Geodesic domes are perhaps the most well-known of the alternative home designs. Developed in the 1940s by Buckminster Fuller, these domes became a favorite of the counter-culture during the 1960s. The almost spherical shape keeps materials at a minimum, reducing costs while maximizing space, and also serves to make them extremely sturdy. On the inside, the owner is free to leave the space open or to erect walls or room dividers, and perhaps a loft, wherever they wish. Domes are also known to be very heat-efficient.
Earth-sheltered homes take a cue from nature in minimizing heating and cooling needs. Despite large daily fluctuations in outside air temperature, temperatures a few feet underground remain quite stable. If your home has four walls and a roof all exposed to the outside, you will lose or absorb heat, depending on the season and need to compensate--generally at considerable expense. If instead, all but one exterior surface of your home is dug into a hillside and topped with several feet of soil, with grass and other vegetation growing there, your utility costs are minimized. Maintenance costs are also minimized because there are no shingles to be replaced and little, if any, repainting to be done.
Another way to keep construction costs down while maximizing insulation is to build with low-cost or even free "waste" materials. For example, some homes have been built using junk tires as their walls. Bolted securely together and in place, and then sheathed with any of several surface materials, the tires form a thick wall with a high R value. Straw bales are another option. The compacted bales trap plenty of air that serves as insulation, and in addition to moderating temperatures, the thick walls muffle sound as well.
What tire walls and straw bale walls mimic is one of the oldest styles of housing in this region, the adobe. And adobe structures themselves are based on the natural principles seen in the earth-sheltered homes. All use locally available, low-cost materials and thick walls that moderate temperature swings, providing coolness in the summer and warmth in winter. In some cases the mud of authentic adobe is replaced with a more durable material but the principle of mass absorbing heat is the same.
Another popular self-reliant housing style is the the log cabin. Log cabins have come a long way from what the pioneers once lived in. Today logs are planed on opposite sides so they sit snugly on top of one another, minimizing the chinking needed to fill the spaces between them. The thick logs provide good insulation, particularly when coupled with interior finishing, and the exterior never needs a fresh coat of paint or new siding.
Construction materials are only the starting point, however, when it comes to building low-cost, energy-efficient homes. Passive and active solar systems for generating electricity and maintaining comfortable temperatures, as well as the home's orientation toward the sun and other such simple planning decisions, can result in a home that is cheaper to build and maintain and more pleasant to live in. As an added benefit, your planet will thank you. And Mother does know best.