Steel framing is another substitute for conventional lumber. Approximately 68 percent of all steel is recycled. Stronger, yet lighter than a wood-framed construction, steel framing has no food value for termites. Steel products are either precut for studs or used in panels to build walls, steel trusses and floors.

Insulated concrete forms, including RASTRA, Autoclaved Aerated Concrete (AAC) and Faswell, were used in the construction of several green homes on the Austin tour. RASTRA, developed in Europe more than 25 years ago, is 85 percent recycled polystyrene and 15 percent portland cement. The RASTRA system produces a monolithic reinforced concrete wall with structural strength, high insulation value

and extreme resistance to fire, wind, insects and mildew.AAC was developed in Europe more than 75 years ago. AAC blocks are one-fifth the weight of conventional concrete because they are 70 to 80 percent air, which significantly improves their insulating characteristics. Blocks are glued together with a special adhesive to form a monolithic wall.

Faswell blocks, made of 85 percent treated recycled woodchips and 15 percent portland cement, were developed in Europe following World War II. Faswell structures allow a slow air exchange, preventing condensation and keeping walls dry.

Bamboo flooring is one of the more unusual

products found in some green homes. Bamboo is a grass that grows extremely rapidly after harvest, as much as 24 inches in 24 hours. Proponents of bamboo flooring point out that no hardwood trees are used in its production and claim it resists scuffing, staining and moisture damage while requiring less care than conventional flooring.

Cellulose insulation, made primarily from recycled newspaper treated with a fire retardant, is used in some green homes. One hundred pounds of cellulose insulation contains 80 to 85 pounds of recycled newsprint. Cellulose insulation is low in “embodied energy,” defined as the amount of energy consumed in producing the product. Fiberglass, rock wool and plastic