lookin for advice

i have a indoor setup out in my shed attached to my garage.problem is i need fresh air for the room but its gunna be a cold winter and i cant heat the shed.i cant have the plant freeze.im thinkin space heater and vent out the top hence hot air out the top to keep cold air out.i have no idea i can post pics of the setup if it would help

Pics would help, the only problem i see is that is will lite up like a Christmas tree to flir if "the man" comes looking around your area.

word i will try to get pics up today.and i have a big hole in the GR already on top its the only way i can regulate the temp. cuz just the 400 mh is alot of heat output.so i have two fans, one pulls fresh air in from the side and one pulls heat out.when the light shuts off its 80-83 F when the light kicks on 6hrs later its like 55-60 F.i have to seal off the in side to keep cold out.kinda get wat im sayin?

Yeah, if it's gettin that cold in only 6 hrs get a space heater so that plants wont be stressing to much.

Seal (and possibly insulate) the shed and build an enclosure inside of the shed for your plants. Ventilate the enclosure to circulate the air inside the shed. Heat the shed to around 65 degrees and open it up briefly every day, during lights on, to get fresh air inside. Keep your min-max temps to around 15 degrees difference and you should be OK.

throw in a couple 1000 wat hps they well keep that shed nice and warm

and have it so your lights go on during the night and off at night that way it well help it from really cold nights and get strain that can handle cooler temps cheers

bad news put space heater in last night and set it for 70 F and the top of the plant got burned pretty bad but the nodes of the plant are fine. i advanced the light so its off from 6pm to 12pm i got camera so pics today

here is wat i got