ZNE codes: getting there with performance trade-offs


To achieve zero net energy (ZNE) building codes, this paper proposes a model for building code regulators to consider that refocuses requirements from the efficiency of specific measures to the overall building energy performance. Using California’s Building Energy Efficiency Standards (Title 24, Part 6) as an example, the proposal presents a framework that establishes code compliance on whole-building performance using either the performance approach (energy simulations) or a new “simplified performance trade-off” pathway that achieves equivalent performance levels. An example of a simplified performance approach has been developed with the intention of allowing simple buildings to determine compliance with the energy code by specifying only a few building and efficiency parameters, including renewable energy system capacity. Building on these results, detailed trade-offs for low-rise office buildings are presented that utilize a selection of specific efficiency parameters that collectively achieve targeted performance levels. All major building components (e.g., HVAC, lighting, and fenestration) are represented and the selection of a less efficient design option triggers a requirement for higher efficiency in other areas such that the desired energy performance is achieved. Finally, we present our recommendations for developing simplified performance trade-offs for a larger set of building types and how our results could inform future code development activities.

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  1. 1.

    Typical building design characteristics are based on criteria defined in the NACM and as described in this paper.

  2. 2.

    A detailed technical report has been prepared for PG&E but has not yet been published for public distribution.

  3. 3.

    This statement is based on anecdotal evidence. Unfortunately, no detailed records are available to determine exactly which building scenarios use prescriptive versus performance compliance and at what frequency. However, anecdotally, small-to-medium-sized buildings with “typical” design features tend to be good candidates for prescriptive compliance.

  4. 4.

    Selection of typical systems for this building type was informed by PG&E’s Code Readiness team leads, and their previously noted team of consultants.

  5. 5.

    Note that this study did not evaluate PV generation in detail but it must be acknowledged that taller buildings may have challenges generating adequate energy on site to meet the ZNE target.

  6. 6.

    While this approach makes sense for California, other states without adopted software tools may need a different approach such as a standalone or web-based tool.


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  2. California Energy Commission (CEC). 2015. Impact analysis, 2016 update to the California energy efficiency standards. 2015. www.energy.ca.gov/title24/2016standards/rulemaking/documents/15-day_language/impact_analysis/2016_Impact_Analysis_2015-06-03.pdf.

  3. California Public Utilities Commission (CPUC). 2008. California long term energy efficiency strategic plan. www.cpuc.ca.gov/WorkArea/DownloadAsset.aspx?id=5305.

  4. California Public Utilities Commission (CPUC). 2011. California long term energy efficiency strategic plan - January 2011 update. www.cpuc.ca.gov/WorkArea/DownloadAsset.aspx?id=5303.

  5. Department of Energy. 2016. “Commercial prototype building models.” www.energycodes.gov/development/commercial/prototype_models.

  6. Hart, R., Athalye, R., Rosenberg, M., & Zhang, J. 2016. Developing commercial code precalculated packages. aceee.org/files/proceedings/2016/data/papers/5_190.pdf.

  7. Pacific Gas and Electric. 2018. “Guide to California climate zones.” Accessed march. www.pge.com/myhome/edusafety/workshopstraining/pec/toolbox/arch/climate/index.shtml.

  8. Rosenberg, M., Hart, R., Zhang, J., & Athalye, R. 2015. Roadmap for the future of commercial energy codes. www.pnnl.gov/main/publications/external/technical_reports/PNNL-24009.pdf.

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This study was funded by Pacific Gas and Electric.

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Correspondence to Dimitri Contoyannis.

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Contoyannis, D., Nambiar, C., Hedrick, R. et al. ZNE codes: getting there with performance trade-offs. Energy Efficiency 13, 523–535 (2020). https://doi.org/10.1007/s12053-019-09785-z

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  • Energy codes
  • Zero net energy
  • Energy simulation
  • Performance