Pursuing the Elusive Goal of a Carbon-Neutral Building

Yale University’s recently opened Kroon Hall is a state-of-the-art model of where the green building movement is headed. Yet even this showcase for renewable energy highlights the difficulties of creating a building that is 100 percent carbon neutral.

Early this year, a new building opened on the Yale University campus that set out to achieve the architectural Holy Grail in the age of global warming — getting to carbon neutral. Designed by Hopkins Architects, a British firm with a long history in the green building movement, the new home of the Yale School of Forestry & Environmental Studies is, on almost all counts, a striking success. It has simple but beautiful lines, incorporates the latest sustainable ideas and technologies without loudly announcing them, and manages to transform what had been a ruined landscape into a green campus. In a feat of no small symbolic value, the school bullyragged the university into shutting down a fossil fuel power plant that had formerly occupied the site.

Yale’s new Kroon Hall promises to change the lives of the people who have begun to inhabit it, and perhaps also beyond, as a model for where the green building movement needs to go next.

Kroon Hall at Yale University’s School of Forestry & Environmental Studies was completed in early 2009. MATTHEW GARRETT

But Kroon is also a reminder of what even some of the best hearts and minds in the sustainable design movement cannot yet achieve. For a “green premium” unofficially estimated at about 5.7 percent of construction cost, the Kroon design team managed to reduce projected energy use and emissions by 61 percent below the levels for a comparable building of conventional design. The biggest savings came not from sexy new technologies but from figuring out how to make the design function like an old-fashioned cathedral, with a slender profile for maximum daylighting, an east-west orientation for greater solar gain on the long southern exposure, careful use of shading, and plenty of stone and concrete to store thermal energy. A solar photovoltaic array and geothermal wells will supply much of the remaining energy load. “We got damned close to carbon neutral,” boasted a construction manager who initially scoffed at the whole idea of green design. But perhaps inevitably, the school will still have to purchase offsets to mitigate the carbon emissions it could not avoid.

Figuring out how to get the rest of the way to carbon neutral, and not just damned close, has become an urgent question as the timetable for global warming has rapidly worsened.

Last year, the United Kingdom imposed a zero energy building (ZEB) mandate on all new homes starting in 2016 — just seven years from now — and on all new commercial structures starting in 2019. Patrick Bellew, a British environmental engineer whose company, atelier ten, worked on Kroon Hall, described the mandate as “a collision of wills between politicos wanting to be seen” to live up to their climate treaty commitments, and developers, designers, and government functionaries, who get stuck with the job of figuring out how to do it.

“Everybody’s freaking about what the potential impact is on the cost of buildings,” said Bellew. Then, echoing Samuel Johnson’s remark about the prospect of hanging, he added, “It does do a terrific job of focusing people’s minds.”

In the United States, interest in zero energy buildings and neighborhoods has also grown, driven by cost and national security issues, as well as by climate change. The Departments of Energy and Defense are currently researching high-performance and “net zero plus” buildings, which would reduce demand by 70 percent and use renewable energy to supply the balance (and in some cases produce a surplus, hence the “plus”). The World Business Council for Sustainable Development has launched a corporate drive for ZEB development, and a separate proposal to make all new structures and renovations carbon neutral by 2030 is also circulating in the building community.

That 20-year time frame may sound relatively comfortable, but actual energy use per square foot in U.S. buildings has not improved much in the past 90 years, since 1920. Buildings here account for 39 percent of total energy use and 68 percent of electricity — roughly half of it from coal. And those stark facts have many green building advocates looking for new ways forward.

Like Kroon Hall, most attempts at sustainable development now focus on the U.S. Green Building Council’s voluntary certification process, Leadership in Energy and Environmental Design (LEED). Builders accumulate points on a checklist of criteria — such as site selection, reduced light pollution, construction waste management, and so on — to achieve a LEED ranking, from LEED certified to LEED silver, gold, or platinum. LEED has functioned, said Bellew, as “a terrific kick up the backside for the industry, raising the level of awareness and understanding.” But it has also served more as a status symbol for an elite fraction of new buildings than as a broad response to a global crisis. So far, 2,300 commercial buildings have earned a LEED rating, with another 17,800 projects in the pipeline.

Critics say LEED is not just too narrow, but undervalues energy performance.

Critics say LEED is not just too narrow, but also undervalues energy performance. “Many of the corporate sponsors of LEED are interested in a focus on products,” said Harvey Sachs, a senior fellow with the American Council for an Energy Efficient Economy. “That’s nice. But the elephant in the room is energy consumption.”

Another voluntary program, run by the U.S. Environmental Protection Agency, ranks buildings by energy efficiency and awards the Energy Star label to the top 25 percent. But Sachs argued that some LEED silver buildings would not qualify. “A green label building is not necessarily an energy efficient building,” he said, and that leaves “the more extreme” critics of LEED “muttering under their breath or shouting to the heavens about greenwash.”

In response to such criticisms, the U.S. Green Building Council (USGBC) commissioned a study of energy use in the 552 buildings that had achieved a LEED rating as of 2007. In many cases, the owners and occupants themselves didn’t know how much energy their buildings were consuming. Only half said they would supply records on actual energy use, and only 121 ultimately delivered.

LEED gold and platinum buildings in the study had been designed to be about 37 percent more energy efficient than conventional buildings of the same type, according to the study by the New Building Institute. But they actually performed just 28 percent better. (Some of the conventional buildings in the comparison also dated back as much as a century.) A researcher on the study said smart meters to give commercial building managers real-time data on energy use would cost $2,000-$5,000, with the likelihood of a rapid payback. But few building owners make the investment.

In a recent article, Environmental Building News didn’t quite suggest that LEED “rip plaques off the walls of underperforming buildings” but said that “to continue leading, USGBC needs to reserve the label ‘LEED certified’ for buildings that have their actual performance documented”¦” Tom Hicks, a vice president at USGBC, replied that LEED now requires buildings to earn at least two points, out of a possible 69, for energy and atmosphere improvements, and it weighs those points more heavily in its overall rankings. Hicks said USGBC is also working to address a separate criticism that LEED ignores how much energy it takes to get people to and from a building.

Most builders tend to exaggerate the cost and overlook the rewards of building green.

While LEED plays catch-up, some state and local governments are working to move sustainable design out into the broader construction community. Boston has implemented a green building code requiring buildings over 50,000 square feet to meet the standards for LEED certification. Portland, Oregon, has developed an ambitious high-performance building program — but can’t go beyond state building codes to make it happen. Instead, the city is now considering a “feebate” system, with new construction permit fees being assessed per square foot, and rebated to buildings that achieve LEED gold and platinum ratings. To address weaknesses in LEED, the buildings would also have to reduce energy use by 35 percent below comparable conventional buildings to qualify for rebates. Building code changes focused on energy are likely to become more widespread because of a residential green building standard approved early this year by the International Code Council, for adoption by state and local governments.

Some jurisdictions are also pursuing a market-based strategy with the idea that simply making people think about how much energy they use will change behaviors and real estate values. In California, commercial buildings now must report their annual energy use to the state, and starting next year they will also have to disclose that information, along with a building’s Energy Star rating, to potential buyers and tenants. In Washington, D.C., large commercial buildings will soon have to make their energy performance a matter of public record. In effect, buildings will sell or rent, like cars, with an estimated miles-per-gallon label.

Most builders have so far missed the economic implications of such changes, tending to exaggerate the cost and overlook the rewards. In practice, the green premium may add 2 to 10 percent to construction costs. But the green label added 10 percent to the sale price for Energy Star buildings and 31 percent for LEED certified buildings, according to a 2008 study from the University of Reading. Studies also suggest that the combination of lower vacancy rates and higher rents adds up to a rental premium of 4 to 11 percent a year.

There’s a sweet spot where going aggressively green gets to be cheaper than a more modest approach

Most builders also seem to be unaware that the cheapest way to avoid wasting energy is to think about it from the start. “You need integrated building and design,” said Harvey Sachs, “with the engineers, architects, and owner talking to each other a lot earlier, instead of just throwing the floor plan over the wall to the HVAC guy and saying, ‘Live with it.’”

There’s actually a sweet spot, said Bill Browning, a partner in the sustainable design firm Terrapin Bright Green, where going aggressively green gets to be cheaper than a more modest approach. Making a building 20 or 30 percent more energy efficient than a conventional design costs more “because you’ve added more expensive measures to the building, but you haven’t cut the basic load enough that you can downsize or eliminate systems,” Browning noted. If you can make the fabric of the building do the work instead, as passively as possible, you can cut the fundamental load of a building in half and “very safely start downsizing and eliminating components of the energy system.”

But that sweet spot fades away, Browning added, as you get beyond an 80 percent improvement in energy efficiency. Then the builder is back in the position of “throwing gazillions of dollars at it, piling on renewable energy systems till you’ve got enough to make it fly.” That means even the best-intentioned buildings, like Kroon, are likely to run up against the “damned close to carbon neutral” limit, and environmental engineers like Patrick Bellew will have ample reason to keep worrying about how to get to the “zero energy” finishing line.

The rest of the building community, meanwhile, still needs to leave the starting blocks.