Grow tent dehumidifier guide: best dehumidifier for grow tent use

Find the best dehumidifier for grow tent humidity issues.

We’ve been fixing grow tent humidity issues for a long time. We’ll show you how to lower humidity in a tent, what size grow tent dehumidifier to buy, what features and options you should consider, and where to place dehumidifiers for best results.

Your goal is to create an environment for your cannabis plants that falls within the optimal humidity levels:

  • Vegetative stage: 40%-60%
  • Flowering stage: 40%-50%
  • Last few weeks or flowering stage: 40% or less

How to lower humidity in grow tent

Before you buy a grow tent dehumidifier there’s a few things you should try first to lower humidity in your grow tent.

Increase your tent’s exhaust fan (and add a filtered intake fan if you don’t have one) to more quickly remove moist air. Use a humidity fan controller to turn the exhaust fan on as needed to keep things within suitable range.

For small and midsize (3×3, 4×4, 5×5) grow tents this usually will be adequate to lower humidity in a grow tent. Learn more about grow tent ventilation setup and how to find the best fan for a grow tent.

In some climates the room air outside tent is very moist. Air conditioning will remove moisture from air, so try running that in the room where you want to lower humidity in your grow tent. If that’s still not enough then you’ll need to buy a dehumidifier.

How big of a dehumidifier do I need for a grow tent?

The proper size dehumidifier depends on your tent’s volume and the severity of your humidity issues. During the dark cycle, humidity levels tend to rise a lot as plants transpire moisture.

Many of the smaller dehumidifier models under $100 seem like the right size be a good fit for a small tent. But those units are not designed to move a large volume of moisture, so they will struggle to keep up with moisture levels.

A larger-sized dehumidifier is needed for grow tents. Dehumidifiers are rated based on the number of pints of liquid per day that can be removed from the air. To be safe it’s better to get one that is more powerful than you think you’ll need, there’s little risk since it will shut itself automatically once it reaches the level you set.

If you are planning to dehumidify the air outside of your grow tent, you can get away with a full-size model. In moist basements during the summertime many homes need to run them full-time.

If your tent is located in similar damp basement conditions, you’ll need a model capable of keeping your basement within check. Otherwise the fresh air you introduce will already be too moist, and when coupled with the moisture introduced by your plants it will become a risk.

Grow shops near me feature an array of large commercial-sized units, but they don’t carry midsize dehumidifiers for grow tents. Typically your best bet to find one is at box stores or on Amazon.

When should I run my dehumidifier in my grow tent?

Your dehumidifier should be set up to run using a humidity controller to keep you within the proper range.

Most models come with a built-in controls to set target humidity level to turn on. Smaller models that lack this feature can be turned on using a digital controller, such as the InkBird Humidity Controller. We use one to optimize humidity levels and it has worked great for years.

You’ll find that humidity levels tend to very when the lights are on vs. off, and as plants get bigger and bushier they tend to transpire more moisture. Using an automated humidity control takes the guess work out of it. Plus they can be programmed to run for a specific range, so they don’t quickly cycle on and off repeatedly.

Keep in mind that if your bucket fills with water the unit will auto-shutoff. So empty it often or it may shut off unexpectedly. And make sure to clean the filter often to keep airflow moving.

Where to place dehumidifier in grow tent

Dehumidifiers can be placed directly on the grow tent floor, out of the way of potential issues with spilled water. Position it so the unit’s fan circulates the dried air, but don’t point it directly at plant if you can avoid it since that air may be very dry.

Grow tent dehumidifiers can also be propped up on an overturned 5 gallon bucket or small plastic shelf if you need to raise the height to facilitate water drainage through a hose.

Your tent should intake fresh air from the bottom and exhaust warmer, humid air at the top. Placing the dehumidfier low has the most impact, since as the tent air warms from the light it rises and gets sucked out of the exhaust duct. Placing a dehumidifier at the top of the tent means the device’s freshly dried air is quickly removed, reducing efficiency of the solution.

For small grow tents you can also place the dehumidifier outside of the tent near the intake fan. This introduces dry air while saving precious space inside the tent.

Choosing the best dehumidifier for grow tent usage

When choosing the best dehumidifier for your grow tent, there’s a few things to keep in mind.

Small dehumidifiers have small buckets, so you may find yourself having to change them often or risk having the dehumidifiers shut off when full.  Emptying buckets sucks. Look for models that allow you to attach drainage holes to a nearby drain to minimize the hassle.

If you don’t have a low drain nearby look for a dehumidifier with a pump so you can pump out that water to a larger container outside of the tent. This ensures it won’t ever shut down due to a full bucket.

Built in humidity controls are included on all but the smallest dehumidifier models. Use a humidity controller if you get a mini dehumidifier for grow tent that doesn’t let you set it.

One of the best dehumidifier options for grow tent usage is to get a model that is bluetooth connected and can be monitored on a phone app. This provides peace of mind so you know things are working as they should.

Word of warning: Make sure to cover all your dehumidifier’s lights with thick black duct tape like Gorilla Tape. You don’t want any light to seep out and interfere with your flowering cycle.

Best dehumidifier for 4×4 grow tent

There’s not a lot of canopy square footage in a 4×4 grow tent, so the best dehumidifier would be small enough to sit under the canopy to avoid reducing the space plants receive light.

Place on the floor or on a small bucket if you need to raise it to angle a drain hose. If you’re using a larger dehumidifier in your 4×4 grow tent you may need to elevate your plants so the canopy is above it. Assuming you have enough vertical space you could put your plants on on upside-down 5 gallon buckets to raise them.

Usually exhaust fans can prevent the need to buy a dehumidifier for 4×4 grow tent setups. Assuming your tent is 7 feet high, 4 x 4 x 7 = 112 cubic feet of air. Not a lot for even a small 4″ inline fan to remove.

If you’re having issues with exhaust rate, reduce bends in duct work and increase air intake volume (using an filtered intake fan or a DIY lightproof baffle). Learn more about grow tent ventilation setup.

If you don’t want to sacrifice room inside of your 4×4 grow tent, a dehumidifier can be placed outside with it’s airflow pointed at your tent intake fan or vent. The air coming out of the unit will be very dry, so placing this air stream closer or further from the intake fan can further lower or raise the humidity of air being pulled in the tent.

Best dehumidifier for 5×5 grow tent

The best dehumidifier for a 5×5 grow tent (or a similarly-sized 60″x60″ grow tent) would be a small model with a built-in humidity control.

If you’re planning to use the dehumidifier’s storage to collect water look for models with larger capacity. If you’re planning to run a drain tube look for models where you can easily attach a hose. Or get a unit with a built-in pump so you can eject the water to a nearby sink or drain.

Similar to the 4×4 tent, a dehumidifier for 5×5 tent grows can also placed outside of the tent to avoid wasting precious space where flowering buds could go.

Best dehumidifier for a 4×8 grow tent

Larger grow tents have more air volume and more room to maneuver. The best dehumidifier for 4×8 grow tent setups would be a mid-sized model targeted for use in small basements.

Place the unit right inside your tent, so that the dry air isn’t being pushed right into any one plant.  Use lots of circulation fans to keep air moving briskly inside the tent to keep everything as homogenous as possible.

If you’re having humidity issues in a 4×8 grow tent you should look into a decent humidity controller which can help you lock down ideal humidity ranges, turning on a humidifier or dehumidifier as needed. In tents this size the humidity levels can vary quite a bit naturally when the lights are on vs. off.  And if you’ve moved up to a 4×8 tent then you are more advanced than a smaller tent grower and likely want to nail down the environment as best you can.

Best dehumidifier for 3×3 grow tent

Most of the time you won’t need to buy a dehumidifier for a 3×3 grow tent or similarly sized grow space (2×4, 32″ x 32″, etc.) The air volume of these tents is small and can quickly be changed over every minute using an exhaust fan running on a low setting. Plus there’s not a lot of space to put one, so you’d need to get a mini dehumidifier for grow tent sizes this small.

If your tent’s enclosing room humidity is too high you can address that with a small dehumidifier. Set it so that room stays at 40-45%, so that the room air pulled into your tent’s intake vent will be slightly dryer then the target tent humidity based on the growth stage you’re in. Decrease target humidity if needed to fine-tune it.

If you do want to locate the unit inside, get a mini dehumidifier with as much water storage as possible to keep it from shutting down when full.

Choosing a mini dehumidifier for grow tents

Using a mini dehumidifier is helpful for small tents because they don’t take up much space. But they have a few drawbacks to consider. Many smaller models don’t move a lot of air, so they may have trouble keeping up with the constant transpiration that you’re looking to eliminate.

Water containers are small, so you’ll need to empty frequently. They often don’t have programmable controls, so they’ll just turn on when a certain predetermined threshold is reached (such as 40%). Many mini dehumidifier models also don’t have drain hoses, not ideal for lower-maintenance usage in grow tents.

Benefits of using mini dehumidifier are low prices and small size. But keep in mind that since your tent exhaust is ideally turning over the tent air every minute, using these inside the tent isn’t always the most efficient way to lower grow tent humidity.

Summary

Picking the best dehumidifier for grow tent humidity control depends on tent size and volume, where you intend to place it, and what options you’ll need (adjustable control settings, water container size, drain tube, drain pump, bluetooth controller, etc.).

A grow tent dehumidier can lower humidity, but there are also there ways to reduce humid air such as exhaust ventilation which can resolve many problems in small grow tent setups without the need for additional equipment.

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Grow tent dehumidifier guide: best dehumidifier for grow tent humidity control
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Grow tent dehumidifier guide: best dehumidifier for grow tent humidity control
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We've been trying to fix grow tent humidity issues for a long time. We'll show you how to lower humidity in a tent, what size grow tent dehumidifier to buy, what options you should consider, and where to place it for best results.
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Happy Pot Farmer
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