I just had a gas heater installed in my 2 car attached garage and need to insulate the attic.  I insulated the walls prior to installing drywall.  R19 maybe. Don't remember.

North Dakota winters get down to negative teens frequently.

1. What R value should the garage attic be?  Not looking to keep it 70 in the garage.  Maybe in the 40's to melt the ice off the cars and such.

Also, there are no roof or ridge vents in the garage.  Should I add some?

The soffits are vented and the gable overhang is vented.  Is that enough venting without adding more?

Thanks for any inputs.

I'd probably tack in baffles, blow in 10-14" of cellulose, and cut in a couple of roof vents, then call it good. Remember that a gas heater is going to throw out a LOT of moisture in the garage.

I hope the OP has a VENTED heater.  A vent free heater is ASKING for trouble, especially in a super cold climate like the OP's.

Ditto on the vented heater comments. I tried a propane torpedo style one in my garage and got a LOT of condensation on everything metal.

Since then I have insulated the walls and ceiling and moved to an electric heater (4800 watt). Quotes I got for running a natural gas vented heater were too high to justify. Doesn't throw out as much heat as the propane one but as long as the wife doesn't open the door on me the shop is comfy to work in after a few hours in the middle of winter.


Did the ceiling with R-40 (or similar numbers) batts because access to the ends wasn't great to put in baffles but I could push in the batts with a stick just fine. My ceiling does have soffit & ridge venting.


Also look at your garage door. First see if you have an insulated one and then think about adding more insulation. If you have a vented heater/electric work on sealing it up as much as you can.

Heater is vented through the roof.  

Garage door isn't insulated yet. The kits I saw at menards were only R-8. Hope I can find something better for the door.

Had a similar situation in which my garage was lacking.  Ended up stocking up on rolls of fiberglass insulation during a sale at Home Depot, cut to fit and slid it in and was able to keep soffit vents clear.  Made a pretty good difference.


For my door, I just had a regular metal one but from another forum I found out about using a radiant barrier.  Came in a roll, cut and fit in the door panels, did not add much weight and helped keep the heat down.

I have an electric water heater and bought on of those water heater blankets to wrap around it.

Garage doors aren't going to get much better than that. You might get up to R-10 or maybe R-12 with a 2" thick polyurethane foam door, but they're inherenlty bad. Also, all of the cracks between panel don't seal air tight and allow leakage. The weatherstripping along the sides and top isn't perfect either.

I'd lay some batts in first, then blow in insulation to get you to about R-50 in the attic. Make sure any light fixtures are IC rated before blowing in insulation. Also, make sure you install baffles to protect you soffit vents. You should also hang some surveyor's tape from the roof truss above junction boxes so that if you ever have to do electrical work after blowing in the insulation you're not digging around aimlessly.