The Zero Effect

The future of sustainable design increasingly means eliminating carbon dioxide emissions, the most prevalent greenhouse gas. But what does that do to architecture?
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From Architectural Record
Russell Fortmeyer

Decarbonated living

Large-scale projects garner attention and offset the most CO2 emissions in a single gesture, but zero-energy single-family homes represent a growing market in nearly every corner of the country. A February 2006 report for the NREL prepared by the National Association of Home Builders (available athttp://www.toolbase.org/pdf/casestudies/zehpotentialimpact.pdf) found that the concept of zero-energy homes would be part of the mainstream residential building market by 2012, and by 2050 could result in reducing by 17 percent the electricity demand for the entire U.S. single-family-home sector. Many of the homes referred to in the study, however, appear business-as-usual, incorporating PVs with higher-performance building materials in a conventionally designed tract home on a cookie-cutter subdivision site. As any sustainable-building consultant will tell you, 90 percent of your opportunities for designing a zero-energy home begin with site orientation.



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Zero-carbon beach resort, Nungwi, Zanzibar
Richard Hywel Evans Architecture and Design have planned to use photovoltaics and wind turbines to power a beach resort for ecoconscious tourists (left). The resort will offset the carbon emissions associated with guest travel.
Rendering: Courtesy Richard Hywel Evans Architects



Zoka Zola, AIA, who practices in Chicago, says unless an architect can decide where to place windows and how to take advantage of natural ventilation on a site, reaching a zero-energy goal through passive strategies becomes difficult, if not impossible. "The discussion should be how to make the building as efficient as possible through its general configuration," Zola says. With her design for a zero-energy house in Chicago, she included south-facing windows, specified 25-percent-fly-ash concrete to provide thermal mass, and devised a layout with courtyard gardens to combat heat island effects. She also helped the client pare his space needs, avoiding the desire to build out the maximum allowable square footage for the inner-city site. Zola planned infrastructure for the eventual installation of PVs on the roof, but advised her client to wait until PV efficiency reached a higher level to bring the house to full zero-energy status.

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Embedded energy or carbon, which takes into account the energy used to manufacture a construction material or product, constitutes an altogether trickier component of the zero-sum game. Zola did not consider the embodied energy in the house, simply because the material information and tools to quantify such things are sketchy at best. For the Lloyd Crossing plan, Mithun did not consider the occupants or the furnishings of a building and only encouraged the use of construction materials with low embodied energy levels. Mithun's Gregory says any master plan undertaken today should consider occupant and operational factors for individual buildings. "This is an emerging issue," he says, noting that most clients interested today are college campuses and other tightly focused building constituencies.



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Hull Architecture Centre, Hull, England Níall
McLaughlin Architects created a zero-energy temporary structure to raise design awareness in Hull. Wind turbines and photovoltaics mounted in a plaza supply the building's energy and feed back into the city's grid.
Photography: © Nick Kane



Ingenhoven began the design process for the Stuttgart station with simple models to test structural solutions. "We wanted to minimize the amount of concrete used, so we needed to find a purely pressure-loaded structure," Ingenhoven says. With Frei Otto and Buro Happold as consultants, as well as a team of German university researchers, Ingenhoven used experience to shape the structure with the models prior to building a digital model that could optimize it. The work paid off in a slim, 14-inch, reinforced-concrete slab across the tracks (compared to Toyo Ito's 7.8-inch slab roof for the Kakamigahara Crematorium, on page 166). Saving concrete cuts down on cement plant production, a notorious source of CO2 emissions.

Although accounting for embodied energy in our buildings represents a challenge (see the related story RECORD, March 2007, at the top of page 170), raising awareness of architecture's effects on carbon emissions has reached a fever pitch. The U.S. Green Building Council announced in November that it would require all buildings going for commercial certification to achieve a 50 percent CO2 reduction over current levels [RECORD, January 2007, page 127] through stricter enforcement of the energy and optimization points in the LEED rating system. As exhaustively noted in the February 12 issue ofEngineering News-Record, there is no shortage of CO2 emissions news-such as the January call from an unlikely industry coalition, including Alcoa, General Electric, and Dupont, for instituting national-emissions limits or the release of the Intergovernmental Panel on Climate Change's Climate Change 2007 report-helping architects wade through the competing claims, various options, and unwieldy concepts remains a daunting challenge. Mithun's Gregory stresses the combined wisdom of multidisciplinary teams as the short-term solution. On the Lloyd Crossing project, the Mithun team included architects, energy engineers, civil engineers, economists, landscape architects, and even a branding company to help the team communicate its ideas to the community. While meaningful change will take time, Gregory notes, "There aren't enough carbon offsets for the entire world."



 

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Originally published in March 2007

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