Embodied Carbon Reference Guides

Hi Everyone,

I just finished my Master’s Thesis on reducing embodied carbon for residential construction. One focus was to simplify material selection for residential builders, to do this I created charts that make it pretty easy (I hope) to identify the materials that should be selected if you’re prioritizing embodied carbon reduction. Take a look at the attached files to see the charts; read on if you’re interested in the data used and how the charts are structured. Please send me any feedback, I’d love to add more material categories and would be happy to work in any updates.

The charts are broken down into the various material subcategories from the EC3 Tool. A scale was created ranging from 0 to the CLF baseline of the subcategory, then the conservative value of the individual material type was mapped to the scale (each 10% has a different color ranging from green to red). For example, in the Board Insulation Chart, the range is from 0 to 9.29kgCO2e. XPS has the highest conservative value at 6.91kgCO2e and scores an 8 on the scale.

Since biogenic carbon hasn’t been standardized, I decided to have it as a separate column. If more than 50% of the EPDs within a certain material type listed biogenic carbon, then I put a checkmark under the “stores carbon” column.

Lastly, I converted the framing member from weight or volume to Linear Foot (I don’t know any builders who buy studs by the pound). If anyone is interested in the conversions let me know and I’ll send you the numbers.

Feel free to use these charts any way you see fit, the more knowledge out there, the better.

Sincerely,
-josh

EC All Insulation April 2021.pdf (520.4 KB)
EC Blanket Insulation April 2021.pdf (1.1 MB)
EC Blown in Insulation April 2021.pdf (424.8 KB)
EC Board Insulation April 2021.pdf (441.6 KB)
EC Foamed in Place Insulation April 2021.pdf (405.4 KB)
EC Framing Members April 2021.pdf (1.1 MB)
EC Joists and Rafters April 2021.pdf (1.1 MB)
EC Structural Beams April 2021.pdf (1.2 MB)

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The insulation chart is awesome, but the structural ones aren’t comparing equivalent quantities. The insulation compares Co2/R which is functionally equivalent, but the structural members are equivalent sizes but not equivalent capacities, it would be interesting if there were a way to compare Co2/ a value of structural capacity.

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That’s a great point! I’ll try to do a comparison based on span tables for the rafters and joists. Regardless, four 2x10s have lower emissions than the LVLs or Glulam beams, which is pretty surprising. Although harvesting more lumber just to store it doesn’t seem like a great idea.

Great work Josh and thanks for sharing. To Melissa’s comment I would add that it would be helpful to display the RSI values used in your calculations for each of the insulation materials being compared. These values differ between manufacturers and databases. It would also be helpful if the table included the GWP of the blowing agents being used in the materials being compared. XPS, for example, can be manufactured using HFCs or HFOs.

I agree with the earlier comment that more detail around the values that were used for insulation materials would be helpful. There is significant variability within a product grouping, so it might be better shared as a range rather than showing so many significant figures which implies a precise value. For XPS, there are a number of variations that have been coming out this year, even from the same manufacturer and the numbers vary greatly based on blowing agent used.

Thanks for the comment!

I’ll upload the excel spreadsheet containing the data for the material categories, once I clean it up.

The charts are meant for quick reference to guide material selection (I’m hoping that builders will pull it up on their phones to help decide between pink rigid insulation or white rigid insulation when at the local supply house), not to specify a certain manufacturer. I know this oversimplifies embodied carbon, but I thought the charts would be useful in steering people away from materials produced with HFCs or petroleum-based products and towards natural, sustainably harvested materials.

As for the blowing agents, as of April 2021, the only blowing agents listed for XPS were HFCs, but this should be made clear in the chart and I’ll add it to my list of updates. I’ll add XPS with HFOs once the EPDs are shown in the EC3 database.

@cheryl.smith @philippe.st-jean I just confirmed with the authors of the EC3 tool that the RSI is 1.0 per square foot or square meter, depending on your settings. I believe this means the unknown variable in my charts is the thickness needed to achieve a specified insulation value. However, for a builder, if a wall assembly is specified at RSI 3.5 (R-20), they could easily calculate the GWP of various materials, then check that a certain sized wall cavity can support the specified amount of insulation value (or vice versa). I know two steps is a barrier, I’ll try to think of a method for combining those variables while still keeping the charts easy to read.

Apologies, what I meant to write is the lambda value and not RSI value of the various insulation materials. The RSI value is held constant across materials in the comparison and is therefore inconsequential. The lambda value, however, can vary significantly between manufacturers or installation detail for the same material (e.g., mineral wool, dense pack cellulose of varying densities, etc.). Thus, knowing both the lambda value and density of the materials used would help better contextualize the results. It’s also important to note that in Canada insulation materials that contain refrigerants with a GWP greater than 150 can no longer be sold as of January 2021. Therein the importance of stating the GWP of the blowing agent to allow for informed decisions to be made across markets.

Thanks for working on this, Josh. Your graphs will also make for good teaching tools!

Thanks, Josh for sharing this!

Thank you, Josh, for making your work accessible / sharable!