New Grower passive air intake?

[the rover]

Hello afn i hope all is well with everyone!!
Building a grow box 2.5 x 2.5 x 4.5 tall using a mars 300 w led .Was thinking of either a 4 inch inline for exhaust at top of box and I've been reading about passive air intake and that i prob wont need a mechanical fan for intake. Has anyone ever used this method? if so do you use just one hole for air intake or multiple holes? Do you think the 4 inch fan is sufficient for exhaust??
Thank you I've learned much from this forum and it is a great resource !!
thanks 1 guy and derek 420 you guys have been very helpful

 

[Albert Eimstoned]

I just use some dryer ducting with the holes that came in my tent. Passive intake works fine. Also a 4" fan is just fine for that space. Are you gonna put a filter on it?

 

[Trapper]

Okay, here's what I know/think.

Temp control is crucial and more difficult with a passive system...but having an exhaust is only
partially passive. the negative pressure created by an exhaust creates a draw that pulls air in
from any source available in order to equalize.

I have a 2 x 4 x 5 tent with a 4" scrubber/exhaust and just a clip fan mounted in front of one of
the lower side vents so it's sorta "semi-active" intake.

My point being that you'll want to be able to adjust the size of whatever intake port you devise.
People also mount computer fans (drawing into the cab) for "micro-active" intake just to help it
along.

My starter tent is completely passive in that the intake is just an open duct leading to below the tent
and the exhaust is an open duct departing from the top of the tent. As warm air departs the top of
the tent (helped a little by the circulation fan in the tent to get the air headed the right direction)
cool air is drawn in from below. So that creates the "air exchange" Works like a charm but the objective
for that tent is just to get the first 30 days or so of veg done. I imagine more exchange would be
called for in flower.

So I would say, one vent is required but it needs to be adjustable so you can fine adjust for temps.

my 2 cents

 

[the rover]

no filter

 

[the rover]

thanks trapper and albert