News Brief

Builders Push “Drawdown Buildings” to Cut Embodied Carbon

Touting the benefits of biobased materials and electrification, a recent study shows how low-rise buildings can become a climate solution.

by P.J. Melton

cover of white paper by Builders for Climate Action

It’s possible to reduce the embodied carbon footprint of low-rise construction projects using conventional materials.

Image: Builders for Climate Action
Embodied carbon represents an outsized portion of greenhouse gas emissions from new low-rise construction, according to a white paper released by Builders for Climate Action. But it’s also possible to reduce that footprint with conventional materials—and even to make buildings a carbon sink by using less common products—according to the report.

The white paper models a range of low-rise structures built with different materials, with the highest embodied carbon (241 kg CO2e/ft2) coming from a building with high-Portland-cement concrete, and extruded polystyrene and spray-foam insulation. A “typical” model (90 kg CO2e/ft2) includes concrete with some supplemental cementitious materials (SCMs), along with mineral wool insulation. A lower-carbon alternative (–11 kg CO2e/ft2) incorporates high-SCM concrete, and cellulose and wood fiber insulation. Finally, the carbon-storing model (–137 kg CO2e/ft2), which the authors refer to as a “drawdown building,” includes:

  • insulated concrete forms with high-SCM concrete
  • expanded glass sub-grade insulation
  • straw and wood fiberboard insulation
  • wood cladding
  • compressed straw panel interior walls
  • ReWall interior finishes
  • wood windows
  • linoleum and Forest Stewardship Council-certified softwood flooring
  • cedar shake roofing

It’s worth noting that drawdown buildings rely heavily on wood products, and there are emerging questions about whether wood is universally a carbon-storing material. (See “The Urgency of Embodied Carbon and What You Can Do about It” for a discussion of this.)

The report also addresses operational carbon emissions, recommending building electrification because grid cleanup at scale is more effective even than net-zero construction. In fact, the report concludes, an energy-efficient drawdown building located in Toronto and using renewable grid electricity would avoid 614 metric tons of carbon emissions over 30 years.

More on embodied carbon

The Urgency of Embodied Carbon and What You Can Do about It

Embodied Carbon Tools: Assessing the Options

Structural Engineers Unite against Climate Change

For more information:

Builders for Climate Action
buildersforclimateaction.org

Published March 2, 2020

Melton, P. (2020, February 25). Builders Push “Drawdown Buildings” to Cut Embodied Carbon. Retrieved from https://www.buildinggreen.com/newsbrief/builders-push-drawdown-buildings-cut-embodied-carbon

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Comments

Kathleen Draper
BuildingGreen Basic Member

March 19, 2020 - 9:09 am

Great article. I am currently designing a 'C sync sanctuary' or what I call my Dwelling on Drawdown project. One carbon sequestration material that most have never heard of in terms of buildings is biochar. Using high heat & low oxygen short term carbon from a wide range of organic materials can be turned into long-lasting carbon (i.e. biochar) that has traditionally been used to increase soil carbon.

I'll be building with straw bale (grown 2 miles from the home) and adding biochar into the plaster covering (biochar adds humidity control, insulating and electro-magnetic shielding properties; more info and pictures here: https://www.biochar-journal.org/en/ct/3-The-use-of-biochar-as-building-m...). I'm also designing it into trenches for water and possibly for electricity (that one needs more investigation). My leach field will have a layer of biochar at the bottom to bind toxins and the lawn will have it to improve water and nutrient holding. Hopefully the driveway will incorporate it as well. 

There are also a growing number of companies embedding biochar in concrete, composite lumber, fence posts, bricks, roof tiles, siding materials and asphalt. It is an exciting time to see how we can maximize carbon storage above ground. 

Also on BuildingGreen

The Urgency of Embodied Carbon and What You Can Do about It