Effective Ways to Increase Humidity in the Grow Room

Last Updated on April 20, 2022 by Gary Stephen

In this article, we will present to you effective ways to increase the humidity of your grow space. Even so, with the absence of humidifier devices. Read through how.

Relationship between Plants and Humidity

Every grower must know that humidity is vital in every plant’s growth. As cultivars lose moisture, it draws in the humidity from the surrounding air for replenishmentSo what happens now if the air in the grow room is too dry to provide the plants with their much-needed moisture?

Some people use humidifiers to resolve such a dilemma. But, what if for some reason this device is not available for you to use?

So, before proceeding, let us first understand the fundamental role of relative humidity. Also, how does it impact the health and growth of the plants?

So, what exactly is humidity?

Humidity or RH, in short, refers to the concentration of water vapor in the surrounding air. It is like atmospheric moisture per se.

Throughout the stages of growth, constant intake of water is necessary to sustain its development. The amount the plant drinks though may vary, depending on the level of moisture in the grow room.

When the humidity is low, the atmosphere tends to be so dry. Thus, the plant’s leaves cannot draw in any moisture from the air. Hence, they pull in more water from the soil through its roots instead.

Since the manner of how the plant drinks its fluids changes, the amount of nutrients it absorbs fluctuates as well. So, having the means to regulate the level of humidity will help you gain control over your cultivars nutrition too.

Ideal Levels of Relative Humidity

Before tackling the impacts of imbalances in RH, let us establish on the ideal levels considered by most cannabis growers. Once again, depending on the plant’s stage of growth, the optimum RH also varies.

Optimum Relative Humidity

Seedling Stage Vegetation Stage Flowering Stage Harvesting Stage
70% to 80% 40% to 60% 35% to 55% 30% to 35%

Effects of Low Humidity to Plants

Scenario # 1: Stunted Growth.

Cannabis plants flourish well in high humid places. Especially, during the early phases of its growth. Their preference changes as they mature. Hence, lower humidity becomes more favorable at the later stages.

If the recommended levels of RH are not sustained throughout its development, then there is a possibility of decelerating its pace of growth. If so, the cultivars may not turn out to be as big and healthy as they should be for their age.

Scenario #2: Restricted Photosynthesis.

Low levels of relative humidity prompt an increase in the rate of transpiration. Thus, making the plants become less hydrated. To mitigate further deficit, the stomata encloses partially or fully as a defense to help conserve the water left within.

Given the circumstance, the mesophyll resistance increases. Thereby blocking the carbon dioxide from penetrating the plants. As an effect, the process of photosynthesis becomes restricted. If this continues for a longer period of time, it poses a great chance of precipitating the death of your cultivar.

Scenario #3: Nutrient Issues.

As mentioned earlier, humidity is one of the determinants of how much water the plant drinks. If exposed to an environment with very low humidity, the cultivars would instead absorb the water from its roots. 

Besides, it isn’t only plain water that’s absorbed, the nutrients from the soil also get sucked in. Too much water from the roots could lead the plants to nutrient over toxicity.

It is like overfeeding the plants with nutrient solutions. The excessive amount causes it to have a condition called nutrient burn. The most common sign for this is the appearance of yellow burnt tips on the leaves. When left unattended, the yellowing can progress up until it turns to brown. It will also curl up and becomes lifeless.

Is it okay not to use a humidifier to increase humidity?

There is the easiest and most convenient way to resolve humidity issues in any grow space. It is through the use of the humidifying machine.

Here are some of our best picks for humidifiers:

Amazon.com: Horticat U80Pro Ultrasonic Mist 80 Pint Per Day Direct Connect  Water Line Commercial Humidifier with Day/Night Modes, Humidistat and  Remote Sensor - Grow Room, Garden, Industrial : Home & Kitchen Horticat U80 Ultrasonic Mist


Amazon.com: VIVOSUN Cool Mist Humidifier, 6L Quiet Ultrasonic Humidifier  for Bedroom (Customized Humidity, Remote Control, Sleep Mode & Auto Shut  Off, 360° Nozzle) : Home & Kitchen

Vivosun 6L Ultrasonic Humidifiers


Ideal-Air™ Commercial Grade Humidifier 75 Pints | Ideal Air

Ideal-Air 700860 Commercial-Grade Humidifier GSH75


Model 50 Mister-Mini Humidifier 24v w/Humidistat

Air Bear 265000-001 Trion Duct Mounted Atomizing 24V Humidifier Mister Mini


Amazon.com: Vornado Evap40 4-Gallon Evaporative Humidifier with Adjustable  Humidistat and 3 Speeds : Home & Kitchen

Vornado Evap40 4 Gallon Evaporative Humidifier w/ Adjustable Humidistat

Nonetheless, this device might be by any reason not readily-available. Then, we are here to assure you that Yes, it is A-Okay not to have a humidifier.

In fact, here are some reasons to prove that you can do away having humidifiers in your grow room:

  • Accuracy is not always on point.
  • It can be pretty expensive and would usually cost you a couple of hundred dollars. Or, even more for a good-quality unit.
  • It may take up a lot of space in your grow room.
  • Larger humidifying units tend to produce a loud noise.

How to Increase Humidity in the Grow Room

By now, we have already established the fact that humidifiers are not an absolute necessity for your grow space. Let us then proceed on how to manage the disturbances in the levels of RH through other means possible.

The combination of two or three of the methods below is enough to deliver the same result as it would in a commercially-bought humidifier device. Here’s how:

1. Reduce room temperature.

Generally, the warmer the air, the lesser its ability to hold moisture. The cooler the air, the more water it can hold into.

Of course, we will not disregard the recommended temperature range for its current stage of growth. If the temperature is already set at a higher-end then it won’t hurt to adjust the rate by a few degrees lesser.

Read Also: When Is the Best Time to Replace Your Carbon Filter?

Here are some of the ways we can induce the reduction of the temperature inside the grow room:

  • Create more ventilation.

This does not refer to powered ventilation. As simple as leaving the door or any hole open for a while is enough to encourage circulation. This easy method facilitates the release of heat out from the room and increase humidity. Thus, it gets exchanged with cooler air.

  • Use an air conditioning system.

If budget permits, an air conditioning system would be a great investment for your grow room. It doesn’t only addresses your concerns with humidity. It is also very effective in resolving any heat issues in general.

Our top picks for air conditioners:

Koldfront PAC802W Portable Air Conditioner

Emerson Quiet Kool EAPC8RD1 Portable Air Conditioner

Honeywell MO Series Compact 3-in-1 Portable Air Conditioner

Ensue 8000 BTU 4-in-1 Portable Air Conditioner

JHS 10000 BTU Portable Air Conditioner

2. Install an LED light system.

The grow lights are one of the major contributors to heat inside the grow space. Thus, when installing your light systems this consideration should be factored in right from the start.

Luckily, LED light emits way lesser heat than any other type of lamps. These types are metal halides (MH), high-pressure sodium (HPS), and high-intensity discharge (HID).

Our top picks for LED lights:

Maxsisun 600W LED Grow Light Full Spectrum

Spider Farmer SF-1000 LED Grow Light

Sunraise 1000W LED Grow Light Full Spectrum

Bloomspect 1500W LED Grow Light Full Spectrum

Exlenvce 1500W LED Grow Light Full Spectrum

3. Integrate lights with cooling systems.

Some growers still believe that hotter bulbs like MH and HPS are still best at producing good-quality buds and higher yields. So, using an LED is not quite a favorable option for you. Then, try integrating your existing grow lights with air cooling reflectors instead. That way, you can still continue to deliver the intensity of light that you would want. Thus, without worrying about the bulb’s adverse heat emissions.

Our top picks for air cooling reflectors:

Giantex 6 Inch Air Cooled Hood Reflector

iPower GLARCL6-A 6 Inch Air Cooled Hydroponic Reflector Hood

Sun System Grow Light Air Cooled Single End MH HPS Reflector

Hydro Crunch 6 Inch Cool Tube w/ Wing Reflector

Hydrofarm RFCOOL6 6 Inch Aluminum Cool Tube HPS/MH Grow Light Reflector Hood

4. Operate grow lights at night.

It is cooler during the night time. Hence, running your grow lights during this period lessens the likelihood of building up too much heat inside the room. You may use either a mechanical or digital timer to set up your lighting schedules.

Our top picks for lighting timers or controllers:

iPower 24 Hour Plug-in Mechanical Electric Outlet Timer

GE 24 Hour Heavy Duty Indoor Plug-in Mechanical Timer

BN-Link BND-60/U47 Indoor Mini 24 Hour Mechanical Outlet Timer 2 Pack

Nearpow Dual Digital Light Timer

iPower 7 Day Heavy Duty Digital Programmable Electric Timer

Opulent Systems 7 Day Smart Digital Programmable Heavy Duty Timer

5. Carefully add more water to the soil.

We have to put much emphasis on the word carefully. There is a fine line between mere supplementing from already overwatering your plants. To do this, you have to check the condition of the soil first. If it looks dry, then you may proceed watering it enough to wet the plants. That moisture will evaporate out into the air thus increasing the level of RH in the room.

6. Mist or spray plain water over the plants.

If the soil is wet already, then it would be more suitable to mist over the plants instead. You may use a typical spray bottle to give you more control over how much water will get released to increase humidity. You can spray the plant several times a day depending on your assessment of the condition.

This quick-fix is only a temporary solution. It is still very effective in helping to balance the moisture levels for the time being.

Our top picks for plant spray bottles and misters:

Mkono Plant Mister Spray Bottle

T4U Plastic Plant Mister

Driew Plant Mister

ITISLL 68oz Garden Pump Sprayer Portable

Vivosun 34oz Hand Held Garden Sprayer Pump

7. Place reservoirs of water.

Put water-soaked sponges and bowls or buckets of water on every corner of the room. It is one of the most basic, yet, effective solutions to increase the humidity in the space. Moreover, this method is definitely super cheap. It won’t even cost a single dime if you already own any of the said materials.

The heat generated by the grow lights and other contributing elements induce the evaporation of air from the reservoirs or containers. This then in effect increases the level of RH inside the room. If this ends up producing too much humidity than you actually need, you can take out one or two of the containers to lessen the moisture back again.

8. Optimize the use of extractor fans.

Extractor fans are essentially used to help the good circulation of air in and out of the grow room. Extractor fans don’t exactly help to increase the RH levels. Rather, it aids to disperse the existing humidity throughout the room.

There are instances where some parts of the room gather more moisture. Hence, this often gives you inaccurate readings. This can be easily avoided by spreading the RH with the use of an extractor fan.

However, there is also a dire consequence of using fans. Incorporating a lot of ventilation can also diminish RH by letting the exchange of air take place too rapidly. By forcefully drawing warm air out, it pushes the moisture out of the room as well.

To optimize the use of the fan, you can instead try to lessen the amount of air cycling from the inside of the room and out. You can do this by keeping the fan speed at the lower level. In doing so, it will help encourage the retention of moisture in the grow space. Thus, while still maintaining good air circulation.

Our top picks for extractor fans:

Yield Lab Pro Series Inline Hush Duct Fan w/ Variable Speed Controller

TerraBloom 4 Inch 160 CFM Inline Fan w/ 0-100% Variable Speed Controller

Vivosun 6 Inch 390 CFM Inline Duct Fan w/ Variable Speed Controller

AC Infinity Cloudline T6 Ventilation Exhaust Fan

Vtronic 8 Inch Mixed Flow Inline Duct Fan

That’s it! Those are some of the solutions we recommend to help you better increase the relative humidity in your grow room. They are more effective without the need for a humidifier machine. It would be great to install combinations of a few methods to ensure it would deliver decent results. Regardless, it is also important for you to check the effects so as not to go overboard with the RH levels as well.

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 MyGardenPlant.com website to make a garden with the proper guide. So, you will get me beside you if you want to know anything about gardening.