The roof on the cargo trailer is some sort of galvalume steel, greyish in color, somewhat mottled. I have an IR thermometer. Yesterday it was in the 60's outside. The sun shining on the white aluminum skin gave me a surface reading of 89 F. When I climbed a ladder and pointed the IR thermometer at the roof surface the reading jumped. Not up but down to 17 F. What!! So what is going on? I've never seen the IR thermostat drop like that when pointed at something that feels warm to the touch. It felt as warm or warmer than the white aluminum sides.