How to Increase Humidity In Grow Tent (8 Tricks to Get Results Today)

How to Increase Humidity in Grow Tent

(Learn Over 8 Relative Humidity Hacks to Increase RH Today)

Understanding how to increase humidity in a grow tent is essential for healthy cannabis plant growth.

Our team of cannabis experts has tested grow tents under various conditions and in this article, we will reveal to you all the hacks and tricks that helped us to increase humidity in grow tent and grow rooms.

If you are suffering from low humidity cannabis you may notice the leaves are very dry, curling, or nutrient burn can occur. Luckily, controlling humidity in grow tent setups isn’t too hard. Keep reading below for tips and tricks you can do today to increase humidity in grow room or tent.

Quick-Tip: This article is broken into three sections: learning the basics of RH, how to raise RH in grow tent (easy), and advanced methods to increasing RH. Click below to skip to the article section that is most helpful to you.

Start Here (If You Are New)

how to increase humidity in grow room

Relative Humidity (Beginners Guide)

Beginner Friendly

how to raise humidity in grow tent

How To
Raise RH in Grow Tent (Free/Budget Friendly)

Advanced Methods

grow tent humidity

Advanced Methods
To Increase RH (Cost Varies)

A Quick Guide to the Importance of Humidity in a Grow Tent

Getting the optimal relative humidity in your grow tent or grow room will:

  • Help Plants absorb nutrients through the leaves
  • Prevent Drying and Burning of cannabis plant leaves.
  • Prevent overworking of nutrient pull through roots.
  • Humidity is different during the young and adult plant stages.

We tested various grow tents under practical growing conditions. We tested a 4 X 4 grow tent in a standard size room. We also ran a 4 X 8 grow tent in a larger room, and finally tested a 10 X 10 in a garage with supported A/C split support. We ran the strains: Wookies, Peanutbutter Runtz, Thin Mints, and Gelato Cookies. In our testing we used sea of green method in the smaller grow tents and automation method in the larger tent. All tips and tricks in this article will help you raise humidity in grow tent setups.

If you are new to the horticulture world, then we recommend you start by learning how RH works in a grow tent and why you need to master an understanding of grow tent humidity.

Constant Variables: We tested with all the same strains. All clones were sourced from the same nursery (Peanutbutter Runtz, Wookies, and Thin Mints) and all seeds were sourced from the same vendor (Gelato Cookies). Two of the grow tents (4×4 and 4X8) were tested inside and the house was kept at 70/69 AC and the 10 X 10 grow tent was supported by a mini-split A/C to balance the California summer heat. 

Learning how to Increase Humidity in a Grow Tent really comes down to your understanding of RH and your specific growing conditions. There are many variables that come into play with relative humidity but trying to achieve the perfect RH can be done in various custom ways. A tiny bit of tinkering can be done to adjust your RH in your grow tent to optimal levels. There is no one right way to do this, so after we give you all the methods it’s your job to test each one until you achieve the RH levels you want in your grow tent.


Increasing RH Index

What is Relative Humidity in Grow Tent?

Relative Humidty = (Vapour Density/Saturation Vapour Density) X 100%


Relative Humidity is measured in % and the higher the RH % in your grow tent, the more water vapors are saturating the air. This is why humidity tends to feel “thick” in the air.

A grow tent with high relative humidity will be very apparent when you unzip your tent and poke your head in. In our testing with grow tents, after a month or two you begin memorizing what the RH levels are just based on how the air feels.

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How Raising Humidity in Grow Tent Helps Cannabis Plant Growth

Relative humidity is measured in %. Once RH levels reach 100% that is when the air cannot hold the moisture anymore and dew, fog, or even rain may result.

Cannabis plants drink through their roots as well as absorb moisture through their leaves.

Measuring relative humidity is important because if humidity is too low in your grow tent then plants are forced to take all the nutrients through their roots. This will result in “nute burns” and decrease the potential growth in trichomes and density of buds.

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How to Measure Humidity Levels

When measuring for RH it’s best to use a hygrometer. 

A great choice would be a hygrometer that has a temperature setting built-in as well as phone alerts to notify you when RH is too low. 

We recommend the Govvee Bluetooth Hygrometer. as it is budget-friendly and allows you to track your process via app.

We also recommend that you only try one or two humidity growth hacks at a time so you can test to see how the results worked. Depending on what stage your cannabis plants are in you will want to aim for the appropriate humidity levels in the chart below.

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Optimal RH Levels for all Plant Stages

Depending on what stage you are in you will need to follow the following recommendations for humidity levels in your grow tent.

Most beginners will usually struggle with increasing humidity in the clone/seedling and early vegetative states.

The reason being is that the plants are much smaller and there is not enough vapor being produced by the smaller plants. This is a common problem for most grow rooms and grow tents.

As the plants grow or you add in more plants into your grow room you will then begin struggling with lowering humidity.

In the case of raising humidity, we have plenty of tips and tricks for you in the next section.

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Increase Humidity in Grow Tent (Beginner Friendly)

Raising humidity in grow tent set ups is not rocket science. Keep in mind everything is relative to your actual grow setup. 

Are you using a 10 X 10 grow tent or maybe a 4 X 2 grow tent? The larger the tent or grow room is and the less plants their are (or smaller plants such as clones, seedlings, baby veg stage) you will most likely struggle with increasing humidity in your grow tent. 

Remember, plants produce vapor as part of the respiratory system. So the smaller or less plants you have the fewer vapors will be produced. This is a common issue for beginners but play with a few of these tricks below and you will understand very quickly how to raise humidity in grow tent setups like a pro.

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Adjusting Fan Speed for Optimal Grow Tent Humidity

Our first hack is something we consider a “foundational” hack. This one trick won’t set the perfect RH alone but it’s important you get it right so it helps set you up for successful humidity levels through every stage of your cycle.

Adjusting your fan is one of the most important foundations of humidity.

The reason being is most people have their fan set on high and often times pointing directly at their plants.

The higher the fan speed the quicker moisture dries which results in low RH. Moisture on early stage cannabis plants is crucial for healthy plant growth.

Action-Item: What you will want to do is turn your fan on a much lower speed and angle it at the mylar wall of your tent or the roof of the tent. This way the air is moving around the tent but moisture is preserved on your plant leaves.

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Temperature Change for Cannabis Low Humidity Issues

Dropping the temperature can also help to raise humidity levels.

It’s common that most people that purchase a grow tent will not really think of adding an A/C in the mix. When we tested grow tents we only had an A/C in our 10 X 10 but ran no additional support for A/C in the 4 X 4 and 4 X 8 grow tent. 

The trick for this is to try to place your tent in a cooler room and make the a/c vent is facing directly down on the roof of your tent. Our usual house setting A/C is at 74 and we ran it at 70 and this help to cool the tent off tremendously and resolve our RH issues with our clones.

If you can shell out some extra money another cheap option is to get ducting from home depot and run the ducting from your house A/C vent into the grow tent directly. This is what we did for our larger 4 X 8 tent and it worked very well. 

The only concern is to make sure your room has more than one vent because if you run ducting from a room with only one vent it will result in a very hot room. 

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The Infamous Wet Towel Hack for Low Humidity in Grow Room

The wet towel trick for raising humidity in grow room or tent has been around for a long time.

The more moisture in your tent the higher the RH. Now, remember, as your plants grow larger the RH will naturally increase, this is only a temporary solution for when the plant size ratio to the room is not balanced.

Grow tents have metal framing so you can wet a towel and hang the wet towels along with the metal framing in the interior. Try to place them where if water droplets fall they do not hit the plants. 

Hanging two wet towels in our 4 X 4 grow tent, plus the temperature drop, and the fan hack was more than enough to achieve optimal results.

If you are dealing with a larger size grow tent or trying to increase humidity in a grow room you will need all the above and my favorite hack of all. Keep reading below.


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Water Tray or Water Spray for Low Humidity Cannabis

"This is by far my favorite hack for raising humidity as it's the same hack million-dollar grow operations use as well"

Peter L.

I have worked with some of the best growers in the industry and was privileged to step into some of the most successful grow operations running over 4,000 plants.

Humidity is a struggle with large grow rooms as well grow tents. A common hack warehouses use is if they want a room more humid they leave the reservoir in the veg room to help increase humidity. In the warehouse flower room the reservoir sits outside as flowering you want to decrease humidity.

So replicating this simple hack in a grow tent or smaller grow room, just imitate a resevoir by taking a tray, bowl, or home depot bucket full of water and leaving it in your tent. 

I also like to get a water spray and three times a day I spray the walls and the floor of the grow tent interior to add extra moisture. 

It’s of extreme importance to note that this is just water and no nutrients in the water. If you accidentally spray with nutrients in the spray bottle and it lands on the leaves with the lights on this causes burns to occur.

If you combine all these tricks you should be able to get a standard size grow tent or grow room to optimal RH levels. If you are dealing with a larger grow tent or room and if temperatures are just too hot then you will need more advanced methods. Keep reading to see more solutions.

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How to Increase Humidity in Grow Room (Advanced)

If you are growing in a much larger space such as a 8 X 8 or 10 X 10 grow tent or even a full grow room then you may need more advanced methods.

Having a large grow room with very small to little plants will be very challenging raising humidity levels.

If you have a few extra dollars to shell out then we recommend you try any of the following below. Just a minor warning, most of these solutions are stand-alone solutions so you will not need to stack any of these methods together unless you are suffering from extreme low humidity.

If you are looking to understand how to increase humidity in grow room setups then these options will work very well.

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How to Raise Humidity in Grow Tent: Supported A/C

If running a ducting system from your house A/C into your tent is not enough then we recommend buying a supported A/C system. You can buy an A/C unit and have it sit outside the grow tent and run ducting into the tent. 

For larger grow tents and grow rooms where you have not yet filled up the entire tent you can place the A/C inside the grow room.

Play with the A/C setting until the optimal RH levels are achieved.

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Humidifier in Grow Tent

Another great option is buying a humidifier. If your operation is small you don’t need a large humidifier just a small one will be fine that can fit in your grow tent.

You will want to closely examine the grow tent RH levels by starting on the lowest setting with the humidifier and working your way up.

A common mistake is leaving your humidifier on full blast and forgetting about it only to come back and seeing RH levels are out the roof.

You will have to refill the humidifier in your grow tent daily but, as mentioned above, you will only struggle with raising RH in your early stages of growth.

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How to Raise Humidity in Grow Tent: Plant Vapor

"Plants produce moisture through vapor in their respiratory system. Find compatible plants with cannabis and purchase a few to add in your tent to raise RH naturally "

Peter L.

Plants give off vapor as part of their respiratory system. This is why later in the vegetative stage when plants become larger RH levels naturally raise.

You will struggle with RH levels if you don’t have enough plants in your grow tent or the plants are too small.

A quick and easy hack is to add more plants. This may seem impossible if you ordered seeds and have no access to a nursery to purchase clones or mid-adult cannabis plants.

You can research what plants are safe to co-exist with your cannabis strains and purchase a larger plant from Home Depot gardening section. Just a few extra plants will help tremendously with vapor production in your grow tent and won’t cost an arm and a leg.

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How to Add Humidity to Grow Room: Misting System

There are many misting systems you can purchase from gardening to even terrariums for reptiles that offer affordable misting.

A misting system is an awesome way to get a steady stream of natural moisture that is automated into your grow tent or grow room.

Just like the humidifier you want to start on the lowest settings and test with your hygrometer through your phone and observe the RH at all times. 

A misting system is a fast way to increase RH but too much humidity is also bad for your plants.

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Why Trust Our Research on Grow Tent Humidity Control

As your grow tent expert I have more than 10 years of experience with growing cannabis. I have worked with some of the top 20 growers in the United States, and have worked in some of the most successful grow operations in California. Raising humidity in grow tent set ups is something I have solved again and again on various situations from grow tent, to grow room, to warehouse production.

I have worked in DWC, RWDC, SOG, and many other hydroponic to aquaponic grow methods. I tested three different grow tent sizes and successfully harvested premium strains in grow tents. Learning how to increase humidity in grow tent comes from experience and all advice given comes from years of trial and error. We hope that this article will help you achieve your optimal RH levels. Happy growing.

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