The door on my room is not painted "flat white" yet...but I was wondering....can I use helium balloons (inside out) to cover it? Isnt that "mylar"? I know its very reflective. I was goingto purchase a mylar blanket on ebay and I saw some "mylar balloons" and I said to myself, "damn, I got like 7-8 helium balloons in mt basement brand new from an x girlfriends job. She brought them home once cuz they were gonna throw them out...and we've never had any helium to fill them. This would be ceaper & faster than ordering a mylar blanket on ebay. Plus its only a 2 foot by 4 foot door. And I have several balloons including a few of those big square/rectangle ones...if this is the same "mylar" than I think it will work great!!
Anything reflective will do, I like mylar because i can staple it on very clean and its nice and orderly. I buy it off Amazon and i get the thicker 10 mil so i can re use it, if for some reason i had to tear my set up down for a period of time.