CFM math !@#\$

Discussion in 'Growing Marijuana Indoors' started by dark farmer, Jan 24, 2010.

1. I'm trying to find some fans to cover my MASSIVE grow space. The math for finding the CFM i need is freaking me out though. Can someone double check me?

Here are the dimensions of my massive space:

WxHxD
16"x18"x8" (in inches... huge, i know)

So in order to get the cubic feet, i divide all my dimensions by 12 and then multiply them together?

(16/12)x(18/12)x(8/12)
i get ~1.4^3

So at a minimum I only need a fan to cover 1.5CFM? A 60mm fan @12CFM would clear the space 8 times per minute?

What am i missing? Why do i feel like i need more fans?

2. you're right on with the math, mate. you've got such a tiny grow area that it doesn't take much more than a small fan to circulate the air through it.

3. Im planning a build with only around 2cbf and plan on using two 80m fans that will give me almost 60cfm =D

I figure once you add in heat etc.. more is better the less. and with two fans you can atleast set up a breeze within the box allowing fresh air in and hot air out. Plus once you add a filter to help with the smell it could cut your cfm down buy 1/3 - 1/2 of what it should put out.

4. Yeah i'm going to use a 60mm for intake, and a 120mm with a filter for exhaust. I really want to make sure i have more going out than coming in. The only problem is that I don't know how to measure how much the filter will affect the exhaust fan's performance.

But just in case, i'll have the intake blowing over a bottle of Ona gel too.

I just finished up the case, so I'm doing a heat test to see how hot it gets in there with 1 80mm exhaust fan.