Embodied carbon is an important and complicated subject. Phius Senior Scientist Graham Wright helps sort it out and discusses Phius’ new REVIVE program in this post.
Let’s talk about retrofit, starting with the proposition that we need to decarbonize all buildings by 2050.
Stopping direct emissions is a good start; the electrification crowd is right about that. But only stopping direct emissions just moves the burden onto the utility/energy supplier, and they have to contend with transportation electrification as well.
The key question for the building sector, and for society at large, is how much effort/investment to put into increasing the clean energy supply, versus reducing the demand by such measures as passive building and heat pumps.
The scale of the required transition is daunting no matter which way we approach it, especially considering that we have to do all of this utility infrastructure and building retrofit work without throwing off a lot of emissions in the process. The embodied carbon crowd is right about that, though I think a materials focus doesn’t go far enough.
One way to get at the balance-of-investment question is with the idea of life-cycle cost. What mix of grid upgrades and building upgrades minimizes the total cost of getting the job done, on an annualized/life-cycle basis? I brightened up to this when it occurred to me that carbon could be included in that calculation by including a cost of carbon. Let’s use full-cost accounting!
That price might be set based on the cost of, say, direct air capture of CO2, that is, at some point it becomes cheaper to actually pull the carbon back out of the air. The full-cost metric I am thinking of would include all of the following:
Tentative name: Annualized Decarbonization of Retrofitted Building Cost (ADORB Cost)
ADORB Cost = sum of the following components, each an annual/annualized cost:
- Direct energy cost. E.g. site kWh * $/kWh = $
- Direct building retrofit measures cost (material & labor) including building-level electrification cost. E.g. ft3 of stuff * $/ft3 = $
- Social cost of carbon, upfront/embodied. CO2e kg * $/kg = $
- Social cost of carbon, operating. CO2e kg * $/kg = $
- Energy system transition cost (e.g. new utility solar + storage). $/MWh * MWh = $
The idea would be that a baseline cost in this sense is calculated for the scenario of continuing to operate and maintain the building as is for some decades. Any proposed retrofit should at least have a lower cost than that, hopefully much lower. Basically one designs as if there’s a carbon price. (In a baseline case I calculated for my apartment, 70 percent of it was the carbon cost of continuing to operate the gas furnace and water heater, even after the grid electricity was completely decarbonized).
This seems useful, but there are a few issues with it, therefore it can’t be our only lens.
It would not prohibit supply chain emissions from the retrofit work. Arguably the ideal is, call it Absolute Zero: No CO2 emissions occur anywhere in the building delivery/retrofit process, supply chain, or the building operating life, at any time. We need to decarbonize everything — the whole economy. In this view, the policy stance is that any carbon capture tech is devoted to removing carbon previously emitted, not keeping up with new work.
All the current net-zero and carbon-neutral programs have this limitation. We can’t really do everything without emissions yet, so in order to convince ourselves we are zero there all these offsets and avoided-carbon credit schemes. I’m starting to agree with the youth climate activists that this is weaselly.
At the system level, it’s tricky to use cost to decide grid-versus-building investment, because those costs in turn depend on which approach we decide to scale up in the first place. Commit to industrialized retrofit construction and those costs can come down. Commit to scaling renewable generation and transmission and those costs can come down.
It’s not clear how to make this full-cost metric take into account that some things just can’t happen fast enough. For example, renewable generation and even transmission may not cost that much, but siting the required high-power transmission lines from remote western wind and solar farms to eastern cities might take too long.
We’ve gotten into trouble across the board lately with our global economy by trying to minimize cost without regard to resilience. It’s more resilient to do extra things to reduce building loads rather than putting the ball in the grid’s court to both decarbonize AND stay up.
Therefore, I am thinking that our new REVIVE Pilot program for building retrofit needs a number of different frameworks. I have listed them below along with a few possible elements of each:
- Retrofit, replace/redevelop, or raze/rewild?
- FEMA hazard assessment
- Emerging climate hazard assessment (e.g. derecho, wildfire smoke)
- Cease direct emissions.
- Use and generate renewable energy (reconsider off-site renewables framework).
- Re-use high-embodied carbon structure.
- Calculate a carbon score (no criterion, just how low can you get, i.e. without offsets).
- Calculate ADORB cost, goal to at least beat the existing condition.
- Use load reduction, grid interactivity and storage to financial advantage.
- Limit the cost burden on low-income people.
- Look to make policy cases for feebates, incentives.
- Design for outages and known/emerging hazards.
- On-site/local power, microgrids, on-site/local repair parts
- Design for low loads.
Quality and Health
- Assess existing deficiencies (EPA indoor air quality risk list).
- Audits: tests, energy models?
- Commissioning & documenting that goals are met (e.g. ASHRAE 202)
- Scope includes operations, not just design.
- Plan covers both an end state and interim retrofit phases.
- Try to cover critical loads in the first phase.
I will have a bit more to say about this at PhiusCon 2021 this October 12-15 in Tarrytown, New York. The REVIVE Pilot program is in pilot phase, looking for sample projects, and the goal is to have an on-ramp in place. The general development strategy is to evolve from informational guidance to hard requirements in an orderly way, preferably without much backtracking.
Our existing Phius Certification program for retrofit projects remains available through the Phius CORE REVIVE 2021 and Phius ZERO REVIVE 2021 programs, outlined in Section 3 of the Phius Certification Guidebook.