[bobeaston]

I have a workshop in my garage and am OK with working there with temps that match outside air, without the beating sun. The east facing dark brown doors used to do a fantastic job of heating the garage far beyond outside temps every morning. ...until...

I also have all 3 solutions mentioned here, door insulation, attic fan and screens.

1. The garage door insulation (radiant barrier reflective foil) virtually stopped the pizza oven effect of sun on dark brown heating. That alone kept the garage from heating up beyond outside air temp. BTW, I kept a set of measurements of surface tempos before and after and could show inside surface temps up to 145 degrees. No longer.

2. My fan installation did not include cutting vents in the door since my garage has a window that I can open to act as the vent. The fan is good for a little bit of air movement. I don't use it much since "little bit" are the operative words and that's not much of a cooling effect. What's more, in the evening or early morning, the fan draws in the ambient 100% humidity as well. For me, it's not worth the money.

3. I also have roll down screens over both garage doors. These are THE BEST part of my solutions because they, and the open window, open the garage up to flowing air driven by ever present breezes in our neighborhood. These alone keep the temp a few degrees below outside air temp.

No, not a lot cooler than outside temp, but a LOT cooler than the radiant power of sun on dark brown doors.