Greenhouse Misting Systems

We built our DIY greenhouse in order to provide the perfect, year around environment for our plants. We want to protect them from cold, wind, bugs and too much sun. The walls of our greenhouse take care of most of it. But, during the hot summer months, there are days when we need to cool things down a bit. We can do that with the combination of proper shading, adequate ventilation and constant humidity.

Ideal humidity levels for most growing environments are from 50-70%. During the hot summer months, the excess heat burns away the humidity that plants need for healthy growth. By adding a greenhouse misting system, we achieve constant humidity, cooling and a convenient system for distributing the fertilizer.

Keeping humidity constant is one of the most important conditions for the optimal growth in the greenhouse. The humidity below 30% forces plants to go into dormancy and they stop growing, or may even wilt and die. The ideal humidity is easily provided with an automatic misting system, which provides a high pressure mist or fog that is easily absorbed by plants, without making them wet. Depending on the shading and ventilation, one to two gallons per hour for each ten square feet of floor area will provide optimal moisture in the greenhouse.

When mist or fog produced by a misting system evaporates, it instantly cools the air and reduces the temperature by up to 30°F. This happens because the evaporation process needs heat. Once the mist absorbs the heat, the temperature in the greenhouse drops.

The misting system is a handy vehicle for an easy distribution of fertilizers. Fertilizers released to plants through mist are easily absorbed through leaves. Such fertilizer distribution is very efficient, even and constant and it reaches all plants in the greenhouse equally.

Misting Fans

The simplest and the cheapest greenhouse misting system is provided by a misting fan. It is actually an ordinary fan, with a water mister installed in front of it. The water mister sprays fine water droplets, which the fan’s spinning blades cause to be distributed to the surrounding air. Misting fans can use high or low-pressure water misters. Misting fans can be mounted to a greenhouse wall or be placed where needed if mounted on something modular like on its own pedestal. Misting fans have to have completely enclosed electrical motors, because of the heavily humid atmosphere of the greenhouse. Regular fans would quickly short in such environment causing failure, fire or worse.

Greenhouse Misting Systems

The disadvantage of misting fans is that they are confined to one part of the greenhouse and the mist cannot reach all plants even if you have more than one fan. Greenhouse misting systems consists of a high-pressure pump and a system of spray nozzles that are distributed in different areas of the greenhouse, which produce super fine drops of water, cooling the air as the water evaporates. The more nozzles that are installed around the greenhouse, the more even the humidity and temperature throughout the space. The increased water pressure can also add more humidity when needed. Depending on their arrangement; misting systems can achieve fast cooling of up to 30 degrees.

The nozzles can be placed where you want them, but they are often mounted under the benches, or in front of the fresh air vents.

With the help of a timer, a thermostat and a humidity controller, you can completely automate the process. With the misting system being automatically activated as the temperature rises and humidity falls in accordance to your preset parameters.


A greenhouse misting system is fairly easy to install.  It is often sold in a kit, which includes a certain number of feet of the mist line and of the supply line (normally PVC pipes), garden hose adaptor, a number of misting nozzles and a number of mounting clamps. Ideally, you should place misting nozzles at the intervals of between three and five feet. While an automatic mister with the timer, thermostat and humidity controller is optional, it would save you a lot of time and effort and would provide optimal growing environment in your greenhouse. It is one of those costs that is really justified in our book.

During the night, the temperature drop increases the humidity in your greenhouse. To avoid too much humidity, set your timer to switch the misting system off during the night. Too much humidity provides healthy environment for the growth of bacteria and fungus, which may negatively impact your plants.

Even if you do not opt for an automated system, you will have a total control of your DIY greenhouse temperature and humidity even during the hottest summer days with a misting system install, which will aid in your comfort. Who knows, a misting system may even mean you spend MORE time inside your growing space.

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