Might I first say that although you may usually think you have an especially specific question, just about 99% of everything has already been answered here. Take a look around, do some archive searching, etc.

That being said... you do not always need an intake fan. For both my flowering rooms I only use an exhaust fan. For 2 1000 watt lights I would use an 8" fan with around 700cfm. With a fan this powerful you should not need an intake fan but the room must be sealed (no cracks or openings) if you are trying to pull air from another area. Are you pulling from the basement and exhausting into the attic? or just pulling air from inside your room and exhausting into the attic? Exhausting into the attic can work great, I do it on more then one room. However the rooms themselves that the air is being drawn from are very cold so its cool air. You cant keep the area your taking air from hot or youll get no cooling effect.

If you can seal the room, then use a large exhaust fan, pull air from the room, and then use another piece of ducting to take air from the area you want. if everything has a good connection and there are no leaks then youll have no problem moving a ton of air through. Remember, you need the fan at the END of the exhaust. This is the most efficient way. This way you can keep the fan in the attic so that it doesnt make noise in your home.

PS. If this is your first time growing, you might try something smaller scale so you dont have a lot invested if something goes sour. just a thought.

this is an old pic but it gives you an idea
Racerx Reviewed by Racerx on . Ventilation Question... 2000 watt grow... Okay, let me start by saying I am a newbie at this stuff. My room is partially set up and I'm at the ventilation part, and I am STUCK =( I have: 25 feet of 6 inch ventilation tubing 6 6 inch ventilation clasps (to make for a more secure connection) a thing that is going to connect to the floor (intake) to the six inch tube two elbows so I won't need to bend the tubing I am going to drill a six inch hole in the ceiling of the room (which is the attic) Outtake will go up there, I Rating: 5