We have a vinyl garage door that faces due East and the garage really heats up in the warmer months because of this orientation. The R-value of door is maybe R-3 +/- according to the manufacturer. I considered adding more insulation on the interior of the door, but that does nothing to reduce the exterior heat input. Would a reflective vinyl approved paint on the exterior of the door help reduce heat absorption in your opinion/experience? Thank you for your time and thoughts on this challenge.
I would recommend a reflective insulation (Foil/Bubble/Foil) on the interior. This will solve your problem. It is called a garage door kit. You can check with RIMA-I members for the kit. There are links to our key contacts at each company and you could quickly copy and paste the same message out to several to get some comparisons. I hope this is helpful. Please let me know if I can be of further assistance.