summer 08 | Centerline

Getting to Zero

Along a typical commercial strip in San Jose, California, an unassuming office building is gaining notoriety for its ambitious sustainability goals. The new offices for Integrated Design Associates (IDeAs) were designed to meeting the goals of net-zero energy and net-zero carbon emissions, new benchmarks for buildings that far exceed current sustainable building practices. Using readily available technologies, the project team endeavored to meet challenging new energy conservation and on-site generation goals that predicted to be adopted industry-wide within the next two decades. Mark Fisher, principal for IDeAs, thinks that zero-energy goals are already within reach for many projects. "We didn't do anything that other people can't do, we just decided to do now what many people will be doing ten years from now," he explains.

The drive towards net-zero energy buildings is the latest phase in the ongoing process of raising the bar on sustainably designed buildings. Since the 1990's the LEED rating system has increased the adoption of green building technologies and spurred competition to reach sustainable building goals. However many LEED-certified buildings did not improve energy efficiency beyond code allowances (though recent updates to LEED and additional proposed revisions have more rigorous energy requirements.) Now a number of project teams are striving for the ambitious goal of creating zero-energy buildings that fully offset their energy consumption and carbon emissions by generating electricity and/or heat onsite using renewable resources.

A number of societal factor are converging to drive this trend. With the devastation wrought by hurricane Katrina, scientific evidence of the rapidly meting polar ice cap, and the attention gained by Al Gore's documentary An Inconvenient Truth, concern about global climate change has reached a tipping point. In a recent speech, Gore told a conference of energy policy makers that the U.S. should transform its electrical grid to rely solely on renewable energy sources within a decade. He likened this goal to JFK's challenge of putting a man on the moon by the end of the 1960s, and that to meet this challenge that U.S. should transform its tax policies to encourage investments in renewable power. In Gore's words, the government should "tax what we burn, not what we earn."

New Policy Directions
Numerous organizations have adopted emission reduction policies for buildings with far-reaching implications. In 2006 the non-profit group Architecture 2030 proposed the 2030 Challenge, advocating the new buildings and major renovations be carbon neutral - using no energy from greenhouse gas (GHG) emitting sources - by the year 2030. The plan advocates an immediate energy reduction target of 50 percent of the national average for each building type, based on the existing building stock. The plan will then increase the reduction by 10 percent every five years, reaching a 100 percent reduction by 2030. These ambitious goals have been adopted by many influential industry organizations including the American Institute of Architects (AIA), the U.S. Green Building Council (USGBC), the Environmental Protection Agency (EPA), and the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE).

Several energy policy actions have been initiated at state and federal levels with zero-energy phase-in plans similar to those in the 2030 Challenge. The U.S. Energy Independence and Security Act of 2007 (EISA 2007) was signed into law in December of 2007, and will have broad implications for energy efficiency of public buildings. The new law authorizes a Zero-Net-Energy Commercial Buildings Initiative within the U.S. Department of Energy (DOE) to support the goal of net-zero energy for all new commercial buildings by 2030. The law also creates an Office of Federal High-Performance Green Buildings within the U.S. General Services Administration (GSA), and puts new and renovated federal buildings on an energy reduction plan that reaches carbon neutrality by 2030. The law also specifies a zero-energy target for 50 percent of the U.S.'s commercial buildings by 2040, and for all U.S. commercial buildings by 2050.

A number of zero-energy policies have also been adopted at the state level. In March of 2008 Massachusetts Governor Deval Patrick announced the formation of a green building task force to develop specifications for the first state-owned net-zero energy building by 2010. The state's plan will encourage universal adoption of net-zero energy targets for all new construction by 2030.

In California a broad series of policy actions were set in motion after Governor Schwarzenegger signed the Global Warming Solutions Act of 2006 (AB32). This law requires California to reduce GHG emissions to 1990 levels by 2020, with later reductions of 80 percent by 2050. Both the California Public Utilities Commission (CPUC) and the California Energy Commission (CEC) have adopted policies for all new residential construction in California to meet zero energy by 2020, and for all new commercial construction by 2030. These policies will drive funding for incentives for net-zero buildings, and will provide the basis for future revisions to California's Title 24 energy code. Panama Bartholomy, Advisor to CEC Commissioner Karen Douglas, says that incentive programs are critical for preparing the market to adopt zero-energy goals. "We have the authority to continue to ramp up efficiency requirements of Title 24, but we can't do it all with standards."

In July The Pacific Gas and Electric Company filed a proposal with CPUC that would double PG&E's budget for energy efficiency programs, including some $60 million to promote adoption of zero-energy buildings. Nick Rajkovic, Senior Program Engineer with PG&E, is helping the utility to structure a series of pilot projects, incentives, and development tools for zero-energy homes and commercial buildings. He explains that "subsidies alone will not change the market," and that design methods and tools will be necessary. PG&E has already been approached by a number of developers interested in doing zero-energy pilots as a way to differentiate themselves in the marketplace. Nick believes that universities, non-profits, and owner-occupied projects pose the best candidates for early adoption. The new incentives for zero-energy buildings are expected to be available in 2009.

If the 2030 Challenge goals are met, the commercial building sector could be a major contributor towards meeting the new GHG reduction goals. Using models of the U.S. commercial building stock created by the Lawrence Berkeley National Laboratory, and assuming current rates for new construction, renovation, and retirement of buildings, we can estimated the collective impact of 2030 goals. The model shows that although the total commercial square footage is expected to increase close to 40%, the resulting CO2 emissions could be reduced by approximately 25% (The reduction is not greater due to the low rates at which existing buildings are retired, only .8% per year.)

Complexities of Definitions
determining if a building is truly zero-energy can be a complex task. A study by Paul Torcellini, Shanti Pless and Michael Deru with the National Renewable Energy Laboratory (NREL), and Drury Crawley of DOE illustrates that our definitions of net-zero energy can influence project design, and how we measure success for these projects.

The authors describe four primary definitions for net-zero buildings - those that are next zero in terms of site energy, source energy, energy costs, or emissions. All four definitions assume that grid connectivity is available so that buildings can export excess electricity, and measure energy use and on-site production on an annual basis. Net-zero site energy buildings produce as much energy at the site as they consume. For net-zero source energy buildings (source ZEBs) one must calculate energy losses from generation and transmission, however for buildings that use natural gas and generate excess electricity on site, this becomes an easier goal that a site ZEB. The authors suggest that buildings should first reduce energy use overall, and produce electricity within the building footprint. Buildings that import renewable supplies to the site (for examples biodiesel, wood pellets, or biomass) or purchase off-site renewable energy, are considered less optimal, as these options provide less of an incentive to reduce building energy loads.

Many practitioners have opted to meet the site ZEB goal, as with this approach there is no need to adjust for grid generation and transmission losses, utility emission rates, or utility cost structures. As these values can vary greatly by location, the site ZEB goal simplifies energy calculations and provides a more level playing field.

Feasibility of Zero Energy
Although many new policies encourage gradual and universal adoption of zero-energy buildings, few feasibility studies of these policies are available. A study by a team of NREL and DOE researchers provides an optimistic outlook and suggests that zero-energy goals are achievable for significant portions of the U.S. commercial Building stock. Using models based on the 2003 Commercial Buildings Energy Consumption Survey (CBECS), the researchers predicted the potential for zero-energy buildings based on several possible scenarios. The scenarios included a bases case with today's standard building with rooftop photovoltaics (PVs), a scenario with currently available low-energy solutions, and scenarios that assume that building energy technologies will improve by 2025.

The simulations show that with an aggressive package of current technologies and practices, 22 percent of U.S. commercial buildings have the potential for reaching zero energy. If these technologies were applied to the entire U.S. building stock, site energy use by the commercial building sector would be reduced 82 percent. The most optimistic scenarios - which assume increased efficiency for lighting, HVAC, photovoltaic panels, and appliances by the year 2025 - show that 70 percent of commercial buildings could reach zero energy.

The study further shows the potential to reach net-zero goals broken down by climate and commercial building sub-sector. ASHRAE climate zones 1-3, which represent roughly the southern third of the continental U.S. and most of California, show the greatest potential for reaching zero-energy goals. Building types with the greatest potential for net-zero energy are warehouse buildings, followed by office and educational buildings. While the authors demonstrate possible outcomes based on the adoption of building technologies, the report does not consider the costs or the economic feasibility of these scenarios. Obviously, reforming the market and cost structures for sustainable technologies will be crucial factors in the adoption of zero-energy solutions.

Early Attempts
One of the first projects to strive for zero energy was the Adam Joseph Lewis Center for Environmental Studies at Oberlin College, completed in 2000. The project by William McDonough + Partners was widely touted as one of the first buildings to be a net-energy exporter. The project's performance was monitored and evaluated by Oberlin faculty member John Scofield, who published his findings in ASHRAE Transactions. However Scofield's findings were criticized by McDonough's office as an unfairly poor report because Scofield included data collected before building commissioning was complete (this discussion is included in the Transactions paper). A more balance assessment of the project was given in a field study by NREL and Oberlin College, which found that although the building fell short of its goal to be an energy exporter, its rooftop PV system provides 57 percent of the building's annual energy demand. In 2006, six years after the completion of the project, an additional 100 kWP (kilowatt peak) PV array was installed as a canopy for an adjacent parking lot, and the building is now believed to be operating as a net-zero energy building.

The Beddington Zero Energy Development, another early adopter, was intended to be the first carbon-neutral community. The project, known as BedZED, designed by Bill Dunster Architects an Arup, and completed in 2002, included 99 low-energy homes in London Borough of Sutton. The project was analyzed in a University of East London student's Mater's Thesis in 2005. The study found that although the project made significant reductions in energy use, including space heating reductions of 88 percent, the project fell short of its overall goal of carbon neutrality.

Current Trends in Net-Zero
The projects at Oberlin and Sutton show that meeting zero-energy goals in operating buildings has been an elusive challenge. Scott Shell, Principal with EHDD Architecture, thinks that energy modeling tools are not always effective for predicting actual operating energy use, and that they are primarily useful for estimating specific loads and as a baseline for compliance with energy standards. However, with ultra-low energy buildings, even minor problems with building operations can seriously affect energy budgets.

For the Chartwell School in Seaside, California, EHDD pursued the goal of net-zero purchased electricity, allowing natural gas for space heating that would not be compensated for with on-site electrical generation. Scott says that the PV system was relatively inexpensive when considered as part of the overall budget for the school. After rebates the system cost was $158,000 only 1.6 percent of the project's construction cost, and with accelerated depreciation the payback period was significantly reduced. "We routinely value engineer 10 percent of a project's cost, of course we can afford this," Scott explains, "but it requires a mental shift to have this as a key goal for a project." He says that when zero-energy is a goal, attaining a LEED Platinum rating is much easier to reach. "You get all the energy credits, the innovation points for zero-energy, and the IEQ points which are relatively easy for high-performance buildings, putting you well on your way to platinum."

When Chartwell first opened and was not meeting its net-zero electricity goal, the school asked Taylor Engineering, the mechanical engineer and energy consultant for the project, to conduct an energy audit and compare it with the energy predictions. The building had been equipped with detailed had been equipped with detailed end-use metering, in part to obtain a LEED credit for energy monitoring, which greatly aided the energy audit process. Gwelen Pliaga, Senior Project Manager with Taylor Engineering, discovered that lighting loads were highest during the evening when the school was largely unoccupied. He was told that a security consultant advised that site lighting be left on all night, though this turned out to consume 20 percent of the building's annual energy budget. Ina addition, two large commercial refrigerators had been donated to the school, but were not included in the design-phase energy modeling, and were using seven percent of the energy budget. (They were later replaced with much more energy-efficient models.) Gwelen thinks that the building can meet its zero-electricity goal, but says that "continuous monitoring and improvement of operations can make or break zero-energy goals, and somebody at the building has to be paying attention to energy use over time." He also believes that improved energy data visualization systems, such as the building dashboards provided by Lucid Design Group, will help building operators keep track of ongoing energy use and identify operational problems.

The San Jose headquarters for Integrated Design Associates (IDeAs), completed in the fall of 2007, was designed to be net-zero in terms of both energy consumption and carbon emissions. The building is housed in a 7200 sf former bank building, and is expected to generate 100 percent of its energy requirements with a building integrated photovoltaic (BIPV) system. The design team that included EHDD Architects, Rumsey Engineers and IDeAs, first designed an all-electric, low-energy building using readily available systems and technologies. Lighting loads are reduced with skylights, high-efficiency fixtures, occupancy sensors, astronomic time switches and daylight harvesting controls. Solar gain is controlled with spectrally-selective glazing. The designers also analyzed plug loads including printers, computers, screens, peripherals and task lighting for ways to further reduce energy consumption.

The building's mechanical system incorporates a high-efficiency exothermal heat pump with polyethylene (PEX) tubing under an adjacent landscaped area that provides the ground-source heat sink. A radiant floor system with PEX tubing is imbedded in a topping slb over the existing slab. A Metasys energy management system by Johnson Controls is designed to optimize this low-energy system by controlling flow rates and floor slab temperatures. The system evaluates the potential floor condensation by monitoring humidity and floor surface temperatures, and is able to provide dehumidification though he dedicated outside air handler which provides ventilation air. Operable windows and sliding glass doors allow occupants to control their indoor environment.

The building was designed to use 60 percent less electricity than Title 24 standards. The project's 30 kWp BIPV rooftop system, with the additional BIPV panels on south-facing shading devices are expected to generate 42,700 kWp per year, meeting the annual electrical demand of the building. The building owners took advantage of several financial incentive programs, including rebates from the CEC, a 30 percent federal tax credit, and 5-year accelerated depreciation. Together these incentives reduce the cost of the photovoltaic systems from the installed cost of $225,000 to an estimated cost (after 5 years) of $48,5000, a reduction of over 80 percent. Energy savings are estimated at $6833 per year, resulting in a simple payback of slightly more than seven years

The project has not been without its challenges. Obtaining the approval and equipment from PG&E for net metering took several months, and the utility would not review the application until the building inspector had verified the installation was complete. As a result, several months passed in which the system produced electricity that could not be used. (PG& E representative say that ten days is the average turnaround time for net meters.) In addition, diodes in the project's monocrystalline BIPV panels failed and had to be replaced. Because the diodes are integral with the PV panels and the roofing system, the manufacturer had to get UL approval for the new design, causing additional delays.

Although not all of the defective panels have been replaced, the system generated an excess of 33 kWH from April through June. The building owners continue to monitor electricity purchased and generate on-site to determine whiter the building meets its net-zero goals on an annual basis. Mark Fisher of IDeAs describes the project as a work in progress and a living laboratory. "It is very efficient, but may never be perfect, as soon as something new comes out we change it." He also says that the project has gotten a great deal of interest from the media, including spots on CNN and NBC, and has attracted a large number of tour groups.

Future Directions for Reaching Zero Energy
In our discussion with professionals for this article, we learned of several net-zero energy projects currently in design and soon to be built. The Research Support Facility for NREL's Golden, Colorado campus looks to be a promising case study. The design-build RFP for the project included a number of required and desired performance goals. As a minimum, the project had to meet LEED Platinum, and had to provide natural ventilation and daylight to all workspaces. Competing design-build teams were encouraged to comply with a maximum energy budget of 5 kBtu/s.f. approximately 50 percent better than ASHRAE standards for the site's climate. Further down the list of desired performance goals was net-zero energy.

The winning team, consisting of Haselden Construction, RNL Design, and Stantec, was able to meet all four definitions for net-zero building as outlined by NREL - net-zero site energy, source energy, cost and emissions. To meet the specified budget of $64 million, the PV system will be financed through a power purchase agreement (PPA),an arrangement by which a third party pays all installation costs, and recovers the investment over time through monthly payments from the building owner. From the owner's perspective the payments are similar to utility payments, though rather than paying a utility they are financing a fully renewable energy source. However, Phil Macey of RNL Design points out that a key to the project's PPA is Congress' continuation of federal investment tax credits for photovoltaic systems currently pending approval in Washington. Without these tax credits it may not be possible to include the PV system as designed, jeopardizing the zero-energy goals.

John Andary, Principal with Stantec, says that reaching zero-energy goals meant that engineering solutions had to lead the design process and shape the building forms. Stantec provided early input in terms of the building's massing, facades, and wall sections, based on previous research and practice. "The key was keeping the building narrow enough for daylight to reach all areas. Once the buildings work for daylight they are easy to ventilate, and all the other aspects fall into place."

The building is configured with two 60-foot wide three- and four-story wings, with PVs integrated into the roof. A precast wall system - typically used for refrigerated buildings - includes thermal mass on the interior, a rigid insulation core, and a concrete exterior finish. Day lighting is distributed into the building with the use of light louvers from Architectural Energy Corporation, the firm that also provided the day lighting analysis. The south facades feature a double skin that will be used to preheat supply air in inter. The design also includes operable windows, in-slab radiant cooled ceilings, and a low-velocity displacement ventilation system integrated with a raised floor.

Due to expansive clay soil at the site, floor slabs be above grade, allowing the HVAC system to use the thermal mass of the crawl space as a "thermal labyrinth," a system that has been used successfully in England and Australia. Unlike the rock bed systems of the 1970s that were frequently plagued with mold and air quality problems, new thermal labyrinths are designed to be accessible for maintenance, with regular airflow to maintain air quality. The NREL project is scheduled for completion in 2010, and we expect the performance to be monitored and reported in detail by NREL.

A much larger zero-energy project also scheduled for completion in 2010 is the ambitious Masdar Headquarters in Abu Dhabi's master-planned city of Masdar City. The design by Chicago firms Adrian Smith + Gordon Gill Architecture, and Environmental Systems Design (ESD) will strive to create the first "large-scale, mixed-use 'positive energy' building, producing more energy than it consumes," according to a project press release. The courtyard building will be shaded by an enormous PV array and will house offices for the Masdar administration, private residences, retail, and leasable office space.

Mehdi Jalayerian, Senior Vice President and Principal for ESD's International Division, says that the initial design process was fully integrated, and the entire design team contributed to the conception of the building from the initial visioning session. "You can't look at the components independently," he says. For example the building's large canopy acts to shade the building and to provide a platform for a large array of PVs that will produce more energy than will be needed by the projects. Mehdi tells us that the future design process will be facilitated through Building Information Modeling (BIM) tools such as Revit, which are becoming more effectively integrated with energy modeling tools.

The building will be one of the first to be completed in the ambitions master plan for Masdar City, a 2.3-square-mile community that will house 50,000 inhabitants. The design by Foster and Partners will create a walled city infused with new technologies that will strive to be a net-zero in terms of carbon and waste. The project's funding body recently announced plans to invest $2 billion in thin-film PV production facilities in Germany and Abu Dhabi, with an annual production capacity of 210 megawatts by 2010. It may seem surprising to see such a large investment in renewable energy technologies from an oil-rich state, but the organizers of the Masdar Initiative are clearly planning for contingencies should the income from oil subside.

As these and other zero-energy projects are completed, occupied, and monitored, we can expect to see a number useful case studies emerge the near future. By adopting net-zero energy as a goal, the building industry has raised the bar for sustainable development, and many developers and building industry professionals are eager to compete and take on these challenges. These targets are also spurring substantial investment from clean tech investors that may lead to disruptive industry breakthroughs and make these goals more achievable.