so your garage will gain 43.2 BUTs per hour or 1037 BTUs per day. Then you have the door, which amounts to zero insulation and would be almost impossible to insulate, and most of all, the roof, unless you have living space above the garage.

The ceiling is where all the heat loss is going to be. Doing only the walls will allow the heat saved to go up through the roof. You need to seal off the ceiling. You can get away with the foil backed foam boards as they are easy to install with long screws and washers and will help reflect heat out and keep it in as well.

Not much can be done with the garage door. Some folks build floating walls with wheels on bottom and design them so they cover over the garage door. Assuming you have another access to garage. Then simply roll them out of way when its nice or when they need to bring the larger projects in and out. Build them in such a way that you have storage on them.
Build box form and shelve it for tools and things.

You should also consider a wood floor, carpet or rubber mat where you stand. Concrete will take the heat right out of your feet and you will feel it at the end of the day.

Okay so I figure I am gonna lose the opportunity to easily insulate if I dont do it now. My thoughts are to go ahead and insulate the walls now while I am rockin'. Now my thougts are to get some reflective insulation rolls to attack to ceiling coupled with a roof mounted vent fan, I am hoping to achieve some degree of comfort. I am also thinkin about attaching some ridgid foam sheets to interior of garage door panels. Thoughts? Comments? Concerns? Advice?

Why insulate if the space will never be heated or cooled? Spend your money on white shingles for the roof; that will at least keep you cooler (but not much) in summer. In winter, you're gonna be cold no matter what you do.

Installing reflective insulation is futile. The heat will already be in the space.

A fan will do what? Exhaust hot air and bring in more hot air? Better to have a fan that just moves air around in the space.

Insulation does not create heat or cooling. Sooner or later, in a matter of a couple of days, the inside and outside temperatures will be the same, no matter what you do.

installing sheet insulation to the inside of the door will change the way it opens and closes. You will need to adjust the spring tension if you do so. You will be better off putting on new door gaskets and seals first if you have not done so. Stopping air infiltration is the first line of defense against heat loss.

Richard, I will heat/cool the space as needed for my comfort while working in their, as it stands however heat swiftly exits the garage when its cold out, heating it is an act in futility. I am hoping to make it able to retain heat. Not sure I agree about the exhaust fan not working. The temp. in the garage often exceeds the exterior temperature, removing this hot hot air and pulling in some from exterior seems like it will help alot. I am under the impression that I can lower my attic temp utilizing the same fan as well. I am just trying to stabilize the climate in the garage so it doesn't swing so quickly between extremes. So Rich how do I make it a hospitable environment to do my woodworking, sounds like you are saying it's all futile. Should I just buy a good jacket and some speedos?

Will definately add some gaskets LLC. You think putting some ridgid foam will add enough weight to affect the door operation?

One last thing, the garage is attached to the house so I can't change shingle color and I need to do something so everytime we open the door to do laundry or something the house drops 5degrees.

NOW he tells us. IF the space will be heated and cooled, there are codes which apply when insulating. Find out what your local requirements are, and follow them.