5.4.3.1 Continuous Air Barrier

The entire building envelope shall be designed and constructed with a continuous air barrier.

The continuous air barrier shall be designed and noted in the following manner:

1. All air barrier components of each building envelope assembly shall be clearly identified or otherwise noted on construction documents.
2. The joints, interconnections, and penetrations of the continuous air barrier components, including lighting fixtures, shall be detailed or otherwise noted.
3. The continuous air barrier shall extend over all surfaces of the building envelope (at the lowest floor, walls, and roof).
4. The continuous air barrier shall be designed to resist positive and negative pressures from wind, stack effect, and mechanical ventilation.

The following areas of the continuous air barrier in the building envelope shall be wrapped, sealed, caulked, gasketed, or taped in an approved manner to minimize air leakage:

1. Joints around fenestration and door frames (both manufactured and site-built).
2. Junctions between walls and floors, between walls at building comers, and between walls and roofs or ceilings.
3. Penetrations through the continuous air barrier in building envelope roofs, walls, and floors.
4. Building assemblies used as ducts or plenums.
5. Joints, seams, connections between planes, and other changes in continuous air barrier materials.

The building shall comply with whole-building pressurization testing in accordance with Section 5.4.3.1.3(a) or with the continuous air barrier requirements in Section 5.4.3.1.3(b) or 5.4.3.1.3(c).

1. Whole-building pressurization testing shall be conducted in accordance with ASTM E779 or ASTM E1827 by an independent third party. The measured air leakage rate of the building envelope shall not exceed 0.40 cfm/ft² under a pressure differential of 0.3 in. of water, with this air leakage rate normalized by the sum of the above and below-grade building envelope areas of the conditioned and semiheated space.

   Exceptions to 5.4.3.1.3(a)

   1. For buildings having over 50,000 ft² of gross conditioned floor area, air leakage testing shall be permitted to be conducted on less than the whole building, provided the following portions of the building are tested and their measured air leakage is area-weighted by the surface areas of the building envelope:
      1. The entire floor area of all stories that have any spaces directly under a roof.
      2. The entire floor area of all stories that have a building entrance or loading dock.
      3. Representative above-grade wall sections of the building totaling at least 25% of the wall area enclosing the remaining conditioned space; floor area tested per (a) and (b) shall not be included in the 25%.
   2. Where the measured air leakage rate exceeds 0.40 cfm/ft² but does not exceed 0.60 cfm/ft², a diagnostic evaluation, such as a smoke tracer or infrared imaging shall be conducted while the building is pressurized, and any leaks noted shall be sealed if such sealing can be made without destruction of existing building components. In addition, a visual inspection of the air barrier shall be conducted, and any leaks noted shall be sealed if such sealing can be made without destruction of existing building components. An additional report identifying the corrective actions taken to seal leaks shall be submitted to the code official and the building owner and shall be deemed to satisfy the requirements of this section.
2. Materials that have an air permeance not exceeding 0.004 cfm/ft² under a pressure differential of 0.3 in. of water (1.57 psf) when tested in accordance with ASTM E2178. The following materials meet these requirements:
   1. Plywood—minimum 3/8 in.
   2. Oriented strand board—minimum 3/8 in.
   3. Extruded polystyrene insulation board—minimum 1/2 in.
   4. Foil-faced urethane insulation board—minimum 1/2 in.
   5. Exterior gypsum sheathing or interior gypsum board—minimum 1/2 in.
   6. Cement board—minimum 1/2 in.
   7. Built-up roofing membrane
   8. Modified bituminous roof membrane
   9. Single-ply roof membrane
   10. A Portland cement/sand parge, stucco, or gypsum plaster—minimum 1/2 in. thick
   11. Cast-in-place and precast concrete
   12. Sheet metal
   13. Closed-cell 2 lb/ft³ nominal density spray polyurethane foam—minimum 1 in.
3. Assemblies of materials and components (sealants, tapes, etc.) that have an average air leakage not to exceed 0.04 cfm/ft² under a pressure differential of 0.3 in. of water (1.57 psf) when tested in accordance with ASTM E2357, ASTM E1677, ASTM E1680, or ASTM E283. The following assemblies meet these requirements:
   1. Concrete masonry walls that are
      1. fully grouted, or
      2. painted to fill the pores.