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Thanks this is going to help a bunch of people.

 

I have a scenario.

 

Lets say i have a 4x4 by7 tent. and i hook up an 8" fan to the top and start sucking air out. All the zippers are closed and the bottom passive vents are open. But the fan is so strong it sucks the tent sides in. Is it okay to run "Negative Pressure" like this? Or does it also suck the air right out the plants?

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Negative pressured is defined as having more air going out than coming in. There’s a long-running debate over whether or not it’s helpful to achieve negative pressure inside a grow tent or grow room. Some indoor gardeners believe it’s helpful for achieving a healthier harvest, while others believe that positive pressure is the key to a large, healthy harvest. So, which side of this argument is correct? Keep reading for a more in-depth look at negative pressure and the effects it has on a typical indoor garden.



THE BASICS OF PRESSURE

Ideally, grow rooms and tents should be sealed up nice and tight to prevent air from leaking through. This is helpful for a number of reasons, one of which is to create a micro-climate where the temperatures are different than the rest of the surrounding area. In most cases, plants and vegetables prefer a warmer, more humid growing environment, so creating a micro-climate similar to this will result in a better harvest.


Of course, sealing off your grow tent also reduces the chance of bacteria, mold, insects and other harmful pests from entering. Although they are too small to see, there are several different types of destructive pests that would be more than willing to wreck havoc on your garden. Keeping it sealed off, however, will greatly reduce the chance of then coming in.



NEGATIVE PRESSURE EFFECTS

Whether it’s positive or negative, pressure is created when the grow room is sealed with a working ventilation system. The intake will pull old air from inside your grow tent and replace it with fresh air; thus, resulting in a pressurized environment.


So, what kind of effect does negative pressure have  a grow room or tent? Typically, it won’t cause any serious issues. The only real problems occur when there’s an excess of negative pressure in an otherwise small grow tent or room. In this case, the pressure may pull the walls in on themselves. It may not immediately tear or destroy them, but over time this excess pressure will keep straining the walls to the point where they collapse.


If you think negative pressure is a problem inside your grow tent, you’ll want to make some changes to fix the issue. Thankfully, turning the pressure in the opposite direction is usually as easy as installing more return vents. Common sense should tell you that a more return vents will equal a greater amount of air being pulled out of your grow tent; thus, creating more positive pressure instead of negative.

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Thanks everyone for the kind words.  

 

We'll have to get into venting for a sealed room as well if co2 is gonna be supplemented

That will be ventilation 102. LOL.   That is a great idea JM, I tried to keep it basic, a overview for someone who knows nothing about it.  I think I will add to this as time allows.  As always great havin ya around bro. 

 

Nice write up offdababa lots of good info!

Thanks moo, turns out I am good for something after all! LOL! 

 

This is very well written AND extremely informative.  Thanks for sharing it

Thanks man, that warms my little heart :D  EK made me do it  :LOL:

 

Thanks this is going to help a bunch of people.

 

I have a scenario.

 

Lets say i have a 4x4 by7 tent. and i hook up an 8" fan to the top and start sucking air out. All the zippers are closed and the bottom passive vents are open. But the fan is so strong it sucks the tent sides in. Is it okay to run "Negative Pressure" like this? Or does it also suck the air right out the plants?

Oh no, it will suck all the air away from the plants and they will die soon! The tent actually becomes a black hole eventually, and if the walls get sucked in too much you risk your whole house being exploded into nothingness and shot across the galaxy!  :bigemo_harabe_net-163:     Seriously though a 8" fan (like a Vortex, ect.)  will do a 10X10 room as our example shows.  :D  At 112 cubic feet your probably exchanging the air in your tent 6 times a minute.  :blink:     It wont hurt anything except make the fan work harder and make your tent look like its on a serious diet.  :LOL:   On a plus side the plants are sure to get awesome air movement, and plenty of CO2. :D    I think its good to run a bit of negative pressure otherwise your tent might explode! Buwhahahahahahaha.... 


Disappointment is caused by unrealistic expectations. / The more I learn about people the more I like my dog. / Whether you think that you can, or that you can't, you are usually right. / Its like everything it depends on everything else. 

 

 

 

 

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I have two vents  to the outside that measure six inches by fifteen inches. The first is about eye level and is  60" above its twin. I'd like to obtain adapters to go from rectangle to round so I can easily create duct work. I feel that ventilation will be my bottle neck and so I want to figure it out first, then Ill decide how much area I can devote to my grow. If anyone would care to offer advice as to how much CPM is can easily and fairly quietly move through vent of this size please?  I seek links for duct adapters as mentioned above , flexible duct work rolls,   and advice of any type to help me stay well ventilated.  Thank you all in advance for your time  

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If I had a 3X3 tent or a bedroom I would use 6" or 8" fans on a speed controller... larger than that I would start thinking about standard rectangle ducting and doing things more HVAC minded.  heres a link for you     https://www.cdicurbs.com/ductcal

 

Duct calculator :D If you dontlike that one, there are others... Its all just math, but were not designing a HVAC system for a hospital here, I think simple is best.


Disappointment is caused by unrealistic expectations. / The more I learn about people the more I like my dog. / Whether you think that you can, or that you can't, you are usually right. / Its like everything it depends on everything else. 

 

 

 

 

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