including wood grain and stucco. It is then cut into panels or lap siding and painted (Temple-Inland, 2003). The final product typically carries a 25-year warranty, is less energy-intensive than metal siding, and considerably less environmentally damaging than polyvinyl chloride (PVC). Another engineered siding product is fibre-cement siding (like Hardieboard). In it, cellulose fibres are mixed with cement to form a dense, durable, fire-resistant surface that promises to take over a considerable portion of the housing market as the movement to ban PVC grows in strength (Wilson & Malin, 1997a). Fibre-cement is also finding growing use in the making of roof tiles. They can be moulded to look like shingles, slate or clay tile, but are far lighter than clay or slate, and they constitute a much more ecological choice than asphalt shingles, which are among the most damaging building materials in widespread use today. The realm of engineered materials contains a spectrum of new products that defy easy categorization. Examples include the increasing varieties of composite lumber, the most common of which combine recycled polymers with wood waste material. The most widely known is TREX, a composite lumber used for outdoor decking. It is considered an ecological product, both because it is a substitute for arsenic-treated wood and old-growth cedar and because of its use of recycled materials. It is a decking material, but it is not a proper structural material, although various other wood-plastic composites (like Nexwood, which combines recycled polymers with rice hulls) can be used for modest structural uses like posts and railings. This sphere of new composites is a tricky area. Not all composites, even making use of recycled materials, are necessarily ecological. Many of them are more