Buildings represent over a third of global anthropogenic greenhouses emissions. Load-bearing elements are the biggest contributor to the embodied carbon of buildings. New pathways for its reduction are to be found in order to avoid extreme climate catastrophes. However, the task of designing building remains very complex and environmental measures often contradict each other. How good is a new design? Is it actually better and more appropriate than previous ones? How can we objectively assess the environmental benefits gained when reusing load-bearing components over multiple life-cycles?