Your gonna have to ventilate just to get fresh air/blow out stale air.Since you are doing C02 you will probably be able to stand more heat...Obvioulsy with CFL or reg flors you will have less heat and you have to be right on the plant...If it were my choice I would get a HPS for flowering and use the Flors for VEG... Check out HTGSupply.com for some inexpensive lights or Insidesun.com (refurbs).. Can you give us some dimensions.. Also this is just my opinion, others are gonna tell you different