Use ducting. You always wanna have the ducting ran as straight as possible. But, you sometimes have to use a bend or two to stop light entering. The exit side should have a length to release heat to a outside source. The entry side just leave a length of ducting to hang outside the tent/grow room.
And don't use cheap ducting. Cheap ducting is not light proof. Order some online or use the insulated ducting from home depot.