By Deborah Mesher, Architectural Designer and Rashmi Sirkar, Intern Architect and Sustainability Analyst
Deborah: What is circularity in the construction industry?
Circularity is an approach to designing materials, processes and buildings that subverts the linear "take, make, waste" approach to construction and looks to create a closed loop system. This can be done by re-using existing building materials through careful deconstruction, using more bio-based renewable materials, using construction methods that allow for easier future disassembly, and/or using locally made products and components.
Deborah: What is deconstruction?
Building deconstruction is an alternative to conventional demolition where the building is systematically dismantled in a way that preserves building elements and materials. Residential building deconstruction is often done manually with lo-fi tools. Deconstruction is also evolving to include more advanced machinery and techniques such as panelized deconstruction in which cranes etc. can be used to take apart and transport entire wall panels rather than breaking it up into its constituent parts like studs and sheathing. Deconstruction is an essential process in a system of “urban mining” and building material reuse - but it is not enough to just deconstruct buildings to keep material out of landfill. There needs to be simultaneous development spatial and logistical infrastructure for salvaged material and a market for them too.
Deborah: What alternative materials are available to us?
If we group products broadly into structure, envelop or interior finishes, there are many bio-based materials that can be used. For structure, low-rise residential construction is already typically wood stick framing, but basements and foundations often use concrete which is incredibly carbon and energy intensive. Locally sourced stone foundations can be a lower carbon alternative to concrete foundations.
Wood fiber insulation and cellulose insulation too can be used where possible instead of petroleum-based insulation products. Thatch and wood shingles have been used as cladding materials for centuries in vernacular architecture and may still be used with an updated design aesthetic. Hempcrete and strawbale are gaining popularity as alternative materials for exterior walls, though difficult to accomplish on tight urban properties.
Interior finishes can include lime and clay renders, linoleum/cork flooring and mycelium composite flooring. Reclaimed wood can be used for floor, wall and ceiling finishes.
Deborah: What potential does the reuse of wood have?
Currently salvaged wood is most commonly used as interior finishes - flooring, wall and ceiling panels. There is also a lot of potential for reused wood in outdoor landscaping where boardwalks, seating, planters and trellises can all be made from reclaimed wood. Technically wood can also be reused as structure - most wood studs that have survived 50-60 years within the walls of an old house have the structural integrity to stand within walls of a new house unless they have been damaged by moisture or mold. However currently there are no testing and certification systems which allow for the general reuse of wood as structure. Reclaimed wood can also be used as feedstock for mass timber manufacturing and wood fiber-based insulation. Smaller quantities of salvaged wood can also be repurposed as furniture, and low quality wood can be chipped up for mulch.
Deborah: What can’t salvaged wood be used for?
As we can see salvaged wood has a pretty wide range of uses since once you plane away the top inch or so the interior layers of the wood can look as good as new. The main process that salvaged wood requires is de-nailing where old and rusted nails need to be removed from it. This can leave various holes in the surface of the piece but will often have little impact on its structural integrity. One of the more common uses for wood waste currently is incineration in waste-to-energy facilities - which can be avoided for higher uses that continue to sequester the biogenic carbon that's locked in the wood.
Deborah: What is emerging in your field that your excited about?
Many things! Including the role of AI and robotics to de-nail wood and process salvaged lumber that can radically reduce the labour input and cost of this material at scale. Also encouraging is the interest that municipalities are showing in understanding low carbon and circularity that can help create policy and regulation that will enable circular construction at scale.
Learn more about Rashmi’s work here.
