Designing for Disassembly

The concept of the circular economy may be defined as a model of production and consumption which involves the sharing, leasing, reusing, repairing, refurbishing and recycling existing materials and products as long as possible.  The AEC industry typically follows a linear model of extraction, fabrication, use, and disposal.  This not only leads to the consumption of non-renewable materials, but results in vast amounts of materials with potential for recycling or reuse to become landfill or worse: incinerated.  A proposed solution to this issue is Design for Disassembly (DfD).  This strategy addresses the reuse or recycling of parts at the end of a building’s life cycle by facilitating the future dismantling of its systems, components, and materials.  Applying the principles of DfD means developing assemblies, components, materials, construction techniques, and information and management systems to enable the circular economy. 

DfD is particularly applicable when considering the wood-based structural framing systems found in many residential and commercial buildings in the United States.  According to recent estimates, over 18 million tons of wood waste is produced per year.  Of that, only 3 million tons of wood waste are recycled while 12 million tons become landfill.  The recent developments in engineered wood products such as cross laminated timber (CLT) mass plywood panels (MPP) offer a promising way to reuse and recycle reclaimed wood from deconstructed buildings.

Currently, there is a number of challenges associated with attempting to reclaim materials, particularly wood products, from buildings designed and constructed through standard methods.  The degradation of structural members through the use of damaging mechanical fasteners, chemical adhesives, hard to separate composite materials, and the drilling or notching of structural members through the installation of building systems are but to name a few.  In addition, high labor costs and loss of investment present economical barriers to the circular economy. 

Through DfD, however, a series of decisions and considerations early in the design process which can greatly increase the viability of reclaiming structural members.  Choosing timber or engineered wood products rather than dimensioned lumber, using bolted connections rather than nails or screws, keeping services separate from structural framing, maximizing the clarity and simplicity of structural design while minimizing the complexity of materials, and ensuring connections are readily physically, visually, and ergonomically accessible are all design strategies which support DfD.  Preparing plans for deconstruction in addition to documenting and identify structural member properties may also ensure wood products are not damaged in the process of deconstruction and make them easier to process for reuse.

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