Your greenhouse can vary in temperatures during the day. To lower the temperatures in the greenhouse it can be important to use various types of ventilation and shading to lower the air temperatures.
Airflow through the greenhouse moves the hot air up and out of the vents using the natural breeze. If you live in an area where the breeze does not happen often, fans can be used to push the air and move the hottest air up and through the vents of the greenhouse.
Shade clothes or blinds of some type in the greenhouse will keep the levels of sunlight from hitting the interior of your greenhouse, which will lower the temperature in the greenhouse somewhat as well.
But even with the best ventilation systems, and the use of the shade cloth you can often find your plants are having a difficult time growing and thriving in the greenhouse. Why? Because the temperatures are still high, most likely over eight degrees during the day, the soil that the plants are in dries out faster. The plants need something a little more to keep them cooler and moist while growing.
Using a misting system in the greenhouse will help lower the temperatures in the greenhouse and add the humidity which some plants need. A misting system is going to put out the finest, smallest drops of water possible. A mist is what you will find in your bathroom after taking a shower, sometimes a little heavier than that.
A misting system in the greenhouse will be attached to the roof of the greenhouse but on the inside so the water can float down onto the plants. If you have a powerful mister, you can have it sit in the middle of the floor and spout water upwards and into the air to float down and land on the plants.
Most gardeners are going to prefer a misting system that is on a timer so that you don’t have to leave the water on and then go back to the greenhouse to shut it off periodically during the day. A time is going to turn the water on for just a few short moments, and then shut it down, several times a day. This is a reliable system to ensure your plants are cooled, moist, and taken care of even when you cannot be in the greenhouse.