There are some Mylar products that reflect energy in the low 90% range,very lightweight(spaceblanket-like) that are readily available.Make sure your wallet is full for a piece big enough to sit under....Look through a McMaster-Carr catalog,they have it.
Anything that is solid white will reflect about 80% of the energy and tin foil reflects about 60%.
Last edited by Booger1; 01-30-08 at 10:03 PM.