Lol, sure, ur "Friend" is growing it..
Well, tell ur friend that he should vent his lights into his roof, or discreetly outside the house thru the roof via some nice lightweight ducting. No carbon filter is required since the air is not mixing in the grow room. This is hooked up to the same timer as the lights.
This should control heat in the grow room, so just a simple thermostat to hook upto his outake vent with a carbon filter that will kick in when the temp gets too high. Vent anywhere that is away from ur intake.