Adding insulation to garge door

[WSSix]

Has anyone done this to help keep the cold out? I'm honestly not at all worried about excess heat during the summer. With this cold snap we have in Atlanta this weekend I'm not comfortable at all. My garage is only a few degrees warmer than outside.

I'm curious as to which material is best for cold weather. I've seen the kits that are hard styrofoam and then there's fiberglass kits. I'm more inclined towards the fiberglass due to weighing less so there's less chance of overloading the door motor. I'm guessing the reflective panels are for heat rejection. Correct?

Suggestion or experience welcome.

Thanks