I have used the foil backed bubble wrap type, of insulation, it works, --but exposed bottom side will start to fall apart in a few years if left exposed, --I tried using 2 layers,- top layer with foil up, bottom with foil down-- works great but it is kind of expensive.
--I also have used a sprinkler on the roof, turned on by a thermo-switch [from Grainger] and a solenoid sprinkler valve, -- so when I was gone to work, the sprinklers would come on by themselves, at 85 degrees [for rabbits and chicken coop] and then turn it's self off again when it dropped below 82, -- so-- I didn't have to remember-- or turn it on before work just in case it might get too hot.
