A green house is a room or building for plants. It has clear walls and a clear ceiling to let sunshine and warming light in for plants. It is called a greenhouse because of the green plants within, not because of the structure's color. A greenhouse can vary in size from a small box to a building with multiple stories and thousands of square feet. Usually a home's greenhouse is significantly smaller than the home.
An attached greenhouse allows residents to garden year-round. In colder climates, it can make it possible to grow fresh food and flowers when they cannot be grown outside. In some cases, when the plant needs more light or some additional heat, it may be necessary to supplement the solar light coming into the greenhouse with full spectrum lights and/or a heater.
- Wikipedia's article on greenhouse
- West Virginia University on Planning and Building a Greenhouse