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In horticulture, a greenhouse is a structure designed to regulate the temperature and humidity of the environment inside it with a view to growing plants.

There are different types of greenhouses, but they all have large areas covered with transparent materials that let sunlight enter and that inhibit the loss of the sun's heat. The most common materials used in modern greenhouses for walls and roofs are rigid plastics made of polycarbonate, plastic film made of polyethylene, or glass panes. When sunlight shines into a greenhouse the temperature inside increases, providing a sheltered environment for plants to grow — even in cold weather. The terms greenhouse, glasshouse, and hothouse often refer interchangeably to buildings used for cultivating plants. Nowadays, greenhouses are more commonly constructed with a variety of materials, such as wood and polyethylene plastic. A glasshouse, on the other hand, is a traditional type of greenhouse which uses glass panes that allow light to enter. The term hothouse indicates the use of artificial heating. However, both heated and unheated structures can generally class as greenhouses. Greenhouses can range in size from small sheds to industrial-sized buildings and colossal glasshouses. The smallest example is a miniature greenhouse known as a cold frame, typically used at home (compare cloche). Large commercial greenhouses are high-tech production-facilities used to grow vegetables, flowers or fruits. Such glass greenhouses may feature extensive equipment, including screening, heating, cooling, and lighting installations, sometimes controlled by a computer to optimize conditions for plant growth. Different techniques manage growing conditions (including air temperature, relative humidity and vapour-pressure deficit) in order to provide the optimum environment for cultivation of a specific crop.

Therefore, the Romans designed an artificial environment, like a greenhouse, to have cucumbers available for the emperor all year. Within the section of agricultural techniques, Soon ui Jeon wrote how to build a greenhouse that was able to cultivate vegetables and other plants in the winter. Experimentation with greenhouse design continued during the 17th century in Europe, as technology produced better glass and construction techniques improved.

As the structure is not open to the atmosphere, the warmed air cannot escape via convection due to the presence of roof and walls, so the temperature inside the greenhouse rises.

The main problem with heating a greenhouse as opposed to a building that has solid opaque walls is the amount of heat lost through the greenhouse covering. Waste heat from livestock can be used to heat greenhouses, e.g., placing a chicken coop inside a greenhouse recovers the heat generated by the chickens, which would otherwise be wasted.

Cooling is typically done by opening windows in the greenhouse when it gets too warm for the plants inside it.

During the day, light enters the greenhouse via the windows and is used by the plants.

Commercial glass greenhouses are often high-tech production facilities for vegetables or flowers.

A style of greenhouse having sloped sides (resulting in a wider base than at eaves height) and using these panes uncut is also often referred to as "Dutch Light design", and a cold frame using a full- or half-pane as being of "Dutch" or "half-Dutch" size.

Hydroponics (especially hydroponic A-frames) can be used to make the most use of the interior space when growing crops to mature size inside the greenhouse. An "alpine house" is a specialized greenhouse used for growing alpine plants.

Today, the Westland and the area around Aalsmeer have the highest concentration of greenhouse agriculture in the world. Since the 20th century, the area around Venlo and parts of Drenthe have also become important regions for greenhouse agriculture. The Netherlands has around 4,000 greenhouse enterprises that operate over 9,000 hectares of greenhouses and employ some 150,000 workers, producing €7.2 billion worth of vegetables, fruit, plants, and flowers, some 80% of which is exported.

Quick Facts

• When sunlight shines into a greenhouse the temperature inside increases, providing a sheltered environment for plants to grow — even in cold weather.
• A glasshouse, on the other hand, is a traditional type of greenhouse which uses glass panes that allow light to enter.
• The terms greenhouse, glasshouse, and hothouse often refer interchangeably to buildings used for cultivating plants.
• The most common materials used in modern greenhouses for walls and roofs are rigid plastics made of polycarbonate, plastic film made of polyethylene, or glass panes.
• Large commercial greenhouses are high-tech production-facilities used to grow vegetables, flowers or fruits.

Source material: Wikipedia - "Greenhouse". Adapted and summarized for DiscoverScroll. Original contributors are credited through the linked Wikipedia article. Read original on Wikipedia. CC BY-SA 4.0. Changes were made from the original.