How do I figure out the CFM rating I need for ventilation?

U

uhhwhat

Well-Known Member
I'm trying to figure out what the minimum cfm rating my venting fan should be. I'm growing in a closet that is about 200 cubic feet and I'm using two 600W lights. The room is soon to be airtight so that I can use CO2 (So I want to keep the temp in the 80's). The lights will be air-cooled with venting that runs from outside the room, through the lights, and back out of the room (about 12-15 ft start to finish). So hopefully the air that's cooling the lights will not move the air inside the room. This makes me think that the grow room volume is irrelevant when determining the proper CFM of ventilation. So, is there a rule of thumb for CFM per watt? Also, am I better off using an intake and exhaust fan with lower CFM ratings, or just an intake with a high CFM rating? The room I'm exhausting into is only 10x14x10 with one window so I will be using a small a/c as well. Thanks for any advice you can offer
 
DubsFan

DubsFan

Well-Known Member
uhhwhat said:
I'm trying to figure out what the minimum cfm rating my venting fan should be. I'm growing in a closet that is about 100 cubic feet and I'm using two 600W lights. The room is soon to be airtight so that I can use CO2 (So I want to keep the temp in the 80's). The lights will be air-cooled with venting that runs from outside the room, through the lights, and back out of the room (about 12-15 ft start to finish). So hopefully the air that's cooling the lights will not move the air inside the room. This makes me think that the grow room volume is irrelevant when determining the proper CFM of ventilation. So, is there a rule of thumb for CFM per watt? Also, am I better off using an intake and exhaust fan with lower CFM ratings, or just an intake with a high CFM rating? The room I'm exhausting into is only 10x14x10 with one window so I will be using a small a/c as well. Thanks for any advice you can offer
Click to expand...
Basically a good solid 6" fan will do you fine. I have a 435cfm fan with 2x1000w and it's plenty. I'm currently running only 15ft of ducting but feel this fan can handle 25ft. My hoods and ducting are 8" but the fan is 6"...I just use a reducer right at the fan. I have a 735cfm 8" fan for my new 3x1000w setup. It's total over kill for three lights in that run.

You basically have two options...6" fan or an 8". The 6" will blow your mind. Anyone who says otherwise doesn't have it set up right.

Make sure the light is at the end of the "run" sucking the line clear. No pushing.
 
U

uhhwhat

Well-Known Member
DubsFan said:
Make sure the light is at the end of the "run" sucking the line clear. No pushing.
Click to expand...
What does this mean exactly? Sorry I'm a little slow :eyesmoke:. I was told to use an intake fan only so that I don't suck the CO2 out of the room.
 
You must log in or register to reply here.
Top