How to Raise Humidity in Grow Tent

How to control humidity in a grow tent is one of the most significant issues facing indoor gardeners. In this article, I’ll tackle how to raise humidity in a grow tent and provide some options to help keep your plants from drying out.

how to raise humidity in grow tent

There are several things you have to keep in mind when you decide to raise plants indoors. This is especially true when you do so inside a grow tent.

Grow tents allow to take care of a variety of plants year round, and grow all types of produce regardless of the current weather or climate zone.

The tents provide a controlled environment and commonly make use of hydroponics rather than conventional soil.

Some of the benefits of using a grow tent are a more efficient absorption of nutrients by the plants and keeping potentially harmful elements found in soil, such as parasites, extra dirt, mold, mildew, and eggs or larvae of plant-eating insects at bay.

Apart from the basics, such as regular cleanup of the system, quality of the seeds and seedlings, and fertilizers, another essential factor to keep in mind, to keep young plants alive and healthy is the humidity of the surroundings. Or simply put, the amount of water vapor in the air.

This article would aim to explain how and why moisture plays this critical role in the growth of plants, as well as ways to increase humidity in a grow tent, should the levels be found to be too low.

Importance of High Humidity

how to raise humidity in grow room

One of the reasons humidity is something that should be kept at a relatively high level is because plants need water to live. While they can get it from the roots, the reality is plants also get water from other parts as well.

In a more specific sense, they also absorb water from their stomata through the water vapor in the air. If there is little to no humidity in the surrounding environment, this will rob them of the opportunity to get water for their growth and development.

Baby plants are in their most critical phase, and they need water in this particular phase, before being “weaned” and prepared for the outside world.

Consequences of Low Humidity

Depriving new plants of high levels of humidity negatively affects their growth. Low moisture forces the plant to exert more effort, and thus possibly shorten its life or delay, or even stunt its growth and development.

how to control humidity in grow tent

Other consequences we associate with a low level of humidity in the growing environment would include leaving the plant to desiccate, thereby exposing the plant to mold and mildew, as well as an infestation of insects like spider mites.

The reason for this vulnerability is plants that are considerably less moist are more favorable and conducive for other organisms to take advantage of and flourish.

How to Increase Humidity in a Grow Tent

Lower Extraction Fan Setting                       

Fans are crucial in every grow tent simply because they allow the air to circulate and be well-distributed by plants. This facilitates the exchange of air inside the grow tent and outside, as fresh air has to be introduced to prevent harmful microorganisms from increasing in number and/or staying in the area. (Read more about fans in my grow tent setup article.)

Having your fan speed set too high, however, will cause the air to dry quicker, instead of allowing the water vapor to settle, and thereby be absorbed by the plants nearby. You could also incorporate a humidifier or dehumidifier in your surroundings as well.

If you plan on doing so, make it a point to keep at least a 60% humidity level.

Lower the Temperature of Surroundings

It’s common knowledge that cool air, due to its relative density, will always sink to the bottom. A lower temperature means the air is relatively moist, thus having a more significant presence of water vapor.

This can be achieved merely by reducing the temperature of the heater or increasing the temperature of the air-conditioning system either of the tent itself or the grow room. Another way for you to do so would be to lower the intensity of the UV light, given that light facilitates the evaporation of water. This is not a point of concern really, given that young plants don’t need that much light.

Have Larger Plants inside the Grow Tent as Well

While some people may think larger plants will rob the younger plants of air, the reality is these larger plants actually contribute to the level of water vapor, and subsequently, the humidity inside the grow tent once you put them inside, alongside the baby ones. Just be sure you don’t overcrowd your grow tent.

Large plants undergo the respiration process as well, and part of this process is that apart from carbon monoxide, water vapor would be released as well. This vapor will then feed the younger, smaller plants.

Also, bigger leaves would mean more stomata, which would imply that more water vapor would get released as well.

Place Water Sources Wherever Possible

One of the obvious and easiest ways to increase water vapor levels is to place water trays beside the air intake tubing or the passive air holes. You can also saturate sponges and put them near your growing trays.

The heat coming from the grow lamp will slowly evaporate this water, and in the process add humidity inside the grow tent.


While keeping things moist inside your grow tent is of utmost importance, one of the things you have to keep in mind is that the water you use should be as clean as possible. Harmful bacteria can cause a range of diseases in your plants, as well as with you. Make regular maintenance an integral part of raising your plants, apart from just controlling the humidity in the grow tent.

Moreover, be careful with adding sponges or small trays of water near fans, given that these are materials that use electricity, and might short circuit when they come in contact with water.

I hope this has helped answer your questions about how to raise humidity in your grow room or tent. I’m happy to answer your questions in the comments or by email.