[Oh Haha]

Depending on what door(s) you have, foam insulation panels are an option. My doors are single units, not new, but they have foam sandwiched between aluminum panels. My garage stays about 50 degrees in the winter, even in below freezing weather.

Now, my furnace and water heater are in the garage so that helps. I can work with no coat nd be very comfortable.

Go to your local Lowe's/Menards/HD and see what they have in stock.

Another area I spent a lot of time on is the rubber seal on teh bottm of the doors. New ones just slide into a channel on the bottom. I get no wind at all under the door. Check for air gaps with the lights off and, if possible, the sun facing the doors. Hope this helps.