Greenhouses trap heat from the sun to create a warm environment for growing plants. Depending on heat levels, greenhouses can either extend the growing season by several weeks or allow for year-round vegetable growth.
The windows of a greenhouse allow solar radiation to enter. As the ground and plants inside the greenhouse absorb the radiation it is changed to thermal radiation, or heat. Thermal radiation has a different wavelength than solar radiation, and it is unable to exit the greenhouse through the glass panes.
Greenhouses can be built in many sizes, shapes and locations, but the four main types of greenhouses are "cold" houses, "cool" houses, "warm" houses and "hot" houses. "Cold" greenhouses depend solely on the heat from the sun to heat the greenhouse, and "cool" greenhouses use additional heat to stay at temperatures just above freezing. "Warm" and "hot" greenhouses use a supplemental heater to maintain consistent temperatures.
Vegetables cannot grow year-round in a "cold" greenhouse because the heat inside is not enough to overcome the freezing temperatures outside and in the ground. If planning year-round greenhouse gardens, install a supplemental heating system for use in the winter. Also remember that high temperatures can affect plant growth. All greenhouse types need ventilation and air circulation.
- Alaska Science Forum: How Do Greenhouses Work?
- TLC Home: Types of Greenhouses
year-round greenhouse use, growing in greenhouses, greenhouse vegetable gardening
About this Author
Heather Lacey is a freelance writer who has been specializing in print and web articles since 2008. She is a regular contributor to "Go Gilbert!," "Scottsdale Health Magazine" and other local publications. Lacey has a professional background in hospitality management, and studied journalism at Phoenix College.