The lean-to greenhouse is usually small, about 6 to 10 feet long. One of its long sides is formed by the side of the house to which it is attached. Relatively inexpensive to make and maintain, its major drawbacks are a lack of space for an expanding collection and a tendency to heat up and cool off more rapidly than is desirable. The attached greenhouse is an extension of one's home, connected at the narrow end rather than the long side, as with the lean-to greenhouse. It is generally large and thus capable of providing more reasonable control over humidity, ventilation and expansion problems.
Some homeowners incorporate a living area into a lean-to or attached greenhouse.
The free-standing greenhouse is unattached on all four sides. It is the most expensive to construct but, aside from some inconvenience of access in inclement weather, it offers maximum light and the best control. Some space must be sacrificed for a work bench and storage area. Visit as many orchid greenhouses as possible, and consult books on and manufacturers of greenhouses before making a final decision. Where space is limited inside the home, window greenhouses offer a prime space in which to cultivate small-growing orchids.