Yes, you can put a dehumidifier in a grow tent, but it is often not the best spot. For most small and medium tents, running the unit in the room that feeds the tent (often called the lung room) works better. The tent then pulls in drier air, and the appliance’s heat and bulk stay out of the canopy space.
Use the inside-the-tent option when the tent is large, the room is already controlled, and humidity still spikes at canopy height.
Quick Answer: Inside the Tent or Outside?
| Placement | Best for | Main tradeoff |
|---|---|---|
| Inside the tent | Large or sealed tents, or spikes that the room unit cannot fix | Takes floor space, adds heat, needs careful electrical safety |
| Lung room | Most small and medium tents with active exhaust | Must be sized for the room air feeding the tent |
| Ducted or separate unit | Multi-tent setups or tight tents | Costs more and needs planning, ducting or a pump |
Can You Put a Dehumidifier in a Grow Tent?
You can, if the tent is big enough for the unit to breathe. The tradeoffs are real, though. The dehumidifier takes floor space, blows out warm air, adds an electrical device near water and may point dry air straight at nearby plants.
If you place one inside, keep it away from leaves, irrigation spray, loose cords and cramped corners. Leave room around the intake and exhaust. Use a separate hygrometer at canopy height, because the unit’s built-in sensor reads the air near the unit, not around your plants.
Safety: keep drain hoses, water lines and buckets away from power strips, light drivers, exposed plugs and extension cords. Use a properly grounded outlet, follow the manual and keep cords off wet floors.
Where to Place a Dehumidifier: Tent or Lung Room
The lung room is the room or closet that supplies air to the tent. Dry that air first and your intake fan brings it straight into the tent.
- If the tent exhausts actively and the room is humid, dry the room first.
- If the room is stable but canopy humidity still spikes in a large or sealed tent, add an in-tent or ducted unit with safe clearance and drainage.
- If the tent exhausts into the same room, humid air can loop back in. Exhaust outdoors or to a separate area when practical.
Place the unit near the air path that feeds the tent without blocking its intake or exhaust. ENERGY STAR advises keeping a dehumidifier away from walls and furniture so air can circulate, unless it has top-mounted discharge. For more on this, see our guide on where to put a dehumidifier.
Recommended Products
Grow Tent-Optimized Unique Design: Equipped with an air duct, this dehumidifier can sit outside your grow tent, channeling moisture out without introducing extra heat that might disrupt plant growth. It’s perfectly suited for 3x3, 2x4, and 4x4 ft grow tents
Superior Humidity Control: This advanced ultrasonic humidifier delivers whisper-quiet, precise humidification with 1% humidity resolution; A highly sensitive external temperature and humidity probe provides accurate environmental readings, enabling quick adjustments
Semiconductor dehumidifiers use thermoelectric cooling to remove moisture from the air. They create a drier, more comfortable environment by reducing humidity and improving air quality.
How to Size a Dehumidifier for a Grow Tent
Do not size by tent footprint alone. A 4×4 tent with a few small plants and strong exhaust adds far less moisture than a dense, heavily watered canopy in a humid basement. Size by the space the unit treats, how damp it is and what your readings show.
- Measure the space. Multiply length x width x height for the tent. A 4 ft x 4 ft x 6 ft tent is 96 cubic feet, but a lung room unit treats the larger room.
- Estimate daily water input. One gallon equals 8 pints. Some water leaves through runoff, so your readings matter more than a generic plant-count chart.
- Log humidity. Put one hygrometer at canopy height and one in the lung room. Check during lights on, lights off and after watering.
- Choose capacity with headroom. ENERGY STAR sizes by room area and dampness: for rooms under 2,000 sq ft, about 20 to 30 pints per day for slightly to moderately damp spaces, 25 to 40 for very damp, and 30 to 50 for wet. It says it is better to oversize than undersize.
- Upgrade if humidity still climbs. If the bucket fills too fast or the unit runs nonstop without hitting the target, the unit is undersized or the airflow path is wrong.
If you already own a unit, measure how much water it collects in 24 hours during your most humid period. If it collects near its rated capacity and humidity stays high, you need more capacity, better exhaust or less moisture looping back into the tent. For tent-specific charts, see our grow tent dehumidifier size guide.
Drainage and Air Circulation
Most portable units shut off when the bucket is full. Many have a hose fitting that can drain to a floor drain, sink, sump or condensate pump, so you do not have to empty it. Keep the hose short, sloped downhill and free of kinks, unless you use a pump designed to lift condensate.
- Level the unit.
- Attach the hose tightly and check it after the first hour.
- Route water away from outlets, cords and controllers.
- Run the unit long enough to confirm water flows out without pooling.
- Use oscillating fans to mix air above, below and through the canopy. Do not blast one plant with dry air.
Air movement matters because humidity is uneven. UMass Extension notes that the highest relative humidity in a greenhouse is generally found inside plant canopies. It also says moving air keeps leaf surfaces from cooling below the dew point.
What Humidity Should a Grow Tent Have?
It depends on the crop, temperature, airflow and growth stage. The table shows ranges many indoor growers use as starting points. It is not a universal rule, so check guidance for your specific plants.
| Stage | Common starting RH | Why it matters |
|---|---|---|
| Seedlings and cuttings | 65-75% | Small roots, so young plants dry out quickly |
| Vegetative growth | 55-70% | Supports leaf growth while airflow prevents wet pockets |
| Flowering or fruiting | 40-60%, lowering gradually | Drier air reduces condensation and disease pressure |
| Dense late-stage canopy | Toward the low end | Tight growth traps moisture and raises mold risk |
Read humidity together with temperature. Relative humidity rises as air cools, so lights-off periods often cause the worst spikes. UMass says condensation forms when leaf temperature falls below the dew point and that the key to suppressing disease is keeping the canopy dry, especially from dusk to dawn.
For the room itself, EPA advises keeping indoor humidity below 60%, ideally between 30% and 50%. Treat that as a mold-risk guide for the lung room, not a plant target.
Troubleshooting High Humidity in a Grow Tent
- Spikes after lights off: start dehumidifying before lights go off, improve air mixing and remove standing water.
- Bucket fills and the unit shuts off: add a drain hose or use a unit with a built-in pump.
- Unit runs nonstop: the room may be too humid, exhaust may be looping back, or the unit may be undersized.
- Passive absorbers do little: they may help in a closet but rarely keep up with plants that are watered daily.
- Leaves feel wet: add gentle canopy airflow and reduce dead zones under thick foliage.
- Frost or weak performance: ENERGY STAR says frost can form on the coils below 65°F, and suggests a model rated for lower temperatures if your space is that cool. Switch the unit off and let it defrost.
- Odd readings: compare two hygrometers and replace weak sensors.
If you would rather fix humidity without another appliance first, read how to lower humidity in a grow tent without a dehumidifier.
Maintenance and Safety Checklist
- Clean or replace the filter as the manual directs.
- Wipe the bucket and drain parts so slime and debris do not block flow.
- Keep the intake away from soil dust, pruning debris and spray.
- Check the hose weekly for kinks, algae and leaks.
- Keep cords, controllers and power strips off the floor and away from water.
- Log canopy and room humidity at the same time daily until the setup is stable.
- Follow local laws and crop-specific guidance for anything you grow.
Related Guides
- Grow tent dehumidifier size guide
- Lower humidity in a grow tent without a dehumidifier
- Lower humidity in a grow tent: airflow, water and dehumidifier
- Does it matter where you put a dehumidifier?
Frequently Asked Questions
Do dehumidifiers work in grow tents?
Yes. They work when sized correctly, drained reliably and paired with good airflow. They are most effective when they control the lung room or a sealed tent environment instead of fighting constant leaks of moist air into the space.
Should a grow tent dehumidifier be inside or outside the tent?
Start outside, in the lung room, if the tent pulls air from that room. Move the unit inside only when the tent is large enough, the room is already controlled, or a sealed setup needs more direct humidity control at the canopy.
How can I dehumidify my grow tent?
Dry the lung room, improve exhaust, use oscillating fans, remove standing water, avoid overwatering, and run a properly sized dehumidifier with drainage. Track humidity at canopy height so you adjust the plant environment, not just the room corner.
Will a dehumidifier raise the temperature in a grow tent?
It can. Compressor dehumidifiers release warmer, drier air as they remove moisture. That extra heat is one reason the lung room is often better than placing the unit directly inside a small tent.
Should a grow tent dehumidifier run all night?
It can run at night if humidity rises after lights off, but use its humidistat or a controller instead of forcing it to run nonstop. The goal is a stable target range, not the driest possible air.
Sources
- ENERGY STAR: Dehumidifiers
- U.S. EPA: A Brief Guide to Mold, Moisture and Your Home
- UMass Extension: Reducing Humidity in the Greenhouse
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