Courtesy : buildinggreen.com
Reuse of materials
The construction sector’s take-make-waste approach to materials needs an overhaul. Materials and construction account for an estimated 11 percent of global greenhouse gas emissions annually, according to the World Green Building Council. At the other end of the life cycle, demolition in the United States annually generates 90% of some 600 million tons of construction-sector debris, according to the U.S. Environmental Protection Agency’s most recent report—that’s more than twice the amount of municipal solid waste from all other sources—and 145 million tons of it goes straight to landfill. Getting trashed alongside are the cultural, economic, and environmental values those materials embody. Indications are, though, that this staggering, decades-long profligacy is about to change.
“We simply can’t afford demolition after 2050,” Julian Allwood, professor of engineering and the environment at Cambridge University, said in a keynote address at a summit hosted recently by the Royal Institute of British Architects and the climate initiative Architects Declare. That’s because the climate emergency requires reducing buildings’ embodied emissions, as well as their operating emissions, to net zero: use less overall, and reuse more. (Embodied emissions are greenhouse gases generated during materials’ extraction, manufacture, and transportation, and during construction and disposal.)
It’s also because the expected doubling of global gross building area by 2060 will take a lot of material. And finally, in a zero-emissions world, there will be fewer new materials available: the techno-fixes that would allow emissions-free energy to supply current consumption levels have no real hope of being fully developed and implemented at scale in the available time, Allwood said. We’ll have to live well with less.
In the coming decades, local availability of materials will transform the design process, and reclamation and reuse will be significant factors, says Felix Heisel. Heisel is the director of the Circular Construction Lab at the Cornell University College of Architecture, Art, and Planning, where he is an assistant professor of architecture. “I see this not as a limit to our design capacity, but as an advantage,” he says. “By starting with the local availability and specifics of materials, and letting these conditions drive the design process, we shift to an architectural language that’s more economic, more ecologic, and, most of all, more meaningful.”
Shifting to reclamation and reuse presents design teams with two main questions: How do we make use of materials in existing buildings that were not designed with reuse in mind? Salvaging from fixed assemblies is such a dirty process—one that releases toxins, pollutes water, and moves large volumes of material—that it is sometimes described as “urban mining.” So the second question becomes: How can we build differently starting now so that, in the future, buildings function as materials banks or depots, rather than as urban mines?
