I was painting the roof of my caravan on morning, and it got a bit hot to keep going, so I tool a break with half the roof done. I had just grabbed some gloss white exterior paint I had laying about.

A while later I came back out, and was working on the inside of the van, and I touched the bare roof under a section where I hadnt painted yet. It was way too hot to touch, out of curiosity I touched a section that was painted, and it was only warm. 

It seems the gloss white, was reflecting massive amounts of heat, compared tothe flat off white of the old paint.

This got  me thinking, My Landcruiser is dark green, and gets really hot in the sun- so I just bought some silver car wrap from ebay to do the roof with, be interesting to see what difference it makes to the heat inthe car.