One of the most important aspects of indoor (and outdoor) cultivation is establishing a climate for your plants to thrive in. Maintaining this temperature over long periods of time can be both time consuming and difficult.

Fortunately, in the modern technological era, we have computers that can do all of this for us with optimal precision and accuracy. These are referred to as climate controllers.

Adding a climate controller to your grow environment will allow you  to save valuable time and energy by providing 24/7 monitoring and adjustments to your grow room. This means that you can set the temperature range, humidity levels, and with some systems even water temperature and pH/ppm levels as well. The system then automatically makes the necessary changes to the grow room to maintain these levels.

Depending on the size and ability of the controller, all kinds of different devices can be connected to the controller. Generally, for smaller grows, simple systems that control the extraction fan is enough to maintain a stable environment. More complex and larger systems will benefit from the addition of an air conditioner, dehumidifier, heaters, foggers, or any other device that affect the environment of the grow room. With the addition of these devices, a greater level of control can be had over the entire system.

How do they work?

Climate controllers work simply by measuring the climate inside the grow room and using this information to decide whether it is below, or above the set range. In the most common example, using only an extraction fan, if the lights are on, and it is a warm day, the grow room will begin to rise in temperature. Eventually, this temperature will become higher than the set maximum temperature of your climate controller. The device will detect this with one of its sensors, and tell the extraction fan to speed up to pull a greater amount of the warm air away from the room, which in turn brings in cooler air to reduce temperatures of the grow room. When the lights turn off at night, the grow room will begin to cool off again, When the temperatures start to dip and go below the set point in the climate controller, the device will sense this, and tell the fan to slow down to conserve the warm air better.

If you have other devices such as heaters, they may also kick on when the temperature dips, allowing for greater control over these parameters. If all your room had was an extraction fan as a variable, this will do fine if the temperatures do not generally dip very low at night, but there is nothing a fan can do to increase the temperatures in a cold grow room. This is why having heat mats, or other forms of heat are often beneficial for places where the temperatures often dip below the desired range.

How do I decide where to set my climate controller levels at?

Consider what crop or plant species you’re growing, and try to mimic the natural climate range that that plant tends to thrive in, and apply it to your own growing climate. Achieving this can be done manually, by measuring the temperatures and humidity levels of your grow room, and playing around with the fan speeds to try and achieve optimal temperatures.

Is it tropical, temperate, or arid in nature? Once deciding this, you may also consider some of the more detailed characteristics of your target crops climate. Does it have a natural dip in temperature at night? Do the light cycles and temperatures change with the seasons?

It is also important to consider the climate your indoor grow room or greenhouse is located. Trying to keep temperate climates indoors in a tropical location, for example, will require a different level of control than keeping a tropical grow room in an already tropical location.

Climate controllers come in extremely handy when managing grow rooms that are very different than the climate in which it is located.

A good starting place for most plants is to keep your room at the same climate that you as a human would enjoy. This means:

  1. 20-30 degrees Celsius
  2. 20-60% humidity

From here you can optimize for the species you are growing. Tropical plants will do better with temperatures from 25-35 degrees, and humidities all the way up to 99%. Cloud forest species, however, will require levels of around 10-20 degrees celsius, and humidity levels exceeding 80%.

We highly recommend you do some research on the plants you are planning to cultivate to see what their normal environmental range may be. Try looking at places like The vast majority of plants will thrive just fine in the above-mentioned parameters.

What is the best climate controller for me?

Every individual grow room will have different needs, and deciding on the level of control can vary greatly. For most smaller grows, having simple climate controllers that only measure temperature and control fan speed are usually sufficient. For larger grows, greenhouses, or grow rooms that are subject to a wide swing in temperatures and humidity on a regular basis would benefit much more from more complex and in depth controllers.

Keeping a grow room within stable temperatures can be hard. It requires constant fidgeting and tweaking in order to get the balance just right. Fan speeds, heat mats and heaters, water chillers, air conditioners, dehumidifiers, and intake fans all have direct implications on the grow room temperatures and humidity levels. Finding the perfect balance, especially in larger grow rooms can be time-consuming and potentially fatal for your plants if left unchecked for too long.

This is where grow room controllers come in. These devices come in all shapes, and sizes, but generally do the same thing. They are like the central nervous system of your grow room, listening to various sensory inputs from inside the grow room, and then deciding whether it needs to turn on, speed up, or turn off certain devices within the room.

Although grow room controllers are generally quite expensive, and in many cases not necessary for smaller grows, they are a valuable investment for anybody with a larger grow room, or interested in saving time through automation. Many hobbyists install grow room controllers for their ability to precisely control their grow room and can be fun to play around with.