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Tutorial Ventilation 101

Fixer

Active member
I forgot to add that the exhaust fan should blow air outside and the door in the room should be closed. Would enough air enter in the room?


Don't worry about make up air unless you live in a new tightly constructed building. You'd know you needed make up air if (assuming the door swings into the room) you shut the door without latching it and it swings open due to the negative air pressure. Most doors are cut 1/2" above the floor and tons of air leaks around them. If negative pressure is a problem you can put a set of vents in a stud bay in the wall and get all of the air flow you need. Having said that I am a fan of closed systems which you'll want if you're going to run CO2. :)
 
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G

grumpyavocado

Don't worry about make up air unless you live in a new tightly constructed building. You'd know you needed make up air if (assuming the door swings into the room) you shut the door without latching it and it swings open due to the negative air pressure. Most doors are cut 1/2 above the floor and tons of air leaks around them. If negative pressure is a problem you can put a set of vents in a stud bay in the wall and get all of the air flow you need. Having said that I a fan of closed systems which you'll want if you're going to run CO2. :)
Thank you for the tip!
 

Erliqin

Active member
a quick question here, for a 4x4x6.6 tent, how much CFM recommended at day and at night, in a cool temps enviorment. it has an AC Infinity 6" duct fan with speed regulator. I use it at settings 2, 3 and 4. Wich are 88, 132 and 176 CFM respectively. depending on the temps. It has a Vivosun 6" filter attached to it inside the tent with negative pressure pushing clean air outside. The light is a sp250 Led wich runs cool, and had to install a secondary light, a HPS 250 for dialing temps and for better yield.

how much CFM at day and night when temps arent an issue? 4x4x6.6 tent. thanks
 

Vanilla Phoenix

Super Lurker
ICMag Donor
a quick question here, for a 4x4x6.6 tent, how much CFM recommended at day and at night, in a cool temps enviorment. it has an AC Infinity 6" duct fan with speed regulator. I use it at settings 2, 3 and 4. Wich are 88, 132 and 176 CFM respectively. depending on the temps. It has a Vivosun 6" filter attached to it inside the tent with negative pressure pushing clean air outside. The light is a sp250 Led wich runs cool, and had to install a secondary light, a HPS 250 for dialing temps and for better yield.

how much CFM at day and night when temps arent an issue? 4x4x6.6 tent. thanks

If you pull 96 cfm thru the tent, you would replace/exchange all of the air 1 time a minute. I would say that would be the minimum I would recommend.

Really though, since your temps are pretty low, I would just use the speed controller on the fan to dial the temps in where you want. I believe for LEDs you want 82F lights on and around 72F lights off. Since you do have a hps in there, you might be able to get away with lower temps because of the infrared coming off the hps. :tiphat:
 

Slim Pickens

Well-known member
Veteran
I've a question regarding ventilation noise.I am venting a 4x4x6 Apollo tent,using a 4" Vortex.My only available vent to the outside is a from a front window facing the street.It can be heard from the front door as well as from the neighbors.I am planning on buying a muffler to reduce the noise.Is there any advantage to buying a 6" muffler?I have been told that increasing the diameter of the exhaust can also help reduce noise,but unsure if there would be any benefit to buying an oversized muffler.

Anyone have experience with this?
 

Smokin Joe

Humpin to please
ICMag Donor
Veteran
A larger exhaust will definitely help reduce air noise and if it is a major concern use a muffler as well.
 

flylowgethigh

Non-growing Lurker
ICMag Donor
I want something to monitor and record the CO2 in the tent, and alarm at high/low levels.

I got 2 of these for $150 shipped: Autopilot APCEM2

s-l300.jpg


They'll at least me know trends in CO2 with activity. Readings of CO2 are within 50 of each other, at 600 PPM. Alarm is OK f you are looking right at the meter
 
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flylowgethigh

Non-growing Lurker
ICMag Donor
The tent environment is quite a challenge, given the requirements for humidity and temperature. I have two possible air replacement streams in the summertime, hot humid outside air, or inside not-so humid cool air from the house. Then there is the room the tent draws air from through the vents, in which room the temp and humidity can be different from the rest of the house. An tent inlet fan can be controlled by temperature inside the tent, and it can draw from inside the cold dry house or the hot humid outside.

Gonna be interesting setting up and getting these tents running in a steady-state condition.

Of course, the first thing I will try is opening the window just enough to get the lung room air close to right with the room door closed, and the passive draw from the exhaust fan of house and outside air, so the tents are good inside. But it may need some more than that...

Anyways, how about an inlet air box? I have dedicated 12" on the side of my tents to an air box. The air box will have a HEPA 3M 1900 filter, be painted glossy so it is cleanable, and may house an inlet air control fan that would work with the main fan.

Post up pics of your filter boxes.

This one not only filters, but it hits the air with "plasma", and has a fan.

https://growershouse.com/agriair-1000-single-14-generator-variable-speed-blower A little spendy IMO.

agriair-1000-with-14-io-generator-filters-and-variable-speed-blower.png


Here's another:

https://hydrobuilder.com/airbox-air-box-jr-hepa-10-intake.html

I think even these, duct taped into a 8" connector pipe, and sealed to a duct openong, would be better than just an open vent.

https://www.amazon.com/LEVOIT-Purif...grow+tent+intake+filter&qid=1610324454&sr=8-7
 
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Im'One

Active member
I have a 9x22 lean to has insulated walls and ceiling. Ceiling is seven foot. It has concrete floor. I have kept a thermometer and humidity monitor in there for a couple of weeks. It runs at 50° and 50% humidity.
I can build one wall with a door and it will keep the grow hidden. There are no Windows but I can cut a hole and install a window banger AC unit that I already have. It never gets extremely cold here.
I just ordered a six inch veeosun fan with humidity and thermal switches, I understand I can only use one or the other. I ordered another fan for six inch ducting and a charcoal inline filter.
I plant to paint the walls, will I also need to cover them with plastic? Would it be best to buy a tent or can I hang a walk of plastic sheeting to shut the back part/grow room from them bring part where I mix nutrients, hang plants, trim etc?
How much area will the six inch fans and filter take care of? I plan on using low heat LED and florescent lighting
 

CannaRed

Cannabinerd
6" fans (depending on make and model) generally move around 400 cubic feet per minute. I'm not sure if that helps, you might be metric. Carbon filters, duct length, and turns or bends in duct all effect the final amount of air removed.

Lots of growers just use white paint, no plastic. Then it can be repainted fresh when needed. Use a mildew resistant paint or additive for extra protection.
You can use plastic for a wall but it needs to be well attached to a frame so it won't suck into the grow area due to negative air pressure from fans. Needs to be light proof plastic so plants hang in dark. They make a panda plastic white on the grow side, black on the back.
Or you could build a wall with studs and Azek pvs panels. It's more expensive, but the pvc is mold resistant, rot resistant, and already bright White.
 

flylowgethigh

Non-growing Lurker
ICMag Donor
That 7' ceiling will limit you to a 7 'tent, which is what it is. When you lose 12" for a flat LED light and fan/filter, then need 9-18" to the tops, and need 6" for drain, and add the height of dirt in the pot, there isn't much left for the plant to grow in.

I bit the bullet and made the decision to vent to outside, and deal with the tent conditions during the grow cycle using the return make-up air that goes into the tent, from the inside the lung room, which is a bedroom in the house. The AC Infinity fans I have will control on temp or humidity, but not both. With no CO2 supplementation, venting the tent is the fan's #1 job, so I think I am going to get the airflow constant, and see what lights on / off do with the temp / Rh.

VPD chart for pot. I think tent pressure affects this too:

https://www.globalgarden.co/knowledge/vapor-pressure-deficit-vpd-explained/

Then there is leaf temp to consider:

https://www.blackdogled.com/lst#Results

Is the washer /dryer in there also? That dryer sure makes some warm moist air!
 
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Im'One

Active member
If I build a wall will
fiberglass panels and white paint designed for wet environments work like a tent? There's no dryer or other appliances
It's a separate building from my home. I am in the country so the odor is not really an issue
I just want to control the humidity and heat. An oil filled electric heater and my windo banger should do that. I can hang a reflective curtain to bounce the light back on the plants. I can vent to the outside and use the fan to provide fresh air.
 

flylowgethigh

Non-growing Lurker
ICMag Donor
My tents are up, fans running, lights burning. I have a lot of work to do to be able to control the temp down while maintaining VPD. Those LEDs do put out heat, and one tent opening isn't enough to vent the heat from the LED down. Plus, drawing more dry air in the tent kills the humidity. For now I am using a couple wet tee shirts hanging up as moisture adders. They take the 21% ambient air to 50% @70*F

Edit. The height of the LED light is the key. I have small plants that don't absorb much of the energy. Lowering the lights allowed me to reduce the power and still get the umoles I wanted, while keeping the heat down. The tee shirts are working, but need to be wet down too often.
 
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ozzieAI

Well-known member
Veteran
what's the best way to vent an airconditioned room without losing all the cool dry air? i live in the tropics so keeping the room cool and dry is a must to stop mould. do i vent slow and steady to allow the aircon to keep up or is there another way to achieve air exchange?
 

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