Once you have decided on the type of greenhouse that is best for you, you can consider the various styles. The glass sides of most hobby greenhouses slope outward gently from eave to sill, and this avoids the look of a commercial greenhouse. A slope-sided greenhouse, with its lower roof pitch and low silhouette, blends well with residential architecture or is an attractive highlight for the garden. And sloping sides give you a cultural advantage over straight sides: they transmit more light from the winter sun when it is low on the horizon.
There are also two types of eaves, straight or curved. For growing, one type is as good as the other, but your home may be more enhanced by straight eaves than by the curved type, and this will help you to decide. However, curved eaves have a softer look that may blend with your architecture instead of appearing to be a stark addition to it. The choice here is really your personal preference.
As a rule, hobby greenhouses are prefabricated, usually in maintenance-free aluminum, though some West Coast firms make models of redwood. Both kinds are structurally designed for the do-it-yourself gardener and, of course, they cost less than custom-built models. Folks handy with tools can assemble one of these prefabricated greenhouses in a few weekends, or a local contractor can erect it for you at a reasonable cost. Greenhouses are delivered ready for installation, but most manufacturers recommend that masonry, plumbing, and electrical work be done by professionals.
An ideal hobby greenhouse includes wide sections of glass for maximum transmission of sunlight, a system of condensation control to prevent unsightly accumulation of moisture on structural members (and an eventual unhealthy dripping onto plants and fixtures), and regulated roof ventilation to provide the very best growing conditions. Glazing may use standard putty or modern vinyl plastics (called dry glazing), depending on the manufacturer. Keep in mind that heat loss through inadequate glazing can be costly.
Manufacturers recommend south, southeast, or southwest exposures for attached even-span or lean-to greenhouses, a south exposure being the best. A west exposure is acceptable if no other location is available, but summer shade is essential to protect delicate plants from the burning rays of the afternoon sun.
If the only spot you have for your greenhouse faces north, do not give up the idea of a winter garden. Foliage plants grow well without direct sun, and shade-loving plants such as African-violets and orchids also thrive in such an exposure provided it is fully light. (A north-facing greenhouse could include fluorescent lights for sun-loving plants.) However, heating costs are higher in a greenhouse with a north exposure.