Cannabis Climate Control – Full Guide for Indoor Grow Rooms

Growing medical or recreational cannabis (also called marijuana, hemp, or cbd) requires a lot of control and precision. So cannabis climate control is a major issue, both in greenhouses and indoor grow rooms.

There are strict regulations surrounding the cannabis industry, like GMP and GAP certifications. So, to successfully grow cannabis commercially, it’s necessary to take full control of the environment. Often to a greater extent than almost any other crop.

Growers always strive to produce the best cannabis, in all aspects. To grow large, high-quality buds, with the right concentration of cannabinoids and terpenes, all while avoiding mold at all costs.

In order to achieve these goals, it’s often necessary to utilize controlled environments, such as greenhouses, indoor grow room, or even grow tents. It’s then possible to control all environmental aspects, including:

  • Lighting
  • Temperature
  • Humidity
  • Airflow
  • Carbon Dioxide (CO2)

Cannabis Lighting Requirements

Light is a basic part of any grow operation, and cannabis grows in particular. Every plant needs light in order to photosynthesize and develop. Cannabis, like any other plant, has its preferred light intensity and spectrum.

Cannabis Day/Night Lighting Regimen

Cannabis also has additional unique lighting requirements. As a photoperiod plant, it depends on light to determine when it’s time to start flowering. More specifically, it requires long periods of darkness to start doing so.

So the ability to provide both full light and complete darkness for long periods is crucial. In indoor grow rooms this is pretty straightforward. But when it comes to cannabis greenhouses, growers need to utilize blackout screens to provide the darkness necessary for flowering.

The day/night regimen needed changes from strain to strain and different growers often have different approaches. But generally, cannabis plants need a long day and short night during the vegetative stage, with longer nights initiating flowering.

Grow Light Types and Energy Savings

One of the most important things to consider when it comes to lighting a cannabis grow op is the technology. Different lights do have different spectrums, but the more important difference is energy usage.

Modern grow rooms often use LED lights, which are much more energy efficient than the older HPS lights. They’re more efficient because they emit less heat, using more of the energy for light.

However, LED lights still emit quite a bit of heat. Especially with the amount of light and intensity needed for commercial cannabis cultivation.

Light Affects Temperature and Humidity

Grow lights, even modern LEDs, constantly radiate heat, which is why indoor grow rooms are often warmer than greenhouses. The additional heat and large amounts of radiation also affect humidity by increasing the plants’ transpiration rates. So overall, lights constantly work to increase temperature and raise humidity.

This is something growers should definitely consider when designing their grow room. Light plays a major part in determining the environmental controls and climate control systems needed to maintain ideal growing conditions.

Cannabis Temperature Control

Like all plants, cannabis likes comfortable temperatures. For most grows, the ideal temperature range is between 65-80°F (18-26°C). Keeping temperatures within this range helps maximize plant growth and development and contributes to large and healthy buds.

There are many types of temperature controllers growers can use to control their environment. The most common of which are HVAC systems, air conditioners, heat pumps, and heating pipes carrying heated or chilled water.

Temperature control is one of the most basic aspects of controlled environment cultivation. It also affects and is affected by other parameters, such as lighting and humidity. Which is why temperature control is at the center of most grow room climate control systems.

Temperature and humidity are especially closely tied, directly affecting each other. So it’s virtually impossible to discuss temperature control without taking humidity into consideration.

Indoor Cannabis Humidity Control

Cannabis growers control all climate parameters, including humidity, and there are several reasons to do so.

Ideal Humidity Range for Cannabis

Cannabis has an ideal humidity range, just as it has an optimal temperature range. Most cannabis growers prefer a range of 40-70% relative humidity, depending on the growth stage.

In terms of VPD (vapor pressure deficit), the ideal range is 0.8-1.1 kPa during the growth stage, and 1.0-1.5 kPa during flowering stages.

Preventing Molds and Mildews

While the ideal humidity range has a huge impact on development, it’s not the only reason to control humidity. Perhaps the biggest issue with humidity is mold. The most common of which being bud rot (also known as gray mold or botrytis) and powdery mildew.

These mildews can devastate any cannabis grow op. Given the right conditions, they can spread rapidly, infecting large amounts of plants. Once infected with these fungal diseases, plants will grow slower, and may eventually shrivel and die.

However, when it comes to cannabis, preventing molds is even more crucial. The cannabis industry has strict regulations, both for medical and recreational products. So growers are extremely limited in the amount and types of sprays they can use to combat these diseases.

On the other hand, there are strict limitations on the presence of molds. So cannabis growers are basically left with one option – to prevent molds from developing in the first place.

Luckily, these diseases can’t develop in any situation. They require high humidity or even dew point condensation in order to do so. If you can successfully limit humidity levels at all times, they won’t be able to develop or spread at all.

Dehumidification Vs HVAC

When it comes to indoor cannabis humidity control, there are two main methods. The first, and only surefire way to control humidity, is by using dehumidifiers. Dehumidifiers such as DryGair use heat exchangers to condense water inside the unit, effectively and efficiently removing water from the air.

The other method is to use HVAC to control humidity. This is a tricky method. HVAC is designed for temperature control, rather than humidity. And although it does remove some water vapor from the air as a welcomed side effect, it’s not incredibly efficient.

So to use HVAC for control humidity, growers need to run it continuously, regardless of the temperature in their grow space. So growers alternate between heating and cooling, in an attempt to maintain the right temperature, yet still keep the HVAC running to reduce humidity.

Needless to say, this method is inefficient, as it means the HVAC needs to stay on. This also requires larger systems and more HVAC equipment to manage the massive amounts of moisture the plants generate. This leads to higher initial costs and operational costs, including maintenance and energy.

Utilizing Airflow to Improve Cannabis Cultivation

Light, temperature and humidity are the most basic aspects of greenhouse or indoor cannabis cultivation. Simply focusing on these three parameters can achieve great results and high-quality buds.

However, to ensure that all plants enjoy their ideal humidity and temperature, there’s another piece to the puzzle – airflow.

Air movement is especially important when it comes to cannabis plants. Indoor cannabis grows are usually crowded, with thick canopies almost overlapping. Add in the fact that cannabis buds are extremely dense, and you get much higher humidity levels inside the foliage and buds, than the rest of the grow space. This is where airflow comes in to play.

Growers use a range of fans, including horizontal and vertical fans, to helps disperse these pockets of humidity, known as microclimates. These help to a certain degree, but they may also create uneven conditions in the space. For example, plants further away from the fans won’t enjoy as much airflow as those closer to them.

Airflow can also be combined with humidity control. DryGair dehumidifiers, for example, come with a patented air circulation system, which disperses the dry air in all directions at once. This creates uniform climate conditions everywhere in the grow room or greenhouse, and ensures mold-free, homogenous products.

Improve Cannabis Growth with CO2

Carbon dioxide is a key element in photosynthesis. So, when there’s enough light, and an ample supply of water, increasing the CO2 concentration in the space can drastically improve photosynthesis. Of course, better photosynthesis improves development and growth.

The average CO2 concentration in the environment is about 400 ppm (parts per million). However, indoor cannabis grows may reach as much as 1,000 ppm, by injecting compressed CO2 into the space.

Avoid Ventilation to Improve Cannabis Climate Control

It’s important to note that many indoor growers use ventilation and exhaust fans at certain times to exchange air with the outdoors. This is usually done in order to release humid air to decrease humidity without a dehumidifier.

However, ventilation directly undermines other climate control efforts. When air is released from the space, you lose precious elements, such as heat and CO2. This means more heating and more CO2 injections, leading to higher energy and operational costs.

Using dehumidification systems to control humidity allows growers to keep their space sealed for longer periods, or even indefinitely. This drastically increases the level of control you can have over your space, limiting expenses in the process.

At the end of the day, growing cannabis indoors, or in a greenhouse, is a business. When expenses rise, profits dwindle, and if a grow op isn’t profitable, it won’t remain in business.

The level of climate control and the environmental controllers a grower chooses to use directly impact costs. They also have a huge impact on product quality, determining income as well.

It’s important to consider every climate aspect of indoor cannabis cultivation. The better the control, the more you can optimize for lower expenses, as well as product quality.

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