Grow Tent Ventilation Kit Conclusive Guide

A great starting point for grow room ventilation kits.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 Specifications

However 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′
Hydrofarm Active Air Inline Blower Fan

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.

A blower fan is a completely crucial part of any grow tent ventilation kit.

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

I think one of the most genius places to route your exhaust is out the laundry ducts. They are already there, and all the neighbours fully expect warm air to come out of that duct in particular. You just need an Y-style adapter which combines both the exhaust of your tent, and the exhaust of the dryer into one tube.  This same idea works with much of the HVAC system of your home, although you will need to adjust the pressure of the blower depending on the diameter and length of this whole system. The numbers I gave in the chart are only for pushing air through the tent, so if your ducting is intense, account for that.
 

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

I said that exhausting out a residential window is very unwanted, but there is one way you can get away with it. There are those adjustable duct inserts which your window slides onto, holding it in place. These products are usually sold with an AC unit, but can be purchased separately. They are great because they turn the reflective vent tube into a nice plastic sheathing which interfaces with your window.
 

Into or Out of The Attic

The last notable place would be the attic. You can opt to just exhaust right in to the attic, and it probably won’t be much of an issue. However, there are also many places you can put the tube which will actually vent right outside from the attic. Take a look around, you’ll find a bunch of them. This is a nice solution if the attic entrance is close, or if you just can’t do any of the other ones.
 

Circulating Air With Fans

Keeping the blower fan going is one thing, that makes sure fresh air comes in to the tent, but that air needs to be circulated the right way once it’s inside. Plants don’t live up to their full potential unless there is a decent flow of air around the leaves. This helps with respiration, the exchange of atmospheric gasses.
 
I had this problem at first, which made me realise just how important ventilation was. Without good air flow between the leaves, your nugs will fail to dense up! Therefore, it’s important to put a few nice oscillating fans below the plants, and also at leaf level, to keep proper circulation flowing all around the plant.
 
I personally have a fan at the very bottom, blowing into the trays to evaporate any excess water which may pool up from feeding. This also keeps air gently circulating below the canopy, which is really important. Not only does it aid respiration, but it also prevents moldiness and other kinds of fungal and bacterial buildup – in some instances. Having clean air constantly circulating is definitely a very important thing.
 

Wind Burn From Fans

A major note of caution – don’t keep the fans blowing on one spot constantly. For the fans around the canopy area, make sure they are either always oscillating, or not directly pointed at the leaves.  As everything in life, too much of a good thing becomes a bad thing. Keeping the fan blowing at one spot of the canopy will essentially give the leaves wind burn. They will curl up into this taco shape, with the edges folded in and curled up.
 
It’s pretty hard to have an oscillating fan in the tent though. As the sides get sucked in from negative pressure, wall-mounted fans will fail to oscillate properly. This is why you need either a separate mounting point further from the wall, or just have indirect air flow. I like the latter option personally. Placing the fan above the canopy, so it’s circulating the air right above the leaves is a good way to go. This way, you don’t have to make the fan oscillate, and the leaves will not get wind burned.
 
So, to cap this section up, air flow inside the tent is very important. However, too constant and direct air flow is a hard no. Definitely avoid this situation completely be either making the fan oscillate, or pointing the fans away from the leaves themselves, like right above the canopy for example.
Curled and clawed appearance from using a faulty grow tent ventilation kit.

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

This is a great option for those of you living in hot climates, looking for a better cooling solution than AC. As we all know, AC is very expensive, and also quite loud. An air hood is a contraption which encloses the bulb in a complete enclosure, and pushes air across the bulb to cool it. The cool thing is, that this air can be exhausted right out the grow room directly through a tube, without needing to be mixed in with the environment at all.
 
This will drastically decrease the amount of heat coming off the bulb, thus reducing the amount you need to cool the tent. This is a fantastic solution, especially if you have multiple HIDs, because that can get very hot very quick. You can even chain the vented hoods together, to share the ventilation environment. Although, it is not recommended to chain more than two HIDs together in a cooling sequence, as the air gets hotter and hotter through every pass. Eventually, it will get to the point of being so hot that it’s not cooling the bulb, it’s just making things worse.
Fantastic grow tent ventilation kit featuring a cooled lighting hood.
Cooled air hood could be a key part of your grow tent ventilation kit.

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.

Blowing air into the air hood is the messier option, as it’s going to result in some of the air being blown out of the little crevices of the hood. However, this will prevent dust from being drawn in, thus keeping the bulb, and the enclosure in general, cleaner. I think that’s probably the best thing about blowing air into the hood.
 
On the other hand, sucking air out of the hood has the advantage that you can actually filter the air coming in from the other side through a carbon filter. This will allow you to just use one blower fan to accomplish all the ventilation in your grow tent, air hood and all. This configuration would go carbon filter -> air hood -> blower fan (sucking) -> ducting.
Hydro Crunch Cooling Tube for a great grow tent ventilation kit.
For a basic grow tent ventilation kit, consider using a growing tube.
Hydro Crunch 6" Cooling Reflector / Tube

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. 

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