Consider the temperature and other climatic conditions of your location. When choosing between a cold frame and hotbed, consider the plants to be grown. Hardy plants such as cabbage need only simple, inexpensive facilities, but heat-loving plants such as peppers and eggplants should have more elaborate facilities for successful production in some of the colder areas of Montana. You can view a clear, printable copy of this graphic if you have Adobe Acrobat software. When selecting materials to construct your cold frame, keep in mind that the inside of the structure will be warm and humid.
Wood is the primary structural component in most cold frames.
Some manufactured cold frames use aluminum, plastic, and fiberglass. Most home gardeners use the materials they have available. When selecting wood, consider its rot resistance qualities. The heartwoods from cedar and redwood provide excellent rot resistance as does pressure-treated lumber. Pine, fir and spruce need to be treated to increase rot resistance.