Quote Originally Posted by headshake
what's up everybody? i've been busy for the past week or so and haven't had time to post. i've added a digital thermometer/hydrometer, two new light fixtures, new bulbs (3 6500K daylight and 1 2700K soft white), 2 120MM fans, and one 80MM fan. the 2 120MM fans are pc case fans and are rated at 72CFM. i'm not sure about the 80MM fan, it is for your car.
To determine how much cooling you need.. take the cubic footage of your area and divide by 5 minutes.

so if you're growing in a 3x3x3 area that would be 27cu.ft.. to evacuate that in 5 minutes you would need a fan the blew about 5.5CFM. However I've never been a fan of the 5 minute rule. I like to use 1 minute for reference or faster if I can help it.

So in this case you would need 27CFM of unrestricted air flow. Computer fans do not have high velocity such as inline fans or squirrel cage fans, therefore I would recommend more powerful fans which it appears you have covered.

Unless you're running CO2, you cannot have too much exhaust.


i currently have them arranged with the two 120MM fans on the sides (where the handles are) and the 80MM on top (blow-hole style). i have the two 120MM fans blowing out and the top one blowing in. i've tried them in the reverse as well.
You want them all set to exhaust. You want to create several passive intakes very low in the box. Your passive intakes must be, at minimum, equal in size and number to the number of exhausts/exhaust holes you have. Furthermore you want to try, TRY, to have all your exhausts setup to the top of the grow area in a blow hole fashion.

This will draw cool air in from the bottom of your grow box.. allow it to travel upward with the rising hot air and back out the box.

The reason you want passive intake is that because unless the intake and exhaust are running equal amount of pressure (flowing the same rate of CFM) then all you're doing by putting an active system in is creating a restriction and turbulent air flow.. basically hot air that just swirls around, inside your grow environment.

So in summary set all your fans to exhaust, put them at the top of your grow box, create as many passive intakes low in the box as you have exhausts...

I have more advice I can give, but give that a go first.
daihashi Reviewed by daihashi on . not your ordinary first grow what's good everybody. i've recently started a grow with some bag seed. it's just some average 'corn...not sure about the strain etc. i'm doing this on no budget and basically just for fun. i say again, i'm trying to spend the least money possible! there is several reasons for this... 1. i don't have a bunch of money to blow on this, again this is just for fun. 2. let's just say someone i share a residence with someone who wouldn't like a visit from the field officer Rating: 5