Not my intention to hyjack ur thread AmazingBlazing, but since my room dimensions are almost identical (4x5x6) and i also use a 400w hps, i take this chance to ask if having an extraction fan is really important considering that my growspace is part of a toolshed that doesnt heat up that much and the doors are opened frequently????And i will have a fan inside do move the air (just to simulate wind conditions)..once again sorry to step in AB....