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ASHRAE Standard 90.1 Performance Based Compliance (Section 11 and Appendix G)

Performance Based Energy Codes

Commercial building energy codes such as ASHRAE Standard 90.1 typically include two types of approaches for demonstrating compliance; prescriptive and performance paths.

  • The prescriptive path establishes criteria for energy related characteristics of individual building components such as minimum R-values of insulation, maximum U-factors and solar heat gain coefficients of fenestration, maximum lighting power allowance, occupancy sensor requirements for lighting control, and economizer requirements for HVAC systems.
  • The two performance-based approaches in Standard 90.1 are the Energy Cost Budget (ECB) method found in Section 11 and the Performance Rating Method (PRM), commonly referred to by its location in the Standard, Appendix G. These methods provide more flexibility by allowing a designer to "trade off" compliance by not meeting some prescriptive requirements if the impact can be offset by exceeding other prescriptive requirements. This is demonstrated using computer simulation to compare a proposed building design to a reference building design commonly referred to as a baseline.

The main differences between the ECB and PRM approaches in Standard 90.1 are the characteristics of the baseline building design.

ECB

  • The baseline is essentially a clone of the proposed design with most of the building components adjusted to “just meet” current prescriptive requirements.
  • A building is deemed in compliance with ECB when the annual energy cost of the proposed design is no greater than the annual energy cost of the baseline building design. This approach is referred to as a dependent baseline.

Appendix G

  • Appendix G uses a more independent baseline where many of the characteristics of the baseline design are based on standard practice, meaning credit is available not only for exceeding prescriptive requirements in the code, but also for exceeding standard practice that is not regulated by the code. For example, in Appendix G credit is available for strategies not credited in ECB such as optimized window area and orientation, selection of more efficient HVAC and service water heating equipment type, right sizing HVAC equipment, efficient use of thermal mass, etc.
  • Appendix G uses a stable baseline approach with efficiency levels set at values that are not intended to be updated with each new addition of the code. Instead, the proposed building energy performance needs to exceed that of the baseline by an amount commensurate with the code year being evaluated.

Tools

Compliance Form — Proper enforcement of performance-based compliance submittals is necessary to ensure consistency and confidence in modeling results, yet, enforcement is a notoriously difficult process. This spreadsheet-based compliance form meets the documentation requirements of Standards 90.1-2016, 2019, and 2022 Energy Cost Budget Method and Performance Rating Method. It helps the modeler establish simulation inputs for the baseline/budget and proposed design models and includes a submittal checklist to ensure that all necessary supporting documentation is included in the submittal. It standardizes compliance documentations and simplifies submittal reviews by code officials and administrators of above code program implementers.

For questions about use or customization of the form please contact the Building Energy Codes Help Desk.

Compliance Form Companion Tool — This Companion Tool is designed to be used in conjunction with the DOE/PNNL ASHRAE Standard 90.1 Performance Based Compliance Form (i.e., Compliance Form). The process is that submitters first fill out the Compliance Form and import the data entered into the Compliance Form into this tool to perform additional/custom calculations. AHJs/RAs can select in-built custom/additional calculations to be performed. Examples of in-built additional/custom calculations include but are not limited to determining performance in alternative metrics such as site energy, source energy or GHG emissions and determining savings by fuel and end use. Please see the "Instructions for AHJs and RAs" tab in the Companion Tool for a complete list. AHJs/RAs can add as many tabs as desired in order to perform additional calculations relevant to the AHJ/RA's program.

Review Manual —The ASHRAE 90.1 Energy Cost Budget and Performance Rating Method Submittal Review Manual (the Manual) is a comprehensive reference for reviewing modeling-based submittals. The Manual is a companion to the DOE/PNNL 90.1 ASHRAE Standard Performance Based Compliance Form and supports 2016, 2019, and 2022 editions of ANSI/ASHRAE Standard 90.1. The forms can be downloaded here.

The Review Manual includes the following:

  1. The review checks to verify that the proposed design reported in the Compliance Form reflects design documents; that the configuration of the baseline/budget model is established correctly, that the baseline/budget and proposed design is modeled as reported, that the simulation is error-free, and that the compliance outcome is established correctly;
  2. Checks to verify compliance with the mandatory requirements of 90.1 relevant to the simulation inputs;
  3. Examples and common mistakes;
  4. The methodology for prioritizing the review;
  5. Simulation reports for common BEM tools annotated with tips on performing specific checks.

ASHRAE Standard 90.1 Adopter Toolkit Navigator provides recommendations for organizing effective and efficient submittal review of projects that follow ASHRAE 90.1 Section 11 and Appendix G, and includes links to the tools and resources available to jurisdictions and beyond-code programs including the following:

Technical Support Document to Facilitate Adoption of ASHRAE Standard 90.1 Performance Rating Method (PRM). This report describes solutions to the common PRM adoption challenges, including calculating energy savings by fuel type and electricity demand savings relative to current code and avoiding “fuel switching” when reporting savings of the proposed design relative to the current code. The calculations described in this technical support document are automated in the ASHRAE Standard 90.1 Performance Based Compliance Form and the Compliance Form Companion Tool described above.

Performance-Based Code Compliance: A Roadmap to Establishing Quality Control and Quality Assurance Infrastructure. This report was completed as part of a research project to facilitate performance-based compliance with commercial energy codes. It provides short, medium and long-term recommendations for streamlining enforcement and ensuring consistency in compliance outcomes. It incorporates input from over 70 stakeholders representing jurisdictions, rating authorities, developers of relevant standards and organizations.

Performance Rating Method Reference Manuals (PRM RM). These documents are intended to be a reference manual for the Appendix G PRM of Standard 90.1. The PRM can be used to demonstrate compliance with the standard and to rate the energy efficiency of commercial and high-rise residential buildings with designs that exceed the requirements of Standard 90.1. The procedures and processes described in this manual are designed to provide consistency and accuracy by filling in gaps and providing additional details needed by users of the PRM. PNNL has created PRM RMs for Standard 90.1 2010, 2016 and 2019.

Training webinar recordings available!  BECP hosted two webinars on forms for performance-based code compliance:

  • Performance-based Compliance Documentation for ASHRAE 90.1 Section 11 and Appendix G — September 29,2020.  Learn more
  • Performance-based Compliance for Submittal Reviewers — December 8, 2020.  Learn more

HVAC System Performance

Total System Performance Ratio (TSPR). TSPR is an approach for rating the efficiency of the entire HVAC system. Unlike a component based prescriptive approach, a system efficiency approach accounts for the interactions between the different components of a system. However, unlike whole-building performance it does not allow tradeoffs between different building systems (i.e., HVAC, lighting, envelope). TSPR evaluates the resources required for an HVAC system to fulfill the function for which it is intended – meeting building sensible and latent loads. TSPR in its most basic form, is calculated as the ratio of the sum of a building’s annual heating and cooling loads to the sum of the annual energy used for the whole HVAC system including heating, cooling, fans, pumps, heat rejection, and energy recovery.

As demonstrated by simplified energy modeling, the TSPR of a proposed building design must be greater than the TSPR of a baseline building design to comply. The baseline system configuration used to represent energy use can be customized to meet any desired level of performance. Washington State’s new energy code uses cycling air source heat pumps with a DOAS with heat recovery as the baseline system (WSEC 2018). The denominator representing energy use can be customized to meet any policy goal. Site energy use, source energy, energy cost, and CO2 emissions are all valid metrics. Washington State uses carbon emissions in the denominator to promote the states policy goal of zero carbon emissions from buildings. A tool created by PNNL to implement Washington State's new TSPR requirement can be found here.

Other TSPR Resources

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