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Option 2. Building Envelope Performance
This option offers two paths for compliance. Path 1 is the prescriptive approach, where air leakage testing results do not exceed the established thresholds. Path 2 allows buildings to show a 25% reduction in air leakage from baseline testing.
Air leakage testing standards Testing should conform to one of the referenced standards:
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ASTM defines air leakage testing criteria. ASTM E779 uses the fan-pressurization method for testing, which is simpler than tracer gas measurements. [81] ASTM E3158 provides a standard method for testing large or multizone buildings. [82] ASTM E1827 determines air tightness using an orifice blower door. [83]
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Residential spaces may also apply ANSI/RESNET/ICC 380 .
PATH 1. LOW AIR LEAKAGE
Projects must conduct an air leakage test no more than eight years before the end of the 12month reporting period that shows the project’s air leakage rates do not exceed those in the Rating System Table 1.
PATH 2. REDUCED AIR LEAKAGE RATES
For older projects that implement measures to improve the project’s air barrier or projects whose initial testing did not result in prescriptively meeting the requirements of Path 1, Path 2 offers an approach for showing improvement over the initial, baseline test. This offers owners and facility managers an opportunity to improve the building envelope through repairs or alterations.
For this path, projects are required to perform two tests. The initial test creates the baseline leakage rates. The second test confirms that leakage rates have been reduced due to the envelope improvements. If the leakage rates decrease by a minimum of 25%, projects will achieve compliance with this credit.
Timing for testing Testing conducted within eight years of the end of the reporting period may be used for this path.
81 ASTM, “Standard Test Method for Determining Air Leakage Rate by Fan Pressurization,” January 23, 2019, www.astm.org/e0779-19.html. 82 ASTM, “Standard Test Method for Measuring the Air Leakage Rate of a Large or Multizone Building,” n.d., https://www.astm.org/e3158-18.html. 83 ASTM, “Standard Test Methods for Determining Airtightness of Buildings Using an Orifice Blower Door,” n.d., https://www.astm.org/e1827-11r17.html.
U.S. Green Building Council LEED v5 Reference Guide for Operations and Maintenance, April 2025 Launch Edition 179