According to the World Green Building Council, buildings are responsible for 39 percent of global energy-related carbon emissions, with 11 percent coming from embodied emissions. Within those different sources of construction-related emissions, there are opportunities for owners to build more sustainable projects. As a construction manager (CM), Skanska USA Building can have positive influence over a project's embodied carbon footprint through the decisions we and the larger team make before and during the construction process.
On our St. Pete Pier project in St. Petersburg, Florida, we were tasked with choosing a metal material for the doors that wouldn't rust near seawater. We chose aluminum, which has a lower carbon footprint than steel and it won't have to be replaced as often as other metals that corrode. (Photo Credit: City of St. Petersburg)
As we construct or renovate facilities like hospitals, universities, office buildings and airports, our efforts to reduce embodied carbon focus on six key areas:
During the early design phase of a project, when the team is choosing which building materials to use, we can have the most impact on reducing embodied carbon. Using innovative tools, like the Embodied Carbon in Construction Calculator Tool (EC3 Tool), we can provide suggestions like swapping out traditional concrete or steel with timber. It doesn't need to be the whole building either—any sort of incremental improvement matters, and there are other options like low-carbon steel.
When deciding on which building materials to use, it's important to keep in mind that while some materials emit less carbon, we should also look at opportunities to reduce the use of materials in general. Are there opportunities to change a building's mass and therefore minimize materials needed? For instance, the incorporation of mass timber will make a structure lighter and decrease the amount of foundation needed. Changing the shape of a building is another way to reduce the amount of materials used on a project. If a building has really thick walls, is it necessary to have that level of thickness for all four sides of the building or just on the side that has the greatest wind shear.
We also consider the long-term effects of the materials we choose for our projects. Are they durable? Are they reusable or recyclable at the end of their life?
On our St. Pete Pier project in St. Petersburg, Florida, we worked with the client to find a resilient material for the doors and certain other metal surface materials because steel, which is typically used, rusts rapidly when in proximity to seawater. We chose to use aluminum where possible, which has a much lower carbon footprint and won't have to be replaced as often as other metals that corrode. An added bonus is aluminum's recyclability: 95 percent of all the aluminum ever created is still in use as it can be continually recycled.
2. Materials transportation
The carbon footprint of a building material also includes its weight, how far it's being transported and the mode of transportation. As a CM, we can plan ahead and have some influence on that mode of transportation. Most manufacturers assume we want the building material as quickly as possible, so they choose the fastest route or the cheapest transportation option. But, if we're planning ahead, we can look at different options like shipping the material in a way that has the least carbon impact. For example, when materials are transported inside shipping containers on the back of semi-trucks, it adds more weight to the truck, which makes the truck use more fuel, adding to the carbon footprint of the material. If the material can be transported in open elements on the back of a truck instead, the carbon emissions will be incrementally reduced.
If we're working on a jobsite in Charleston, South Carolina, and we need to order a curtainwall from Quebec, we can discuss transportation options with the manufacturer, such as truck, rail or ship. Since Quebec and Charleston are located along the Atlantic Ocean, shipping the curtainwall by barge would emit the least amount of carbon. This is because the fuel calculated in the embodied carbon footprint of the curtainwall would be spread out among the many items being transported on the barge versus the fuel calculated for a truck to carry just the curtainwall down the East Coast.
3. Craft worker transportation
How our craftspeople get to the jobsite is also part of the overall embodied carbon footprint for a project, but it's very location-dependent. When we have projects in cities like New York City or D.C. with extensive mass transit options, many construction workers will ride the subway to and from work. This makes it easy to keep the craft worker transportation portion of the project footprint low, because riding mass transit is much more sustainable than driving. However, with project sites in suburban or rural areas it can be more challenging. There are solutions to explore, such as promoting carpooling for craft workers who live near one another or providing bus or van services from hub locations.
4. Waste
When looking at the embodied carbon footprint of a building, waste includes anything that's coming off the jobsite. While not a big footprint in terms of carbon, one of the biggest challenges in this category is employee food waste because single-use plastic is hard to recycle onsite and items like greasy paper wrappers can get tossed into recycling bins, contaminating an otherwise recyclable load. Cutting back on packaging in general, and specifically plastic, is where we can make a big impact. For example, using water coolers instead of disposable plastic water bottles can lower waste and the embodied carbon footprint of a jobsite.
Currently, Skanska USA Building is considering the TRUE certification program for some of our clients, which calls for deep reductions of a facility's waste starting back at the material source and extending all the way to how the product might have a useful life above and beyond traditional recycling opportunities.
Emissions from energy use during construction includes the energy we're using in our project trailers and throughout the jobsite, like for safety lighting or operating equipment. As a CM, our greatest opportunity to impact energy is when we have the ability to require a net zero carbon approach for the whole project, or where net zero energy trailers are deployed. Energy use is also reduced through employing efficiency strategies like installing better insulation and occupancy controls in our trailers or adding a vestibule to the entrance to reduce heating and cooling fluctuations.
6. Fuel
The fuel portion of a project's embodied carbon footprint includes measuring the fuel emissions being released from any construction equipment or vehicles used. Implementing a "no-idling" policy on a jobsite is an easy way to reduce carbon emissions, often already being done in urban settings. Using alternative fuels in construction equipment and vehicles allows them to run as sustainably as possible.
Small changes can have the biggest impact
At Skanska, we're committed to achieving net-zero carbon emissions by 2045. In order to do that, we're taking actionable steps towards achieving this goal. In our fight against climate change, it's important to keep in mind that any level of positive impact is beneficial as we strive to create a more sustainable future.
Myrrh Caplan
Sustainability Director
Email Myrrh Caplan