Life cycle assessment can deliver sustainable century structures
Spend enough time in old cities, even in the U.S., and you’ll see plenty of historic buildings that have stood for hundreds of years. Many of them are still in use, serving modern functions. They might need renovations to keep them suitable for modern life and standards, but they’re clearly built to last. Year after year, decade after decade, new skyscrapers crop up around them. Yet they stand the test of time. These old buildings also provide a blueprint for modern construction when it comes to life cycle assessment, measuring the environmental impact a building will have over time. Not surprisingly, buildings that last for a century or more have lower total impact. No building is more sustainable than one that can stand and be useful for 100-plus years. That might change the way we design cities for the next century.
In a study published in Architectural Engineering and Design Management, Rob Marsh, head of sustainability at Danish firm C.F. Møller Architects used life cycle assessment to determine the environmental impact of buildings of various ages in Denmark. As with the rest of Europe, Denmark has no shortage of old buildings. Marsh found that compared to buildings with a life span of 50 years, those lasting 80 years reduced environmental impact by 29%. Buildings lasting 100 years reduced impact by 38%, and those lasting 120 years lowered impact by 44%.
Architects and engineers typically assume a life span of 35 to 60 years for new construction, but in reality, these buildings can be useful long beyond that timeframe.
“The challenge for construction professionals is therefore between balancing empirical and environmental concerns that point towards longer building life spans, and shortening retrofit cycles to meet new demands,” Marsh wrote.
For a building to serve a purpose for a century or more, it needs to be adaptable to changing circumstances and functions.
“New buildings need to be designed to allow for future functional changes and retrofitting, and there is a need to examine the nature of changes that can be expected to occur in buildings over time. There is a need to develop specific design strategies that can increase the ability of buildings to accommodate change,” he wrote.
The Right Stuff
How long a building will last is, of course, down to how sturdy the materials it’s made from are. Some elements won’t last 100 years no matter what, though, and Marsh recommends designing around these in such a way that they can be replaced with minimal retrofitting. Lightweight claddings, for example, can make it easy to remove and recycle shorter-lived materials.
Life cycle assessments can also lead to better-designed building materials that last longer. Sherwin-Williams has a team in its sustainability department that does nothing but perform life cycle assessments. They’ve improved the design of coil coatings that go over metal building materials. What at first seems like a small improvement makes a big impact, because when a coil coating has to be replaced, so does a giant sheet of metal.
“It’s very easy for us to make a coating that we would characterize as more environmentally friendly. But if it only lasts one year versus 50, then you’re doing a lot more damage,” Christian Zimprich, Sherwin Williams’ coil coatings marketing manager, told Building Design + Construction. “The longer the coating lasts, the longer the lifespan of the building itself.”
It’s equally important to ensure that at the end of the life cycle, building materials can have a second life as part of a circular economy.
“If the whole building ends up in a landfill, that’s a much more significant impact on the environment than if you’re able to take a large portion of that building and recycle it and make another building,” Zimprich said.
Through the five stages of a building’s (feasibility, design, construction, operation, and demolition) life span, a life cycle assessment can reduce energy use, stimulate innovation, and build a more sustainable world. It can give a full picture of what tradeoffs must be made to minimize waste and maximizing life span before a single load of concrete is poured.
“LCA results can help answer numerous questions that arise during the design and construction of a green building. It can reinforce the decisions taken by architects by providing a scientific justification,” the American Institute of Architects says.
For architects bidding on new projects, a life cycle assessment can land clients that are focused on making sustainability part of everything they do, including the building where they conduct business. It can be part of a lasting legacy, a new skyline, or a towering monument to green building that long outlives the builders.