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Building Code Board of Appeals <br />Packet <br />May 12, 2025 <br />Page 6 of 64 <br />This reduces costs by clarifying this air -sealing <br />detail is only necessary between conditioned and <br />unconditioned space. (LECC) <br />[Clarification] [Cost reduction] <br />9. Table R402.5.1.1 Air Barrier, Air Sealing, and Insulation Installation is <br />amended by changing the text in the cell of the "Walls" row and the "Air <br />Barrier, Air Sealing Criteria" column as follows: <br />The junction of the foundation and sill plate shall be sealed. The junction <br />of the top plate and the top of exterior walls and interior walls that are <br />adiacent to or abut unconditioned space shall be sealed. Knee walls shall <br />be sealed. <br />This offers an alternative metric for measuring air <br />leakage. The original metric, air changes per <br />hour, is easier for large homes to meet and harder <br />for smaller homes to meet. (Note: these rates are <br />applicable to Climate Zone 5; see LECC for rates <br />for other Climate Zones.) (LECC) <br />[Flexibility] [Cost reduction] <br />10.Section R402.5.1.3 Maximum air leakage rate, item #1, is amended to <br />read as follows, with the rest of the section and exceptions to remain: <br />1. Where complying with Section R401.2.1, the building or the <br />dwelling units or sleeping units in the building shall have an air <br />leakage rate not greater than 3.0 air changes per hour, or 0.17 <br />cubic feet per minute per square foot 10.86 L/(s x m2)1 of the <br />building thermal envelope area or the dwelling testing unit <br />enclosure area. <br />