Even though that 1000 w hps should kinda act as a heater during the day, putting a space heater in there and experimenting with it a little bit until you get to the temp you want is probably the best way.

Your gotta be careful where you plug it in though, Space heaters use alot of electricity. I would use a totally different outlet from the 1000w hps. If i use my heater, two lights, and all of my fans all at the same time The power goes off and I have to go reset the breaker.
drudown11 Reviewed by drudown11 on . Goldy Locks - Now it is too cold at night. :( - Tech minded peoplez help Live in Los Angelos: 45°F - 70°F HI/LO temps 1000W HPS bulb, in a 12x16 foot room with a window. Intake Box fan in the window. I have the fan on 24/7. Exhaust 400CFM inline fan sucking through my cool tube and out of an attic vent at top of house. Rating: 5