New grower here! Need help understanding my ventilation system.

mikaroni

mikaroni

Active Member
OK, so I have my grow tent and LED light setup. Now I am trying to piece together all I need for my ventilation setup, and I am a bit confused. All of the videos I see online show this:
<-ducting <-inline fan (used as exhaust fan) <-ducting <-carbon filter. And that's all they use.
So am I supposed to have a second inline fan to bring in air from outside the tent like this?
space between carbon filter <- inline fan <- ducting? (also at the top of tent right across from the carbon filter?)

All the videos I see just use the rectangle cutouts at the bottom of the tent for air flow into the tent, but I am certain that would be considered quite the light leak that I hear is a big no-no.

OR... can I just buy another of the exact inline fan I have, and set it on the floor with ducting to shoot fresh air in?
I bought this inline fan for my carbon filter: https://www.amazon.com/gp/product/B074XBXFPD/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
 
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Mr_X

Mr_X

Well-Known Member
i use a carbon filter and 2 small portable fans for my grow tent. one fan blowing on top of the canopy and the other blowing under the canopy pointing towards the soil and under the leaves because thats where aphids like to lay their eggs (under leaves and in the soil)FAN.jpg
 
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Dank Bongula

Dank Bongula

Well-Known Member
You do not need a fan on the bottom to pull air in. This is called passive intake. Basically as the exhaust pushes air out from the top, air is naturally pulled in from the bottom flap because of the pressure change.

If you research passive or active intake, you can find different setups that may or may not work for you, some use fans, some do not, others use longer intake tubes and show you how to set these up to avoid light leak if your tent happens to be in a room where you cannot isolate the light to your liking. I was worried about light leak as well so I put my grow tent in a spare room that is easy to keep dark

I myself have a 2.5ft x 2.5ft x 5ft tent and am growing three inside. My bottom flap (passive intake), facing the wall, but not against it is open. I set the passive intake away from any direct light and opposite of my exhaust in the top. I have a fan in the top to use as exhaust if/when I need it. I do not use a carbon filter setup. Inside I have a small fan for air circulation. My humidity and temps stay pretty constant so I do not use the exhaust fan right now...if I did, my humidity would drop into single digits and then I would need to add a humidifier. I don't want to.

You environment can be somewhat controlled in your home, and then even further controlled by the tent, but some things are just unavoidable...you may find your setup and environment may require more or less ventilation to control temp and humidity and you may also need a humidifier or dehumidifier. There is no one way to set up your tent, but you can tailor it for your needs to an extent.
 
mikaroni

mikaroni

Active Member
Dank Bongula said:
You do not need a fan on the bottom to pull air in. This is called passive intake. Basically as the exhaust pushes air out from the top, air is naturally pulled in from the bottom flap because of the pressure change.

If you research passive or active intake, you can find different setups that may or may not work for you, some use fans, some do not, others use longer intake tubes and show you how to set these up to avoid light leak if your tent happens to be in a room where you cannot isolate the light to your liking. I was worried about light leak as well so I put my grow tent in a spare room that is easy to keep dark

I myself have a 2.5ft x 2.5ft x 5ft tent and am growing three inside. My bottom flap (passive intake), facing the wall, but not against it is open. I set the passive intake away from any direct light and opposite of my exhaust in the top. I have a fan in the top to use as exhaust if/when I need it. I do not use a carbon filter setup. Inside I have a small fan for air circulation. My humidity and temps stay pretty constant so I do not use the exhaust fan right now...if I did, my humidity would drop into single digits and then I would need to add a humidifier. I don't want to.

You environment can be somewhat controlled in your home, and then even further controlled by the tent, but some things are just unavoidable...you may find your setup and environment may require more or less ventilation to control temp and humidity and you may also need a humidifier or dehumidifier. There is no one way to set up your tent, but you can tailor it for your needs to an extent.
Click to expand...
I have a window in the room. But I also thought that I have to have the window open to let fresh air in and to shoot the exhaust out of it as well, no? I was thinking of keeping the blinds closed, and having a thin black sheet over that too so air can get in still. Light will get in this way still though. I'm confused about the whole window thing as well.
 
MickeyFins

MickeyFins

Well-Known Member
That's a nice inline you're buying. You don't need a second. As Dank mentioned you can open a flap near a wall for air intake if you're concerned about light leakage. Or if you want to get fancy i suppose you could put a cardboard box or something by the open flap with a couple holes.
 
Dank Bongula

Dank Bongula

Well-Known Member
No, you don't have to do that, but you can if you want and if it works for your trees. Depending on how many people are in your house, the co2 could be higher inside and that only helps. Plus if the window is open, you are subject to fluctuations in temp and humidity as well as an open door to pests.

Sometimes recycling the air inside your grow room does not work to improve the conditions inside your tent because your room is closed...in that case you can use ducting and fans to pull air from another room or outside and use ducting and fans to direct air to another room or outside.

People also put screens over their ducting to avoid pests from using the ducts as an entry way to the tent...so if an open window in your environment helps you, then you can definitely use fans and ducts and screens to push and pull air out the window.

There is no one way to do this...we all live in differing environments and have differing methods to control that. You just need to find a system that works for you.

Set up your light, your tent, your circulation fan(s) and your exhaust fan and open a panel at the bottom of your tent. Drop your hygrometer and thermometer in your tent. Turn everything on and in an hour check your readouts...is it within range for what you need to grow? Then make adjustments from there.
 
Dank Bongula

Dank Bongula

Well-Known Member
MickeyFins said:
That's a nice inline you're buying. You don't need a second. As Dank mentioned you can open a flap near a wall for air intake if you're concerned about light leakage. Or if you want to get fancy i suppose you could put a cardboard box or something by the open flap with a couple holes.
Click to expand...
Definitely! The cardboard box trick is an excellent idea I had forgotten about.
 
mikaroni

mikaroni

Active Member
Hmm, interesting. I don't really have a way to direct air to/from other rooms other than the AC vent in the ceiling. So, do you think I do need the window cracked open a bit? I mean, there is a screen on my window, so I don't think bugs coming in would be much issue. The cardboard box that mickeyfins suggested might be a neat idea.

Another question I have now, is would only one of the little flaps being open work for air to come in, or should I open both sides? Thanks for the answers so far guys! :D
Oh, I should mention too, that I am thinking of buying a CO2 tank for the room. Not sure if that changes anything though in regards to air requirements.
 
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J

JimmyJackCorn

Well-Known Member
I used a two-meter length of ducting on my passive intake to cut down on light leak.

As an aside, it helped me direct my intake to a part of my shop with cooler air (I have a 600W HPS in a 4x4).
 
Dank Bongula

Dank Bongula

Well-Known Member
You would have a way to direct air to other rooms if you buy ducting and another fan. I'm not saying you need to, just that it is an option that some people do.

I can't tell you if you need your window open or not...I don't know the temps of your region.

Generally speaking you want to keep your tent between 70-85°F and 40-75% humidity depending on whatever stage your plant is in.

Intake fans, exhaust fans, lights, circ fans, humidifiers, dehumidifiers, and ducting all play a part in controlling this environment inside your tent. Start with what you have and see where you are with everything on in your tent.
 
mikaroni

mikaroni

Active Member
KK, will do! But one thing is for sure, I need to move the exhaust air out of the room, correct? out a window or out of the room. I assume it would be pointless to just have it shoot into the room itself.
Can the passive intake be on the same side as the exhaust fan pointing out?
 
Dank Bongula

Dank Bongula

Well-Known Member
mikaroni said:
KK, will do! But one thing is for sure, I need to move the exhaust air out of the room, correct? out a window or out of the room. I assume it would be pointless to just have it shoot into the room itself.
Can the passive intake be on the same side as the exhaust fan pointing out?
Click to expand...
That is not for sure...you need to set all your shit up and turn it on and see what happens.

If you can control your temps and humidity with a couple circulation fans and no exhaust or no intake fan, then that is fine too...if you have an exhaust fan on and your room just keeps getting hotter or won't cool down then yeah, makes sense to exhaust somewhere else - shoot it out the window or into the hallway or just leave your room door open if that works. If you have your exhaust fan on and your humidity is in single digits, then you you may need a smaller one or one that you can hook up a thermostat or speed controller to control how much air is being pulled and for how long...and maybe a humidifier as well.

Shoot for having your intake opposite of your exhaust port. Helps eliminate short circuiting of airflow in your tent.
 
G

GKM420

Active Member
I ended up buying a second inline fan for active air intake because I was having a big problem controlling heat and humidity levels. Using a second inline fan helped a lot with keeping my heat levels down. I was able to drop the ambient tent temperature by about 2-3 degrees Celsius. Doesn't sound like a lot but it brought my temperatures from 'too hot' to 'still a bit too hot but acceptable.'

My tent is also in a room that's not ideal for growing, so my case might be an outlier. My tent is stuffed into a corner of a room, and I suspect the air is a bit stagnant back there. Having the active intake heIps combat that problem a bit. I understand for most folks the passive intake is all that's needed.
 
Rurumo

Rurumo

Well-Known Member
It depends on the temperature of the room your tent is in. Your tent will always be hotter than the room it's in, but the temperature differential is what determines whether your tent will be cool enough even with adequate ventilation. I vent from the tent into the same room during winter, but I vent out the window during the summer. I have a strong fan so to have enough passive ventilation, I use the 3 built in mesh vents at the bottom of my tent, along with two 8" duct holes-I put a 4 ft lenght of ducting into those holes and turn them 90 degrees to help keep out light, and then put pantyhose on the end to keep out dust/hair. I also put a layer of pantyhose over the mesh vents. You are right about light leaks, but I find as long as light isn't shining directly on the vent, it won't create a major leak, so I keep a large piece of cardboard leaning over each vent-tapped in place.-I also block the side openings and cut a hold in the bottom of the cardboard to let in air-Some people make boxes to do the same thing-you create a barrier that blocks the light but that the air can travel around. Idk what kind of cfm you're working with, but you might not need that much passive ventilation, or you can make it easier on yourself and go with an intake fan.
 
mikaroni

mikaroni

Active Member
Dank Bongula said:
That is not for sure...you need to set all your shit up and turn it on and see what happens.

If you can control your temps and humidity with a couple circulation fans and no exhaust or no intake fan, then that is fine too...if you have an exhaust fan on and your room just keeps getting hotter or won't cool down then yeah, makes sense to exhaust somewhere else - shoot it out the window or into the hallway or just leave your room door open if that works. If you have your exhaust fan on and your humidity is in single digits, then you you may need a smaller one or one that you can hook up a thermostat or speed controller to control how much air is being pulled and for how long...and maybe a humidifier as well.

Shoot for having your intake opposite of your exhaust port. Helps eliminate short circuiting of airflow in your tent.
Click to expand...
Awesome, thanks! I installed the intake fan (the ducting won't come in for a day or two still). The morning temp in my tent with light on and intake fan and oscillating fan going is 79 degrees with humidity of 21-28% with a humidifier running. Yesterday afternoon it got to 95 degrees and 16% humidity with no intake fan installed. I'll mess around with it more. I have 2 tester seedlings in there right now. Again, thanks for the help guys!
 
Dank Bongula

Dank Bongula

Well-Known Member
mikaroni said:
Awesome, thanks! I installed the intake fan (the ducting won't come in for a day or two still). The morning temp in my tent with light on and intake fan and oscillating fan going is 79 degrees with humidity of 21-28% with a humidifier running. Yesterday afternoon it got to 95 degrees and 16% humidity with no intake fan installed. I'll mess around with it more. I have 2 tester seedlings in there right now. Again, thanks for the help guys!
Click to expand...
You can also mess around with the location of your humidifier...if it does not have any status lights/LEDs on it, or they can be covered without fucking with the controls, then you can place it inside your tent for the life of your grow...alternatively, you can place it outside the tent, inside the room and see if that helps, giving you more room inside your tent. I have seen people run from seedling to flower on 30% rH with lots of airflow and it worked for them.

I myself am in a very dry environment so my supplemental humidity comes from a humidifier in my room and a few full cups of water inside...I also have a contraption inside the tent that holds a clean damp cloth near the passive intake if I need to bring it up quickly.

You're on the right track...you'll get it figured out as you go and learn your own tweaks for your own environment.
 
MickeyFins

MickeyFins

Well-Known Member
mikaroni said:
KK, will do! But one thing is for sure, I need to move the exhaust air out of the room, correct? out a window or out of the room. I assume it would be pointless to just have it shoot into the room itself.
Can the passive intake be on the same side as the exhaust fan pointing out?
Click to expand...
I just vent in the room myself. Not an issue it’s just O2. It’s not pointless. That inline you’re getting has a setting and sensor to adjust fan based on temp and humidity.
 
MickeyFins

MickeyFins

Well-Known Member
Dank Bongula said:
You can also mess around with the location of your humidifier...if it does not have any status lights/LEDs on it, or they can be covered without fucking with the controls, then you can place it inside your tent for the life of your grow...alternatively, you can place it outside the tent, inside the room and see if that helps, giving you more room inside your tent. I have seen people run from seedling to flower on 30% rH with lots of airflow and it worked for them.

I myself am in a very dry environment so my supplemental humidity comes from a humidifier in my room and a few full cups of water inside...I also have a contraption inside the tent that holds a clean damp cloth near the passive intake if I need to bring it up quickly.

You're on the right track...you'll get it figured out as you go and learn your own tweaks for your own environment.
Click to expand...
I agree with Dank with that AC inline you can set RH boundaries. For my small little 2x2 tent i use a cheap little 500ml mist humidifier on a 3 sec on/off pulse that i refill once per day because it doesn't take much space and is super cheap - for a bigger setup you may need a bigger humidifier. Or as Dank mentioned adding wetted towels, open water, etc. in the tent - will help with the humidity. I shoot to keep it 45-55% but honestly it's fallen lower without much harm.
 
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