Proper Ventilation help plz

Getting ready for my 400w switchable coming this week any inexpensive ideas on getting some ventilation. I already have a fan blowing cross my plants.View attachment 1546669View attachment 1546670

You'll need an active outtake and a passive intake. With a 400watt you can probably get away with a 4" inline fan and ducting--depending on the size of the enclosure. Most guys would probably tell you to step up to a 6" and tune it down.

Just blowing air over the plants isn't going to do much for you. You need to be moving fresh air into the enclosure, and moving warm air out. One inexpensive solution I see guys do is to outtake with computer fans, but I don't think that'll do much with a 400 watt light in there.