On May 27, 8:16*pm, ransley wrote:

I put foamboard I painted flat black behind single pane to insulate it
in our -20f lows, the sun Melted the foamboard and cracked 2 windows,
Just painting it dark brown reduced heat absorption so it worked. It
was Non Uv glass so I bet the UV cooked it.

Why would you paint the foam board black or any other dark color?
That's guaranteed to heat up and create a lot more thermal stress.

R