Ranking of top embodied carbon materials in buildings

LCA Data & Tools
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Does anyone have data that would help establish a list of materials ranked by their GWP in buildings? I realize that this is a tall order due to the variables (building type, stages considered, geographic location, building system scope, modeling completeness, etc.).

I have researched this some to try and develop a list, but always come up short after the top 5 or so materials, and think that data from a number of robust WBLCAs might extend the ranking list to the top 10 or 15 materials.

Colorado is in its first year of implementation of the Buy Clean Colorado act and is interested in this type of information for considering how this act might evolve in the future. Buy Clean legislation has expanded to 4 or 5 states, and national legislation is on the agenda as well, so this is becoming an important topic.

One good research paper on this topic published in Nature Communications by Zhong and others can be found here:(Global greenhouse gas emissions from residential and commercial building materials and mitigation strategies to 2060 | Nature Communications).

Other research papers I have found focus on the top five or six construction materials in use: steel, concrete, aluminum, copper, wood, and glass, looking at the historical and future material flows from a supply and demand perspective. This type of research also delves into material intensity for different building types, but again from the perspective of the top five or six materials.

Are others in the community working on this topic?

Thanks, Bob Redwine, Colorado Embodied Carbon Collaborative

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HI Bob,

We have collected our Tally-modeled projects over the last few years into a database to identify the top materials per sf of project area. Most of the analyses are mostly structure/envelope, so it’s biased towards those. We do have several analyses that include a host of interiors materials, and a few that also include MEP systems (post processing) and site work.

Based on this we identified our top 15 materials for action in our recently released Sustainability Action Plan. We are going to formalize or find low-carbon products in these categories and the include performance specs so that any substitutions are not higher carbon. Plan is here: https://lmnarchitects.com/lmn-research/2024-sustainability-action-plan

You’ll also notice we are identifying 3 other top lists of materials for other criteria: Chemical of Concern, Equity and Supply Chain, and Circularity.

Top 15 materials for Embodied Carbon action (this is a combination of carbon density within buildings and our ability to get EPDs for them):

  • Structural Steel
  • Concrete
  • Mass Timber
  • Rebar
  • Metal Deck
  • Fireproofing
  • Insulation
  • Glazing
  • Mullions
  • Cladding Materials
  • Carpet
  • Drywall
  • Metal Studs
  • Acoustic Ceilings
  • Furniture – Workstations

-Kjell

Kjell Anderson FAIA, LEED Fellow
Principal, Director of Sustainable Design

LMN Architects
lmnarchitects.com

M 206 812 6546
O 206 682 3460
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Thanks Kjell!

This question came up from the Office of the State Architect here in Colorado as they look for possible improvements to their first buy clean version trotted out on January 1st. Granted, buy clean bills tend to focus on products instead of raw materials, so maybe a list of products like you have listed would be best for the buy clean advocates.

For the heck of it I built the ranked list of raw materials below based on my experience and what little I have found in researching this – maybe it will spur some ideas. The ranking is roughly based on total embodied emissions globally, so wood makes it on the list due to the larges quantities of it used.

I left out refrigerants and their leakage, but not sure I should.

1 Steel (of any kind – rebar, metal deck, metal studs, sheet metal, etc.)

2 Cement (wherever it is used – concrete, masonry mortar/grout, stucco, cementitious board, adobe bricks, etc.)

3 Brick (clay-based)

4 Aluminum

5 Plastic (all the poly’s we use: vinyl chloride, styrene, urethane, ethylene, propylene, carbonate; and acrylics, phenolic resins, etc.)

6 Wood (when ignoring the biogenic properties)

7 Copper

In the product list you provided the only things I would add (rarely modeled) are office and residential equipment, including HVAC. Also, your “carpet” category might represent all the other flooring types that can be big contributors.

Bob Redwine

Colorado Embodied Carbon Collaborative

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Bob,

While we all would like to create lists like this, there are too many variables to make a list that is fair. I can take concrete using Type 1L portland cement with high percentage of supplementary cementitious materials (SCM) and compare it to light wood framing from forests that are not sustainably managed and all of a sudden the concrete is better than wood. If you read info on EPDs and PCRs they say not to compare them against other materials. They say that since not all PCRs and EPDs are created equal. EPA’s efforts to encourage better PCRs will help that but could be years away. The best thing to do is whole building life cycle assessments similar to what Kjell is doing so that you are now looking at the whole life cycle of a building (and material) instead of just one moment in time. If I’m replacing a material 10 times vs a product that lasts longer, that has to be taken into account since it will result in lower embodied carbon over time. So let’s not develop simplistic lists and encourage manufacturers to produce more robust EPDs so that we can start comparing similar products.