Sustainable Proof

While the rush to build sustainably may be somewhat tempered by the economic downturn, a 2008 study conducted by the Washington, D.C.-based U.S. General Services Administration of 12 federal buildings demonstrates that buildings designed to be sustainable deliver on their promise of resource savings and greater occupant comfort.

Prepared by GSA’s Public Buildings Service’s Office of Applied Science in conjunction with Pacific Northwest National Laboratory, Richland, Wash., and the University of California Berkeley’s Center for the Built Environment, the study sought to answer the question, “Does sustainable design deliver?”. Within the 171-page report, “Assessing Green Building Performance,” researchers carefully analyze and then conclude that GSA's green buildings outperform national averages in all measured performance areas, including energy, operating costs, water use, occupant satisfaction and carbon emissions. This detailed study demonstrates that green buildings are a good long-term investment.

RESEARCH DESIGN

GSA owns and leases more than 354 million square feet (33 million m²) of space in 8,600 buildings in more than 2,200 communities nationwide. It is America’s largest public real-estate organization and bears a unique responsibility to demonstrate sustainable leadership. As local, state and federal policy makers consider mandating green-building guidelines, it is important that government leaders demonstrate that require- ments are workable and produce tangible benefits to building owners and occupants.

Although GSA had been applying sustainable-design principles to its buildings since 1999, in 2003, the group established a goal of achieving Washington-based U.S. Green Building Council’s LEED Silver for all new buildings. To determine the potential added benefits of sustainable buildings, GSA commissioned a comprehensive post-occupancy evaluation of 12 of its sustainably designed buildings in the summer of 2007. The selected buildings reflect different U.S. regional climates, various uses (courthouses, offices, etc.), and a mix of build-to-suit leases and federally owned buildings. Seven of the buildings were LEED certified at various levels and one was LEED registered. The remaining four were designed to meet the requirements of other programs, including the Washington-based U.S. Environmental Protection Agency’s Energy Star and California’s Title 24 energy standard. The table, page 38, identifies the GSA buildings evaluated as part of the study.

Several factors influenced the selection of buildings for the study, including buildings built or remodeled since 2000 that included sustainable design or energy efficiency as a key design consideration. Another important factor was the ability to collect a minimum of 12 months of operating data, beginning no sooner than six months after the building-occupancy date, and occupants’ willingness to participate in the post-occupancy study.

Building representatives provided utility bills, maintenance budgets and supported an occupant survey for the key data inputs. The performance data then was compared to industry baselines developed from GSA; the U.S. Department of Energy, Washington; International Facility Management Association, Houston; Building Owners and Managers Association International, Washington; EPA; University of California Berkeley’s Center for the Built Environment; and the Energy Information Administration, Washington. Because the researchers evaluated actual, not modeled, building performance, the results were considered reliable and objective.

STUDY FINDINGS

The study confirmed that specifically incorporating energy considerations, such as Energy Star and Title 24, into design leads to improved energy performance. For example, those buildings that received more LEED Optimize Energy Credits had lower energy-use-intensity estimates. The measured energy performance of each building also was compared to the Commercial Buildings Energy Consumption Survey, or CBECS, national; CBECS regional; and GSA

Building representatives provided utility bills, maintenance budgets and supported an occupant survey for the key data inputs. The performance data then was compared to industry baselines developed from GSA; the U.S. Department of Energy, Washington; International Facility Management Association, Houston; Building Owners and Managers Association International, Washington; EPA; University of California Berkeley’s Center for the Built Environment; and the Energy Information Administration, Washington. Because the researchers evaluated actual, not modeled, building performance, the results were considered reliable and objective.

STUDY FINDINGS

The study confirmed that specifically incorporating energy considerations, such as Energy Star and Title 24, into design leads to improved energy performance. For example, those buildings that received more LEED Optimize Energy Credits had lower energy-use-intensity estimates. The measured energy performance of each building also was compared to the Commercial Buildings Energy Consumption Survey, or CBECS, national; CBECS regional; and GSA national averages. All the buildings performed better, some up to 40 percent better, than their respective CBECS averages and most performed better than the GSA goal. (Every four years, the Energy Information Administration collects CBECS data on building characteristics and energy use from thousands of buildings across the U.S. A building’s comparison baseline is the average of those buildings in the CBECS survey that have similar building and operating characteristics.)

In addition, carbon-dioxide equivalents for the buildings were calculated using the Energy Star Portfolio Manager program, an interactive energy-management tool developed by the EPA. All buildings studied were below their CBECS average, and all but one was below the expected CO2 equivalent emissions for Energy Star-rated buildings.

For water use, researchers calculated a building baseline based on occupancy. Approximately half the buildings used less domestic water than their baseline, though all the buildings together averaged only 3 percent better than baseline-performance expectations. The study’s authors cite the greatest difficulty in water calculations because of the lack of metering data on potable water use compared to landscape and process water use. While some buildings implemented low-flow devices, water conservation was not a universal high priority across all 12 buildings. Despite the complexity concerning water savings, the top one-third of the buildings in the study were performing 39 percent better than their baselines.

According to the occupancy surveys, GSA’s sustainably designed buildings demonstrate a 27 percent higher occupant satisfaction rate than the national average. The Center for the Built Environment developed the national average based on more than 48,000 survey responses across 335 buildings. In fact, all 12 GSA buildings scored better than the national average for U.S. commercial buildings in terms of overall building and workplace quality, IAQ, cleanliness and quality of maintenance. The biggest factors adversely influencing occupant satisfaction were poor acoustics, lighting and maintenance problems.

GREATER INTEGRATION YIELDS RESULTS

The two LEED Gold buildings in the study demonstrate that integrated design—a necessity to achieve a Gold rating—consistently achieved higher levels of performance on all measures. The Curtis National Park Service Building, Omaha, Neb., was in the top one-third for energy performance while its water costs were 91 percent below baseline and its domestic water use was 50 percent below baseline. Its CO 2 emissions were 34 percent lower than baseline, averaging 1.9 tons (1.7 metric tons) per person. The Omaha Department of Homeland Security building’s Energy Star rating also placed it in the top one-third for energy efficiencies. Using rainwater harvesting and low- and auto-flow fixtures resulted in water costs 66 percent below baseline with domestic water use 58 percent below baseline. (To read about this project, see “ecommercial,” page 36 of eco-structure’s January/February 2007 issue.)

Although the 12 buildings in total were only 7 percent better than the national average for operations-and-maintenance costs, the top-performing one-third were 41 percent below U.S. commercial buildings’ average. IFMA and BOMA provide the main source of statistics on the state of commercial buildings. Once again, the two LEED Gold buildings scored the highest, partly because of lower utility and janitorial costs, recycling efforts and green-cleaning practices.

LONG-TERM RAMIFICATIONS

Although GSA’s study involved a small number of buildings, it included more than one-third of the agency’s LEED-certified buildings. The best performing buildings were those that took a fully integrated approach to sustainable design. This approach has helped GSA meet its mandate to deliver buildings that use substantially less energy, cost less to operate and maintain, and lead to greater occupant satisfaction. During challenging economic times, the entire building community—public and private—will benefit from achieving these same performance standards.

Scott Florida writes about architecture and sustainability from Oakland, Calif.

KEY FINDINGS

Compared to national averages, buildings in the Washington, D.C.-based U.S. General Services Administration’s post-occupancy study achieved:

• 26 percent less energy use (65 kBtu per square foot per year vs. 88 kBtu per square foot per year)

• 13 percent lower aggregate maintenance costs ($2.88 per square foot vs. $3.30 per square foot)

• 27 percent higher occupant satisfaction

• 33 percent fewer carbon-dioxide emissions (19 pounds per square foot per year vs. 29 pounds per square foot per year)

GSA’S Office of High-Performance Green Buildings

Announced in early 2008, the Washington, D.C.-based U.S. General Services Administration established an Office of High-Performance Green Buildings with a mandate to ensure all federal buildings are meeting sustainable-design and energy-reduction targets of the Energy Independence and Security Act of 2007. The office works in conjunction with the Washington-based U.S. Department of Energy’s Office of Commercial High-Performance Green Buildings, which has the same responsibility for private-sector buildings. The newly created GSA office will address new, renovated and leased buildings' life-cycle costs and operating procedures, as well as design and construction. The legislated mandate requires federal buildings achieve a 30 percent reduction in total energy use by 2015 relative to 2005 levels. It also requires new and renovated federal buildings to achieve a 55 percent reduction in fossil-fuel use by 2010 from 2003 levels with complete elimination by 2030. For more information, visit www.gsa.gov.

Post-Occupancy-Evaluated GSA Buildings