How The Greenhouses Work
It’s amazing what a greenhouse can do to growing plants. It allows plants to grow larger and stronger than they
would when not covered. So how does a greenhouse accomplish that?
A greenhouse is a structure made of glass or plastic walls and a plastic roof. Basically, it can either be a
complete glass house or complete plastic greenhouse. It is built to trap as much heat as possible.
Origin of greenhouses
The history of greenhouses can be traced back to the Roman times when they were used to grow exotic vegetables
and fruits. Many emperors would have their favorite vegetables cultivated in greenhouses.
Cultivating crops out of season gave man a way around the laws of nature. This alluring feat gave inspiration to
new methods of constructing structures dedicated to plant growing. Treasured glass became the most appealing
material for greenhouse construction. Exploring the plant world and practicality of growing useful, exotic
varieties gave way to the construction of bigger and more elaborate greenhouses, of which still stand today.
Working of a greenhouse
Greenhouses create a heated shelter for plants by trapping solar radiation heat. The artificial environment
created for warming and circulating air helps to sustain plant growth when normal temperatures outside are not
favourable, i.e. cool or variable. The glass (or plastic) covering of a greenhouse allows heat to penetrate and
begins to warm up the plants and the soil inside.
When air close to the soil is warmed up, it starts to rise, and then cooler air in the surroundings replaces it.
This repeated cycle causes the temperature within the greenhouse to increase faster than the air on the outside,
resulting in a warmer micro-climate.
In climates that are temperate, all the heating may come from the sun, but in cold climates, it may be necessary
to artificially heat the greenhouse to avoid temperatures going below freezing. In some cases, central heating of a
building may be used to provide heat to a greenhouse.
However, in cases where access to central heating is not possible, heat may be provided by use of natural gas,
or heating fans, regulated by a thermostat. The high costs of heating a greenhouse have prompted the use of
alternatives, such as solar batteries, or even animals as sources of
While radiation from the sun easily gets through a greenhouse, the heat released by plants and the soil doesn’t
escape easily; another factor that helps to trap heat inside. While this is good for warming purposes, it can cause
overheating, in which case it is necessary to devise heat control mechanisms.
Special ventilation is used to allow hotter, lighter air to escape upwards through vents near the roof, while
cooler air descends towards the soil. As well as maintaining constant temperature, ventilation helps to cycle
carbon dioxide used by plants to make food.
Watering plants in a greenhouse is usually accomplished by use of an automated watering system, which is more
reliable and consistent. Dip irrigation, wicking and capillary mating are some of the automated watering techniques
used in greenhouses. It is more practical to build a green house close to a water source.