UBCs Design for Deconstruction research initiative included the development of a mock-up wall section constructed using design-for-deconstruction principles. The mock-up was subsequently deconstructed to test the ease of disassembly and the quality of materials salvaged from the deconstruction. This phase of research also produced assembly details of that mock-up and a number of other potential configurations that would allow for a variety of insulative values. Image credit: Design for Deconstruction in Light WoodLandfilled wood is a big part of Canadas construction, renovation, and demolition (CRD) waste problem. The average lifespan of a building in Canada is around 70 years before it is demolished, and in rapidly densifying cities, the actual lifespan can be much shorter. Wood waste makes up 40 per cent of CRD waste; nationally, this means that about 10 per cent of all residual solid waste is wood waste. This equates to approximately 3.6 million tons of wood being landfilled each year.Much of this is clean woodincluding dimensional lumber, old growth timbers, and structural compositeswhich could have been reused or repurposed. Yet the existing construction industry works as a linear economy which does not support the reuse of wood materials, and so wood is relegated to disuse, where its bulk adds to overtaxed landfills and its decomposition releases CO2. A small percentage of Canadian wood waste is recycled through waste-to-energy conversion via incinerationbut this eliminates the possibility of any further reuse and also results in greenhouse gas emissions.The existing construction industry works as a linear economy which does not support the reuse of wood materials, and so wood is ultimately relegated to either landfill or incineration. A circular economy of wood for allow for the repeated reuse, remanufacture, or upcycling of wood products. Image credit: Design for Deconstruction in Light WoodFuture Vision & ResearchLooking holistically at a multi-generational life cycle for wood, architecture graduate Kaia Nielsen-Roines thesis research, entitled Seven Generations of Wood, envisions construction practices and recycling methods that would allow wood to be reused in light-frame construction for at least seven generations of buildings, or approximately 500 years of continuous use. This is achieved through design-for-deconstruction practices that adapt standard light wood frame construction details to allow for ease of disassembly and material recycling. The thesis also identifies material recycling technologies that would allow for common wood construction materials to be cycled back into the built environment. Proposals include making finger-jointed lumber from salvaged dimensional lumber, strand-based composite wood products (such as OSB and LSL) from solid wood, cross-laminated wood tiles from salvaged plywood and OSB, and wood fibre insulation from many different types of waste wood.How do we move towards such a vision? In order to build cyclically with wood waste, several roadblocks need to be addressed. For example, currently any piece of wood reused in a building for structural purposes must be signed off by a structural engineer. This is a good requirement for large beams and other non-structurally redundant members, however, there is a case for changing this requirement for light wood frame systems, which have high levels of structural redundancy. Canada should adopt the policy of Washington State and Oregon, in which any wood coming out of a light wood frame building is automatically accepted as Grade 2 lumber for reuse in buildings.Large-scale sorting and storage of wood materials is also a roadblock to effective wood reuse. The models for tackling this already exist. The city of Seattle has developed a reuse hub which collects, sorts and resells construction materials of all kinds. Similarly, Habitat for Humanity ReStores throughout Canada have a similarif smaller-scalesystem for reselling construction materials.Since using wood waste entails the labour-intensive removal of connectors, it is likely that it will not be economically competitive with the current commodity. However, carbon accounting regulations could give an advantage to reused wood. Currently, several Canadian municipalities, including the City of Vancouver, offer pathways for gaining compliance credits if design-for-deconstruction methods and recycled materials use are demonstrated in a building permit application. Such policies rewarding the use of recycled wood are key in encouraging wood reuse. Similarly, waste management policies, such as the elevated tipping fees for wood disposal currently in effect in Vancouver, can encourage wood recycling. However, effective recycling pathways need to exist to gain benefit in separating wood from regular CRD waste.More research is needed on using recycled lumber in CLT, engineered wood products, and insulationincluding research into adhesive interaction and other technical issuesto ensure that these are equivalent and reliable products.The re-finger jointing of wood is a promising possibility for the reuse of wood. This requires research into the processes and requirements of the finished wood, and testing of the reliability of wood that has been finger-jointed a second time. From a structural standpoint, the joints of a finger-jointed board are much stronger than the wood itself, and defects could be cut away from salvaged wood to make a clearer and straighter board than can typically be produced from fresh wood.Another mechanism that could potentially help with wood recycling is an internet of things-based system to track wood pieces across generations of use. A scannable QR code, for instance, could link to information on the physical characteristics and history of a piece of wood, and would be useful in determining the possible future applications of that material. For recombined products such as finger-jointed lumber, an IoT system would help ensure uniformity for further recycling. Such a system could also aid in preserving pieces of material history, in the case of recycling old growth timbers from very old buildings.The front view of the finished wall mock-up. The constructed mock-up was designed with an R-22 effective insulation factor to conform with the recommended requirements established by the city of Vancouver. Image credit: Design for Deconstruction in Light WoodCurrent ProgressFortunately, there is increasing engagement from within the architecture and construction industry and from government at various levels to move towards a circular model of wood use. Changes to wood disposal regulations in a number of Canadian municipalities has started to divert some clean wood from landfills. For example, in Vancouver, there are additional tipping fees for disposal of mixed construction waste, and savings when wood is separated out for recycling. Additionally, a minimum percent of building materials must be recycled from houses built prior to 1950 in order to obtain building permits for new construction on those sites.From the industry side, there are a number of businesses that are currently at the vanguard of a circular construction economy. Among these are building material recycling companies that turn waste wood into new construction products, like Vancouvers Urbanjacks; construction and architecture firms designing buildings that can be deconstructed and salvaged and which make use of recycled and low-carbon materials; and deconstruction companies such as Vema in Vancouver and Ouroboros in Toronto who dismantle buildings rather than demolishing them, so that the component parts can be reused and recycled. There are also related stakeholders working to track, audit, and divert waste materials from landfills: Vancouver Island consultant firm Light House recently developed the Building Material Exchange (BMEx) which connects contractors, individuals, and organizations to allow excess construction materials to be shared in the local construction industry, rather than going into landfill.The federal mandate to create a net zero construction sector by 2030 adds further impetus to reforming the way in which our industry uses wood. Some of the barriers to reusing wood at an industry scale include lack of infrastructure for salvaging and recycling wood, limited policy clarity on reusing wood in construction, and the perceived and actual cost barriers to reusing wood.The mock-up modifies light-wood frame construction by replacing nailed connections with screwed connections or double-headed nails to allow for disassembly, omitting any plastics or adhesives from the assembly, and using wood fiber insulation for exterior insulation and vapour-open batt insulation to allow for a breathable but air-tight building envelope. Optionally, it is also recommended to use cladding and interior finishes that can be removed and replaced to allow for simplified repairs and access to the service cavity. For additional air-sealing, the exterior joints of the sheathing panels and interior edges of windows and doors are sealed with flashing tape. Image credit: Design for Deconstruction in Light WoodDesigning for DeconstructionOne significant barrier is the labour required to deconstruct as opposed to demolishing a building. Wood frame buildings constructed after 1950 in Canada are generally difficult to deconstruct: the use of construction adhesives, spray foams, nail guns, and toxic materials (such as asbestos and lead) make successful deconstruction challenging, and the materials extracted from such projects are often damaged and unsuited to reuse. A solution to this issue is to plan for a buildings end-of-life by designing it for deconstruction, so that its material components can be disassembled and reused or recycled with minimal effort and limited damage to the materials. While design for deconstruction is not a new concept, there has been little concentrated research on developing standardized methods for design-for-deconstruction of light wood frame buildingsthe construction method for the majority of Canadian houses. A single 130 square metre (1,400 square foot) house that is designed for deconstruction could allow for the reclamation of about 30 tons of wood.In order to promote design for deconstruction wewith the support of Canada Wood Council and Forestry Innovation Investmentrecently produced a free Guidebook for Design for Deconstruction in Light Wood Frame (blogs.ubc.ca/design4deconstruction). Our suggested construction details and materials take the approach of minimally changing the process of building light wood frame to allow for deconstruction. For example, we suggest changing nails to screws and using minimal tapes, with no foams or adhesive membranes.We are currently researching how to create wood insulation from waste wood, using a bio-based binder of waste wool from the wool industry. There are already examples of recycled wood construction products being produced in Canada: BP Canada produces wood fibre insulation in part from solid construction waste wood, Trillium CLT makes several versions of cross-laminated wood tiles from plywood and other composites, and salvaged finger-jointed lumber is being produced by Urbanjacks in Vancouver. A small but growing contingent of the construction industry is moving towards a circular economy of construction.Kaia Nielsen-Roines thesis research, entitled Seven Generations of Wood, envisions construction practices and recycling methods that would allow wood to be reused in light-frame construction for at least seven generations of buildings.ConclusionThe potential for wood reuse in the construction industry is massive, and while this largely untapped resource is gradually getting more attention, there is much room for growth. The solutions to infrastructure and policy issues surrounding wood reuse have already been trialed in other cities: for Canada, it is largely a matter of implementation. Beyond these practicalities, there is a need to develop the design standards, material technologies, and cross-industry relationships that would make a circular construction economy of wood profitable and sustainable.Looking at the whole lifecycle of woodand the possibility of multiple generations for the same wood productis required to make the most of the wood we generate in Canada. Envisioning what needs to be done through multiple uses of the same piece of wood will allow us to respect this key material resource, while providing the most benefit to people and to our environment.The post Reuse of Wood Construction and Demolition Waste: Potentials for Canada appeared first on Canadian Architect.