ventilation-helpp!!!

so we're building the first grow box now, we have it light tight, etc.

the step we're on now is venting.

we have the exhaust portion taken care of equip with carbon filter.

now the question is intake:

do i have to have an intake fan blowing air in, or is there going to be enough fresh air coming in through the cracks so to speak?

need an intake... use a PC fan and power it with a cell phone charger

Yorty said:

need an intake... use a PC fan and power it with a cell phone charger

Click to expand...

you use a dc converter and such for that im assuming?

na just use an old cell phone charger or drill charger of some sort. Cut the wire short and split the cord in half. It works well just tie the ends together into the red and black wires from the PC fan and it will power it

anyone else like to chime in?

If heat is not an issue, will passive air be sufficient for a fresh supply of air?

Plants need air. Def want an intake fan. What kind of lights are you using? Get a thermometer/hydrometer and monitor the environment. The hotter it gets, the more air needs to flow. There is a website that has PC growboxes that might give you some ideas. Think its stealthhydro.com or something. or google PC growbox

when i add an intake fan, the hot air at the top of my room gets moved around the rest of the space, making it hotter......

i remove the fan and, through passive intake, the temp goes down.

If your fan is big enough then just make a good size hole towards the bottom away from the intake side of your room

If you do a passive intake it shoud be able to supply 80-90% of the air being pushed by the exhaust.......I didn't see any dimensions for your cabinet, exhaust fan size, or any pertinent info to accurately size an intake.

So I will give you a couple scenarios.......these are for passive air supplies

3" exhaust fan: 2.5-2.75"d passive intake

4" exhaust fan: 3.5"d intake or 2-2" intakes (one on each side provides good air movement through your plants)

hope this helps a little

Btw--if temps become a problem then use your existing exhaust fan and add the next size down for an intake fan........use a little 4" or 6" inline duct booster not a pc fan.......those 4" inline boosters are $20-$25 with a cord attached (thats hydro shop prices-prob less at the hardware store)

-OitW

I checked your grow.....put a couple passive intakes in the sides of that cab......good luck

Thanks for the input guys, i think we will try passive intake and test out our temps, if need be put an intake fan in.

techtoker said:

Plants need air. Def want an intake fan. What kind of lights are you using? Get a thermometer/hydrometer and monitor the environment. The hotter it gets, the more air needs to flow. There is a website that has PC growboxes that might give you some ideas. Think its stealthhydro.com or something. or google PC growbox

Click to expand...

we're using CFLs, you can take a look at it in my sig.
we have a thermo/hydro meter already

&thankss homie

HydroBandits said:

anyone else like to chime in?

If heat is not an issue, will passive air be sufficient for a fresh supply of air?

Click to expand...

not to be anti-social, but you are not getting good advice. yes, you can use a passive intake with a fan on the exhaust. its done all the time. i have a veg room and a flowering room with passive intakes. in fact, in both rooms there is enough air coming in from the cracks that i don't even have a hole cut for incoming air. you only need enough air to replenish co2 and cracks are more than sufficient for that.

Intake fans are unnecessary, air will flow in as fast as the exhaust fan pulls it out if you have an intake slightly larger than the exhaust.
Old in the way, I regard you highly as almost all of your posts I have read confirm everything I have learnt, but I've never heard of having a passive intake smaller than the exhaust, could you explain the reasoning behind this? I'm guessing it's to do with maintaining negative pressure, but wouldn't it place a restriction on the exhaust fan and make it work harder to flow less air?
Hydrobandits, do you have an oscillating fan to circulate air within the grow area? This should keep temps down, not that they should get too high unless you got cfls covering the walls!

Yes we have an oscillating fan and i dont think temps will be too much of a prob.

Hairy Bob said:

Intake fans are unnecessary, air will flow in as fast as the exhaust fan pulls it out if you have an intake slightly larger than the exhaust.
Old in the way, I regard you highly as almost all of your posts I have read confirm everything I have learnt, but I've never heard of having a passive intake smaller than the exhaust, could you explain the reasoning behind this? I'm guessing it's to do with maintaining negative pressure, but wouldn't it place a restriction on the exhaust fan and make it work harder to flow less air?
Hydrobandits, do you have an oscillating fan to circulate air within the grow area? This should keep temps down, not that they should get too high unless you got cfls covering the walls!

Click to expand...

Hairy Bob said:

IOld in the way, I regard you highly as almost all of your posts I have read confirm everything I have learnt, but I've never heard of having a passive intake smaller than the exhaust, could you explain the reasoning behind this? I'm guessing it's to do with maintaining negative pressure, but wouldn't it place a restriction on the exhaust fan and make it work harder to flow less air?

Click to expand...

Yes, the goal in my outline is for maintaining negative pressure which allows for a more effective odor control installation......this will restrict the fan to some extent but its negligable....this scenario also assumes that even the best cabinet is not truly airtight. So flow-through volume should be close to the fan capacity when air is pulled in from other cracks and seams

Old in the Way said:

Yes, the goal in my outline is for maintaining negative pressure which allows for a more effective odor control installation......this will restrict the fan to some extent but its negligable....this scenario also assumes that even the best cabinet is not truly airtight. So flow-through volume should be close to the fan capacity when air is pulled in from other cracks and seams

Click to expand...

You talk a lot of sense, thanks for explaining that to me!