One factor at the heart of a building’s sustainability is the volume and type of greenhouse gases (GHGs) it accounts for. Looking at energy use in isolation is insufficient because it does not address the source of the energy. For example, a miserly high-performance building heated with natural gas and supplied with electricity from coal-fired power stations could easily have a larger carbon footprint than a similar building of mediocre efficiency running on a mix of wind, solar and hydroelectric power.
Buildings also need to be held accountable for their indirect GHG emissions, such as those released when the buildings’ location and inaccessibility by public transit tend to force workers to commute via private car. Finally, GHG emissions are also affected by water use, wastewater output, trash generation, business travel, consumption of office supplies and manufacturing of computer equipment used on the site, so all those need to be assessed in order to determine a building’s GHG footprint.
The Alliance decided in early 2010 to have a GHG assessment performed by a team of graduate students from the University of Colorado/Denver (UCD) under the direction of Dr. Anu Ramaswami. The team used 2009 data and followed a protocol developed by the World Resources Institute that categorized emissions into three groups: Scope 1 emissions, from on-site combustion of fuels in “owned or controlled” boilers, furnaces or vehicles; Scope 2 emissions, those that are incidental to purchased electricity used in owned or controlled operations or equipment; and Scope 3 emissions, which are all other indirect emissions.
Since the all-electric building burns no fuels on site and owns no company vehicles, its Scope 1 emissions were zero. And since it purchased RECs for all electricity consumed, its Scope 2 emissions were also zero. That left Scope 3 emissions, which required estimating the size of inputs in several categories (commuting, waste, wastewater, potable water, business travel, manufacture of computers used at the Center, and office supplies) and multiplying each of them by an appropriate emissions factor taken from reputable sources.
This analysis gave a total of 581,000 tons CO2e (carbon dioxide equivalent) per year. It also revealed that over half of the Center’s emissions were due to personal vehicle use (26 percent from commuting and 28 percent from business travel), even though only about one-quarter of the building’s tenants drive to work. Commuting by bus accounted for 15 percent, business travel by air for 13 percent, and office supplies for just under 12 percent. The remaining 6 percent was attributable to waste, wastewater, potable water and computers.
The student team concluded its report with suggestions for mitigating the Center’s energy and GHG footprints. Among others, the report stressed ways to cut down on transport-related emissions. These included incentives to use lower-carbon ways of getting to work, such as discounted bus passes, secure bike parking areas and ride-to-work days. The team also suggested allowing flexible work schedules (such as 10 hours a day, four days per week) and telecommuting. Teleconferencing was also suggested as a means of reducing business-related travel. Combining all these methods would reduce the Center’s GHG emissions by an estimated 17 percent compared with the business-as-usual case.
Finally, the UC Denver team used information from a tenant survey to assess the shared services offered by the Alliance Center. In general, those services (telephones, Internet, recycling, kitchenettes, meeting spaces, audio-visual equipment, copiers and copy paper) were used frequently and received mostly “good” to “very good” ratings. Among the exceptions were shared copiers and copy paper, which tenants rarely or never used; over half of the tenant organizations had their own. When tenants were asked to suggest shared services or amenities that the Center did not then offer, the top four items (each suggested by more than half of respondents) were a rooftop garden, composting, achieving zero net emissions, and greywater reuse.
