I would suggest not splitting it in half....you will need more flowering room than for vegging. I suggest using 1/4 for vegging, and 3/4 of the room for flowering. Although there is nothing wrong with 1000 watts for vegging, it think its overkill. I would suggest saving money on both equipment and electricity by going with a couple of 4 ft flourescents that you can pick up for $15 each at Home depot. That would reduce the heat quite a bit, but you will still need better exhausting. I would suggest a 6" fan. They run around 700 cu ft per min. (CFM). If you exhaust near the top of the room (heat rises), you will not need another fan to bring in fresh air, as long as the opening is about 3x bigger than the exhaust..... and it should be nearest the floor of the room. That is called a "passive intake"
In the vegging area, using fluorescent lights, will not add much heat if any. You should have a fan inside the room to move the air around.

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