When choosing a style for your greenhouse, there's several things to consider. You'll want a style that blends with your house and property, is easy enough to build for your skill level, and is the size that serves your purposes best.
Freestanding Greenhouse Styles
Freestanding structures are great for the flexibility they allow a homeowner. They can be positioned anywhere on the property and can be built in any size or style. The most common freestanding designs are the Quonset, gable roof, gothic arch and slant-wall architectural styles of greenhouses.
Greenhouse styles include dome, Quonset, gothic arch, tri-penta, slant-side, gable roof, A-frame, straight-wall lean-to, slant-wall lean-to and curved-wall lean-to. Coverings like polyethylene are flexible and work well with dome, Quonset, gothic-arch, tri-penta and curved-wall lean-to designs. Other shapes are better suited for rigid panels like glass or plastic. Rigid panel designs include gable roof, A-frame, straight-walled and slant-walled lean-to greenhouses styles.
Unusual styles such as the tri-penta and the geodesic dome buildings are eye-catching, but they require a good deal of skill to construct. They may also be more of a challenge to heat and cool. The gable and Quonset designs are energy efficient and relatively simple to construct. Although an A-frame design is very simple, the usable growing space is small and the narrow shape makes it rather problematic.
Attached Greenhouse Styles
An attached greenhouse is a great option for many homeowners. Where space is limited, they are very useful. This style of greenhouse is also economical, as you are constructing only three sides of a structure. If you heat your greenhouse, you are also eliminating some fuel costs due to the wall shared with your house.
You may choose to have an entryway from the greenhouse into your home. This provides access to your greenhouse without leaving your house. To keep it simple you can forego the interior door, and simply install an exterior door to your lean-to.
An attached greenhouse can take advantage of your home's existing utilities to provide heat, electricity and water to run your greenhouse. This can be fairly simple, and far less costly than providing utilities to a freestanding structure.
City code may require a solid foundation for an attached greenhouse, and the joints between your home and your new structure should be properly sealed.