Sustainable Buildings Start With Sustainable Materials

Lendlease's Sara Neff on how multifamily developers can reduce carbon emissions at the onset of their projects.

Sara Neff

Buildings are more than the sum of their parts. However, as the construction sector is responsible for approximately 40 percent of the world’s CO2 emissions, those individual parts can play a critical role in capping global temperature rise at 1.5°C to protect our planet from the worst impacts of climate change.

One way that multifamily builders and developers can lower the carbon footprint of a new-construction building is by choosing more environmentally friendly building materials. Some options are new and some are tried and true, but all can help to reduce embodied carbon, which is the carbon released during the manufacturing, production and transportation of building materials. By constructing a project with reduced-carbon steel, green concrete or mass timber, for example, developers create a more sustainable building and set an example of environmental stewardship.

Reduced-carbon steel

Steel is the backbone of our modern cities. From the innovative steel skeleton frames that held up the first skyscrapers to the super-tall structures going up around the world today, the dense urban environments that many of us call home would not be possible without steel.

Unfortunately, steel happens to be a significant contributor to global greenhouse gas emissions. The iron and steel manufacturing process accounts for approximately 7 percent of global CO2 emissions, according to the International Energy Agency. And as buildings and infrastructure together consume half of the world’s annual steel production, any efficiencies in steel use that the commercial real estate industry can implement will go a long way toward mitigating steel’s contribution to climate change.

Decarbonizing the steel sector will require several strategies, including electrification of manufacturing facilities, better recycling of scrap, carbon capture and storage and improved access to competitively priced renewable energy for steel producers. These efforts could impact steel prices in the short term, though cost will come down over time as more low-carbon steel becomes available. This is why it is important for commercial real estate firms to partner with organizations such as ResponsibleSteel and The Climate Group’s SteelZero initiative, to reduce emissions across the supply chain by driving up market demand for net zero carbon steel.

Lendlease committed to using lower-carbon steel on a new transformative project. Claremont Hall is a mixed-use academic and residential building located on the historic Union Theological Seminary campus in New York City’s Morningside Heights neighborhood. When complete, the building, which is targeting LEED Gold certification, will provide approximately 165 condominiums offering a mix of one-, two-, three- and four-bedroom residences, as well as 54,000 square feet of classrooms, academic offices and faculty-designated apartments. Claremont Hall’s environmental successes go beyond LEED: More than a quarter of the steel-related emissions at Claremont Hall were eliminated on this project through the use of reduced-carbon steel.

Green concrete

Another ubiquitous yet carbon-intensive building material is concrete. The production of Portland cement, the key ingredient in concrete, requires intense heat and leads to significant carbon dioxide off-gassing, which is why the concrete industry is responsible for approximately 8 percent of anthropogenic carbon emissions.

The most straight-forward approach to making concrete more sustainable is to reduce the amount of cement in the concrete mix. For decades, manufacturers have been hard at work trying to find durable, lower-carbon alternatives to include in their concrete mixes, and we are just beginning to see real solutions that can work at scale.

Green concrete is currently being used at The Reed, a 440-residence tower under construction in Chicago’s South Loop neighborhood. It is the first application of a proprietary concrete mix from Chicago-based McHugh Concrete. Created in partnership with Oremus Material, this concrete mix replaces up to 60 percent of the traditional Portland cement with ash and slag, a glassy waste product formed in blast furnaces during the steel production process. Opting for green concrete at The Reed will reduce the building’s overall embodied carbon emissions by over 10 percent.

Low-carbon concrete has been shown to be stronger and longer lasting than regular concrete. However, it can also increase construction costs by 1 percent to 2 percent and impact project schedules. As with lower-carbon steel, elevated costs for this material will come down as it becomes more commonplace in new construction.

A secondary benefit to this particular concrete mix is a smoother finish compared to traditional concrete. That will be important at The Reed, as the Perkins and Will-designed high-rise will feature an industrial-chic aesthetic incorporating exposed concrete ceilings and columns for loft-like interiors.

Mass timber

Just as fashion trends can come back in style, construction techniques can as well. The retro-cool material that many in commercial real estate are turning to as a way to reduce their carbon footprint is perhaps the oldest building material there is: wood.

Wood is renewable, strong, easy to work with, offers biophilic benefits and weighs less than concrete and steel, reducing both the size of necessary foundations and transportation impact. Even better, wood actually sequesters carbon, further reducing the embodied carbon footprint of mass timber buildings.

While a mass timber building typically has a higher up-front cost in comparison with a traditional concrete structure, mass timber buildings often experience total life-cycle cost decreases due to an estimated longer lifespan and because the wood has salvage value if the building is demolished.

Lendlease has a long track record with mass timber construction. For example, First Community Housing recently tapped SERA Architects and Lendlease to design and build a transit-oriented affordable housing project close to San Jose’s Diridon Station. The 365-unit McEvoy Apartments housing development has an ambitious goal to achieve LEED Platinum. One of the principal ways the two-building project will get there will be through the use of a mass timber frame in a traditional lateral system.

McEvoy Apartments will also implement novel prefabricated technologies during construction – a technique that is easy to execute with cross-laminated timber and other engineered wood products. Constructing modules in a factory setting and transporting them to the job site reduces the need for truck deliveries, drives costs down and accelerates the speed to market.

The efforts at McEvoy Apartments complement that work with mass timber that Lendlease has already successfully delivered, including five mass timber hotels.

Looking ahead

Turning the tide of climate change will not be easy. However, innovations in building technology can help to mitigate the effects of this crisis and any additional costs should fall to the wayside as more developers opt to implement them in their projects. Time is a critical factor in addressing this global threat, which is why multifamily developers should act now, take the lead and implement the use of sustainable materials in their projects.

Sara Neff is the head of sustainability for Lendlease.

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