Experience with outdoor grow room during winter months?

Does anyone have any tips growing in an outbuilding outdoors as far as climate control is concerned. Temps can drop as low s 10 degrees. I have a container that is 5' x5' x 12' tall I was considering using for a grow room this winter. I want to run 1000 - 1200w each level if I am able to have enough head room for sog on each. My biggest concern is climate control in maintaining lights on temp. I may be possible venting or doing sealed co2 depending on if my buddy comes through with a burner. Electricity consumption is not an issue so I will be running electric heater during lights off but lights on is where I need advice and some ideas to maintain temp. Any tips or advice on climate control for this outdoor grow room would be greatly appreciated. I have a few ideas rolling around but Im hoping someone has some experience with this. Thanks in advance

have insulation and a heater set to turn on only at night or when its cold

Will I need cooling with the ambient temps that low? If so how many watts can I run before running into high temps issues in a grow room that size with low outside temps?

just test it out man, if u have good circulation then you shouldnt have too many problems u dont want pockets of hot air forming in the room. i have experence w/ this a bit but it was only for one season and a single 400w hps everything went well but i had good ventalation and the light itself during the day was enough to keep it warm "smaller space" if u have to u can get power strips and sockets that plug into them then go get some CFL's 40-60watt and keep plugging in one light at a time un till u get to the temp u want it to be ( these cfls would be on the floor under the canopy these cfls will create warm air and u can use a small fan to keep it circulating) as long as its warm where the plants are np right? hope this helps just got inside from trying my last harvest

Appreciate it. I am only doing this for 1 round. I thought about hooking up some cfls to a thermostat for lights on to come on. I am leaning more toward co2 because it will be a pain to vent considering it is a metal box.

when it gets too cold , a heater turns on, when it gets to hot a intake and exsaut come on intil the temp is lower enogh. HID lights put off Lots of heat, more than you think, I have 2 600s running in a small shed with intake and exsaust and i run my lights at night, and it still gets to hot in there, if it is above 30 out side