How to Raise Humidity in Grow Room Without Humidifier?

Humidifying grow room without humidifier- sounds quite impossible, right?

But we can bet, it is NOT.

In fact, we’ve figured out 3 DIY tricks and 2 cool products(that won’t break your bank) as easy ways to raise humidity in grow room. And we’ve got enough proof to assure you that they actually work.   

Some of these methods are easy. And some are not as easy as “buying a humidifier and set it right”. But we did our best to make things easy for you.

At the end of this post, we’re certain that you won’t have to buy a $200 humidifier just to keep the air wet in the grow room.

Let’s dive deep-

Grow Room Ideal Humidity: What and Why?

There’s nothing ‘absolute’. So, through different stages of grow, ideal humidity changes its definition.

But we can give you a generalized list-

  1. During Cloning: 70-80%
  2. During Vegetation: 40-60%
  3. During Flowering: 35-55%
  4. During harvesting: 30%-35%

And why it’s so essential to maintain humidity in such a manner? Have a look at the next section.

Why Ideal Humidity Is Important To Maintain?

It’s not rocket science that grows plants need water to live. And the source it through the root, and through the ‘Stomata’.

Stomata is present across all the green parts of a plant, which is in direct touch to the air. So, instead of water, stomata intakes ‘water vapor’ through them for the plants.   

When there’s no abundance of water vapor in the air, it affects negatively on the growth and health. It also shortens their lives and stunts their development. Eventually, serious issues like dehydration, stomata closing, plant desiccation, insect infestation, etc take place when there’s not enough humidity grow room.

Coming back to the point once again, appropriate humidity is a MUST for growing plants.  

Before We Start-

We will be taking through a series of tips and recommendations to raise your humidity without a humidifier. But all of them are equally efficient. Some will go slow, and some will raise humidity instantly.

To understand and optimize any of these techniques,  you have to be certain whether there is actually low humidity in grow tent or room. And a cheap hygrometer for grow tent will do the job. There’re also digital meters available, which can monitor both temp and humidity at one place.

Here’s Our Favorite Analog Hygrometer: Dr.Meter S10

Here’s Our Favorite Digital Hygrometer(with Temp): AcuRite 01083

DIY Tricks to Raise humidity Without Humidifier

Built Your Own Diy Grow Room Humidifier

It’s an obvious fact that more water flows around the grow system will evaporate more water, resulting in more humidity. The same theory works for static water sources like Ice and wet sponges as well.

And that’s how we’re going to build our diy grow room humidifier.

Have a look at the list of water sources in a grow system-

Dynamic Water SourcesStatic Water Sources
Water trays
Drip watering system
Smart Pots
Water Tub(wide mouth)
Dump(wet) sponges
Wet TowelsGallon counter

The dynamic water sources are quite of the system demand. If your system doesn’t support, you can’t just use them to deliver water vapor.

But the static sources might be very effective here, as they are not the requirements of the system.

Take ‘putting a dump sponge’ as an example.

If you put a few wet sponges somewhere near the light sources, the heat from the light will evaporate the sponge water. The same thing can be done with hanging up wet towels as well.

Result? More humidity around the room.

You can do the same with the gallon counter as well.  If you set the watering system right, the gallon counter will be the water container. If it’s placed in a not-so-cold place inside the room, that might work as a humidifier as well.

For both of these systems, adequate heat and airflow is a must to maintain good humidity for grow tent. So, place them somewhere with a decent temperature, and abundance of air flow.

To make the system effective, here are some tips-

  1. Make sure a good air flow right onto the surfaces of these water containers.
  2. Don’t overheat the water to vaporize quickly. Hot vapor can call upon sudden rise on the temperature.
  3. Purify every drop of water that’s being used both in dynamic and static water sources.
  4. Keep the water sources at a decent distance from the lights. Closely placed lights and water sources might lead to a short circuit.

Optimize Extractor Fans for More Humidity

Fans do play the important role of venting air in & out in a grow room or tent. Those fresh air brought in by the extractor fans also brings on a constant drop of humidity level.

As a matter of fact, faster running fans cause the air to dry faster.

But there is no way to just stop these fans, and let the humidity rise in the grow room. That’s absolute nonsense.

But what you can do is to optimize their speed and run-time.

What we mean is, you should aim for the minimum speed of the fan, along with a minimal number of hours when they’d run.  For the whole optimization, using fan controllers is a good idea. Here’s one that we’d prefer within a low budget.

However, you can also read our detailed guide on how long to keep fans on in grow room.

Now, do a few trials with different fan speed and find the minimum speed which gives you an ideal temp of 68-77°F, and ideal humidity of 60% or less.

Also, reducing the number of extractor fan is an effective idea. Lesser in number, but bigger is capacity- that’s what the extractor fan system should be in a grow room.

Here’s a relevant video we’ve found in this regard-

Keep The Ambient Temperature Cool

No matter it’s grow room or tent, there might be a surrounding environment of it. Let’s call it the ‘Ambient’ environment.

If it’s a tent, it might be somewhere in a room, closet, basement, etc. If it’s a room, the ambient environment will be on the other side of the walls.

No matter what, the temperature of this ambient environment directly affects the temperature of the room/tent itself. And as you know, the temperature has a direct impact on humidity-

  1. High Ambient Temp- High Grow Temp- Low humidity
  2. Low Ambient Temp- Low Grow Temp- High Humidity

When it’s summer, the 1st situation is more likely to take place. So, keep a good ventilation system on work to keep the room cool. Also, you can try using an air cooler or air conditioner if your pocket permits so. Keep the doors and windows open, and bring on as much natural ventilation as possible.

However, there is a special situation where the ambient temperature of a tent is likely to dangerously. At that’s even regardless the season.

And that is- when you vent into the same room.

So, you’ve to take special care to keep the grow tent container room cool. Using a mini split ac along with a dehumidifier might help. But if you ask our honest opinion, you should not try for humidifying the grow tent without a humidifier.

Products to Raise Humidity Without Humidifier

In this section, we’ll be showing you guys some DIY humidifier grow tent that you can make right at your home. They’re cheap, they’re simple and guess what, they Works!

Fine Spray Bottle/Misters

Spray bottles can add noticeable humidity in any room. As grow rooms are almost sealed, this will work even better in here.

Now, when it comes to grow sprayers, there are a lot of types of them. Have a look-

Pressurized Sprayer Bottle

They are manual, with a sprayer head and a container. Can hold up to 2 liters of water. Good for raising humidity in small grow tent or room. As there’s no electric and only mechanical system involved, the price is also within a low range.

Our Top Pick: COREGEAR Ultra Cool XLS
Our Budget Pick: Solo 418-2L Hand Sprayer

Battery Powered Sprayer

In a battery-powered sprayer, no pumping is needed at all. There are a few batteries that will do the job of spraying the water into the air. With the wand(included), you can target specific areas of the room to spray water on. Usually, they come up with a higher container capacity too.

Our Pick: Instapark Battery Operated Sprayer


When it comes to facilitating the ultra-low-volume of mist for grow room use, Foggers or Atomizers are the go-to choices. Instead of water splashes, it will spray fog of up to 10-46 microns. And it won’t gravitate and will give a solid boost at the humidity level of the room.

They can contain up to 2-3 gallons, and we found it enough for even a 20×20 grow room.

Our Pick: Hudson 99599 Electric Fog Atomizer

Swamp/Evaporative Cooler

Through many methods of DIY humidifying, you might have to increase the temperature of grow room. We mean, those methods ask for water containers, which will naturally evaporate water when there’s enough heat around.

But this might cause a dangerous raise at the temp, right?

To meet both ends of cooling and humidifying, swamp coolers are on rescue. It’s also called evaporative cooler, which brings us to it’s working principle.

You see, when water is converted into a gaseous state, it requires energy. And that energy is sourced from the heat energy nearby. Swamp coolers, therefore, does the same thing. As a result, the temperature is dropped to a significant level, and cold water is released.

So, it works as both air conditioner and humidifier at one place.

And that’s exactly what we are looking for, right?

Our Choice(for grow room): COSTWAY Evaporative Air Cooler with Humidifier
Our Budget Pick(for grow tent): NewAir Evaporative Air Cooler

Some Tips Before We Finish

Keep Abundance of Air Flow(Specially Above the Plant Canopy)

All of these efforts are provided to let the plants transpire properly. And that brings us to the responsibility of adequate airflow on the plant canopy. This will ensure no moisture buildup around the plant leaves.

If you don’t do so, plants will never get the benefits of all the humidifying efforts you’re putting around the room.  

Find the Perfect Mix

See, there are a number of DIY hacks and products which can let you raise the humidity in grow room without a dehumidifier. But you might find the optimal grow room humidity with one or more than one tricks combined.

So, we would recommend you to keep experimenting with all the tricks/products that we’ve listed and find the best combination for you.

Keep An Eye On The Temperature

Temperature  has a very direct impact on the humidity and vice versa. So, the high temperature might induce more humidity, provided that there are ample water sources inside the room.

But in the rise of cheap humidifying, don’t raise the grow room temperature too high. That might ruin the whole crop.

FAQ(Frequently Asked Question)

Question: At which stage, plants require humidity at it’s best?

Answer: For all kind of grow plants, it’s the cloning stage where they require optimum humidity(60-70%).

Question: Does a mix of bigger and smaller plants help?

Answer: Yeah, it does. Because larger plants are likely to leave more vapor around their leaves, smaller ones will be in a humid environment. But this will also create discrimination of light power as well.

Question: How to check the relative humidity of my grow room?

Answer: You can use either a cheap analog hygrometer or go for a slightly pricier digital humidity(and temp) monitor.  

Question: How to raise humidity in grow tent without humidifier?

Answer: in case of a grow tent, all these tricks and products will work. All you have to do is pick up the intensity of action according to your grow tent size.

We will be happy to hear your thoughts

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