a cheap way to cover the walls in your grow room is go to wal mart and get to the camping section and purchase some of those emergency blankets the are just as reflective as mylar and it will only cost around 10.00 to cover your whole closet this is what i use and it works great i pay 1.97 for a 4x6 sheet i seem to have no problem with it good luck check out some threads and try to go hydro you wont be dissapointed