My Net Zero Conundrum
Rather than focus on individual building NZE, shouldn't we be considering individual building performance, before renewables, as a higher benchmark?
By JEAN CARROON
Why would we want an individual building to be its own energy plant? This has never made sense to me. The scale seems inefficient and the potential of many existing urban buildings for net-zero energyProducing as much energy on an annual basis as one consumes on site, usually with renewable energy sources such as photovoltaics or small-scale wind turbines. (NZE) is limited. But many people I admire seem besotted by NZE. What am I missing?
To avoiding sounding as naïve and uninformed as I really am, I did some research, which was limited by time and my own ability to understand the issues. What I found substantiated some of my concerns, but definitely broadened my perspective. I concluded that NZE is appealing exactly because of its scale. It is an avenue to improving building performance that is accessible to individual building teams. It is aspirational and raises the bar for design and construction while delivering bragging rights.
However, I am still left with questions and challenges.
I have seen the swooping graphs of energy use spread over a year in NZE buildings, which often show many months of using the surplus energy from other months. If all buildings in an area are on the same curve, aren’t we asking either buildings or utility companies to have giant storage capacity? Are storage systems capable of meeting this need on a large scale, and are these systems good for the environment?
A Rocky Mountain Institute study from 2015 partially answered these questions. Researchers examined the value and location of batteries on the electrical grid and found that behind-the-meter storage provided the largest number of services to the electricity grid at large.
The 2016 BuildingEnergy Boston Conference + Trade Show featured two sessions, "Lightning in a Bottle Parts I and II," that addressed these challenges. Storage is both possible and valuable in our electric system, but few seem to be addressing the impact of batteries on the environment. Aren’t they material- and energy-intensive to produce? Don’t all batteries need to be disposed of at some point, and isn’t that a problem because of toxic metals? More questions. More worries.
A NZE goal is accounting, pure and simple, and while it should begin with conservation and a high quality building, it doesn’t have to. Touted as the “Largest Net-Zero Energy Commercial Office Building in the U.S.,” the design of the all-glass La Jolla Commons targeted an unremarkable consumption level of 41.5 kBtu1,000 Btus/ft2 and achieves NZE with directed biogas and on-site fuel cells.
It’s better than not being NZE, but not as good as actually making a less consumptive building. Teaming NZE with performance systems, like Passivhaus, Living Building Challenge, or even LEEDLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. , is important to ensure that the energy use intensity (EUI) has been reduced before renewable energy is added.
NZE ignores full carbon/environmental impacts by focusing only on end-use energy. Focusing only on EUI still allows oversized, transportation-dependent buildings using lots of materials to be labeled “high performance.”
The data on what we are doing to the planet is sobering. Global extraction of raw materials has tripled since 1970, while global population has only doubled. The average material use per person grew from 6.4 tons to 10 tons between 1970 and 2010.
Not once in the last 40 years has materials extraction declined even during times of recession. Efficient use of materials is essential and our aspirational goals should include whole building/life-style carbon accounting to encourage reuse, to encourage building small, and and to encourage strategies that allow freedom from carbon-intensive transportation (including both construction and occupancy). We need to be confident that any carbon we spend to achieve a NZE goal has a reasonable environmental payback, which, I suggest is 10 to 20 years.
Is NZE the right scale if resource efficiency is the goal? Photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. systems, wind turbines, and even hydroelectric power stations are more efficient and cost-effective at a larger scale than a single building.
“The Future of Solar Energy,” a 332- page report published by MIT in May 2015, celebrated the opportunities of solar energy while including a recommendation away from net-metering policies for distributed solar, finding that utility-scale solar rather than residential-scale is a more affordable pathway to meeting energy requirements. Needless to say, this is a controversial issue, but we must be rigorous in challenging our own biases and reaching for the best solutions for the built environment.
I question whether scattered renewables are as efficiently and effectively maintained as centralized systems. I didn’t find much discussion about this in my research, other than a few papers from the United Kingdom asking the same question.
For me, NZE buildings harken back to the Autonomous Houses of the 1970s and the appealing, but regressive, idea of being “self-sufficient.” In Philip Slater’s 1970 book, The Pursuit of Loneliness, he said, “It is easy to produce examples of the many ways in which Americans attempt to minimize, circumvent, or deny the interdependence upon which all human societies are based. We seek a private house, a private laundry, self-service stores and do-it-yourself skills of every kind.”
Stewart Brand was more succinct. Commenting on self-sufficiency in The Co-Evolution Quarterly in 1975, he said: “It is a damn lie."
A better benchmark
This all leads to my final conclusions and questions. Not every existing or new building in an urban setting is going to lend itself to NZE. What happens when new buildings, which may improve a community, shade an existing solar system essential to an NZE building? Rather than focus on individual building NZE, shouldn’t we be considering individual building performance, before renewables, as a higher benchmark?
I like the idea, found in a 2012 paper by Nick Grant of Elemental Solutions, that proposed energy demand targets be set for all buildings, new and old, independently of any renewables that may be purchasable or located on site. Even though this system doesn’t address carbon accounting, wouldn’t it instill higher overall performance in our building stock than a NZE moniker?
If we conclude, as we seem to, that we don’t need to worry about the environmental impact of batteries or the efficiency of small-scale renewables, then let’s focus more aggressively on NZE communities instead of NZE buildings. NZE communities aren’t a new idea — ecodistricts have been around for almost a decade — but the idea seems to be gaining traction and publicity.
In March 2016, the Cambridge, Mass., "Getting to Net Zero Action Plan" was presented at the BuildingEnergy Boston Conference + Trade Show. The Architecture 2030 Challenge and The Living Future Institute now have 2030 Districts and a Living Community Challenge respectively, which imagine sharing resources from building to building.
I was heartened to find a 2016 paper from the American Council for an Energy-Efficient Economy (ACEEE) about zero energy at scale. It calls out numerous initiatives happening at the local, campus and development levels and proposes a framework — CITI2zero (Community-Scale Integrative & Transformative Infrastructure for Zero Energy).
The Citi2Zero framework proposes five components:
- People — to influence policy, behavior, and investment.
- Renewable Infrastructure — to optimize the grid and integrate storage, charging, controls, and distribution.
- Buildings — combining new and old to have a combined NZE.
- District Fabric — integration of infrastructure informed by land planning and urban design.
- Finance — at every level, to maximize economics and financing efficiency.
This is a framework I can heartily support, although I will still harangue about moving beyond EUI in our building evaluations.
I conclude that, like many green systems or goals, a NZE building is an incomplete and even simplistic metric at the wrong scale. However, it may contribute to integrated designBuilding design in which different components of design, such as the building envelope, window placement and glazings, and mechanical systems are considered together. High-performance buildings and renovations can be created cost-effectively using integrated design, since higher costs one place can often be paid for through savings elsewhere, for example by improving the performance of the building envelope, the heating and cooling systems can be downsized, or even eliminated. solutions and a better overall building. I certainly understand the appeal and celebration of achievement on an individual project level. Although I am still not sitting on the NZE building bandwagon, I am waving more enthusiastically to my friends and mentors who are.
Jean Carroon is one of five principals at the design firm Goody Clancy. This column was originally published in the Spring 2017 issue of BuildingEnergy, a publication of the Northeast Sustainable Energy Association.
- Amy Glickson for NREL
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