more intake or exhaust

im making a grow box right now and i need to know if i need more intake or exaust??
i have 6 pc fans and a clip on fan.. wanted to use 4pc fans near light for exhaust and then 2 pc fans on bottom of box for intake and im ganna use the clip on fan as a intake at plant level.... does that sound good or do in need more exhaust

what kind of light(s) are you using? How big of a box? Hard to say with that info. If you're lights are not that hot, CFLs or T5HOs, then you should be okay. If you have a small box with a 400W HPS then you might need more cooling. I find in my closet (3X5X that one 80cfm fan is fine. The general rule of thumb is get your cubic feet (heightXwidthXheight in feet) and divide by 7.5. That is a general rule of thumb to give you how many CFM you need in a grow area. In a small space with hot lights you would need more. I have no idea how many CFM you get from a computer fan though.

imo id say exhaust is better than intake, but theres nothing like fresh air!

well im using a cabinet from home depot ...
inside i plan on having 2 100w hps bulbs in there.... this is how i want to hook up my fans... im not sure what cfm is but after doing the math u said (30x19x34 =2.5x1.5x2.8=10.5/7.5=1.4) so i only need 1.4 cfm?? well if you can help it would be nice

no one has any input on this>>>??

can anyone tell me weather they think i need more intake or more exhaust.... should i flip the clip on fan as an exhaust??

the only real way you can tell man is by trial and error, it looks like a good plan and setup you got but you never know, i tried using some pc fans and they kind of suck really-there great for cfl grows but hps are too warm i think and they dont move enough air. i would get at least 2 in total-one for in and one for out, then put 1 or 2 pc fans right on the bulbs- it really helps its what brought my temps down from 90 to 78-82. im using a 400w hps in a wardrobe i bought from walmart and its pretty small like 19 inches by 4 feet by 6 feet tall. I have one clip on 6 inch for intake and one for exhaust and one directly blowing on my hps bulb and a 10 in fan on my girls directly and its perfect in there for them. you can check em out if you wnat my grow is kind of the same size as yours https://www.rollitup.org/indoor-growing/216660-3weeks-flower-lemon-pics.html pc man hope i helped a bit.

and to answer the question yes the biggest fan should be for exhaust-you wnat the hot air out- cold air will replace it

yeah i was thinking that i should have the big fan as exhaust it just would be WAY easier to make it an intake... i dont want the fan componets inside the grow room... wanted to just make hole and have it flush with the back but i guess i will fix that ... yeah i didnt think that the pc fans would do that much but i figured they will help some .. more then hurt.... and for my lights i have one of those stiff exhaust for dryer and made 2 holes in it for lights to poke out a lil and the ends of the tube go to the back of my box and ganna have pc fans inside the axhaust tube to draw air out...

I would say set it up and run it for a few days first and keep checking temps. The HPS bulbs can put out a lot of heat so just becareful. While testing it, take readings several times throughout the day to get a good idea if certain times of the day it gets to hot. In such a small area, you might want a little extra cooling just to be on the safe side as your lights will be close to your plants.

thnx both of you i will use the faq that hairy bob gave me and will run it for a while like defcon9 said... thnx

They have 100W HPS lights? That's news to me.

yup you know the big bright lights ppl have on their roof that lights up the whole yard....
Lights at lowes
http://www.lowes.com/lowes/lkn?action=productList&Ne=4294967294&category=Security+Lighting&N=4294904065http://www.lowes.com/lowes/lkn?action=productList&Ne=4294967294&category=Security+Lighting&N=4294904065

There is no 100w hps on that website, at least not using their search function. There is a 100mh, but the hps come in 70w and 150w flavours.