How to

10 May 2021

The Importance of Having a Good Dehumidifier in Your Grow Room

Humidity can be one of the most challenging concepts for a beginning cannabis grower to master, as marijuana plants require different humidity levels at each different phase of their growth. While young clones and seedlings prefer an ultra-humid climate, flowering plants and developing buds can be destroyed by the same levels.

Thankfully, there is one piece of equipment that can help a grower regulate humidity levels better than any other: the dehumidifier. Quite literally the opposite of a humidifier, dehumidifiers actually remove water vapour from the air, collecting the excess moisture in a basin which can then be discarded. The ability to remove moisture from the air inside of a grow room puts control over humidity levels and thus plant health back in the hands of the grower.

Humidity Control in Your Grow Room

Humidity levels play a vital role in the health of your plants at every stage of their growth, though humidity requirements for various stages differ drastically. Seedlings and clones prefer a high-humidity environment, such as a humidity dome, while the same conditions in a flowering room will almost certainly lead to bud rot and other diseases.

Though there is no absolute rule regarding humidity in the grow room, there is a general consensus amongst growers that clones and seedlings require the greatest amount of humidity, plants in veg a bit less, and flowering plants the least still. Typically, growers tend to keep their clone rooms between 70-80% humidity, veg rooms between 60-70%, and flower rooms between 40-60%.

Growers will often employ humidifiers during the vegetative stage, particularly in dry, arid climates, as well as when air replacement inside the grow room occurs quickly and pulls the humidified air from the room via fans and ducting. This can be a careful balance to strike, and many growers have opted for automated control panels to maintain proper levels.

Once plants have begun developing and stacking buds, however, too much humidity quickly becomes a problem. Depending on the number of plants and the amount of space, humidity levels can quickly soar. Without proper airflow and circulation, moist air will stick around inside the grow room and spur on the development of mould, powdery mildew, Botrytis, or any other number of diseases. A number of pests appreciate a nice, humid environment as well, such as fungus gnats and whiteflies; proper airflow and replacement, as well as humidity control, are critical in their prevention.

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Types of Dehumidifiers

There are a few different types of dehumidifiers available, so it’s important to understand what you’re looking for.

  • Compressor – Compressor dehumidifiers draw air over a filter and then onto cooling coils, causing warm air to condensate and collect in the unit’s water tank, similar to the operation of a standard refrigerator.
  • Desiccant – Desiccant dehumidifiers draw air over a filter but do not contain compressors or cooling coils. Instead, the air is passed over a wheel containing a desiccant of some type, such as silica gel, which absorbs the moisture from the air.
  • Peltier – Dehumidifiers utilizing Peltier technology create a thermo-electric charge which converts electricity into temperature variations. Peltier dehumidifiers contain a cold metal surface on which condensation forms, which is then collected in the unit’s water tank.
Grow room with dehumidifier

Picking the Best Grow Room Dehumidifier

The desire to remove moisture from the air during the flowering period is what spurs many growers to purchase a dehumidifier, though many growers use them during the veg period also, depending on the climate. For example, a humid, equatorial climate will require dehumidification throughout the various phases, while a dry, mountainous climate may require additional humidification to meet plant needs. These are essential factors to consider when deciding on the best dehumidifier.

Dehumidifiers come in a variety of sizes and capacities, and their prices vary as well. For the modest home grower working in a grow tent or small grow room, a unit with a small, compact design may work perfectly. For a large grow room or greenhouse, a larger unit will be required. Many larger models possess the ability to be connected to a drain hose, making it unnecessary to empty the water tank when it fills.

Smaller units, however, often require the grower to regularly empty the catch basin, which varies in capacity from unit to unit.

Some factors that growers should take into consideration when deciding on a dehumidifier include:

  • Size – Dehumidifiers come in a variety of sizes. If you’re growing in a small grow tent rather than a large grow room, you will not need the dehumidification power of an industrial unit. Instead, opt for a small dehumidifier with a smaller tank capacity, such as a pint dehumidifier. You may have to empty the water tank more often, but your plants won’t find themselves in an indoor desert, and you’ll save yourself a lot of money. Smaller units are also favourable for those short on space, such as the Pro Breeze Electric Mini Dehumidifier, a portable dehumidifier with a half-pint capacity. Other small units include various models from Eva-Dry, a well-known producer of portable dehumidifiers.
  • Moisture removal – Some dehumidifiers are just not powerful enough, and others too much so. Most home dehumidifiers remove between 25-50 pints of moisture per day and are adequate for small grow rooms or tents. Frigidaire, for example, produces models in 30, 50 and 70-pint capacities. Larger size dehumidifiers are typically capable of removing upwards of 80 pints of water per day, with some units removing as much as 25 gallons of water per day.
  • Square Feet – Measure your grow space carefully and calculate how much dehumidifying power your garden will require. Many home units can dehumidify between 1,500 and 3,000 sq. ft, though some higher-end units, such as the hOmeLabs Energy Star Dehumidifier, are built to tackle over 4,500 sq. ft.
  • Still water – Still water in your grow will raise the humidity, undoing the work of your grow room dehumidifier. Be sure to monitor the amount of water remaining in your grow room, vacuum or soak up any runoff from watering plants, and ensure that your reservoir is covered and not being evaporated by your grow light.
  • Lighting – Traditional HID grow lights (MH, HPS) operate hot, which reduces humidity in your grow room. Newer LED grow lights run cooler, but many still contain ballasts which can send temperatures skyrocketing. Be aware that as temperature increases, humidity decreases, and when the lights go out, humidity levels will rise, possibly requiring you to run your dehumidifier throughout the night cycle. Many units include an auto-shutoff feature to turn off the unit when desired moisture levels are reached and avoid excessive power consumption.
  • Additional Features – Many dehumidifiers come with additional bells and whistles as well, such as variable fan speeds, ultra-quiet operation, turbo mode for faster dehumidification, internal humidistats, and LED indicators to alert the grower of the current relative humidity and when to empty the tank. Many companies additionally offer warranty coverage for their units.

Dehumidifiers are an incredible piece of technology that can play a vital role in the health of your plants and the success of your harvest. With many sizes and options available on the market, you can choose a unit specifically catered to meet your demands, from a tiny unit for a small space to a massive, air-conditioner-sized unit for commercial grow rooms.

Whichever you choose, be sure to stop by Marijuana Grow Shop and check out our continually-updated growing content for more information on maximizing your yields.

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Post author
Michael Richey
Michael loves to grow cannabis and write about what he learns along the way. His best friends are his dogs and marijuana.
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