On the tradeoffs between embodied and operational carbon in building envelope design: Research Paper from UW-IDL

Thank you so much for this!  We have been trying to focus on this idea of balance, and we do need more studies! In case it is helpful, here is an article we helped with focusing on this idea: https://www.architecturalrecord.com/articles/15852-taking-a-holistic-approach-to-embodied-carbon And one we authored about a PHIUS project we are working on (with Bright Power and Carmel Pratt): https://passivehouseaccelerator.com/articles/a-delicate-balance-weighing-embodied-vs-operational-carbon-part-two

Adding another article - about smart vs. deep energy retrofits - from Lori Ferriss and Elaine Hoffman   

Sorry, posted the presentation instead of the paper - take 2.

Jesse, Thanks for sharing this article.  We are currently working on this very problem to minimize carbon emissions through envelope redesign on a higher-ed renovation.  This is a very helpfull article and outlines a sound methodolgy for comparing the operational and embodied carbon impacts of different building envelope scenarios.  

Thanks to those who have responded (17 and counting) to the informal survey on envelope v building performance actuality, and especially to those who have sent great papers to link to in our series. The narratives are quite interesting. For those who haven’t responded (and since the thread changed): https://docs.google.com/forms/d/e/1FAIpQLSf_rmv3R3Igrw2EudaxhNYuZzaXJRQ5... I’ll announce the results later so as not to bias anyone before they respond. -Kjell Fro

Hi Kjell I clicked on the link and it says the file does not exist. Thanks, Pablo Pablo La Roche Principal

Apologies. This one reportedly does: https://docs.google.com/forms/d/e/1FAIpQLSf_rmv3R3Igrw2EudaxhNYuZzaXJRQ5tjTL2IXTdYJtTJ5cow/viewform?usp=sf_link

Jean, wondering if you did any analysis of the embodied carbon vs operational carbon of improving the air tightness of the envelope of your building? Was that part of the full overclad option? I am guessing that super insulation and triple-paned windows would have limited impact if you are not able to acheive a significant improvement in airtightness. I know that airtightness can be particularly challenging in renovations. 

While informal and not scientific at all and ham-handedly written as a survey, we have 31 responses so far, anonymously collected. I’ll leave it open for a bit longer. Questions: Shifting Mech $$$ to Envelope? Have you worked on projects where this has occurred (also savings some energy in the process) 1. How often does this occur (in your direct experience)? (Results: 25.8% Never! / 58.1% Sometimes / 16.1% Often / 0% Always!) 2. How often do you think it would occur on your projects if energy modeling/cost modeling were earlier and better? (Results: 0% Never! / 45.2% Sometimes / 41.9% Often / 12.9% Always!) Narrative responses. I assume that these are ok to share anonymously since they were submitted, but to give anyone a chance to opt out of that I’ll not share them for a week. Please let me know if you don’t want me to share your narrative response with this group. Many people included some useful detail and I will review and see if there are general conclusions. My conclusions: 75% of us have seen this cost shift to be true at least sometimes, but no one has seen it on all projects. We generally believe this cost shift to be possible a bit more than we actually see it, and this could be because we don’t get the energy and cost modeling needed to prove it to our clients. -Kjell From: K

Check out this paper: https://link.springer.com/chapter/10.1007/978-3-030-04293-6_2 Optimized building tends to be more passive and favors towards embodied carbon.  Also see attached slide.  

Doug - we certainly accounted for reduced air infiltration in the window replacement and the overclad options, and the energy model was calibrated with blower door tests of the existing conditions. We did not account for embodied carbon of improving air-tightness outside of the window scope becase based on the blower door test, the vast majority of leakage occured at the glazing. We have not run a carbon tradeoff study to evaluate the embodied carbon of air sealing/weatherstripping against improved energy performance, but I expect the embodied carbon would be incidental compared to the savings. I would be very interested to see such a study if someone else has performed one.

What a great study by UW-IDL!  Really enjoyed this. There were two concepts missing, coming from our firms multifamily experience, for consideration: 1) They mention the exact amount of EC of the decreased air infiltration to be unavailable, and I would agree it’s difficult to calculate.  But I wonder if this above-code airtightness triggers ERV's on a project, and then there is somewhat more drywall and ductwork in that option (added EC).  Even on code min airtightness we strongly advocate for ERV's.  Just for thoroughness thought I would mention it– since we would be hesitant to say that providing ERV’s (vs exhaust only) was not a worthwhile embodied carbon investment.  I believe ERV usage was in their energy models because they were using IECC 2021 which requires them in multifamily.  At least in NYC, we haven’t adopted this yet and you can still provide a multifamily project without supplying each habitable space with fresh air. : / 2) The decarbonization of some grids, are relying on energy efficiency to make their goals achievable.  How much so, it doesn’t seem to be public information.  It’s a sensitive topic.  Urban Green in NYC published a report that shows we have a lot of winter peak capacity as electrification increases winter electricity use primarily.  So even if a project when balancing EC/OC over the next 30 years and is in an area with plans to decarbonize the grid fast, may show that a super low EUI does not have a carbon benefit – they may still want to do it to make sure a renewable grid will work?  Does someone have more info on this??

This presentation recently on PassiveHouseAccelerator on carbon tradeoffs that also took embodied carbon of refrigerants into account showed that PH was a smaller total carbon proposition. (https://passivehouseaccelerator.com/videos/not-a-tradeoff-ph-efficiency-and-embodied-carbon-irl) I have not read all of the reference papers in this thread yet but it will be great to better understand the interrelationship between passive performance and total carbon for various building types.

Sara -- I am not sure how localized the effect is, but the Cambium grid carbon projections factor in the impact of electrification on the grid at some level; check out section 3.1 of the documentation for a brief discussion and references to some of the related scientific literature.

This is definitely an interesting conversation. From a simplistic approach, perhaps the cost accounting of envelope vs MEP trade-offs is a good starting point. I remember Don Davies at MKA saying that in a basic approach, at least for structural systems, cost = carbon. Not perfect, but as I said, a simplistic starting point. One of the conversations at the Tempe summit was around Passive House envelope and the “tunneling through the cost barrier” model of yielding super simple and low cost mechanical approaches. To be honest about that carbon conversation we should also be bringing in the embodied carbon of the MEP systems. Smaller simpler systems are cheaper but also lower embodied carbon in most cases. The classic example of the super insulated envelope resulting in a simple $100 electric wall heater that runs <100 hours a year is a great example of this vs the complexity of heat pumps and their associated embodied carbon and refrigerants. It would be good to take a time-dependent approach to carbon accounting to get this right though – using hourly grid carbon profiles, e.g. from WattTime – to really capture the carbon impacts of different measures and when they impose load on the grid. We should also be using long term marginal emissions in such trade-off calculations for all our new construction projects that are adding net load. I have to say I am already mourning the loss of the rich in-person dialog we had in Tempe – just not the same typing notes back and forth via email… Seattle SDL crew – I am serious about seeing how we can get together here! Hit me up if you are interested and we can get something on the calendar! Peter Peter Alspach, PE Principal | Director of Design Performance NBBJ 223 Yale Avenue North SEATTLE WA 98109 Direct: 206.621.2279 Mobile: 206.816.4902 nbbj.com NBBJ is a certified CarbonNeutral® company From: Chris Sa

Thank you to everyone on this post, and thank you Stefan for sharing that presentation from PHA.  It really explains the necessity of PH level efficiency, and how grids from a GHG impact perspective are really quite large geographic areas.  I generally whole heartedly agreed with the presentation but I am stuck on the second point where they emphasized that the 2030 or "7 years left" timeframe is a bit unfair when justifying the EC investments in operational performance.  I just cant shake the idea that everything we are doing now is spending our carbon budget before we tip 1.5, and that we are on track to spend it all 7 years. So emissions averted now have more weight. But of course we want to make smart investments, so if a carbon payback is a little more than 10 years it probably make sense. Is this "carbon budget" the right way to look at this....? It was actually Gretta that really crystalized that for me, if I understand it right.  Best regards to all you incredible people working on this.