8 Tips To Regulate The Heat Of Your Cannabis Grow Room

When growing indoor cannabis, one of the trickiest problems to contend with is the room temperature. The temperature must be precise, and if it fluctuates too high or too low, it can drastically impact your plants.

Failing to regulate the temperature in your cannabis grow room could lead to inadequate growth and death. Is your cannabis grow room too hot? If so, the hard work you poured into those plants may all be for nothing.

Heat Can Hurt

All plants are finicky, especially when you are growing them indoors. Plants that are overheating can begin to exhibit signs of stress, resulting in spindly plants that do not flower or fruit properly. These plants also are much more susceptible to disease.

At high heats, they are susceptible to things including:

- Root rot 

- Spider mites

- Powdery white mildew

- Nutrient burn

Even though cannabis has the nickname “weed” due to its ability to grow just about anywhere, it does not hold up well under high heat. Heat affects the plants in many ways– when heat is too high, it impairs seed germination, causing issues before the plant even begin to sprout.

Excessive temperatures limit the process of photosynthesis, stunt enzyme activity, and lead to a lack of protein production. However, the plant will still produce sugars in temperatures above 85ºF.

The sugars will be distributed throughout the plant when the temperature is above 60ºF. If the plant isn’t warm enough, the sugars cannot move where needed, causing the plant to suffer and become frail.

If temperatures are above 85ºF during the flowering stage, the heat will stunt the bud growth. This can result in a loose and airy bud that lacks potency and smell. If left in high heat for too long, the plant may end up dying.

Leaves may wilt and turn brown, the roots will rot, and the entire plant itself will begin to droop.

How To Tell When It’s “Too Hot”?

Cannabis is a tricky plant to grow indoors, and there is an ideal temperature range that all growers should know. The perfect temperature range varies based on the plant subspecies, but for the most part, 66ºF is ideal for root growth, and a range between 70ºF and 80ºF is best for aerial growth.

The maximum temperature for successful growth should not exceed 85ºF, while the minimum temperature should not drop below 65ºF.

Signs that your cannabis is suffering from high heat include:

- Leaf edges curling upwards

- Drooping or wilted leaves

- Drooping or wilting of the entire plant

- Development of foxtails - the plant grows a new bud on top of the first one.

Is Your Cannabis Grow Room Too Hot? Here Are 8 Tips!

Increase Air Exchange

Air exchange is crucial for keeping the temperature in check in your growing room. It prevents mold and helps the plants grow and build stronger stems and branches. Ceiling fans can help keep air moving, reducing the chances of moisture lingering on the plants, which enables the development of mold or fungus.

An HVAC system with accurate thermostats is the best way to maintain ideal growing conditions for cannabis grow rooms. A regular fan, such as a box fan or tower fan, can help eliminate stagnant air in your grow room as well.

Rethink Lighting

1. Lighting may not be one of the first things that come to mind when you think temperature control, but the type of lights in your grow room can actually play a significant role in high temperatures. Both plasma and HID lighting produce a substantial amount of heat.

In an enclosed space, the lights can contribute to rising temperatures. Lighting can drive the temperature up, especially in small rooms with poor ventilation. The longer the lights are on, the more heat builds up in the room.

Consider switching to LEDs, which do not produce as much heat. Ducted reflectors will also help with the issue, as they pump their heat directly outside. Compact fluorescent light bulbs, or CFL bulbs, are great for seedlings and clones but do not work well for flowering.

Another option to keep in mind is running your lights through the night, which can help with temperature and cost. Ambient temperatures tend to be lower at night, as are energy costs in many places.

Nutrient Concentration

Nutrient concentration is another factor in room temperature control. Plants conduct their own type of air conditioning, which is called transpiration. During this process, plants increase their water uptake, disrupting the finite balance in a hydroponic setup.

Transpiration is like sweating for plants, except the moisture for cooling is pulled from the ground into the plants.

If the plants have too much transpiration, toxicity problems can arise as the plants try to adjust. Along with increased moisture intake, they pull in more nutrients from the soil along with it. As such, the cannabis plant can easily receive too many nutrients, which will lead to ill effects.

To help avoid this, adjust the nutrient-to-water ratio in the reservoir. Some growers advise reducing the nutrient concentrations by around 20% in hot conditions.

Boost CO2 Supply

Boosting your CO2 supply to your grow room offers many benefits. Not only does it help boost yields and fatten up the buds, but it also allows the grower to capitalize on higher temperatures.

With extra CO2, plants can handle the higher temperatures, which is beneficial as the plants can flourish even in slightly higher heat.

However, growers should be careful not to increase CO2 concentrations too high as CO2 can be harmful and deadly. Always use calibrated and accurate CO2 sensors and alarms to ensure safe conditions.

Focus on The Roots

Plants are considerably more resistant to heat if the roots are kept cool. Ensure you water the plants regularly, especially when it’s hot, as it helps with keeping the roots moist and cool. When the roots are cool, the plants are less likely to suffer. Plus, they can recover more rapidly from a hot spell.

For best results, keep the roots at consistent temperatures to ensure they remain healthy. Growers should keep soil temperatures at about 80 degrees Fahrenheit. Monitoring with a soil temperature sensor is the best way to ensure your keeping ideal soil conditions.

Try Out Supplements

There are various supplement options to boost your plants. Some can help protect your cannabis plants, enabling them to become more resistant and recover quickly from heat stress.

If you use supplements and nutrients, only get ones from the same company, as the manufacturer tests them together to ensure they don’t harm the plant if or when combined. This will help avoid unexpected issues, such as lockout.

Control Humidity

Humidity goes hand in hand with temperature; they correlate inversely. Warmer air holds more moisture, so as temperature increases, humidity decreases and vice versa.

In early growth stages– seedlings and clones, ideal humidity is vital for success. Up until the plants have reached their mid to late flowering stage, high humidity levels are essential.

Once the plants have reached their final growth and flowering stage, relative humidity should remain in the lower range, as high humidity can allow diseases to flourish. Diseases could sweep through and ravage the entire crop.

So, in the early stages, a humidifier could work wonders with boosting your crop. However, in the later stages, you need to be cautious and in control of the humidity.

You can control humidity with humidification/dehumidification systems tied directly to the grow room’s HVAC system.

Consider A Swamp Cooler

Swamp coolers, which utilize a primary air conditioning principle (evaporative cooling), are another option to consider. Since substances such as refrigerant and water absorb heat when converting from a liquid to a gaseous state, these coolers can work wonderfully in grow rooms.

Swamp coolers (or evaporative air conditioners) use a fan to move hot air through water-moistened media, which evaporates water from the air. Heat is removed from the air as the water evaporates (i.e., the air cools down). The cooled air is blown into the room using a blower motor through a vent.

Swamp coolers can work wonders, resulting in a drop in temperature of up to ten degrees. However, they can increase humidity, which may not be the best choice for your grow room.

Bringing Everything Together

Temperature control in growing rooms is vital for a plentiful harvest. Growers can use several tricks and tips to help regulate the temperatures in their growing room, from air exchange and carbon dioxide to humidity control and swamp coolers.

Each grow room is different, and not all of these tips will be ideal in every situation. Every grow room is unique and will require various tweaks for optimal temperature control. However, it is vital that all growers thoroughly evaluate and regulate the temperature of their cannabis grow room.