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Originally published in OAA Profiles 2009.
ONE OF THE FUNDAMENTAL ASPECTS of sustainable design is a focus on getting more out of the resources we use. Be it energy, water, materials, components, whole buildings or urban infrastructures, we need to get more useful service from the resources we put in. At present we have a mentality of consumerism which leads to massive use of nonrenewable, primary resources, which are often extracted with great environmental damage, and create a huge amount of waste. Construction and demolition waste (C&D) contributes about 35% of the total waste stream in Canada1, and the Worldwatch Institute estimates that by the year 2030 the world will have run out of many raw building materials and we will be reliant on recycling and mining landfills.
Yet the concept of waste does not really exist in nature. In a biological ecosystem all material is used in some way; the residual products from one species or process are utilized by another. In an ideal industrial ecosystem, resources would not be depleted any more than those in a biological ecosystem; a piece of steel could potentially show up one year in a drinks can, the next year in an automobile and 10 years later in the structural frame of a building.
Existing buildings and infrastructure are a huge store of potential resources, not something to be thrown away. In Europe, the expected life of a building is usually at least 60 to 100 years and many buildings last considerably longer. In North America, much shorter time periods are typical! Buildings are long-term resources that need to be allowed to evolve and change with societies’
changing needs; otherwise they often deteriorate and end up being demolished. In the book How Buildings Learn, Stewart Brand talks about “blue jeans buildings” – buildings that, like a good pair of jeans, age honestly and elegantly over time. This requires acceptance of buildings as evolving entities where the design and construction phase is just the start of a long process of change over the life of the building. Yet this is alien to the current ways in which buildings are considered and managed. A starting point for any project should be – can we reuse and adapt an existing building? Demolition should be a last resort, and even then, can we reuse components from an old building into a new structure avoiding the use of new materials? This preserves much of the value of the components and minimizes reprocessing that is often required when materials are recycled.
Adaptive reuse of existing structures is now relatively common for heritage structures, as they are seen to have cultural value, but it is also essential to take a similar approach for many other existing buildings. There are measurable environmental gains to be achieved through the maintenance, conservation, improvement and evolution of the existing building stock. These buildings represent a major investment in natural and human resources. Their maintenance and conservation can significantly reduce the volume of demolition and construction waste, but also reduce the demand for new materials that would be needed to build replacements, thus conserving the embodied energy that has been invested in the construction of the existing buildings. Embodied energy is the energy invested in creating the materials in the building and assembling and maintaining them on site through the life of the building (the cradle to grave approach). Comparisons suggest that the embodied energy saved from renovating an older building rather than building new can be equivalent to 10 to 25 years of operating energy use. Furthermore, the construction process on site has significant environmental impacts from noise, local pollution, traffic disruption, watercourse pollution, etc. Conservation of existing structures can significantly reduce this.
There are also potential sustainability benefits from conserving existing structures that go beyond the individual building. Urban density, urban sprawl and the impact of development on the use of cars are all relevant to the long-term viability of cities. Utilizing the existing urban fabric can be a vital component of urban revitalization efforts attracting people back to city centres, rejuvenating old neighbourhoods, and reversing the trends for suburbanization. Building conservation can act as a very visual catalyst to changing the attitudes of people to consumption and encourage recycling. We should remember that sustainability is more than just about green technologies; it also encompasses local community issues and economic aspects. Here reuse of buildings (not only heritage buildings) may have particular benefits as a locally valued resource and offer potential for attracting economic benefits. Examples of old buildings that have evolved and been adapted in an effective manner to serve a new use include 401 Richmond St. in downtown Toronto, an old industrial building converted into a centre of design-related companies, and the BMW’s flagship store in downtown Toronto located by the Don Valley Parkway, which was a adaptive reuse of an old factory building into a car showroom and offices.
In projects where adapting and reusing a whole building is not possible, reuse of components may be an alternative strategy. Reuse of individual components extracted from the demolition of one project in a new building is commonly known as “component reuse.” Structural components, such as beams, columns or non-structural components, such as cladding panels, bricks or staircases, are taken from one project and used in another. This is not yet common, other than for heritage components, but increasingly architects are looking for ways to integrate reused components into their designs.
Reuse of components is different from recycling, where a material is fed back into the manufacturing process. From an environmental, and economic, point of view, reuse of reclaimed components is usually more beneficial than recycling of materials. Reuse generally requires little reprocessing, so greater environmental benefits often result, compared to recycling. Reuse is not usually possible for materials such as in-situ poured concrete, which is destroyed during the demolition process (and can be crushed for use as aggregate), but is more realistic for components that can be deconstructed undamaged.
Architects recognize that there are some significant differences to the design process if reuse of construction components is a goal of a project. Reclaimed components do not generally come “off the shelf” and sometimes their performance specifications need to be established. Often they are identified on demolition sites by salvage contractors. Thus, when proceeding to construction, the required size or type of component may not be readily available. An architect can redesign to suit available salvaged components or choose whichever oversized components are readily available recognizing that “using reclaimed materials adds a whole new level of complexity to the project”3. Reclaimed components may not be readily available off the shelf, and may be difficult to source. One of the principal challenges with component reuse is to co-ordinate demand with supply, and this can affect the whole design and construction process when “reclaimed materials do not show up at the right time, in the right amount or the right dimension” 4.
For some projects the starting point for a new design may, in the future, be an inventory of the available materials from salvage. For structural design, the size and length of the available members will then determine the spans and spacing possible in the new structure, so that structural efficiency can be maximized from the available components. The design team may be required to take on considerable additional research at the front end of the project to identify, locate, inspect and choose appropriate components.
Architects and engineers can develop working relationships with salvage and demolition contractors so they can easily find available salvaged materials, thus improving their choices when these components are required. Alternatively, it may be possible to purchase a suitable building already condemned for demolition, that contains appropriate components, and reuse as many of these as possible in the new project. At present, the difficulties inherent in the incorporation of salvaged materials into new buildings can discourage clients and designers from embracing reuse, unless it is for principled, rather than financial reasons. Although the cost of materials can be lower through reuse, these may be offset by higher labour costs and increased design fees resulting from more research required by the design team. However, green building ratings such as LEED™ and GreenGlobes recognize the importance of reuse of whole buildings and components, and encourage designers to look at reuse strategies. LEED™ awards credits for reusing 75% or 95% of the existing building structure and shell. Further credits are available for utilizing previously used components, and for locating developments in urban areas, which encourage consideration of existing urban buildings for reuse. The Mountain Equipment Co-op has focused on a reuse strategy in several of its recently constructed stores. Its Ottawa store used many components from the previous building on the site to create the new building. In some areas, specialist reused materials procurement consultants are emerging and their experience can reduce the risks of disruption or delay. In future, the demand for reclaimed components is likely to quickly change with altering priorities, and as salvage contractors become more aware of the value of the components they extract.
Dr. Mark Gorgolewski, BSc, MSc, PhD, LEED AP 1, is a member of the OAA Sustainable Built Environment Committee and a Professor & Director of the Graduate Program in Building Science, Department of Architectural Science, Ryerson University, Toronto.