Page 15 - Zero Net Energy Case Study Buildings-Volume 1

INTRODUCTION ZERO NET ENERGY CASE STUDY BUILDINGS, VOL. 1
The National Institute of Building Sciences (NIBS) is the organization chartered under the fed- eral Energy Policy Act “to develop commonly agreed upon definitions for NZE and NZER18 “. As of summer, 2014, NIBS is in the process of gathering detailed input from a broad group of stakeholders from industry, government, trade associations and the nonprofit sector involved in all facets of building design, construction and operations. The results of the exercise will be published and made widely available to government and industry to “support the developing de- mand for NZE and NZER buildings.” The output of this effort is expected to develop and advance consensus understanding in this important area19.
Targeting ZNE—Establishing the Right Energy Budget
As noted at the beginning of this Introduction section, design of a building for ZNE performance
follows this general four-step process:
• Set the energy performance target
• Design to this target
• Build to this design
• Monitor, diagnose and correct actual performance
These steps can be followed for any of the three ZNE metrics described: Site ZNE, Source ZNE or TDV ZNE. Each case study project provides insights into the many different issues surrounding the process of design, building and performance monitoring for each specific type of building project. However, each project has a common approach to the first step: setting the energy performance target or energy budget. Targeting a cost-feasible, technically-feasible and operationally-feasible energy budget will minimize the required investment in a renewable energy system—often the most expensive component of a ZNE building. All of the case study buildings discussed in this monograph start with this idea: make the building as energy-efficient as possible and go from there.
A proven approach for initial targeting is to base the energy budget on a known set of bench- marks of measured energy use of comparative building types20,21,22. These benchmarks provide a feasible design target given the current state-of-the-art, which in turn provides a first estimate for the size of the renewable energy supply. The benchmarking approach for setting energy budgets was used for the two case study buildings at UC Merced (Case Studies #5 and #6.).
With “TDV=0” having been established by the CEC as the building code definition for ZNE in California, builders are likely to begin to emphasize it in preparation for the 2020 targets affect- ing the residential new construction market. Since “TDV=0” requires the smallest, least costly renewable system of the three metrics discussed in this Introduction, this definiton of ZNE will have first cost advantages compared to the other definitions for the foreseeable future.
18 NZER is an acronym for “Net–Zero–Energy–Ready”, which is a building with sufficiently low energy demand to achieve ZNE performance, but without the installation of any on-site renewable energy system. Note also that “NZE” and “ZNE” are used interchangeably; “ZNE” appears to be nomenclature used consistently on the California state level, while “NZE” seems to be preferred on the federal level.
19 http://www.nibs.org/?page=hpbc
20 K. Brown, “Setting Enhanced Performance Targets for a New University Campus: Benchmarks vs. Energy Standards as a Reference?”, Proceedings of the 2002 ACEEE Summer Study of Energy Efficiency in Buildings. 4:29-40.
21 Architecture 2030 Challenge and 2003 Commercial Buildings Energy Consumption Survey (CBECS), U.S. Energy Information Administration.
22 For laboratory buildings: http://labs21benchmarking.lbl.gov/
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