Getting to Net- Zero Energy: Lessons Learned from a Living Building Challenge
Submitted on June 24, 2011 - 4:19pm
Washington University in St. Louis
Kevin Smith, Associate Director, Tyson Research Center, Washington University in St. Louis
Neal Schaeffer, Project Manager, Facilities Planning and Management, Washington University in St. Louis
Daniel Hellmuth, Principal, Hellmuth-Bicknese Architects
Matt Ford Solutions AEC
In 2008, Washington University in St. Louis committed to the construction of a new building at its environmental field station, Tyson Research Center. This project, the Living Learning Center (LLC), would attempt to meet the rigorous Living Building Challenge, which includes, among other requirements, annual zero-net-energy operation. Post-construction building monitoring indicated that the LLC would not meet the goal of net-zero energy without significant alterations, including changes to building envelope, mechanical, and solar systems. Here, we describe the mistakes, corrections, and lessons learned that ultimately led to successful certification in 2010 as one of the first net-zero energy Living Buildings.
As an environmental research station, many of the programs at Washington University’s Tyson Research Center (TRC) fundamentally relate to environmental sustainability. Additionally, part of TRC’s mission is to serve as a showplace for sustainable building technologies at Washington University in St. Louis. For this reason it was clear that the need for a new building at TRC would ideally be met with a facility designed and constructed to meet the highest standards of sustainable operation, including energy self-sufficiency in the form of annual net-zero energy. The Living Building Challenge combines high standards of construction and operational sustainability with integration of the built and natural environments, thus the LLC was designed to meet this certification standard.
Within the scope of the Living Building Challenge, the project goal described in this Case Study is the design and operation of a building that uses net-zero energy over the course of a 12-month period.
The LLC was designed to meet net-zero energy through operational efficiency and electrical production from photovoltaic solar panels.
The building envelope was originally designed with cost-prohibitive SIP (structural insulated panel) construction, which was replaced during design with wood frame and batt insulation construction as part of a value-engineering process.
Highly efficient, variable-refrigerant-volume air source heat pump HVAC and heat-recovery ventilation were designed to provide year-round building conditioning with minimal electrical consumption.
As constructed, LLC’s electrical demand would be offset by a 17 kW roof-mounted photovoltaic system.
Achieving net-zero energy required detailed monitoring of total electrical consumption and photovoltaic electrical production for a 12 month period substantiated by utility statements and building monitoring data loggers.
Summer 2008: First design meetings
November, 2008: Approval of project
December, 2008: Construction of LLC starts
May, 2009: Construction of LLC completed
January 2010: Energy monitoring indicated that a significant energy debt had been incurred, especially during the month of December. Meetings were held to identify issues in energy efficiency and to develop solutions and an external energy auditor was hired to identify building performance issues.
January-May 2010: Improvements, adjustments, and additions were made to building envelope, insulation, HVAC, building monitoring, and photovoltaic systems to re-position the LLC to achieve energy neutrality.
October 2010: Certification of the LLC as a Living Building.
Original building cost (including soft costs): $1.48 million
2010 efficiency improvements: $63,000
2010 photovoltaic system additions: $28,000
All financed from University funds
The original building, as constructed with respective value-engineering conditions, did not operate as a zero-net-energy building and was consuming more electricity than it was producing, especially the during cold winter months. After six months of operation it was clear that several issues needed to be addressed.
A combination of design features (e.g., large, operable, overhead doors) and cost decisions (e.g., replacement of SIP construction with frame and batting) led to a less-efficient envelope than had been originally assumed. Post-construction we found that additional sealing, insulation, and installation of storm panels to windows and doors in winter was necessary to improve building performance.
The variable-refrigerant-volume air source heat pump HVAC system did not meet the performance estimates that were used when modeling building performance and thus electrical consumption was much greater than anticipated, especially during the winter. Additionally, cost considerations meant that less photovoltaic capacity was installed than was needed. After adjusting the HVAC system to improve performance, building energy requirements were re-calculated using actual data. As a result, the photovoltaic solar system was increased to 23 kW total to account for previous underestimates of building energy demand.
Ultimately, during calendar year 2010 the LLC operated in an approximately net-zero energy fashion and was certified as a Living Building. Energy monitoring and performance improvements continue.
Net-zero energy is a rigorous challenge in climates such as the Midwestern United States, and if this goal is part of a construction project, all design, cost, and construction decisions must be weighed against their effects on electrical consumption and production. At Washington University, future value engineering decisions will not only take project costs into account, but will now include long-term impact estimates of how value engineering decisions affect performance and energy efficiency.
Energy conservation is generally more cost-effective than renewable energy production, and therefore should be weighed more heavily during the design of a net-zero energy building.
Detailed energy modeling, which was not part of the design process for this project, is essential to meeting a stringent performance goal such as net-zero energy.
Although not required for certification, Living Building Challenge projects will ideally include both predictive modeling during design and performance modeling during occupancy to efficiently meet this challenge. Similarly, building commissioning at occupancy, though not required, is essential to ensure maximum value is being gained from energy efficient technologies and building designs and to identify and respond rapidly to performance, design, and construction issues.
Architecture and Landscape Architecture, Biological Sciences (includes Ecology), Environmental Studies and Sciences, Sustainability Studies and Science
For more information on this project, click here.