i'm no expert on growing, but do know that celotex is a great insulation (sit on it for a minute and you will feel the heat)it's most commonly used in the cavity of buildings, floors and for warm roofs so i was wondering if it may cause problems with heat?, i have a small greenhouse for growing and use celotex on the back as it's next to a fence to reflect the sunlight to the back of the plant, and my plants always grow evenly back and front,so it seems to work ok for me, sorry i can't help you any more than that, and the best of luck on your grow:thumbsup: