Why Net-Zero Energy Is a Goal We Can All Get Behind
By Brad Liljequist
Reading BuildingGreen’s provocative “Net-Zero Energy Isn’t the Real Goal: 8 Reasons Why” sparked a lot of emotions and thoughts—ranging from strong agreement to a fair amount of “Yes, but….”
Zero energy by itself has never been the full, holistic goal—which instead perhaps is best stated as: “to reconstruct our human community to use and generate energy in planet- and climate-positive ways.” Achieving this goal will require a narrative of positive change over time, in which zero energy (ZE) and its successors have played, do play, and will continue to play an important role.
We need to remember there are still only several hundred truly zero-energy buildings, which at this point are hardly a Godzilla threatening to bring down the grid. Solar energy is only 2.3% of U.S. electricity production, and the oft-replicated California duck curve (complete with its faulty y-axis solar generation net-zero point, as shown in the article) represents a single (worst-case) day in a specific, solar heavy grid. It’s not close to universally applicable nationwide. In addition, utilities have solutions too, particularly in large-scale vertical mechanical storage such as rail or two-cell hydro, meaning buildings don’t have to solve grid renewable variability on their own.
Zero Energy’s Successes
Establishing a positive, accessible brand and well-defined performance goal for built environment climate solutions—Most of the people reading this have struggled at some point to build enthusiasm for efficiency with mainstream audiences. Zero energy’s greatest strength may be as a tangible marketing concept that has already gained buy-in across all levels of the built environment. In 2001, we had 10,000 visitors to zHome (the first certified Zero Energy community in the United States), who came from all walks of life, responding to the gee-whiz, high aspiration, can-do message of zero energy. Today, zero energy, zero carbon, and zero emissions have become common parlance, all the way to President Biden. We must appreciate that ZE and its kin are a hard-won, collectively held brand, of which our community is the collective steward. Yes, we should evolve it conceptually, but we should also protect its market resonance and have care with our critiques.
Creating a portfolio of technically compelling, human-scaled examples of deeply efficient clean-energy buildings that catalyze climate-positive change—The hundreds of zero-energy buildings now serving their occupants provide an incredible sample of fully electrified, deeply efficient buildings that use 70%–80% of the energy typically consumed. That as a collective they are also beautiful, functional, cost-effective, and loaded with co-benefits clinches the deal. The strength of this vanguard in providing living proof that deep efficiency is not only possible, but even yields a better building, cannot be underestimated. Washington State’s adoption of a commercial energy code that effectively requires super-efficient, electrified, heat-pump-based heating was successful in part by having compelling, real examples to point to.
It is also critical to recognize that our entire built environment climate regulatory framework is based on energy, not carbon metrics at this time—and zero energy is the stretch performance goal for these tools. Washington State and, just last week, Colorado have adopted energy benchmarking legislation as a tangible first step in driving carbon mitigation. Do not discount the driving role energy savings performance contracts and similar funding mechanisms play in pushing code and legislative requirements. These metrics and tools are just starting to shift to carbon. We should not make a broad language transition from energy to carbon until the whole infrastructure of carbon-based funding mechanisms and international standards is in place.
Closing the circle on climate responsibility through a full renewable offset—Zero-energy buildings, which demand a 100% renewable energy offset, have been a key part of helping people to take full responsibility for their carbon footprint. As “zero” language has made its way into the mainstream, this is perhaps its strongest conceptual kernel. Also, the cohort of zero-energy buildings sporting a full solar rooftop helped seed the growth of commercial rooftop solar, which is well underway.
My primary reservation with the article—focused on some very specific phraseology—is the use of strong declarative statements in the eight key points, i.e., “NZE buildings use energy at the wrong time,” or “NZE buildings lack the flexibility to shift loads in real time” (which could have been easily ameliorated by the inclusion of “can,” as in “NZE buildings can…”).
There is nothing inherent in zero-energy definitions or practice that enforces these outcomes, and in fact, I’d argue the opposite. For example, every zero-energy building I am aware of includes some form of higher-performance envelope. This, combined with also-typical heat-pump-based heating, radically reduces the energy demand of the buildings not only overall, but at the peak grid-demand points the article highlights. The midday solar trough is a somewhat different matter, and applies to every electron generated by net-metered solar in the world, not just those located on zero-energy buildings—leading to the grid optimization discussion below.
A Note on Embodied Carbon
Finally, with regard to zero energy not addressing embodied carbon—well, yes, that’s why the International Living Future Institute (ILFI) launched the Zero Carbon certification four years ago, including embodied carbon requirements. The time is right to further strengthen embodied carbon standards, reducing construction carbon and addressing carbon sequestration opportunities (such as through forestry practices). Many project teams are doing the type of embodied/operating carbon tradeoff analysis pioneered by groups like the Carbon Leadership Forum and KieranTimberlake, which will influence design at the outer limits of efficiency as well. It is likely these will start to be internalized in zero-carbon systems.
Zero carbon is the future, but zero energy still plays an important role
I believe zero carbon is the brand and metric of the future. We should continue to evolve and build on it to include not only grid optimization, but also neighborhood-based and other solutions. As mentioned above, however, so much of our built environment climate-solutions infrastructure is based on the language and metric of energy (e.g., energy codes, energy efficiency, energy use intensity, energy services contracting, etc.), that we need a locomotive to continue to pull that organizational and cultural train forward. While energy currently plays a surrogate role for carbon in most of these settings, the shift is just starting.
Zero carbon should include grid optimization
I think the best, core point of the article, which it addresses from numerous angles, is that it is time for these zero systems to address the energy-using and -generating framework as an ecosystem—and it absolutely is.
The impulses of zero-energy and zero-carbon approaches that internalized grid-source carbon loading, but included no way for a project to respond, were understandable but misguided. Grid optimization turns this on its head with a positive, holistic structure to improve the interactivity of the whole system. The good news is that there is an array of fairly-easy-to-implement solutions. In particular, using water as thermal storage should not be underestimated as a solution due to its low cost, ability to be delivered as a retrofit, and in particular its benign, commonplace nature (just wait for our first lithium war). To echo the point made by Cara Carmichael at the Rocky Mountain Institute, the high carbon grid peaks of today will be different tomorrow, and we should be careful to not build those into building design, but rather provide for flexible response over time. And I would suggest that, given the strength of the “zero” brand, grid optimization be included into the zero carbon concept, rather than running alongside. I fear it is too specific and obscure to gain traction on its own, and to echo the article, it is time to pull all the pieces together under one integrated system.
The best buildings are already incorporating grid-beneficial load shifting, often simply in response to peak demand and rate structures established by utilities to promote building/grid integration. For example, the McKinstry-developed Catalyst building, registered for ILFI Zero Energy and Zero Carbon certifications, is heated and cooled by the brand new all-electric South Landing energy district, which includes thermal storage to fully enable off-peak heating and cooling. Similarly, McKinstry is supporting a large municipal school district in its pursuit of zero-carbon energy use. The district’s local utility has both peak demand and rate structures which significantly incentivize use of off-peak grid electricity, as well as self-use of onsite solar generation. In response, through thermal storage, solar angle, combining night flush with delayed mechanical cooling, switching, and other strategies, McKinstry is creating a grid-responsive portfolio.
Let’s not inadvertently kill the goose that lays the gold egg. We have spent years building acceptance for zero energy, which now has traction in the broader culture. As a community, we are sometimes too ready to forget narrative and solve for all problems at once. We have a terrific start; let’s build on it and adjust. Timing is everything: just as offsite zero-energy renewables and zero carbon had their right launch times, so do these new topics. Now is the time to expand our zero-carbon approaches. But zero energy has some good runway left too.
Brad Liljequist leads Zero Carbon and Energy programs for McKinstry, which has nearly two dozen zero-carbon and -energy projects underway. Previously, Brad led Energy and Carbon programs for the International Living Future Institute, where he launched the Zero Energy offsite renewable pathway, as well as the Zero Carbon standard. He also developed zHome, the first certified Zero Energy community in the United States (now celebrating its tenth anniversary) and wrote The Power of Zero: Learning from the World’s Leading Net Zero Energy Buildings.
(2021, July 6). Why Net-Zero Energy Is a Goal We Can All Get Behind. Retrieved from https://www.buildinggreen.com/op-ed/why-net-zero-energy-goal-we-can-all-get-behind