During the summer, greenhouse temperatures outside can raise the temperatures inside a greenhouse. The rise in temperatures can ruin vegetation. Damages include reduction of stem strength, reduced flower size, reduced leaf size, flower bud abortion and reduced growth late. Greenhouse temperatures can rise during the day because of the enclosed space in a greenhouse and the greenhouse effect. There are many ways to reduce this access heat including ventilation, shading, and misting.
Ventilation is critical to controlling heat generated inside a greenhouse, especially during the summer time. Ventilation systems remove heat from a greenhouse via vents located at the top and lower floor area. These vents should be equal to about 20% of the floor space. The roof vent should be able to open at a 45° angle above the horizontal beam. This allows for warmer air to rise and escape while the cold air is pulled through side vents. These roof vents can be electric or hand cranked. Establishing a pattern creates air circulation. Fans can be used to create cooling air. Forced air ventilation is a popular choice. Choices can include fog cooling, and pad and fan cooling.
Shading another great way to cool down a greenhouse from high temperatures. Shading can cover the roof, and is dependent upon the local climate, greenhouse design, and light requirements for plants. Greenhouse employees should use the minimum amount as possible. Excessive shading can cause plants to “lean” or “reach” for light. This act creates plant stems at awkward angles, and not straight vertical stems. Shading can come in a variety of knit size, shape, and fabric.
Misting is a form cooling that can occur in greenhouses. Similar to fog, small drops of water suspended in air are used to alleviate heat from a greenhouse. Mist is more visible than fog, due to refraction and reflection of light. Variables such as humidity, and temperature play a part in creating mist and will be discussed below.