Galvanized steel, aluminum, wood and plastic piping are all adequate materials for building a structurally-sound greenhouse. Each type of material excels in one or more areas of greenhouse construction. Using the proper type of material to construct a frame is vital to the strength and efficiency of a finished product. The location, size and frame design of the greenhouse determine the best type of material to use during greenhouse construction. Using the wrong type of material to build a greenhouse will increase the chances of the frame becoming damaged in colder months or collapsing under the weight of snow or the pressure of heavy winds.
Areas prone to snow and consistent cold weather throughout winter require a greenhouse frame capable of holding the excess snow weight and resist becoming brittle when subjected to cold temperatures. Plastic piping does not have the ability to hold the extra weight subjected to a greenhouse by heavy snow and it becomes brittle when subjected to long bouts of cold weather. Galvanized metal and aluminum are good conductors of heat and will increase the difficulty of heating a greenhouse; the metal frame is not internally insulated with foam or fiberglass insulation. Wood framing materials do not require additional insulation to contain heat and will support the extra weight applied to the structure from accumulated snow.
Larger greenhouses require additional support to ensure the structure does not fail. Plastic piping does not have the strength to span long open areas without additional support. This eliminates installing additional supports, increasing the usable area of a greenhouse. Both types of metal and wood have the ability to span long distances if the frame components are sized to support the size of the structure. Another factor has an effect on the best type of material for a greenhouse frame.
The frame style of a greenhouse is another factor that determines the best type of material to use for a structural frame. Specially designed and pre-fabricated trusses are needed when using either type of metal to create a rounded greenhouse frame. Wood also requires special fabrication techniques to form large radius curves for a greenhouse frame. Plastic piping has the ability to bend into large radius trusses as long as the pipe is sized correctly to ensure a strong greenhouse frame. All materials are best when matched to the size, shape and location of the finished greenhouse frame.