The reason for ventilating a grow room is simple; cannabis plants need fresh air. Therefore, every grow-op requires air exchange. That means cool, fresh air in, and stale, hot air out. Too many growers get ventilation wrong and encounter all kinds of problems later in the grow. Bugs, fungi, and mould love a hot, humid environment with poor airflow. Like it or not, ventilation is essential to cannabis cultivation.

Outdoors, the wind naturally circulates air so cannabis plants can grow healthy and strong. A light breeze strengthens stems and helps plant leaves transpire. Plus, it makes it that much more difficult for creepy crawlies to take up residence in the cannabis garden. If you are growing indoors, you must control airflow and maintain air exchange artificially. Below, we break down ventilation for the ordinary decent home grower.


Most home growers grow weed in grow tents. Modern grow tents are designed to house your ventilation system. All you need to do is put together the right kit. Ideally, you should be considering ventilation as part of your initial grow plan. The lights you choose and the size of your grow space will dictate the type of ventilation system you must utilise.

The four pieces you can’t do without are an intake fan, exhaust fan, ducting, and duct tape. If you want to mount your extractor fan inside the roof of the tent suspended from the poles, use chains or cable ties to secure it in position close to the ventilation hole. That will be in the top corner of the tent, or actually in the roof depending on the model.

Marijuana Growing Room Fan


Make sure your ducting is a matching size for your grow tent. Otherwise, you will need clamps and reducers. Line ducting straight up with the exhaust fan and duct tape it on securely. Then, run more ducting through the hole in the tent, without any bends if possible. You can attach a carbon filter to your extractor fan and suspend it from the roof too. Alternatively, you can put the filter on the floor and sit the fan on top, running ducting vertically through the roof.

Outside ducting will need to connect to a vent or window to exhaust hot air from the grow tent. Inside the grow tent, it is also important to maintain good airflow. Clip-on fans or an oscillating fan is all you need to create a light artificial breeze. Take care they are not too powerful or positioned too close to plants or they could suffer "wind burn".


Air should be exchanged every 1-2 minutes in order to maintain optimal temperatures and humidity. The aim is create negative pressure or suction. So you want to see the walls of the grow tent sucking inward when your ventilation system is up and running.

Your intake fan needs to be positioned near or at ground level to connect to the hole in the bottom corner of the grow tent. Keep that ducting straight and use duct tape to secure in place. Again, the external ducting must connect to a source of fresh air, ideally a vent or window. Later, we explain how to do this discreetly.

Cannabis Extractor Cannabis Growing Room


Micro-growers cultivating a handful of plants or less in a cabinet or wardrobe can keep ventilation very simple. In fact, it can cost you nothing. If your micro-grow is in a spare room, you can open a window a couple of times per day to let some fresh air in. For those using LED, CFL, or lower power HID 250W lighting systems, excess heat is not an issue.

However, this technique is weather dependent and certainly not perfect. Plus, you will need to invest in an alternative odour control system. High humidity can usually be curbed with a dehumidifier and a small oscillating fan. All things considered, if you are just cropping a few fast and furious autos, you can probably get away with it.


It’s advisable to invest in some wicker blinds and secure them in front of the window you plan to use for ventilation. It will cover up what’s going on in the grow room and still let the air in. Then you can start connecting up your ducting. Many will just board up the window by drilling some plasterboard or plywood onto the window frame with a cut-out hole for the ducting to pass through. A quick tip is to make sure to cut out the hole first!

Humidity and Temperature Cannabis Cultivation Dehumidifier


The tried and trusted trio when it comes to eliminating cannabis odours are hands down the intake fan, outtake fan, and carbon filter combination. If you are already investing in fans and ducting, it makes sense. For the grower that wants to be certain that odour is under control, this system is the best.

However, some promising odour-eliminating devices that can dispense neutralising agents round the clock are on the market. That being said, they are currently unproven technologies. There is also plenty of snake oil out there, so do some research and be shrewd.


Greenhouse growers should make sure they have multiple vents that can be opened and closed as required. Most basic, plastic-covered greenhouses have ventilation flaps that can be easily opened and closed manually. Worst case, you can open up the doors a little or remove a window pane or three from glass greenhouses.

Letting the breeze in makes all the difference. A greenhouse can get really humid, especially when it’s packed with lots of leafy cannabis plants transpiring. Indoors or outdoors, as plants mature, they will expel more water vapour and increase the relative humidity in the cannabis garden. Good airflow is essential in every growing area. During late bloom, most greenhouse growers with fat flowers will open up all vents and maybe even DIY a few extra to avoid bud rot.

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