Quote:
Originally Posted by bubonicplague
is two 120 mm computer fans at the top of it with passive intake at the bottom going to be enough ventilation?
|
Hey, well that doesn't sound like enough ventilation to me, however I'm no expert. I just built a box of my own and its close to your size, mainly taller. I started with a 5" duct style inline fan and it didn't do very well. I had to upgrade to a bigger vortex type fan, too much now.

I recommend only 1 good outgoing fan at top with passive intake at bottom. If you seal your box somewhat you'll get negative pressure and air will flow through nice. If you're considering adding a carbon filter later make sure you get a good fan. With that first inline I had no air would move through it once I added the carbon filter, with the new fan it will hold paper to the filter. The first fan was rated at 250cfm or so and the second around 165cfm, so those numbers don't mean a whole lot, its the design of the fan that matters. Computer type fans are useless for sucking air, just blow it around a bit.
Your lightening doesn't sound good enough for 3 plants, I think you would need more once they got bigger, again I've never actually grown yet, just passing on what I've been reading. I also don't think you'll have room for 3 plants, unless you squish them together. My plan was to have 3 in my box, I just transplanted into 2 gallon pots and I can hardly get 3 in there if I wanted to, lucky only 2 sprouted. 3 would fit if I staggered them I suppose.
Well hope this helps a bit, here's a link to my grow box, it might give you some ideas, you can see both fan type on there.
http://forum.grasscity.com/grow-room...ox-design.html
Good luck and happy growing!!