"Just tell me which the most sustainable material is: Wood, Steel, or Concrete?" Have you ever heard (or asked) a question like this? It epitomizes the problem many engineers have with the study of sustainability; the fact that sustainability is not an inherent property of a material. One cannot attribute a number to sustainability, so there's no modulus of elasticity to measure, no ... [Show full abstract] strength-to-weight ratio to compare. And even if you could make an apples-to-apples comparison between materials, somehow comparing the recycled content of steel with the renewable aspect of timber, for example, it would not give a meaningful answer in deciding which material is best for a particular application, or, in our case, a particular building.