Mastering “How to Cool Down Greenhouse”: Top 10 Effective Ways

As a cannabis grower, you must know that the temperature inside your greenhouse can significantly impact the quality and yield of your crop.

As time goes into summer, the temperature will continue to rise. While the purpose of a greenhouse is to keep plants warm, overheating can create its own set of problems. Increased susceptibility to insects, increased disease risk, reduced yields, and reduced crop quality are just some of the issues that extreme temperatures can cause. Therefore, maintaining greenhouse temperatures at ideal levels is critical in regions with exceptionally high summer temperatures, as few crops thrive in hot temperatures.

But if you use the right tools and techniques, you can effectively reduce the temperature in your cannabis greenhouse and keep your plants healthy and happy. This blog will explore ten practical ways to cool your greenhouses and keep your plants thriving.

First of all, there is a problem we need to understand.

how to cool down greenhouse

Is It Too High a Temperature for Your Greenhouse?

Generally speaking, anything above 90°F (32°C) is too hot for your greenhouses. So it would be best if you did everything possible to keep your greenhouse below 90 degrees. Living in an area where the standard temperature is 100 degrees Fahrenheit (38 degrees Celsius) can become a struggle.

If your greenhouse temperature rises rapidly in summer, you must take proper steps to maintain perfect plant conditions.

What is the Optimum Temperature in the Greenhouse?

Generally, 80 to 85°F (26 to 29°C) is the ideal plant temperature. But for marijuana, marijuana plants prefer temperatures of 70-85°F (20-30°C) during the day when lights are on, and nighttime temperatures range from 65 to 68°F.

You can give your plants the optimum desired temperature despite the high summer temperatures. However, the steps to cooling your greenhouse and what you need to do to keep it cool depend on what you're growing and where you live.

10 Effective Ways to Cool Your Greenhouse

1. Monitor Your Greenhouse Temperature

It is crucial to monitor the temperature in the greenhouse regularly.

You can use a thermometer or digital temperature monitor to keep track of the temperature and make adjustments if necessary. A standard thermometer can help you monitor the temperature to ensure optimal growth.

2. Install Shading or Reflective Materials

Installing reflective material is one of the most effective ways to cool a greenhouse. These materials can help block excess sunlight and heat, reduce greenhouse temperatures, and are cost-effective. Some options include reflective paint or even aluminum foil.

Shading paint--reflective paint filters part of the sunlight to avoid damage to plants caused by direct exposure to extremely high temperatures. Layers can be added to the conservatory during the hot summer and washed off when the weather cools.

Of course, shading paint is unsuitable for all greenhouses, so choose suitable shading materials according to different greenhouses and climates.

3. Use Proper Ventilation and Air Circulation

Proper ventilation and air circulation are critical to maintaining a healthy, relaxed greenhouse environment. The ventilation methods to balance indoor temperature can be divided into passive and active.

Reduce cooling costs through passive ventilation

The main benefit of passive ventilation is its relatively low cost. The initial investment is low compared to active systems.

Passive ventilation is the process of supplying and exhausting air to and from an interior space without the use of mechanical systems. It refers to outside airflow into an interior space due to pressure differences created by natural forces.

Two types of natural ventilation exist in buildings: wind-driven and buoyancy-driven. Wind-driven ventilation is caused by the differential pressure that the wind creates around a building or structure and openings around the perimeter that allow airflow through the building. Buoyancy-driven ventilation occurs due to directional buoyancy created by the temperature difference between the interior and exterior.

Naturally ventilated buildings are sometimes referred to as "breathing buildings" because the internal heat gain that causes the temperature difference between inside and outside is produced by natural processes, including heat from people, and the effect of wind is variable.

So passive ventilation is natural wind. Therefore, every greenhouse needs to have roof vents and wall vents. Airflow can also be quadrupled by simply using the side and bottom vents. Leaving your door open can also help keep your greenhouse from getting too hot. Growers operating in areas with solid summer winds and many open spaces can use vents well. Growers can also customize greenhouses with doors, shutters, louvers, and other ventilation channels to improve airflow to cool overheated plants.

NOTE: Be careful with natural winds, which can also be hazardous if your area is prone to strong winds. Be sure to find a greenhouse suitable for the wind gusts in your area.

If you have a medium or large greenhouse, or if the outside temperature is too high, more than natural ventilation may be required. That's why you must resort to mechanical ventilation, such as using an exhaust fan. A sound ventilation system will help blow out hot air and bring cooler air into the greenhouse.

Reduce greenhouse temperature through active ventilation

Active ventilation is the most effective way to ventilate a greenhouse and help reduce temperatures, but it requires increased operating costs and maintenance. Active ventilation is essential when greenhouse temperatures climb and passive ventilation cannot be regulated.

Fans are a simple and effective way to circulate air and cool your greenhouse. By moving air around, fans help prevent hot spots and distribute cool air evenly throughout the space. You can use a combination of ceiling and portable fans to create a breeze and keep your plants cozy. Ensure the fans are positioned so they blow toward the plants but not directly at them, as this can cause damage.

There are several options for fan systems. However, there are several factors you must consider before installing any fan system.

First, the fan should be the right size to allow adequate air circulation in the greenhouse. You must find the right lover for your greenhouse structure to get the most out of it. You can find a professional to help with this problem.

Another factor is that you should consider fan placement. For the fan to perform to its total capacity, you should mount the fan at the top of the structure, as the hot air will move upwards (for exhaust fans), and this way, the airflow will be over the plants.

Be sure to clean and maintain the fan system regularly. Cleaning fan blades, belts, and motors and removing dirt, weeds, or grass from shutters and shutters are critical to ensuring a long system life.

For cannabis growers who need more cooling capacity, more powerful options such as evaporative cooling are available.

4. Install an Evaporative Cooling System

Evaporative cooling systems are a great way to cool a greenhouse without using much energy— an effective and relatively cheap add-on.

These systems work by cooling the air with water as it passes through a wet pad or filter. As the moisture evaporates, it absorbs heat from the air, which helps cool the temperature inside the greenhouse. These systems can be installed on the greenhouse's roof or walls and combined with other cooling methods for maximum efficiency.

Fan and pad systems are the preferred methods of evaporative cooling. Typically, the system consists of a cellulose pad, pump, reservoir, and fan. First, the cellulose packing is soaked with pumped water. Excess water is then collected into a storage system. An exhaust fan opposite the mat then draws air into the wet surface, evaporating the water into the air while cooling the greenhouse. Evaporative cooling works better at lower relative humidity, so this method is especially effective in drier regions.

Choosing an evaporative cooling system that is easy to maintain is best. Also, regular cleaning of the evaporation system can increase its efficiency.

5. Install the Air Conditioner

Portable AC is an excellent option for cooling large greenhouses. They are energy-efficient and cost-effective. In addition, most of them have a dehumidification function as part of the system.

Thus, they will help regulate humidity levels while keeping the greenhouse cool. Additionally, growers with a sloped greenhouse attached to their houses can vent air conditioning into the greenhouse.

But it should be noted that the dehumidification function of the air conditioner cannot be compared with the dehumidifier and the integrated HVAC system. Therefore, choosing other methods is best if you have high dehumidification requirements.

6. Use a Misting System to Cool the Air

A misting system is an excellent method to cool down a greenhouse and give plants the needed moisture. These systems work by spraying a fine mist of water through nozzles into the air, evaporating and cooling the surrounding area. Install a misting system throughout your greenhouse or target specific areas with a portable misting fan.

You must monitor the humidity levels in your greenhouse, as too much moisture can lead to mold and other problems.

Also, be aware that misting systems and atomizers do not work well in areas of high humidity because the air already contains too much moisture.

7. Optimize Your Greenhouse Layout

The layout of the greenhouse also has an impact on its temperature. Consider orienting the greenhouse in a direction that receives the least direct sunlight.

8. Use Drip Irrigation

Overhead watering increases the humidity in the greenhouse, making the air feel hotter. Drip irrigation is a more efficient way of watering plants and helps keep the air in your greenhouse drier and more relaxed. Watering your plants regularly will keep them healthy and ensure the heat doesn't stress them out. As I mentioned, plants absorb the needed water and evaporate the rest. Making sure your plants have the right amount of water will ensure that the transpiration process occurs.

9. Use a Shade/Curtain System

Shading systems are usually used in conjunction with other cooling systems. Shading systems reduce stress on plants and improve the greenhouse environment. Shade cloth cools the greenhouse by blocking the amount of light entering the greenhouse. Curtain systems can be used inside or outside, with outdoor use installed over the greenhouse's surface to create a screen over the cannabis plants, but interior shades are more common. Internal drapery systems are often retractable, allowing the grower to decide when to reduce the amount of light entering the structure. Growers should purchase curtain material from durable polyolefin film with a robust monofilament yarn construction.

When choosing a window covering system, there are several designs to consider. Gutter-to-gutter systems use less shading material but create more prominent tufts when stretched. Truss-to-truss systems are the most common and can be configured in various ways. Many greenhouses are now using a flat truss-to-truss system because it reduces the greenhouse area that needs to be cooled.

According to different greenhouse environments, shade cloth size and thickness to choose the suitable material, cooperate with professionals to help growers make the right decision.

10. Combining Methods

A combination of cooling methods may be the most effective way to cool a greenhouse. Experiment with different techniques to see which works best for your needs. Through trial and error, you can create the best environment for your cannabis crops to thrive.

In conclusion, cooling your cannabis greenhouse is essential to keep your plants healthy and productive. Otherwise, crops will be more prone to worms despite your efforts and even begin to wilt or dry out in hot weather, causing much damage. Therefore, plan carefully and pay attention to details before cooling your greenhouse to avoid pest infestation and high temperatures. Using these ten effective cooling methods, you can create the best growing environment and ensure a successful harvest.


1. What is the most effective method of cooling a greenhouse?

The most effective method of cooling a greenhouse is using a combination of shading, ventilation, and evaporative cooling systems.

2. What is the cheapest way to cool a greenhouse?

The cheapest way to cool a greenhouse is by maximizing natural ventilation and using shade cloth.

3. How do I keep my greenhouse from getting too hot?

To prevent your greenhouse from getting too hot, use shades, increase ventilation, use wet wall systems, or install a greenhouse cooling system.

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