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Tips for ventilating your Grow Room

One of the most important parts of your grow room set up is good ventilation as stifled air can lead to stunted growth, plant disease and pest infestations. Good ventilation is important for your plant’s growth cycle, as it helps to supply CO2 and promotes photosynthesis.  

There are several ways in which you can keep your grow space ventilated, which can make it overwhelming for the beginner grower. So, to put it simply, ventilation is used to bring fresh, clean air into the space, while also removing old, humid air too. The idea is to offer your plants a consistently fresh stream of oxygen and nutrients to help them thrive in the grow space. 

Why is my grow space so hot? 


There are two main reasons why your grow space is overheating – even if you currently have ventilation set up. The first is transpiration. As the temperature rises, and plants take in the nutrients from the soil, they will move it through the stem to the brands, leaves and flowers. The plant will then transpire through these areas. As such, the transpired water evaporates and produces a high level of humidity in the grow tent

Heat from grow light

The second synthetic cause of a hot grow space is the heat emitted from the lighting. As with any small space, lighting can become incredibly hot, and without proper ventilation this can cause the grow space to become far too hot for your plants to thrive.

What do I need to ventilate my grow space? 

Below are the main components you’ll need to ventilate the grow space. It’s recommended that the grow space has completely new air every three minutes. This is known as a ‘three-minute air exchange’. 

Exhaust Fans

To reduce the heat, and to provide your plants with fresh air regularly, you’ll need an exhaust fan.

The benefit of running an exhaust only system is the negative static pressure it creates. This static pressure draws fresh air into the room while also removing the old. 

Carbon Filters

In an exhaust fan, the air only passes through the system once. This means you need to make sure as much odor and organic compound is removed within one hit. To do this this, you should install a carbon filter, and have the air exposed to the filter for as long as possible. 

Carbon filters are particularly important for those growing in a communal or living space. The filters are very dense, making them great for removing and absorbing odors and particles before the air escapes the grow space. 

Oscillating fans

Using additional oscillating fans will help to keep the air moving around the grow space until it can reach the exhaust. These are simple clip-on fans which can be attached strategically around the space. 


Ducting is a tube that connects to the exhaust fan outside the grow tent. If you’re pushing all the humid air out of the space, you also need to remove it from the outer area. Ducting can be used to channel the air out of a nearby window. 

Similarly, depending on where you choose to place your carbon filter, ducting can be used to create a tunnel between the filter and the fan, so that no particles escape during the transition. 

How should I set up my ventilation? 

It’s common knowledge that heat rises. As such, it’s best to set up your exhaust fan at the top of the grow space. The end that will be emitting the air will need to be just outside the grow space. If you’re using an Herbal House grow tent, you can rest assure that the pipework for the structure of the tent is strong enough to hold all your ventilation equipment and lighting. In fact, the ELITE grow tents are the strongest available on the NZ market. 

Next, you’ll need to add the carbon filter to the front of the exhaust fan. This is so the air travels through the filter before it leaves the space. Connecting the two can be done with ducting. 

On the other end of the fan, ducting could be connected to direct the hot air out of the window, or to be dispersed in the outer area of the grow space.

If you are looking to bring new air into the space with a passive system, you will need to create a large intake hole in the bottom corner of the grow tent. Alternatively, you can create several smaller intake holes. 

For an active intake process, you will need two exhaust fans: One to bring in the air, while the other removes it. The removing fan will be placed at the top of the space, while the other at the bottom.

Lastly, to keep the air moving, you can also use oscillating fans that can be clipped onto the tent structure. These are optional but handy for cooling down lighting. 

You will need to take into consideration the heat emitted from lighting if you choose to use something other than LEDs. LEDs are a much better choice for growing spaces as they emit very little heat – making it easier to control the overall temperature of the grow space. 

How to select the correct fan for my grow tent? 

In order to choose the right sized set up for your tent, you first need to measure how much air needs to be moved per minute in cubic feet. This can be done with this simple calculation: 

Length x Width x Height / 3 (Minutes)  

This calculation will give you the amount of air you need to be removing from the space. This number is then matched to the correct filter.


Room size: 10’x12’x8’ (960 cubic feet) 960 cubic feet / 3 minutes = 320CFM 

For this room, you would need a 150-500MM carbon filter with a 150MM inline fan.

However, you should also take into consideration the temperature of the room in which your grow space is in. This is where you’ll be bringing the air in from. If the air coming in is too hot, you’ll need a fan that can cope with extracting it. For hot rooms, add an additional 20% to the CFM. 

In a similar sense, other accessories will also add heat to the room and as such, you’ll need to factor this into the CFM too. For example, when using LEDs, you might need to add another 20%, while a carbon filter might require an additional 60%. 

Understanding ventilation can be incredibly tricky and technical. But also crucial for a successful yield. There are several CFM calculators online that can help make things a little simpler. In terms of considering room temperature and other accessories, this will be a case of trial and error. 

Of course, if you need any more information, you are more than welcome to get in contact