Most people investing in a greenhouse for gardening year-round are primarily worried about wintertime. But gardeners should also be concerned about how to cool a greenhouse in summer.
Summer months become steamy and hot when the temperature shoots up several degrees higher than usual. It causes serious issues for plants growing inside the greenhouse.
Thus, bringing down the temperature inside your greenhouse is essential so plants can propagate healthily even in summer.
This article will explore some of the great ways to keep a greenhouse cool in summer. However, before exploring them, let’s find answers to some critical questions about greenhouse temperatures.
What Should be the Ideal Temperature inside a Greenhouse?
Temperature is an essential factor that significantly influences plant growth inside a greenhouse. There are three temperature points: minimum, maximum, and optimum.
However, the temperature you should maintain inside your greenhouse will depend on the plants you are harvesting. While some plant species prefer warm temperatures, others love a relaxed environment.
Keep in mind the optimal temperature for crops. It’s the temperature at which plants propagate most rapidly. So the optimal temperature for cool-season plants is usually about 21 degrees C (70 degrees F).
However, the optimal temperature for summer crops can be as high as 32 degrees C (90 degrees F).
What Temperature is Too Hot for Greenhouses?
The temperature inside a greenhouse shouldn’t be over 32 degrees C (90 degrees F).
It’s too hot. If you find your greenhouse temperature elevating above 90 degrees, take immediate action to reduce the temperature and retain the ideal condition for your crops.
10 Ways to Cool your Greenhouse in Summer
No matter how much the temperature shoots up in summer, find different ways to let your greenhouse plants grow healthy by getting a perfect temperature.
However, note that the temperature you need to drop will depend on where you live and the type of plants you are cultivating.
1. Get a Thermometer
It’s probably the first thing to consider while wondering how to cool your greenhouse in summer. A thermometer can monitor and adjust the greenhouse’s temperature as required, ensuring optimal growth.
2. Make a Shade
Does it sound like a no-brainer? Maybe you can significantly reduce your greenhouse temperature by creating a shade. It’s clear that the shade blocks the sun and its heat rays, making the temperature inside cool.
So how to create shade? Well, there are many ways, like –
- You can tactically place large-leaved plants in places that act as shields against sun rays, like on the southwest side of a greenhouse.
- Alternatively, you can get shade cloths to create shade. It will block 50% of the sunlight while offering sufficient rays for your plants to take photosynthesis.
3. Ensure Excellent Airflow Inside your Greenhouse
Greenhouses should be well-ventilated as they will allow sufficient airflow. However, remember that greenhouses rarely feature a properly ventilated structure. So you should ensure your greenhouse is ventilated before opting for other cooling options.
A proper ventilation system will drive out hot air and allow cool air to enter your greenhouse. During intense summer days, the internal greenhouse temperature will surpass the external temperature by nearly 20 degrees F.
Such a temperature can hamper the healthy growth of your plants. In such instances, mechanical or natural ventilation can keep the temperature inside cool.
However, you can use base vents and side vents for natural ventilation. And roof vents will multiply the airflow.
You can even leave your doors open to allow entering more cool air. However, a natural ventilation system won’t be sufficient for big-sized or medium greenhouses. Thus, you need to apply mechanical ventilation like exhaust fans.
Large fans, coupled with proper ventilation, can substantially drop the temperature inside the greenhouse.
4. Use Evaporative Systems
This is a reasonably economical greenhouse cooling option. Evaporation systems cool greenhouses up to 10-20 degrees by evaporating water.
However, they function better during low relative humidity. A fan-and-pad cooling system is one of the most common evaporative coolers for greenhouse.
The pads draw in the warm air with the help of the fans and lower the greenhouse. They have a water supply atop and a gutter to collect water onto a pad. Then, the water transforms from liquid to gas, absorbing the heat.
5. Avoid Water Stress
It’s essential to keep watering your plants in the greenhouse. Plants keep themselves naturally cool by transpiration – the process by which plants lose moisture through stomata or leaf pores. The leaf surface cools down like we sweat with the loss of water.
If plants cannot transpire appropriately, they can overheat and droop. Ensure your plants get enough water to pull up from the soil to stay relaxed and unstressed.
Check for indicative signs of heat stress. For example, dry out young foliage, burnt leaves, or wilting plants.
6. Damp Down Your Greenhouse
Here’s another trick to cool your greenhouse and plants in severe heat – damping down! This process involves wetting hard surfaces like staging and paths and boosting the temperature inside the greenhouse.
While the moisture level in the air increases because of evaporation, the crops in the greenhouse withstand the heat. A higher humidity level also keeps the pests that sustain dry conditions away.
However, you can dampen your greenhouse as often as possible when it is too hot. But don’t overdo it! Try to do it at least once in the morning and once in the evening.
7. Get a Fogger or a Misting System
Besides evaporative coolers, you can also avail yourself of other cooling systems, like a fogger or misting systems. These systems are designed to reduce the temperature quickly to a greater degree. Interestingly, both systems function the same.
They pour out water droplets through nozzles, making the temperature cool. The only difference is that the cooling capacity of foggers is more efficient, and they discharge tinier droplets.
A fogger or mister would be a good choice for cooler regions.
8. Get a Portable Air Conditioner
Most portable air conditioners are energy efficient and come with a dehumidifier as a system’s part. They help in balancing humidity levels while reducing the internal greenhouse temperature. This would ideally be the best option for big greenhouses.
Fascinatingly, you can tactfully vent your air-conditioner into the greenhouse if it’s attached to your house. However, the downside is that air-conditioners can be heavy for a slim budget.
9. Install Greenhouse Fans
Consider the following factors before setting your greenhouse fans or any other fan system:
Ideal fan size
You need to choose the perfect fan size for your greenhouse. Next, check out the ventilation rate ideal for your gardening structure. If required, you can hire a professional to help you with it.
However, fans offer one air exchanger up to 8 feet every minute.
Location (where to install)
Install greenhouse fans at the structure’s top. While hot air moves up, airflow will be above the crops. Gardeners install exhaust fans to evacuate the hot air.
But, first, set the intake shutter vent on your greenhouse’s opposite side. It would help if you placed it at the bottom to pull in the cool air.
You can add louver vents and a standard fan labeled for the greenhouse to enhance the airflow. If you set the vent behind the fan, it will pull cool air from outside. Placing them at the top of your greenhouse walls will discharge hot air.
(Note: Maintain the fan systems regularly by cleaning the motors, belts, or fan blades. They will last you long.)
10. Cultivate Plants Strategically
You can apply this natural trick to maintain an appropriate temperature for your plants to grow healthy in summer. Plants have natural evaporation properties to keep them cool.
So propagate large-leaved plants such as fig trees and grapevine to deal with the higher temperature.
You can build your greenhouse close to deciduous trees that can serve as year-round shade during summer. Their big leaves will transpire moisture while shading the soil. However, they can even be used as shades.
Leaves will shed in winter, providing sufficient sunlight during winter. These trees will have leaves in spring, offering the shade you need for the scorching sun.
Creating a greenhouse near any tree isn’t recommended, especially for those far living North, as it may cause damage. In such n instance, shade cloths might be a better option.
If you don’t maintain optimal temperatures inside your greenhouse, you will risk all the hard work you gave to cultivate your favorites.
Scorching temperatures summon pests that damage your crops. The plants will dry out, after being exposed to such a high temperature.
When the temperature is cool, it offers a better environment for plants or vegetables to grow. So take every necessary step to keep your greenhouse cool during the scorching summer months.