Wednesday, September 12, 2018

Carbon Group Post 8: Contribution of Buildings to Climate Change


If you’ve been following these blog posts, you know that structural materials have inherent, or embodied, environmental impacts. The magnitude and range of environmental impacts differ among structural materials, and many of those differences have been discussed in previous blog posts related to the SEI Sustainability Committee’s technical report, Structural Materials and Global Climate. The contribution of structural materials to climate change, relative to a building’s overall environmental impact considering its entire service life, is low. This may leave structural engineers wondering why they should minimize the climate-change contribution of structural materials. The short answer is that materials’ relative contribution may not be relatively small for much longer.

Current situation
When evaluating the full environmental impact of a building over its entire service life, the scope of the assessment is considered in four stages: manufacturing (including material acquisition), construction, operation, and end-of-life (demolition, reuse, or recycling). For a building that is built in the United States, and which likely uses energy from nonrenewable sources, it is common that the energy used to heat, cool, or otherwise operate the building during the operation phase dominates its environmental profile. This means that 85 to 95% of the climate-change impact from buildings is due to the energy used during the operation life-cycle stage.

Ratcheting down
This relatively large contribution by energy use to a building’s environmental impact was identified by several organizations as a place to focus reductions. Groups such as  Architecture 2030 sprung up to try to tackle this challenge, and the LEED rating system more-heavily-weighted its credits toward energy use reduction targets.  On the enforcement side, code requirements within the International Energy Conservation Code are becoming more stringent with every code cycle.

These factors are all believed to be contributing to a steady decline in the energy use, and thus the contribution to climate change, of buildings during their operation. And while the overall contribution of a building to climate change is reducing, with all other things being equal, the relative contribution to climate change from structural materials will increase.

For more information on why reduction of carbon dioxide equivalent emissions is important in general, see chapters 1 or 2 of Structural Materials and Global Climate or check out these blog posts.

Figure 1: Operational and embodied carbon leading up to the year 2050.

A new opportunity
This greater impact of structural materials puts more control in the structural engineer’s hands related to reducing the overall environmental impact of buildings. With that opportunity for greater influence has emerged a new movement, called the Structural Engineers 2050 (SE 2050) Commitment Initiative. Modeled after the Architecture 2030 challenge, the SE 2050 initiative aims to reduce the embodied carbon (CO2e or climate change) impact of structural materials both initially and over time.

With the successful publishing of the Structural Materials and Global Climate report, the SEI Sustainability Committee is now working to launch the SE 2050 Commitment Initiative. Please reach out to any of the committee members if you are interested in getting involved.

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