For light reflectivity, mylar. But if you want the material you use to also serve as a wall or to light-proof then use panda film, mylar is no good for those goals.
ok thanks toasty!! check out my current grow im going to flower next week and would love your input or advice! <3 http://forum.grasscity.com/indoor-g...t-grow-custom-built-600w-room-og-kush-17.html
I just got some shit thats called orca film, its pretty tight. i guess it mimics the skin of an orca whale which i guess is the best thing out that reflects light right now.