Negative pressure in grow tent

Growroom Design
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I recently went from veg to flower in in 4X4 grow tent. Previous to this, I left the 2 7X15 vents open for airflow, but now that I am in flower I have to close those to prevent light from entering my tent. I replaced the openings with 6’ ducting X 2, but now I have negative pressure in the tent.

Is it better for me to reduce the amount of air the fan is trying to pull out of the tent or should I try to allow more air into the tent? I understand that a little negative pressure is OK but my tent is really pulling in.

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As long as the tent stays cool, I wouldnt stress over it. You could try a fan speed controller. Two six inch intakes and one six inch exhaust should be ideal for airflow.

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And if the tent is crowding the plants sometimes the tents come with extra struts you can set to help hold it out. :tent:

99

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I thought mine was REALLY pulling in too but it held up for the duration, its just the negative pressure itself, good to have to an extent, Does it pull in so much you look alot of room ?

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You need some negative pressure to keep in the smell, just not enough that the stitching bursts or you struggle to open the room door :grin: Are you using a carbon filter? they reduce the flow a fair bit.

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If you have a small sealable cord opening near the bottom or anywhere in the tent, you could possibly rig up an intake with some 2 inch PVC pipe and a small filter.

But otherwise I wouldn’t really worry about the negative air pressure unless if it’s so great that it starts stressing the tents fabric by the poles.

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Negative pressure is your friend for stealth. My tents always look like Kate moss’ cheeks. I know my filtration is doing right then lol

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I will give a dissonant voice on it i guess.

The air flow in the space where the plants are living is more important than we usually think. By default, you must be able to chill one hour in the zone without any discomfort. Under the lights. Simple tricks, no complex science involved. Without any pity with environmental errors, but universal (even for fem factories) in the great results you can get.

We’re all used to read than a negative pressure is a security question, but in fact this is the absence of positive pressure that must be aimed. Not the same thing.

The enemy with negative pressure is the aerodynamics rules involved. With a high pressure, it virtually draw a direct line from the intake to the extra for the airflow, and everything outside this thin line is turbulence. Like the old plane wings, it’s a bunch of “micro-tornado” of old and saturated air that turn on themselves. No need to say than in this conditions, ventilators only create more turbulences and don’t help much for the air exchange around the plants.

In the case than you absolutely want this negative pressure (because short to set an active intake or limited on the optimization for a bunch of reasons), the miracle product is this one :

The yellow tubes are called airsocks, it’s just a textile tube but builded for an optimal distribution of the intake. It’s used for active intake, but with a crazy negative pressure (like walls of the tents “bended”) it work with passive intake.

You place it on the ground (instead on the roof like the photo) on a “circuit” that cover all the perimeter of the space. it will slow down a lot the air exchange (your plants will thank you both in yield, time and disease/pest costs for that) and it will broke enough the thermodynamics effects created by the negative pressure/lights heat. In bonus : it filter your fresh air, it’s cheap, easy to set, “machine-washable” and most of the time (EU) growshops have versions for us.

Optimally and with the “airsock perimeter”, you will cut a (mostly) centered holes for the outake/carbon filter in the roof of the tent (pain in the ass to do on some tents).

But i repeat, if you’re feeling in your crop like on holiday in a Caribbean island in winter with a nice breeze on the whole body : you win the battle. Specially if you’re close to ear the ocean with your imagination and a fat blunt lmao.

best vibes for your plants

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Growth inside the tent…is it at all affected by positive pressure or negative pressure within the tent?

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If you’re not worried about smell so much you want positive pressure from a clean filtered air box. This way you’re not sucking contaminants into your tent. This is how hospital operate to keep rooms safe for people who are immune compromised.

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