Top 5 Ways To Control Humidity In The Grow Room

Last Updated on April 25, 2022 by Gary Stephen

Humidity is what helps to keep your plants nourished and hydrated. It is one of the vital elements for transpiration. Thus, it is imperative to maintain it at appropriate levels at all times. If left unregulated, this can increase and cause condensation within the grow tent. It is a well-known fact that excessive moisture is unhealthy for plants by any means. Now, we cannot let that ruin our cultivation, aren’t we? In this article, we will explain what causes condensation to occur. Moreover, we will also teach you five effective ways to help control the humidity in the grow room.

How does condensation take place?

Control Humidity In Grow Room

Condensation is being brought about by high levels of humidity. 

Humidity is the capacity of the air to hold moisture in relevance to temperature. In principle, the warmer the temperature, the higher the capability of the air to absorb water. Vice versa, the cooler the air, the lesser moisture it can hold.

Grow tents and grow rooms are enclosed spaces by themselves. That is why it is easy for humidity build-up. When this saturated air comes into contact with a colder surface, it loses some of its ability to hold the water.

As that happens, it prompts the release of the excess moisture into the surrounding. Thus, forming visible droplets of water onto the colder areas in your grow room. This is what we call condensation. It is the physical process of transforming this water vapor into dewdrops.

There are two main reasons why condensation happens:

  1. Changes in temperature either inside or outside the grow room.
  2. Changes in humidity levels inside the grow room.

Condensation takes place when the room temperature and humidity are within favorable levels. It is more likely to occur when the humidity is high while the temperature is low.

Optimal temperature and humidity levels

Both of these elements are relative to each other. Thus, it is important to keep its readings within the appropriate levels. Even so, these ranges may differ depending on the plants current stage of development.

Seedling Stage

This is the initial stage of development. During this phase, the roots of the cultivars need to absorb as much water as they can for their nourishment. In that sense, a high humidity setting of 75% to 85% is suitable for its growth. The young seedlings also thrive best at a temperature of around 74°F to 75°F.

Vegetative Stage

By this time, the root system has already developed. Thus, we can now lessen humidity levels to 45% to 55%. Meanwhile, the temperature still remains almost within the same average range of 70°F to 78°F.

Flowering Stage

This is a very critical stage of growth as the flower or buds are being formed. During this phase, it is best to keep humidity at minimal to only about 35% to 45%.

The temperature ranges might differ though. It will depend on whether you are supplementing the space with carbon dioxide or not. On a regular rate, 68°F to 75°F would suffice. But if you choose to incorporate CO2, the ideal temperature will rise to around 75°F to 82°F.

Harvesting Stage

This is the final stage of development. During this phase, the humidity should be at its least to prepare the buds for harvesting and drying. A range of 30% to 40% is all you need to maintain at this stage.

The optimal temperature is also varied depending on the time of the day. In the daytime, a temperature of 65°F to 74°F is suitable enough for the plants. But during the night time, the temperature should be set a little bit cooler.

Seedling Stage Vegetative Stage Flowering Stage Harvesting Stage
Temperature 74°F to 75°F 70°F to 78°F 68°F to 82°F 65°F to 74°F
Humidity 75% to 85% 45% to 55% 35% to 45% 30% to 40%

Effects of high humidity in the grow room.

You might be wondering what makes it so important to manage the humidity levels in you grow space. Here’s why:

  • Mold and mildew growth

Mold and mildew are common to occur in an indoor grow room. Both are easy to treat if detected early. Yet, if left unattended, it can also mess up your entire harvest.

Molds appear as small cotton puffs that can progress other serious infections.  Moldy buds are unsafe to consume. Thus, batches afflicted with such would likely end up not usable at all.

Now, mildew is a type of fungal infection. Most often it appears as white patches of powder scattered on top of the leaves. It can also spread across other parts of the plant leaving it useless too.

  • Bud rotting

This is another type of disease that destroys the buds or the flower of the plant. It is often hard to detect because the infection starts in the dense core and then spreads outwards. 

What makes bud rotting so devastating is that it can release its own spores. In that manner, it can also affect and damage the nearby plants as well.

  • Plant suffocation

When the temperature inside the grow room increases the plant’s stomata will tend to close off. This is the cultivars defense mechanism to prevent water loss. But, the closure of the pores also means that transpired gases and water vapor are not released too. As a result, the lack of movement in and out of the plant causes it to suffocate and worse, die.

Ways to control high humidity in the grow room.

Now, onto the highlight of the article. Here are our top 5 ways to help you manage high humidity and prevent condensation in the grow room.Ways to control high humidity in the grow room.

  • Seal your grow room or tent to control humidity in the grow room

Your goal here is to prevent outside air from penetrating inside the grow space. Introducing this air will cause fluctuations in the temperature and humidity levels. And we know that disturbances in both can result in condensation and may end up ruining your plants.

Thus, proper sealing of the grow room is necessary in this case. You can install foam insulators to act as barriers from the outside environment. Moreover, you can also use spray foam to conceal any possible openings in the space.

Our top picks for foam insulators and spray foams:

Smart Shield Reflective Insulation Roll

US Energy Products Reflective Insulation Shield

Supershield Multipurpose Reflective Foam Core

Great Stuff Gaps & Cracks Insulating Foam Sealant

Dap Tex Plus Window & Door Foam Sealant

Loctite Foam Window & Door Sealant

  • Check the settings of your air conditioner to control humidity in the grow room

Temperature is concurrent with humidity. When the temperature is up, so as the likelihood of having humidity.

There are two things affected if your AC has incorrect settings or is malfunctioning. These are the thermostat range and short cycling.

The thermostat range becomes a problem when it is smaller compared to the size of the AC. Oversized ACs tend to rather run on shorter cycles. In effect, it is consuming more energy and produces unstable temperature and humidity. Thus, the fluctuations in these levels cause the condensation to take place.

Moreover, short cycling can also occur even in undersized ACs. Thus, it is best to check if the size of your grow room is compatible with the capacity of your air conditioner. 

Our top picks for air conditioners:

Koldfront PAC802W Portable Air Conditioner w/ Dehumidifier & Fan

EdgeStar AP8000W Portable Air Conditioner w/ Remote Control

Emerson Quiet Kool EAPC8RD1 Portable Air Conditioner w/ Remote Control

  • Promote air circulation to control humidity in the grow room

Ventilation is one of the most important factors in any grow space. If humidity issues still exist despite sealing the room and provision of AC. Then, most often than not, your ventilation is the problem.

If you don’t have a ventilation system yet, you might want to consider installing one. If you already have it though, check the appropriateness of the setup. By principle, the more ventilation valve there is, the more humid air is likely removed.

Moreover, you can also choose to increase the fan speed. This action will further push the humid air out of the room.

Our top picks for ventilation systems:

Vivosun 4 Inch Inline Fan w/ Speed Controller, Filter & Ducting Combo

GreenHouser Hydroponics 6 Inch Filter & Ventilation System Combo

Topolite 8 Inch Inline Fan, Carbon Air Filter, Ducting Combo

  • Discard unnecessary water sources

You have to remember that when there is water, there is the humidity too. Excess water will evaporate in the atmosphere. As a result, it raises the level of humidity in the room.

With that, it is advisable to remove unnecessary sources of water. Check your drainage from time to time to ensure that the water is flowing and not stagnant.

  • Reduce plant density & defoliation to control humidity in the grow room

Plants, by nature, emit carbon dioxide. The accumulation of this element can in effect increase humidity. So by reducing the plant density, CO2 is being lessened as well.

To read more about plant densities, please read this article: What is the Ideal Size of the Grow Tent Per Plant?

If it is not possible to cut down on the plant density, then defoliation is another great option to consider. Defoliation is the intentional trimming of the plants leaves to reduce its size. The bigger or denser the plants, the more it tends to release water vapor too. Thus, defoliating the cultivars every now or so will help to reduce humidity in the grow room.

In conclusion, humidity is vital in any indoor grow room. But, too much of it can cause more harm than good to the plants. The moment you see condensation, that is a sure warning that humidity levels are way off than normal.

The solutions we presented above are a few of the simple things you can do to manage humidity. Remember that not all grow rooms are created equal. Thus, it is always a trial and error to check which method works for you the best.

Gary Stephen
Gary Stephen

Hi, I am Gary Stephen. I have been gardening for a long time. Gardening gives us much benefits and pleasure. Many of us desire to have a garden, but it cannot fulfill the desire for the proper guide or instruction of gardening. So, I am eager to help them. For this purpose, I have developed the website to make a garden with the proper guide. So, you will get me beside you if you want to know anything about gardening.