The January 1, 2027, mandatory compliance date (MCD) for ANSI/RESNET/ICC 301-2022, including Addenda A, B, C, and E, is approaching. The updated standard introduces changes to field verification, documentation, testing, and energy modeling that HERS Raters, Rating Field Inspectors (RFIs), and HERS Modelers should be familiar with before the transition. Although the MCD was postponed to allow additional preparation time, voluntary use of the updated standard has been permitted for several months. Accredited software versions supporting ANSI/RESNET/ICC 301-2022 are already available, and many rating professionals have begun using the new and updated standard software since July 2026. The following are the latest software versions compliant with the updated standard as of the publication date of this article. Raters are encouraged to use the most current versions to ensure all available updates and hotfixes are included: REM/Rate 2025, 301-2022 mode (hotfix 36) Ekotrope 5.2.3 EnergyGauge 8.2.00 HouseRater 4.2.4 APEX 1.11.1 (available soon) Additionally, ANSI/RESNET/ICC 301-2022 incorporates provisions from addenda to the 2019 edition that were previously adopted into the RESNET HERS Standards. As a result, some rating professionals may already be following many of the updated requirements. It is also important to note that the RESNET HERS Standards modified the adoption of ANSI/RESNET/ICC 301-2022 with Addendum 83i, 90i, and 98i. Under Addendum 98i, wall orientation remains optional for HERS ratings and is not affected by the January 1, 2027, mandatory compliance date. However, several changes warrant particular attention to ensure field data collection and energy modeling practices are ready for mandatory implementation. Changes to Field Verification and Documentation ANSI/RESNET/ICC 301-2022 introduces new minimum rated features and additional documentation requirements. HERS Raters and RFIs should review their existing field verification procedures and data collection forms to ensure all applicable procedures are followed and data is captured. Roof Shape and Eave Geometry Additional information is required to accurately model roof and attic insulation conditions. Field verifiers should document the roof type (flat, hip, gable, shed, etc.) and relevant eave geometry, including roof slope, ceiling framing height, and eave height and length. These measurements help determine whether roof geometry limits the available space for insulation at the attic perimeter. When the available height is less than the specified insulation thickness, the modeling software can account for the reduced insulation at the perimeter. Domestic Hot Water, Clothes Dryers, and Ceiling Fans Additional equipment characteristics must be documented where applicable, to ensure accurate energy modeling. These include: Domestic Hot Water: First-hour rating, in gallons per hour. Clothes Dryers: Whether the dryer is vented or ventless. Ceiling Fans: Energy consumption in watts, consistent with updated EnergyGuide labeling. Fenestration Documentation For fenestration products without National Fenestration Rating Council (NFRC) ratings, signed and dated manufacturer documentation may be used to establish the U-factor and solar heat gain coefficient (SHGC). Appendix B provides additional clarification on the use of default values and acceptable sources of documentation. Central Fan Integrated Systems (CFIS) CFIS equipment must now be documented even when the system does not qualify as Dwelling Unit Mechanical Ventilation System (DUMVS). Field documentation should include damper information, fan model number, operating controls and runtime, and airflow for each operational mode. On-Site Energy Production and Battery Storage For homes with on-site renewable energy production, documentation must identify the status of Renewable Energy Certificates (RECs), including whether they have been retired, retained, sold or transferred, or if their status is unknown. For homes equipped with battery storage systems, field documentation must include the battery type, storage capacity in kilowatt-hours (kWh), and efficiency. Through-Wall HVAC Systems Field verifiers must document the area of exterior walls occupied by through-wall HVAC equipment. This area is modeled separately from the insulated/framed wall area to ensure accurate calculations the wall’s thermal performance in energy modeling software. Changes to Field Testing Protocols ANSI/RESNET/ICC 301-2022 references the updated testing protocols established in ANSI/RESNET/ICC 380-2022. These updates include several clarifications to infiltration and duct testing procedures, particularly for specific building conditions. Important updates include: Clarified infiltration testing setup requirements for attics, crawlspaces, and basements. Additional instructions for handling mechanical openings during infiltration and duct testing. Clarified infiltration testing procedures for dwelling units adjacent to other dwelling units, including opening adjacent units to the exterior when possible. Untested Duct Systems Updated modeling guidance addresses circumstances in which duct systems are not tested. These provisions were previously introduced through Addendum C to ANSI/RESNET/ICC 301-2019. Although the changes primarily affect energy modeling, field verifiers should understand the criteria for applying these exceptions. They should also consider how omitting duct testing may affect the HERS Index and applicable program compliance requirements before determining whether an exception is appropriate for a particular project. The specific criteria and modeling assumptions for untested duct systems will be addressed in a future article. Changes to Energy Modeling and HERS Index Calculations HERS Raters and HERS Modelers will encounter new or revised software inputs corresponding to the field verification changes outlined above. While some updates primarily affect documentation requirements, others may influence calculated HERS Index scores. The extent of these impacts will vary depending on the characteristics of each home. A summary of the findings from RESNET’s initial Impact Analysis is available here. Additional findings from the broader follow-up Impact Study will be discussed in a future article. Preparing for the Transition Although many rating professionals may already be implementing portions of ANSI/RESNET/ICC 301-2022, the approaching mandatory compliance date provides an important opportunity to review existing practices and prepare for full implementation. HERS Raters, RFIs, and HERS Modelers should take the following steps to ensure they are prepared: Review field documentation procedures to ensure new minimum rated features and equipment characteristics are being captured. Become familiar with updated testing protocols, particularly requirements affecting infiltration, duct testing, and adjacent dwelling units. Review software inputs and modeling changes to understand how the updated standard affects their work. Evaluate representative projects to identify potential changes to HERS Index scores, particularly for homes with CFIS equipment, battery storage, or through-wall HVAC systems. Coordinate with Rating Quality Assurance Providers to address questions, update internal procedures, and identify any additional training needs. Conclusion The transition to ANSI/RESNET/ICC 301-2022 introduces important changes, although not every requirement will be new to every rating professional. Many provisions have already been incorporated into existing standards or are supported by accredited software currently in use. The successful transition will depend on understanding which changes affect field verification, documentation, and energy modeling practices, and making any necessary adjustments before the January 1, 2027, mandatory compliance date. By reviewing these requirements and preparing in advance , HERS Raters, RFIs, and HERS Modelers can minimize disruptions, maintain consistency in their rating practices, and ensure they are prepared to implement the updated standard. Article 1 in the ANSI/RESNET/ICC 301-2022 series
