Flowering rooms and vegetative rooms have different temps assuming they are each sealed. Personally I would consider having a exhaust fan for each room with a variable speed controller. It will give you more control with your temps. Always go bigger then tone back. It's hard to make stuff more powerful though. You will want to have bigger lights in the flowering room which will cause more heat. A veg room, depending on you climate and lighting choice may not even need an exhaust. Passive intakes are good though in both rooms though (like a breath of fresh air).