The hps does put out a lot of heat but you have to keep in mind that its only running 12 hours a day instead of 18. A ten degree drop is fine as long as your temps stay under 85 and above 65 degrees. I usually run mine about 80 lights on and close to 70 lights off. You could always get one of those mini space heaters on a timer or an inline fan to blow room temp air into the room while the lights are off. Whichever you decide, just make sure that you havent created any light leaks. Hang out in that room with the lights off for about 10 min so your eyes adjust and youll be able to find any leak. Good luck!