Hi, just a little info on how reflective thing's are:
Aluminium foil is 55% reflective on the dull side, 70% reflective on the other. If it's creased it only reflects 35% of light.
Mylar reflects 92-97% of light and 85% of heat.
Foylon reflects 95% light and 85% heat.
White paint reflects 75-85% of light, but does not reflect heat. This is only if it's flat and non-glossy. Glossy paints reflect only 55-65% light.
Though it might be helpful