Insulating materials and methods for battery box

It is cooling down now but just a week ago it was like upper 80s to lower 90s and sunny. Things baked in the sun. I am finishing a fat tire 3.4kwH build atm and need to make a battery box. I want to make sure this thing is as cool as possible. So far, I have the following plan.

- White paint wooden/particle board box 1/4" with small orange accents
- 1/4" packing foam between batteries and box
- Vent holes in front of the battery box but how do I make this water proof? Do I need this?
- Do I do a double layer? So particle board -> foam -> particle board?

Any other suggestions?

Looks like you are more concerned with limiting the effect of solar radiation externally heating up your battery box. What about making a simple removable cover out of reflective material (mylar blanket or refletix?)

What kind of batteries?

If you insulate too much wouldn't you run the risk of trapping battery heat in the box?

lipo. yeah solar radiation. i also dont want to make it too weird or eye catching.