A greenhouse can shelter plants from cold temperatures, wind, rain, snow, and hail while absorbing heat from the sun. In the summer, a greenhouse can overheat, causing the plants growing inside to suffer. If you are growing plants in a greenhouse this summer, you need to take some steps to control the temperature.
One way to decrease the temperature in your greenhouse is to ventilate it. You can do this simply by opening all of the doors and windows to allow hot air to escape. If your greenhouse has a hinged roof, you can prop it open to keep hot air from accumulating. If your greenhouse has a polyethylene roof and walls, you can roll up the plastic sheeting to allow hot air to escape and promote air circulation.
Fans can push hot air out of your greenhouse and draw in cooler air. Do not place fans at ground level or near the roof. Instead, put them about five or six feet high in front of vents or louvers. This will draw air over and through the plants. You can hook fans up to a thermostat for a semi-automated cooling system. Fans with wet pads can provide evaporative cooling and keep moisture in the environment to prevent plants from drying out. A greenhouse full of plants releases moisture into the air and provides evaporative cooling.
Shade reduces the amount of solar energy that enters a greenhouse and thereby controls the temperature. You can create shade in your greenhouse with liquid shading compound, shade cloth, or leafy vines growing over the top.
Another way to keep the interior of your greenhouse cool is by manually spraying it with water when it gets too hot. You can also use a misting or fogging system to add moisture to the air and keep plants from drying out. Misting and fogging systems require less energy than fans. Be careful to avoid the growth of algae, fungus, and bacteria.