I have been to a number of sustainability conferences and events this year and I have noticed that circular economy seems to be the latest phrase being used to describe sustainable construction materials. In the various keynote speeches that I have heard, it seems to have replaced phrases such as life cycle assessment (LCA), life cycle costing (LCC) and embodied green house gas emissions. This raises the question: how is circular economy different from these other terms?

LCA, LCC and embodied emissions calculations are all still relevant today and especially when a product consumes energy over it’s lifetime. Their purpose is to show which material or product produces the lowest environmental impact over it’s whole life from manufacture to disposal (cradle to grave). One of the most typical decisions involves the selection of a building’s superstructure and the comparison of timber, concrete and steel.

However, circular economy takes a slightly longer term approach and has a greater focus on the material or product at the end of its life. When the material or product has reached the end of its life, circular economy prefers the component to be reused in its existing form rather than just recycled. In order to facilitate reuse, designers are encouraged to consider how the building will be disassembled at the end of its life and this process is called design for disassembly or design for deconstruction.

Circular Economy and Buildings

Kasper Guldager Jensen of 3XN architects gave an excellent presentation entitled Circular Sustainability at the Finnish Green Building Council’s recent Green Celebration event.

He claimed that a new building can be prepared for a circular future at a cost of only an additional 0.35% of the construction budget. In other words this is the cost of designing for disassembly. This calculation is based on a 42 000 m² new build Danish office building which has a budget of 115 million euros.

When we consider the end of this building’s life then the demolition costs are € 2.15 million at today’s rates. Jensen claimed that in the future companies will not have to pay for the demolition of a building that has been designed for disassembly.

Instead the owners of these buildings will earn money from the disassembly and harvesting of materials to a value of approximately 4% of its new build value. The owners of the Danish office building that was used as a case study will actually be paid € 4.7 million for the building materials at the end of the buildings life.