When growing plants indoors, few factors can impact your cultivation as much as the temperature you maintain in the grow room. If the temperature gets too high, plants can suffer serious damage. To prevent this, it is essential to have a proper ventilation system that keeps the room cool without excessive cost. This guide will show you the best way to set up an effective cooling system, keeping you happy year-round while others struggle to keep their plants cool.
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Perfect Temperature
Most people think they can just feel whether the room is too hot, but there is no reason not to use a thermometer to know if the temperature is ideal. With a thermometer, you can ensure the grow room stays between 75–85°F (24–29°C). The maximum temperature your grow room should reach is 90–95°F (32–35°C).
Invest in an Exhaust Fan System
Exhaust fans are one of the most important components of a ventilation system because they pull hot air out, allowing fresh cool air to enter. Note that the fan must be strong enough to circulate the entire volume of air in the room several times per hour, ideally every few minutes.
A simple calculation can help you determine the fan system you need:
- For a 23” x 23” (63.5 x 63.5 cm) grow tent with a 250-watt HPS system, you need a 4” exhaust fan and controller. This is the smallest fan and tent you would likely use.
- For a 40” x 40” grow tent, use at least a 6” exhaust fan. This is one of the most common sizes for indoor growers. Again, ensure you have the proper controller. For larger rooms, add 1 inch (2.5 cm) to the fan size for every foot (30 cm) of room length. This general rule covers most cases, but check further if using more powerful lighting. For LED systems, this is usually sufficient to ventilate the room properly.
These exhaust fans should be installed near the ceiling, as hot air rises. This means the duct bringing air into the room should be near the floor and slightly larger than the fan you are using.
Use Oscillating Fans
For indoor air, it is important to circulate it throughout the room to reach every plant. In addition to moving air in and out, you will need oscillating fans to blow air between plants, keeping them cool.
These fans may not move enough air to cool the room on their own, but they are still important. They also simulate natural wind, helping stems grow strong and preventing weak growth. Use a few wall-mounted or 10” (25 cm) floor fans to maintain airflow.
Consider Adding CO2
Supplementing CO2 is crucial, regardless of your room or ventilation setup, because you must ensure the room has not only sufficient air but also enough carbon dioxide.
Adding CO2 ensures plants have enough “food” and can increase yields beyond expectations. In some cases, growers report a 50% increase in yield with just a small change in ventilation. Place the CO2 system on the wall opposite the ventilation system, above the plants, so CO2 falls onto the plants rather than being produced below.
Controlling Humidity in the Grow Room with a Dehumidifier
One part of the ventilation system you might not think about is removing accumulated humidity when growing plants in an enclosed space. Many types of diseases can develop in a damp environment, so if you want healthy plants, this is definitely something to consider. An added benefit is that it can increase resin production, which is encouraged in drier conditions.
During different growth stages, you should maintain different humidity levels:
- During the propagation stage, humidity should be 80–90%
- During the vegetative stage, humidity should be 60–70%
- During the flowering stage, humidity should be 40–60%
Today, there are many types of dehumidifiers on the market, so make sure you choose one that best fits your plant size, controlling humidity while matching your available space.
Using the Best Ventilation System
With a proper ventilation system, you can rest assured that your plants will thrive even without constant monitoring. Proper ventilation and air circulation are essential for plant safety and long-term productivity. As long as you consistently remove hot air and bring in cool air, your plants will avoid the health issues that often arise in high-temperature conditions.
However, growing healthy indoor plants also requires other factors, growing methods, and auxiliary equipment to support optimal growth. You can explore grow lights, accessories, and more on our website here: LED Grow Lights.