Steel is not always an appropriate substitute for concrete however, and some of the most imaginative contributions of the green building movement have been in finding ways to reduce concrete use, our second main strategy to mitigate concretes environmental impact. Concrete is an excellent foundation material, for example, but it can be used more intelligently for major material savings. The typical North American home uses nearly 14 tons of concrete in its construction (Loken, 2002a), but much less might be used to better effect. One strategy is pier foundations, using reinforced concrete piers, formed by construction tubes made from recycled paper (like Sonotubes), in conjunction with recycled-plastic or fabric footings. While they are currently used more often for decks, they have great potential for buildings, particularly on ecologically fragile sites. Another strategy is foundation insulation placed to insulate the surrounding soil, thereby reducing frost depth of the soil and the required depth of the footings. Another possibility is slab on grade or floating slab construction that in most cases will reduce the amount of concrete by eliminating foundation walls. Still another is engineered thin-wall foundations150 rather than 200 mm. (six rather than eight inches) thick, a strategy developed in Canada (Loken, 2002a). A major way to reduce concrete use is to utilize precast rather than poured concrete. Using precast can substantially reduce waste, as material quantities can be more precisely estimated and excess material can be reused. Higher strengths are also possible, consistency increased and insulation can be built into many precast systems. The Waterloo Ontario Green Home, one of Canadas pre-eminent Advanced Houses, built in the early nineties, featured precast concrete foundation walls in the form of 8 foot x 16