DESIGNING FOR ZERO CARBON
OBSERVATIONS
Observations A Period of Transition As pointed out in the Introduction to this volume, these case study projects were designed in a period of transition from an emphasis on zero-net-energy (ZNE) buildings (emphasizing on-site renewable energy systems) to all-electric buildings. The continuing goal is the reduction of carbon emissions caused by buildings but the design strategies are shifting focus to reflect the fact that the electric utility grid is moving toward carbon-free production within 25 years. ZNE buildings with on-site solar photovoltaic systems would nearly eliminate their operating carbon emissions by having minimal dependence on a largely fossil-fuel-based electric utility grid. But any all-electric building in California will effectively achieve the same type of emission reduction once the electric utility grid is 100% zero-carbon as mandated law (SB100). Since this law just went into effect in 2018, the transition in design emphasis has only just begun. In many ways, the five case studies in this volume reflect the transition underway—all have roofmounted solar photovoltaic systems of sufficient size to offset the annual energy demand of the building and were designed to be all-electric for project-specific reasons. While all five designs bear the hallmarks of ZNE buildings, they nevertheless also display the design strategies of the near future for energy-efficient, zero-carbon (operational) buildings. Continuity: Proven Design Strategies In addition to being transitional, the case studies in this volume show a continuity of design strategies with those employed by the case study projects of the previous volumes of this series, some of which were all-electric. (See the Prologue on page xii of the introductory sections.) These basic design strategies are proven successful at this point. However, there also continue to be issues with some aspects of these strategies that were not uniformly addressed during the design of even these exemplary projects. • Building metering and performance verification When ZNE performance was the primary goal in previous case studies, planning during the design phases for energy metering of both the subsystem energy use (heating, cooling, lighting, plug loads, etc.) and the solar PV production was essential. Comparison to energy modeling results and troubleshooting subsystem inefficiencies were important aspects of achieving ZNE performance. Despite the transition to a decarbonized utility grid and the corresponding relaxation of ZNE as the ultimate design goal, energy metering nevertheless still has value for the facilities management of the building, identifying patterns of energy use or possible equipment malfunctions or just inefficient operation. Metering is also particularly useful to maintain maximum operational efficiency of the solar PV system, still a relatively unfamiliar system for most facilities maintenance staff. In two of the case study buildings in this book, however, the building metering system was not only not planned or installed initially, but their utility net-metering was not even separated from existing buildings present on the site. This condition is in the process of being corrected in both cases, so that important data for the new structures will begin to be collected in the near future. Energy efficiency and optimal solar PV system performance will still be high operational priorities in our decarbonized building future, both for individual owners and the public utility operators. Systematic metering will help to ensure this. • Commissioning and control systems This decarbonized building future will be characterized by sophisticated, “smart” buildings 116
Designing for Zero Carbon: Volume 1
