NGBS Interpretation: 2020 NGBS 701.4.3.3 Multifamily Air Leakage Alternative

Published Tuesday, June 9, 2026

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. 

Download the Detailed Interpretation