I am just about finished setting up my first grow room. I have 10 600w mh/hps lights with air cooled hoods. I have the lights in 2 rows of 5 with a carbon filter at the beginning of each row and exhausting the air outside. It is a 12x24 room with an 8ft cieling and I have a 3 ton A/C heating and cooling unit. I also have a 700cfm intake fan. My concern is that I live in a northern climate and when my lights are off the intake fan is going to be pulling alot of cold air (in winter months) into my room. Should I have the intake fan turn off when the lights go off? Won't this lack of fresh air hurt my plants? Also I am trying to find some kind of Hepa filter to put on my intake to keep out bugs, contaminants etc but can't seem to find one that would fit on a 6in intake ducting. Any suggestions? Thanks in advance for any input