Valerie Eacret for Zondits, July 9, 2015. Image credit: storkman
Upgrading a 1980s building to a net zero powerhouse doesn’t have to cost more than a conventional retrofit. The Zero-Net Energy Center in San Leandro, California, has proven that. At this facility, electrical apprentices start their careers in sustainable buildings by gaining experience in emerging technologies and electrical systems.
Zero Net Energy Center: San Leandro, CA
High Performing Buildings Magazine, Summer 2015.
The Zero Net Energy Center (ZNE Center) exceeded its energy goal its first year of operation, producing an excess of 69,071 kWh over modeled calculations, and realizing a net savings of more than $15,000 in energy bills. It produced 20.83 kBtu/ft2 of energy in its first year, and consumed 15.32 kBtu/ft2, for a net energy use intensity (EUI) of –5.49 kBtu/ft2 (Figure 1). The ZNE Center proves that retroffiting a decades-old commercial building can result in net zero energy performance with the same budget most projects use to achieve code compliance. And, it earned a dollar-for-dollar appraisal on its high performance building improvements.
Net Zero Design
While many active and passive systems contributed to the performance of the ZNE Center, the effective integration of systems enabled the 75% energy-use reduction (compared to similar buildings from the energy.gov Building Performance Database). Integrating HVAC, lighting and plug load solutions with envelope and renewable energy systems resulted in drastic energy cuts and savings. Ongoing commissioning is verifying the optimal functionality of each system.
HVAC. HVAC system selection depended on its ability to optimally integrate with the project’s need to provide heating and cooling and desire to use mixed-mode ventilation, and the building’s existing conditions, which included its wide, single-story plan and suboptimal orientation for passive conditioning. The team selected a two pipe variable refrigerant flow (VRF) condensing unit/fan coil system (See VRF System and Figure 2). The VRF system performs better and cost $1 million less than a traditional code baseline forced-air HVAC system. Additionally, the VRF system eliminated the need for roof mounted units, which would have increased the roof retrofit cost and reduced the area available for PV.