CERTIFICATION AGENCY INTERPRETATION & GUIDANCE
Our NGBS Interpretations and Guidance documents provide clarifications on technical and verification issues related to NGBS Green certification
File Under: Chapter 3: Scope
The 2025 NGBS Scope and Administration allows for the certification of “Accessory Structures.” In the 2025 NGBS Definitions section, the Accessory Structure definition aligns with the ICC International Building Code (IBC) and the ICC International Residential Code (IRC), but also confers the Adopting Entity flexibility in what buildings are treated as accessory. The 2025 NGBS Appendix B sets out the Conformance Criteria for Accessory Structures and establishes authority for Accessory Structures to attain a conforming designation if compliant with NGBS criteria.
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File Under: Chapter 12: Certified Path for Single-Family Homes & Townhouses
Home Innovation has clarified that the Tropical Zone exemption in Practice 1205.7 applies to kitchens, bathrooms, and laundry areas—not solely bathrooms. While the exemption text references “bathroom floor area,” the intent of the Consensus Committee was to allow natural ventilation in any space covered by Practice 1205.7 when the openable window area is at least 14% of the floor area of the applicable room. Because kitchens, bathrooms, and laundry areas all generate moisture, particulates, and other indoor pollutants, a properly sized openable window may be used in lieu of a dedicated mechanical exhaust system in these spaces within the Tropical Zone Climate.
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File Under: Chapter 7: Energy Efficiency, Chapter 11: Existing Building
Home Innovation has determined that 2020 NGBS projects pursuing the Chapter 7 Prescriptive Path may use the alternative building envelope air leakage testing metrics and methodologies introduced in the 2021 IECC Sections R402.4.1.2 and R402.4.1.3. Specifically, dwelling units or homes 1,500 square feet or smaller may demonstrate compliance using a maximum leakage rate of 0.30 CFM50/ft² (1.5 L/s/m²) of enclosure area based on weighted-average unguarded compartmentalization testing, in lieu of the ACH50 limits required by the 2018 IECC. This interpretation recognizes that ACH50 disproportionately penalizes smaller, high-density housing due to their lower volume-to-envelope ratios, despite strong air sealing performance. By allowing the 2021 IECC testing option, the NGBS maintains rigorous energy performance expectations while providing a more equitable compliance pathway for small homes and multifamily dwelling units. This interpretation was originally effective October 27, 2023, and was revised on June 1, 2026.
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File Under: Chapter 7: Energy Efficiency, Chapter 11: Existing Building
Home Innovation has determined that I-1 occupancy buildings and accessory structures, such as standalone amenity buildings and clubhouses, are eligible to use the Multifamily Air Leakage Alternative under 2020 NGBS Sections 701.4.3.3 and 11.701.4.3.3 regardless of story count, provided they comply with the commercial provisions of the IECC. While the NGBS language references multifamily buildings four stories or more in height, the underlying intent of the alternative is to align with the IECC's exemption from building envelope leakage testing for buildings governed by the commercial code. Because I-1 occupancies and accessory structures are required to follow the commercial IECC regardless of height, they meet the basis for the alternative and may utilize it even when fewer than four stories tall.
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File Under: Chapter 9: Indoor Environmental Quality, Chapter 11: Existing Building
Home Innovation has determined that testing is not required to comply with Practices 902.2 or 11.902.2 when a project demonstrates compliance through the ventilation provisions of the 2021 International Residential Code (IRC). While the IRC contains ventilation testing requirements, those provisions are located within the Energy Conservation chapter rather than the Mechanical chapter referenced by the NGBS, creating ambiguity as to their applicability. Based on the development history of the 2025 NGBS, the structure of other NGBS practices that separately identify testing requirements, and the fact that ventilation testing is addressed elsewhere in the standard (e.g., Practice 902.2.2 for exhaust airflow testing), Home Innovation concluded that IRC ventilation testing was not intended to be a condition of compliance with Practices 902.2 or 11.902.2.
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File Under: Chapter 3: Scope
The 2025 National Green Building Standard (NGBS) introduced a property-level certification for existing multifamily and mixed-use buildings in Section 305.3. This option presents a streamlined process to certify an entire property rather than individual buildings.
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File Under: Chapter 12: Certified Path for Single-Family Homes & Townhouses
To ensure comparable energy performance across the available Ch 12 compliance options, a new lower ERI Target is required for the ERI Target compliance path. Any home pursuing this path must have an As Designed ERI value equal to or lower than the values included in this interpretation.
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File Under: Chapter 12: Certified Path for Single-Family Homes & Townhouses
This interpretation allows homes seeking 2025 NGBS certification following the Chapter 12 Certified Compliance Path for Single-Family Homes, Townhouses, and Duplexes to be deemed compliant with § 1203 ENERGY EFFICIENCY if the home meets the mandatory requirements listed in 1203.1 and qualifies as an ENERGY STAR Single-Family New Homes (Version 3.2 or later).[1] This interpretation is consistent with NGBS 701.1.5 Alternative Silver level compliance, which allows any building qualifying as an ENERGY STAR Version 3.2 Certified Home to achieve the Silver level and Home Innovation’s interpretation to accept later versions.
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File Under: Chapter 11: Existing Building, Chapter 13: Commercial Spaces
This interpretation clarifies that the 2025 NGBS allows a flexible, whole-building compliance approach for existing mixed-use buildings, resolving apparent conflicts between Chapter 11 (residential) and Chapter 13 (commercial). Projects may certify (1) the residential portion only, (2) residential and commercial spaces separately, or (3) the entire building under Chapter 11 using performance-based energy and water criteria. The whole-building pathway is especially appropriate when commercial tenant spaces are not being renovated, enabling certification based on overall building performance without requiring full commercial compliance under Chapter 13. This approach aligns with the NGBS’s intent to prioritize measurable energy and water reductions while accommodating real-world renovation constraints.
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File Under: Chapter 11: Existing Building
Practice 11.901.2.1 in the Existing Buildings chapter includes the same text as 901.2.1 in the Indoor Environmental Quality chapter for New Construction. Although point values are not included for 11.901.2.1, they are specified for 901.2.1. Home Innovation has determined that the omission of point values for 11.901.2.1 was an editorial error. The same point values were intended to apply.
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