This year, I finally got the white elastomer roof coating
on the utility trailer. I forget the brand, but the pail was $120.
With my car breaking down on the way to BRC, I had to leave both car and trailer behind in Nebraska and get to BRC in another car.
But, I did get to test the trailer out in temperatures of 95F to 100F in the day, with down to the 40s and 50s at night.
Trailer: 8'x5' half-inch plywood, two coats of paint (inside and out), no windows or skylights, shade structure, directly in the sun, not air tight but close to it. No swamp cooler.
By using a cheap indoor/outdoor temperature reader with a min/max feature and an outdoor probe, I found:
- once the sun got up, the indoor temperature lagged around 5 degrees behind the rising outdoor temperature (with me in it or not),
- even with it in the sun, the indoor temperature usually matched the peak outdoor temperature, and only on a few days got 1 or 2 degrees above it,
- as the sun went down and the outdoor temperature dropped, the inside temperature dropped along with it, lagging by 8 to 10 degrees, and took typically twenty minutes to match the outdoor temperature once that stopped falling.
I was amazed that in the sun the closed plywood box didn't act like an oven. I can certainly see how a shade structure keeping the direct radiation from the sun off of such a painted trailer would perform so well.
So these conditions had similar air temperatures to those at BRC, but didn't have the same really hot sun-heated ground that we have radiating heat all around at BRC.