How to Stop Condensation in Grow Room? [6 Methods]

When the relative humidity rises over 70%, it causes condensation in a grow room. Result? Grow room becomes prone to molds, mildews, etc. In worst case, plants feel suffocated.

Now, the $1M question is- How to stop condensation in grow room?

You can stop condensation by replacing the air in the room or removing moisture from the room air.And the best ways to do this is by using dehumidifiers and some other methods.

And here’s how we can help you to do that?

Go through the whole piece and you’ll become an expert about grow tents and condensation. Let’s jump right into the details-

What causes condensation in a grow tent?

In case of grow tent or grow room, condensation can occur rapidly. It all happens, thanks to relative humidity.

Now, what is relative humidity?

Simply put, the ability of air to hold water at certain air temperature.

If the air temperature is high, then the relative humidity becomes high. This is because heated air has more volume and is lighter.

Let’s clear this out with an example-

If your air temperature is 60F then it can hold 4oz of water in it. Let’s imagine that your grow room has 60F and 2oz of water in its air. So, your grow room air is holding 50% of its capacity.

Now, if your room temperature decreases to 40F then it’s capacity decreases to 2oz. And if it holds the same 2oz water as before, then voila! Now your grow room air has 100% relative humidity.

When this saturated air touches a cold surface, it sheds the extra water in it. If the humidity is excessive, then we see droplets of moisture.

As a result, you get condensation.

Whenever the air temperature drops, your grow room becomes more prone to condensation. Some other factors like-

  • Inside room temperature
  • Outside temperature
  • Different temperature air mixing together

Play roles in this condensation game.

If you had the question, ‘why is there condensation in my grow tent?’ – then we hope that you’ve got your answer.

6 Methods to Get Rid of Condensation in a Grow Tent

Now that you know how condensation happens and why it’s bad for you, we think it’s time that we explore the solutions.

There are different methods to solve this issue. But the end goal of these methods is to reach any of the two outcomes (Explained in the intro).

Here go the methods-

Seal Your Room

Sometimes outside air gets into the grow room. When this happens, two things might take place-

  1. Your grow room air temperature fluctuates
  2. Relative Humidity fluctuates

Both of these factors are crucial for condensation.

Commercial builders use foam insulators to seal the high-end rooms from the outside environment. This same technique is also used in refrigerators.  

You can use spray foam insulators to do this. The technique is to create a thick layer. This layer acts as a barrier between your grow room and the outside environment.

So, sealing your grow room or grow tent can help with the condensation problem.

Check Your AC

We already have discussed how temperature determines the relative humidity of a grow room. Also, how this relative humidity is closely linked with condensation in a grow tent or grow room.

So, if there’s something wrong with your AC then this could also cause condensation.

If there’s temperature fluctuation in the air conditioning system, then two factors might be responsible for this.

These factors are-

  1. Thermostat Range
  2. Short Cycling

Thermostat Range: Let’s imagine the range is between 70 F to 75 F. At the upper edge of this range, your AC cycles on to keep things cool. At the lower edge, it shuts off to keep things at normal temperature.

If your Ac system is oversized, then it will tend to run-

  • In brief periods or
  • In short cycles

As a result, your AC eats up a lot of energy and create an unstable grow room environment. In this unstable environment, temperature and humidity spike up and dip from time to time. Therefore, you get condensation.

Short Cycling: When you have an undersized or oversized AC then short cycles happen.

A graph of proper temperature and humidity graph looks like a long shallow wave. When short cycles occur, the graph looks like a jagged reading of spikes.

This spike brings in condensation in your grow tent along with molds and other harmful things.

So, check if your room size or tent size is compatible with the AC you are using. See if it’s raising humidity in grow space. If you’re using the wrong one, then change it.

Allow Proper Air Movement

If your room is sealed and your AC is okay, then you probably need good ventilation to fix this condensation problem.

If you increase ventilation, then you’re removing humid air from the room. So, you’ll get a low RH air. Or you can increase the humidity level by decreasing the ventilation amount.

If you don’t have a ventilation system, then install one. Many people use a can style exhaust fan for this process.

If you have one, then you need to make it more effective. You can do this by making the ventilation intake hole widened. Sometimes, this increases the risk of a light leak. Or you can increase the number of fans.

Another way to make ventilation effective is by implementing a proper fan runtime schedule.

So, remove the air from your grow room or tent to solve your condensation issue.

Consider the Standing Water

This is the simplest and cheapest method of solving grow room condensation. But growers tend to overlook this simple solution.

At first, check if you have stagnant water. If yes, then see if your drainage is working properly.

Any water surface will release water into the air. Be it temporary stagnant water on the floor or a water reservoir.

Also, stop overwatering your plants. Making the drainage system more effective won’t solve the problem if you continuously overwater your plants.

Either take actions to remove the water quickly or cover the reservoir or stop overwatering the plants.

Reduce Plant Density

Plant density is another factor that controls humidification. High plant density,

  • Displaces air
  • Breaks Wind
  • Creates uneven spreading of CO2
  • Increases RH

With every extra plant, comes extra transpiration. And extra transpiration causes extra humidity. If you don’t level up your ventilation or dehumidification, then the extra humidity will simply condense.

This will more like humidifying without humidifier. But this time, you didn’t ask for it.

If this is the case for you, then extra ventilation, proper sized AC and other methods won’t for you. You’ll need the help of our last method.

Get a Dehumidifier

If you are thinking of rolling out your car and getting the first dehumidifier from your retailer, then stop.

Residential dehumidifiers are a bad choice for grow rooms or grow tents. The reasons are-

  • These are inefficient
  • Grow room workload will ruin those

There is a rule of thumb that plants release around 97% of the water they absorb. So, you can easily understand how good the dehumidifier has to be.

Determine what dehumidifier you need and how many you need based on your room or tent size.

Other Methods

Other methods include defoliating the plants and using an absorbent surface.

If your humidity level is totally uncontrollable then you can sort out big leaves or bushes with a lot of leaves. After sorting those out, cut a little. Just Don’t go all berserk on those.

Also, you can use a soil that can keep water. Sandy soil is a great example of this. It keeps much water underneath it. Thus your grow room gets less water surface.

Some even suggest keeping bowls of salt inside grow tents. But we don’t really recommend this method.

Extra Tips

Here are some tips that might help you during this problem-solving period.

  1. Use a Hygrometer to keep track of your RH.
  2. Before ventilating check up the outside humidity. If it’s more humid outside, then don’t ventilate.
  3. Check if your dehumidifier has an automatic shut off. If not, then set a timer and keep track of the water collection.
  4. If your dehumidifier doesn’t have any drainage system, then check when it’s full. Just don’t forget to drain timely.


Question: Grow room window condensation, what can I do?
Answer: Keep your windows open a bit. Use the second lock. If you’re dumping your extraction inside your house, then find alternatives.

Question: Loft grow condensation is taking place, what to do?
Answer: Use something to insulate your tent. Therma foil or tin foil bubble wrap insulation are common choices. Besides this, you can use a heater.

End Note

If not fixed timely, condensation can bring serious damage to your plants. You might lose a huge portion of your yield to molds and other harmful entities.

You’ll find many temporary hacks to solve this issue but remember those are like gambling. It might cure your condensation problem temporarily but in the long run, might make you suffer.

So, use proven and scientific methods. Increase your yield and be a happy grower.

Good Luck and Happy Growing.

We will be happy to hear your thoughts

      Leave a reply