What does 'sustainable' mean? Sustainable building materials, Part 2

In the last blog I talked about the term ‘natural’ in relation to buildings and sustainability, concluding that it was unhelpful at best, as it doesn’t really tell us anything about a product’s provenance, sustainability, or even level of processing (e.g. wood-fibre board and strawbale and are both described as ‘natural materials’ but neither would exist in their useful form without mechanised human intervention).