Of the core things needed to operate a grow tent, ventilation is not one that most beginners think to stress. It seems to be a pretty straight forward task, but actually getting the perfect air flow is an art. Also, the difference between good and perfect really does make quite a big difference. It’s advisable to spend some time planning out your ventilation system, getting a really good grow tent ventilation kit, to get the results you need.
Without a proper grow tent ventilation kit, the air around the plants will not get circulated, air will not be filtered, warmth and excess humidity won’t be exhausted. All these things will eventually build up to create a really sub-optimal conditions for marijuana, but perfect conditions for mold and little bugs.
I’m going to go over some guidelines that I’ve found to be very useful in determining the right ventilation system. There are so many different cool things you can do with ventilation, to get that perfect atmosphere.
It’s important to keep everything stealth and proper. Reducing noise and eliminating smell are very important if you want to go stealth, so I’ll talk about that. Negative pressure plays an important role in getting rid of smell, so make sure you read that section.
Blower Fan SpecificationsHowever you configure the ducting, all the air movement is powered by a blower fan. A blower fan moves a large volume of air in one specified direction. There are many different brands of blower fan, check out our blower fan buying guide if you need a few suggestions. Some of them have horrible bearings which wear out quickly and produce a loud noise, especially over time. These fans are measured in CFM, or cubic feet per minute. That’s now much air they move. A 100 CFM air blower moves 100 cubic feet per minute of air. In my 4×4 ft tent, I have a 170 CFM air blower, which does quite well. However, it is recommended that for a 4×4 tent, you have at least 200 – 300 CFM of air movement, so maybe I should upgrade. If you want a good rule of thumb, here is a chart:
|CFM||Grow Space (ft)||Grow Space (m)|
|100||2′ x 2′ x 5′||.5m x .5m x 1.5m|
|150||3′ x 3′ x 6′||.8m x .8m x 2m|
|200-300||4′ x 4′ x 6′||1m x 1m x 2m|
|300-500||6′ x 6′ x 6′|
This thing is a savage inline blower fan, the cornerstone of my grow tent ventilation kit. It’s what I’ve been using for just around three years now, and it’s still going hard. The noise is moderate, but the durability and performance is absolutely insane. I only have the 4″ version for my tent without the speed controller, and even that is great. I would get the 6″ version nowadays though, for additional suction. Sometimes it gets too hot in the summer, so I would recommend that. Not much else beats this on Amazon – this is a really solid product, and the reviews speak for themselves.
Keeping Negative Pressure
One important thing that I’d like to mention is keeping an environment of negative air pressure. This helps keep the smells out of the room, forcing all of it out he ducting while fresh air gets sucked in. Positive pressure on the other hand blows air out the seams of the tent, which is not good at all. If the fabric of your tent doesn’t get sucked in under the negative pressure shortly after you zip it up, you need more CFM.
Smells are just one of the reason for negative pressure though. A negative pressure will give you flexibility in the future to acquire air from a variety of external places. For example, if you have a constant suction of air from the tent, you can daisy chain tents together with tubing, essentially connecting their ventilation systems. You could draw the hose out your window if need be, and draw in some fresh air. Also, negative pressure means you are also getting strong exhaust, which you can also direct wherever you please. I’ve heard of people exhausting inside their homes during winter, no use wasting all that nice energy, am I right?
Where to Exhaust
For most of us, exhausting inside is not going to do the trick. Also, I wouldn’t recommend it anyways, it was more of a joke. It’s important for the air to keep circulating in your grow room, so I usually prefer to run my exhaust outdoors. The only problem with that is legality. If you don’t live in a country where growing is legal, a big loud exhaust tube is going to be a dead giveaway. For this reason, you should consider some clever alternatives to running a reflective tube out your window.
Out the Dryer/Range Hood/Bathroom Vent Ducts
The Cold Room Ducts
I grow in the cold room, it’s dope. Mine is right underneath the front porch stairs, just a nice bunker of concrete. Practically all cold rooms offer some kind of ventilation tubing pre-configured, to keep the mold and mildew at bay. You can re-purpose these fine ducts, and also have a fantastic place to put the tent itself. The outside of these ducts are usually angled downward, and the noise is not too apparent coming out, it’s a very stealthy approach.
Out a Window, AC Style
Into or Out of The Attic
Circulating Air With Fans
Wind Burn From Fans
The above images are good examples of wind burned marijuana leaves. They can gave a clawed up or taco shaped appearance. Sometimes, people can confuse this for nitrogen toxicity – which also manifests itself with the claw. If you have a constant flow of air on the plant and it’s giving a claw like appearance, try scaling it back a little bit and see how it affects the leaves.
If the wind burn persists, then it can eventually get a really crispy and burned up appearance. This is from having all the water sucked out of it all day long, it’s just not good for any living organism. You can see tinges of brown around the outside of some of the leaves in the picture on the left.
Cooling HID Bulbs With Air Hoods
If you’re chaining together multiple air hoods, or if you just want really good air flow, you can have a second blower fan dedicated strictly for the air hood. Some people like to put the blower fan before the light bulb, thus blowing air over it, while others like to configure it after the bulb, thus sucking air over it. They both have their ups and downs, but I prefer having the blower fan suck air into the enclosure, and then blowing it into a tube, to be eventually exhausted. You can hook this tube up to the main air outlet which is already being pumped out of your tent, to make the system integrated.
These are two of the most fantastic cooling solutions I have seen online. These two choices give you a great flexibility. Which one you buy will depend on the kind of setup you would like to make, and how much you would like to expand the setup in the future.
The top reflector is standard practice – it’s the one I would get. They are easy to upgrade, tried true and proven. They do cost a little bit more, but I wager that the ability to expand is worth it, but that’s up to you.
The bottom tube reflector is great for somebody with a smaller bulb who would like to save a little bit of money. It’s also a more sleek and space efficient solution, if that matters to you.
Concluding Grow Tent Ventilation Kit Guide
I hope you see how important ventilation can be, especially in a grow tent. There are some really cool setups you can accomplish with a good grow tent ventilation kit, so it’s nice to look around and make everything perfect. Even once you’ve bought the equipment, there are so many ways to set it up, it’s always good to experiment.
Hopefully with my chart and advice, you can buy all the right gear the first time around. The only way to really do this is to understand what you need and how to make this happen depending on your setting. Good luck with your grow tent ventilation adventures, and thanks for reading.