How Does a Greenhouse Work?

A greenhouse works by taking in sunlight and heating it up. This process is the conversion of solar energy (sunlight) to thermal energy (heat). Greenhouses are designed to allow sunlight to filter through the walls and ceiling. The sunlight warms the trapped air inside, creating chemical reactions. These reactions help the plants to grow to their full capacity while protecting them from outside elements. It is a well-known fact that plants grow better when they have temperate heat and a good water source. A greenhouse gives them both.

The composition of a greenhouse is key. Typically, greenhouses are made of plastic or glass. The purpose is to trap as much light and heat as possible, which plastic and glass do. The plants and soil inside absorb all the sunlight and then reflect it back out. As the solar energy is redirected, however, it is changed. Sunlight is composed of shortwave infrared radiation that is able to pass through the greenhouse's exterior. These waves turn into longer-wave infrared radiation after absorption by the plants and they are no longer able to pass through the greenhouse's exterior.

With more sunlight coming in and more energy being trapped, everything inside the greenhouse heats up further. The plants, soil and circulating air grow warm and moist. This process is called convection, which means that as the plants heat up, they release moisture. This moisture produces humidity within the greenhouse. Humidity is water vapor, which is a greenhouse gas.

When planning a greenhouse, pick a construction site where it will receive optimal sunlight throughout the year. Consider temperature fluctuations of the different seasons in your area and choose your plants accordingly. The temperature inside the greenhouse will always be warmer than the air outside. In freezing climates, however, artificial heat must be provided to stabilize the temperature and allow the plants to continue their growth. On the other end of the spectrum, a greenhouse can become too hot and must be cooled down. A good ventilation system is crucial in the event that hot air must be released. Some people do this by opening the doors of their greenhouse. Others spray the floors with water.

By offering shelter from the elements and an optimal environment for growth, vegetables, fruit and ornamental plants can be cultivated and grown regardless of the weather or climate outside. All that is needed is a well-built greenhouse and plenty of sunshine, along with proper maintenance provided by the grower.