Another very important factor in sustainability lies in how long a product will last. Durable products won’t need to be replaced for many decades, which means less energy and materials are required in the long run. And very important: durable products need less maintenance. As maintenance has also environmental and ecological impact, less is better.
Last, but not least, some natural materials such as timber are not firesafe. To become fire safe, fire retardants need to be added. Buildings that are not fir safe are not sustainable, and neither the use of often toxic additives.