Looks like you're up to a good start. The first thing that came to my mind was why you didn't take advantage of all that space and throw 2 or 3 ( or 6) lights up? anyway.. If temps are really cold at night you should run your light at night, say 7 pm to 7 am, that way during the coldest part of the evening, the light will warm up the room a little. This also helps in summer when we get those hot days. If the light runs at night you will save money cooling the space, guaranteed. I think that if you seal the room with some panda film it will help it keep heat in the grow room, and the cold outside. There is a manufacturer that makes wall mounted heating fans. Very similar to a wall mounted fan, in concept. They oscillate, have diff heat levels, etc. I can't find the link right now(google it). You generally do not want the room to get below 60 degrees fahrenheit. You can buy a cycle timer that will run for much more specific times as a pose to your typical timer that you would buy at walmart that all work in 15-30 minute intervals. A good cycles timer can run cycles such as on for one minute, off for an hour. etc. etc. they're a handy tool in the grow room, as you can use them for CO2 controls, Exhaust fans, drip emitters, air and water pumps. etc. etc.
