Routing house air condition to grow room

[Deuce5]

I'm currently looking at having a house built. I plan on having a 4x4 closet built in near the attic. The room will be sealed with normal drywall walls. I plan on running LEDs (between 250w to 350w) I may throw in a 150w HPS, that I have laying around. I'm try to figure out if I should route a vented duct from the main home AC system, into this room or have some fresh air routed from outside or the interior of the house. I'm want to avoid supplementing co2. I'm thinking a 4" inline exhaust fan will do the job. I only have 2 successful grows in a armoire under my belt, so any assistance would be greatly appreciated.