While these simple questions provide a fair overview of the environmental concerns around materials, the specifics for every product or product category might be quite different. A quarried material, for example, would require a much greater concern with the raw materials phase than the manufacturing phase. And some productse.g. asphalt shingles that constitute big problems for municipal landfills, or toxic items like arsenic-treated woodwould require higher priority concern for the disposal phase. It is also interesting to note that, while most experts agree that the long life of building materials is an important fact, in recent years increasing attention is being paid to the embodied energy, resource and pollution impacts of building materials. As new LCA data emerges, the impact of building materials upstream (in extraction and processing) is being recognized as much greater than experts previously believed (Trusty & Meil, 1999). As we will see, the evaluation of materials can be quite complicated. The very priority of use and performance for a building material means that it is often not an obvious matter of comparing one material to another. Environmental impacts depend very much on how the materials are used. It might be more sensible to compare, for example, one wall assembly with another wall assembly (or even one building with another building), rather than simply the components within them.