How to Control the Temperature in a Greenhouse – 9 Methods


Greenhouses can be useful for growing plants year-round, especially if you live in areas with cold seasons. But a greenhouse can only be useful if it is kept at the right temperatures that are beneficial for the plants you are growing inside of it.

There are many methods to control greenhouse temperatures, including doors and windows, roll-up vents, fans, heat mats, hay bales, jugs of water, wet walls, shade cloths, heaters, and even systems that let you monitor and change the temperature in your greenhouse using a phone app.  

Throughout this article, you’ll learn more about maintaining the right temperature in a greenhouse, including:

  • What is the ideal temperature for a greenhouse?
  • How do you monitor, reduce, and increase the temperature in a greenhouse?
  • Is there a way to control the temperature in a greenhouse remotely?

What Is the Ideal Temperature for a Greenhouse?

The ideal temperature for your greenhouse will really depend on the type of plants you are growing. Having the greenhouse kept at the right temperatures will encourage optimum plant performance and transpiration rate, which ensures proper nutrient uptake leading plants to yield healthy flowers and fruits. In general, the best temperature range for a greenhouse for most plants is between 80 to 85 degrees Fahrenheit (27 to 29 degrees Celsius).

A greenhouse temperature that is too low or too high could stress your plants, and stress, in turn, could lead to mildew, mold, or pests, and generally unhealthy plants.

9 Proven Methods to Control the Temperature in your Greenhouse

Using Natural Ventilation

Greenhouses come in various sizes and designs. There are full-size glass greenhouses, and there are smaller, simpler ones, called cold frames. Some more expensive greenhouses might also come with various amenities like benches, electricity, solar power, and lighting.

One of the most important considerations, however, is heating and ventilation. After all, the primary purpose of greenhouses is to have a regulated environment for your plants so that they can grow year-round, not matter what the external temperatures may be.

The most natural way to ventilate your greenhouse is to incorporate vents in the design by adding doors and/or windows. Opening doors and windows will allow the hot air inside the greenhouse to escape as well as allow for proper air circulation. This is also a very effective way to lower the temperature inside for the plants.

Some greenhouses are designed with hinged roofs, and you may prop them open when it gets too hot so that hot air doesn’t accumulate inside. Some greenhouses also use polyethylene roofs and walls, and growers can increase the ventilation of the space by simply rolling up the plastic sheeting.

Setting Up Fans

Putting up fans inside your greenhouse can help push out hot air and draw in cooler air, or in other words, it helps circulate air. This is why it is also important to strategically position your fans and make sure they are placed in a spot where they can function most efficiently. Do not place a fan on the ceiling or ground level, for example. Instead, place it five to six feet (1.52 to 1.83 meters) in front of a vent to draw the air through and above the plants.

There are fans that you can hook up to a thermostat, which will allow you to create a semi-automated cooler, where the fan can be programmed to turn on when the temperature gauge reaches a certain temperature. There are also fans that have wet pads, and they provide an evaporative cooling effect, which keeps the environment moist, which prevents plant material from drying out. 

Using Heat Mats

If you are using your greenhouse or at least a part of it for germinating or starting seeds, you might consider using a heat mad, as seen in this video:

These heat mats warm up the soil temperature, so you don’t have to worry about the soil getting very cold, especially in the winter. These mats are controlled by a thermostat to stay on until the soil reaches the correct temperature that is ideal for starting the seeds you’re attempting to grow.

Jalape_o_Pepper_Lines (4)
Jalape_o_Pepper_Lines (4)

Heat mats are placed on a flat and dry surface, close to a power source so you could plug them in. You can set a thermostat to the right temperature needed for your soil, so that you can monitor and also automate your heat mats to shut off when the temperature is high enough.

Heat mats are also very helpful for other plants if you don’t have a heater in your greenhouse.

Placing Jugs of Water

Photo by Gveter2

A jug of water, or several jugs of water for a large greenhouse, can be helpful in both cooling as well as heating up your greenhouse.

In the summer, placing the bucket or jug of water in a shaded area can help cool the greenhouse, as the water will passively absorb heat from the air inside. As the temperature goes up, some of this water evaporates, which helps to take out some of the heat that builds up inside the greenhouse.

Instead of using water tubs, some growers use foggers and misting systems, or they might manually spray the air with water to reduce heat in the greenhouse.

In the cooler months, placing jugs of water in areas that receive sunshine can help keep your greenhouse warm. For better results, place black garbage/plastic bags over the bucket or jug as that will help to increase the heat absorbed and allow for a higher temperature of water, which will result in a warmer greenhouse.

Controlling the Shade

Shade helps reduce the temperature inside your greenhouse as it reduces the amount of sunlight that enters through the glass or the plastic covering. You can use different types of shade, from more permanent solutions like liquid shading compounds, or more temporary methods such as cloth or fabric to block off sunlight as needed. Some also go the more natural route to have leafy vines grow over the greenhouse walls and roofs.

Using a cloth or material gives you the most flexibility since you can remove and reposition it as needed.

Installing Wet Walls

A wet wall is an active cooling mechanism where you use a gutter at the top which collects water which then trickles down into a pipe. This collection pipe is connected to a filtration system, and the water gets recirculated, which helps cool the greenhouse.

When using a wet wall, you will need to monitor your greenhouse’s humidity levels. If the humidity gets too high, you will need to cut off your wet wall’s water supply.

“Populating” the Greenhouse or Adding Hay Bales

A greenhouse full of plants provides a natural evaporative cooling effect when plants transpire and release moisture into the air.

Filling up the greenhouse with as much soil and plants that space can hold gives your greenhouse a bigger thermal mass. Doing this helps control the temperature as the thermal mass retains the heat overnight.

Another option would be to place hales of bay inside to add to the thermal mass. The hay bales get soaked because they hold on to a lot of water. As such, it helps regulate the temperature inside the greenhouse.

Adding a Heater to Your Greenhouse

If you live in an area that gets quite cold in the winter, you might consider placing an electric heater in your greenhouse to keep your plants warm. You can choose between a central heating system or a local heating system. Central heating uses a boiler that heats with steam or hot water to burn various fuels. The boiler is placed in a central location in your greenhouse and is best used in large greenhouses.

On the other hand, a local heating system is a heater that is usually placed in one area or one end of the greenhouse. It can be a convection heater, a radiant heater, or a unit heater, and can be removed or unplugged when not needed

Using a Remote Temperature Monitoring System

You can always monitor your greenhouse’s temperature by putting a thermometer inside. A thermometer is usually enough to tell you whether you need to increase or reduce the heat until you reach the ideal temperature that’s best suited for the plants you’re growing.

If you want to monitor your greenhouse’s temperature while you’re away at work or on vacation, you may want to set up a remote temperature monitoring system.

There are now advanced systems that allow growers to monitor temperatures and other environmental conditions of their greenhouse anywhere by using their mobile devices or smartphones. These systems offer cloud functionality and enable you to change the settings, readjust temperature limits, and even arm and unarm alarms, whether you’re laying in bed or out at the beach!

Closing Thoughts

A greenhouse gives you complete control over the temperature or your plants’ growing space. This control allows you to provide your plants with the ideal growing conditions so they can produce more flowers and fruits and so they can grow without you having to worry about problems like frost, too much heat, or even insects.

But your greenhouse can only be effective if it is kept at the right temperature that is best suited for the plants you’re growing. We hope that these methods will be helpful in providing ways to control the temperature level of your greenhouse.

Here are Some of my Favorite Gardening Products and Tools

Thank you for reading this article. I hope you found it helpful for growing some new plants in your home or garden. Here are some products I like that I hope you’ll also find helpful. These are affiliate links, and I am compensated for referring traffic. But in all honesty, these are the exact product that I use or recommend to everyone.

Soil: For high-quality soil, I really like Fox Farm Ocean Forest. I do all my growing in containers and this soil has worked great for me. I like how they use nutrient-rich contents like earthworm castings, bat guano, and composted crab and fish.

Fertilizer: Currently I am using a seaweed-based organic fertilizer call Neptunes Harvest. This is a great milder fertilizer option if you want to use something organic. If you want a more powerful fertilizer, I recommend Fox Farm Liquid Nutrient Trio, lots of people have had great growing success with this product.

Pruning Shears: Pruning shears are one of the most useful gardening tools to have because it’s important to prune your plants to keep them healthy. The pruning shears I recommend are the Gonicc 8’’ pruning shears. I like them because they are built sturdy and work both on bigger and smaller plants, so you don’t need to have multiple pruning shears.

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Supriya

Hi! I'm Supriya. I'm a home cook, bulldog mom, spicy food lover, and founder of The Spicy Trio. I have been a home cook for about 15 years and have been growing plants for the past six years.

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