Hey you wont need space heaters lol, jsut make sure your soil temp is 70degrees and your leave zone will be nice and tosty! Remeber humidity and tempature go hand in hand! watch both. To solve your soil temp issue, just elevate pots above floor 2-3feet and keep your HPS 25inch alway from top of plant! I know i know people suggest differnt distances, 25inch has worked GREAT for me at my enviroment setting. GL and you will find that this is just the beggining of your grow op,

once u start you dont stop!!