Air flow?

knnthc93

knnthc93

Well-Known Member
Can someone help me out. I have a 20x10 grow space. A intake fan pushing air though two air cooled hoods then out of the room. Do I need another intake for the room? I tried to reseach it but I am not getting any solid info. Thanks
 
zem

zem

Well-Known Member
it is better to use the fan as exhaust instead of intake. 20x10 is big room, do you grow the whole area? if so you will need a strong fan that changes the air about 3x/minute. if you only grow a small part of room, calculate the volume of your grow (LXWXH) multiply by 3 thats the cfm you will neeed for the fan. if you want to place second fan put them both as exhaust, and not 1 exhaust and 1 intake...
 
knnthc93

knnthc93

Well-Known Member
Well right now I am only growing in a small area, I have the intake fan running all the time. I also have a small heater to keep the temps up as well as a fan. I just have a fan sucking air in and it goes through the reflectors and out of the box. Not using an exhaust
 
mrwood

mrwood

Well-Known Member
zem said:
it is better to use the fan as exhaust instead of intake. 20x10 is big room, do you grow the whole area? if so you will need a strong fan that changes the air about 3x/minute. if you only grow a small part of room, calculate the volume of your grow (LXWXH) multiply by 3 thats the cfm you will neeed for the fan. if you want to place second fan put them both as exhaust, and not 1 exhaust and 1 intake...
Click to expand...
In general, I agree with using fans for exhaust and not intake.
However, it sounds like he is going through A/C reflectors then out, so he could be OK. Plus, he has a big room. Depending upon the layout, he made need fan support on the exhaust AND intake to the room.

In addition, I believe the ventilation recommendation is to achieve a room change once every 3-5 mins, not 3x per minute. This factor is routinely express both ways, but there is a big difference. Three room changes a minute (in this big of an area) would be a big fan and some serious negative pressure!

If your temps are OK and the plants are happy, you should be fine. You don't mention any filtration or any problems, so you may just want to continue your research as a paperwork exercise.
 
zem

zem

Well-Known Member
mrwood said:
In general, I agree with using fans for exhaust and not intake.
However, it sounds like he is going through A/C reflectors then out, so he could be OK. Plus, he has a big room. Depending upon the layout, he made need fan support on the exhaust AND intake to the room.

In addition, I believe the ventilation recommendation is to achieve a room change once every 3-5 mins, not 3x per minute. This factor is routinely express both ways, but there is a big difference. Three room changes a minute (in this big of an area) would be a big fan and some serious negative pressure!

If your temps are OK and the plants are happy, you should be fine. You don't mention any filtration or any problems, so you may just want to continue your research as a paperwork exercise.
Click to expand...
I think that if he needs a second fan, he will be better using both as exhaust and create more areas for passive intake. the cfm of the fan needed is typically 3x/minute but that is only for the grow space for example, I have a 4ft high grow table in 8 ft high room and table LxW is 6x3 which makes the volume of grow area 4x6x3=72cf so I would need 72x3= 216 cfm fan which sounds resonable considering that I can grow 1Kw in that space. he doesnt need to calculate the whole room space except if he was to grow it entirely
 
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