What is a Greenhouse?
A greenhouse is a structure usually made of glass or plastic that is warmed by incoming sunlight and the heat from hot interior surfaces is retained in the building by the roof and wall. This warm air lends itself to a more ideal growing environment for plants in all seasons. These structures can range from small, hobby size sheds that easily fit in your backyard to very large buildings for commercial growers.
Though the small garden shed greenhouse might have a few accessories like heating, cooling and lighting, most will be simple plastic greenhouses that use the natural solar radiation for heating yearlong. The larger commercial installations normally have all the above equipment and are run by highly sophisticated computer systems.
The sunlight is trapped within the greenhouse and the “energy” heats both the plants and the ground inside. Since this warms the air near the ground, it is prevented from rising and flowing away, which is where hot air normally goes. Greenhouses are also known as solar greenhouses and the very small ones are called cold frames.