ZNE Verification Methodologies Phase 2
Client: PG&E
Project Dates: December 2018
Project Team: TRC and Resource Refocus
project summary
modeled and monitored energy use and generation from a community of ZNE homes
Pacific Gas & Electric (PG&E), on behalf of the joint California Investor Owned Utilities (IOUs) contracted with TRC to develop methodologies for verifying predicted or measured energy performance of Zero Net Energy (ZNE) buildings in California. This report represents the Phase 2 deliverable of this effort, which builds on the work of Phase 1 to develop verification methodologies for validating predicted and observed energy performance of ZNE buildings in California.
This report provides a deeper analysis of issues raised during Phase 1 and expands to consider issues for several building and project types including commercial buildings, multi-building projects, retrofits, and community scale ZNE projects.
This report addresses the following study objectives:
Assessment of key issues affecting ZNE verification including metrics, challenges with modeling ZNE buildings, challenges with field data collection and entities for tracking ZNE performance.
Assessment of ZNE design and performance for a broad set of projects involving single family residential, multifamily and commercial buildings, ZNE retrofits and campus/community scale ZNE. The quantitative analysis conducted deeper dive on persistence of savings, impacts of the changes in Time Dependent Valuation (TDV, defined in section Key ZNE Terminology) values between 2013, 2016 and 2019 on ZNE design/performance and the cross-walk between these TDV values and site energy performance. The report addresses the differences between ZNE Code, ZNE Site/Source and Zero Net Carbon metrics.
Key Findings
building D energy use and generation
A building can be both ZNE Design and ZNE Performance, but each of these requires a separate verification process.
There are various ZNE metrics that are being used by entities in the state of California and across the country. The choice of metric also affects the choice of verification method and the data relied upon for ZNE verification.
There are several programmatic and non-programmatic efforts that have a need to verify ZNE design and/or ZNE performance. Each has a unique verification needs based on whether they target ZNE design or ZNE performance metrics.
ZNE remains a developing approach to building energy efficiency, so definitions, strategies, and metrics are still evolving.
As metrics and standards for verifying ZNE status continue to develop and evolve, the details of verification requirements with also need to evolve, but the overall approach and strategy recommended in this report will still be valid.