Adaptive Buildings: Innovating Away Demolition Waste
By Jared Goldman, Circular Triangle Advisory Board Member
When we think about waste, usually the first thing to come to mind is a trash can and a giant landfill. This is a vivid image, but in fact construction and demolition (C&D) waste accounts for more than twice as much waste than municipal sources. Unsurprisingly, construction and demolition waste is generated in both the creation (construction) and destruction (demolition) of buildings, but the waste contribution of these processes is not equal. Construction accounts for only 10% of waste while demolition and renovation contribute the other 90%. This means that we can reduce the waste generated in construction and demolition significantly by focusing on limiting the waste generated in demolition.
In recent years there has been an increased focus on reusing byproducts of demolition in future construction projects as next use materials. Most common among next use applications is converting bricks, concrete, and glass into aggregate (basically rubble) which can be used to create more concrete. While this is a promising step in redirecting C&D waste from landfills, it is still imperfect. The reduction of waste is admirable but inefficient. The conversion from products that are created from raw materials (bricks, glass, concrete) back to the raw materials themselves (rubble/aggregate) essentially degrades the quality of the materials and forfeits the energy (read “carbon”) that was put in during the production, thus creating an energy deficit. The second principle of circular economy is to keep products and materials in use at their highest value possible, so while using aggregate materials is a form of reuse, there is a better, more circular way to address this problem. The energy and material value loss can be avoided by rethinking the design of buildings so that demolition and remodelling can be accomplished without losing the refined qualities of the building materials.
One way to eliminate the carbon cost of demolition is by building with mass timber. Mass timber is the result of layering pieces of wood together to make larger, denser pieces. Due to their density, mass timber is fire resistant, sturdy, and structurally reliable. Additionally, mass timber requires less energy to produce per unit than steel and concrete, leading researchers to assert that a mass timber building would reduce the carbon footprint of a building project by 26.5% compared to a traditional building design. Mass timber structures are highly reusable, composed of a pinned-together timber framework that can be reassembled to fit a wide variety of needs. This offsets the carbon cost of demolition by keeping the structural elements of previous builds in a highly refined state to be used in the future. Using this adaptable model greatly reduces the waste generated and energy lost in the demolition phase.
Mass timber projects are already in practice around the world; the HAUT apartment building in the Netherlands is one such example of the future of building innovation. We need not look as far as Europe to find mass timber advocates. Sidewalk Labs, an affiliate of Google, recently launched Factory-made Mass Timber Buildings. This project is designed to provide the infrastructure and research capacity to make modular mass timber buildings profitable. There are also numerous interested parties in North Carolina excited to join the movement but current building regulations slow down the adoption process.
Construction and demolition account for a large proportion of the total global waste produced. In order to reduce this burden on the environment we need targeted solutions. Material reuse has been identified as a possible solution but current practices fall short of efficient reuse of construction and demolition byproducts. To overcome this obstacle we must prioritize building materials and designs that plan for efficient end of life reuse (Principle 1 of circular economy). Material reuse is more efficient and effective if it is designed into the building from the beginning. One solution is mass timber buildings. These structures are made of durable materials that provide energy savings in every stage of the construction process and facilitate easy redesign and reuse. While we still have a long way to go to achieve zero waste in construction and demolition, there are great advances being made to prioritize sustainable building systems around the world.
If you want to learn more about how modern problems impact the state of the built environment, check out this article on COVID and adaptive building.
