You should since your box is enclosed. Fresh air needs to go in too. You could use those 4" - 5" computer 12V case fans. They are very effective, the best mini vent fans really. But you'll need to wire them to a DC converter. I would put two 3" intakes on the bottom, and one 4" exhaust somewhere on top. That would be enough ventilation.
Aliens Reviewed by Aliens on . The start of my 1st box.( critics required) CFL POWERED ive been gathering materials to build this 3x3x3 box for the last few weeks and i finally got building, i got most of it figured out, i snap some quick pics to share with you guys and maybe get some tips and advise. as you can see im missing some light sockets. there will be a total of 12 lights. i will starting 4 plants from clones in here. for veg stage: 8-26w 1600 lumen 6500k total=208w 12800 lumens for flower 8-19w 1200 lumen 2700k 4-26w 1600 lumen 6500k total= 258w 16000 lumens Rating: 5