Most old buildings are demolished, but some cities are beginning to design them for reuse from the start.

Many people are now attempting to recycle their newspapers, plastic bottles, and aluminium cans in order to reduce household waste. But few of us consider the enormous amount of waste produced in our names in a different way: the buildings in which we live.

The construction industry is the world’s largest raw material consumer. New buildings alone account for 5% of global annual greenhouse gas emissions. The majority of that material will only be used for one building and will be disposed of once the building reaches the end of its lifespan, which is typically between 30 and 130 years.

“For example, we’re attempting to put recycling out on the street, but in the background, “There’s this construction industry that [in the United States] produces twice as much waste as each of us produces at home,” says Felix Heisel, an architect and researcher at Cornell University.

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Cities around the world, however, are beginning to pay more attention to the idea of recycling building materials, and some have even passed ordinances requiring building constructors to do so. Meanwhile, architects are devising methods to construct new structures that are designed from the start to be disassembled.

So, how might a city built on these principles look? Experts envision cities with exposed wood and steel aesthetics, requiring few outside resources to sustain their construction industries, and being both greener and more flexible, able to respond to housing shortages or retrofits with ease.

However, the road to these new recyclable cities will be long and will necessitate the development of new tools, marketplaces, and incentives. Perhaps a completely new way of thinking about ownership and our place in the built environment.

Building demolition is frequently simple: a bulldozer or excavator can reduce a house to scraps in a matter of hours. However, this has a significant drawback: all of the material in the house, now broken and mixed together, cannot be reused and must be burned or transported to a landfill.

But it doesn’t have to be this way. The city of Portland, Oregon, in the United States, adopted a deconstruction ordinance in October 2016, requiring that residential homes built in or before 1916 (later updated to 1940) or earlier be “deconstructed,” rather than demolished.

“The majority of houses demolished in Portland in 2015 were mechanically demolished. Today, most are disassembled by hand by deconstruction contractors, and the materials are salvaged for reuse “Shawn Wood, a city construction waste specialist, agrees.

The decision was prompted by a wave of demolitions in the city that began in 2014, as well as concerns about waste and the environmental consequences of burning or dumping debris. A number of other cities in the United States have followed suit, including Milwaukee in Wisconsin, Palo Alto and San Jose in California, and San Antonio, Texas, as of September 2022.

When I talked about design for disassembly, [people] told me it was never going to happen. There’s really come a change from that to now – Leonora Eberhardt

However, deconstruction presents some difficulties because most buildings are not designed with it in mind.

One issue is the amount of time and effort required. A house demolition may take two days, but deconstruction may take ten.

If the materials recovered during deconstruction are valuable enough, their sale can cover the cost of the extra time and labour, but as Heisel points out, we often don’t know what’s inside buildings ahead of time. He is working on ways to use tools such as Lidar (light detection and ranging) and construction data to assist workers in quickly estimating what and how much re-sellable material is hidden behind walls. Another issue is that materials that have been treated with potentially toxic chemicals or that have been composited, When wood, concrete, and steel are bonded or welded together, they can be difficult to separate and often impossible to repurpose.

These issues, however, could be addressed if builders adopted an ethos known as “design for disassembly,” in which buildings are designed to be easily disassembled from the start.

Designing for disassembly is a very old technique at its core. Consider nomadic people’s homes, such as yurts and tipis, which are regularly disassembled due to the need to move them on a regular basis. Traditional Japanese architecture and exhibition spaces such as the UK’s Crystal Palace are notable examples.

However, in recent decades, some designers have pushed for disassembly plans to be incorporated into office buildings, apartments, and modern houses.

So, what makes a building designed for disassembly different from one that isn’t? One significant difference could be the preference for more easily recycled or reused materials, such as wood and steel, over others, such as concrete or drywall.

Another distinction is the manner in which parts are joined. Builders would avoid hiding connections in hard-to-reach places or creating unbreakable bonds; instead of welds and chemical adhesives, designers might favour removable bolts or mechanical fasteners. Even minor changes, such as swapping nails for screws, could make it easier for future workers to disassemble and reuse wood pieces rather than throwing them away. Connections can also be standardised to make it easier to swap out or move pieces. This modular design approach would make it easier for future residents to repair, replace, or add fixtures such as overhead lighting or windows. With the turn of a few bolts, entire wall panels could be removed. Rooms could even be completely repurposed with little effort, such as an office becoming a bedroom or even a kitchen.

This ethos has manifested itself in a number of working groups and construction projects, including Carnegie Mellon University’s Intelligent Workplace and NASA’s Sustainability Base. However, it also fits into a growing number of government regulations centred on the “circular economy” – a broad term for ideas aimed at reducing humanity’s environmental impact by recycling and reusing products and materials as much as possible. Several certification schemes, such as the UK’s Breamm and Germany’s DGNB, as well as the EU’s circular economy action plan, provide incentives.

In 2021, Sadiq Khan’s office as Mayor of London issued guidelines for large construction projects in the UK capital, requiring them to complete whole-lifecycle carbon assessments and circular economy statements before receiving approval.

Andrea Charlson and According to the built environment lead for ReLondon, a collaboration between the mayor’s office and London boroughs, design for disassembly fits into the London plan. Projects will be required to submit circular economy statements, which will demonstrate how the development will reduce material demands and “enable building materials, components, and products to be disassembled and reused at the end of their useful life,” according to Charlson.

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