NORMATIVE APPENDIX B—
PRESCRIPTIVE CONTINUOUS AIR BARRIER
(This is a normative appendix and is part of this standard.)
The continuous air barrier shall have the following characteristics:
a. It shall be continuous throughout the envelope (at the lowest floor, exterior walls, and ceiling or roof), with all joints and seams sealed and with sealed connections between all transitions in planes and changes in materials and at all penetrations.
b. The air barrier component of each assembly shall be joined and sealed in a flexible manner to the air barrier component of adjacent assemblies, allowing for the relative movement of these assemblies and components.
c. It shall be capable of withstanding positive and negative combined design wind, fan, and stack pressures on the air barrier without damage or displacement, and shall transfer the load to the structure. It shall not displace adjacent materials under full load.
d. It shall be installed in accordance with the manufacturer’s instructions and in such a manner as to achieve the performance requirements.
e. Where lighting fixtures with ventilation holes or other similar objects are to be installed in such a way as to penetrate the continuous air barrier, provisions shall be made to maintain the integrity of the continuous air barrier.
Exception: Buildings that comply with (c) below are not required to comply with either (a) or (e) above.
Compliance of the continuous air barrier for the opaque building envelope shall be demonstrated by one of the following:
a. Materials. Using individual materials that have an air permeability not to exceed 0.004 cfm/ft2 under a pressure differential of 0.3 in. water (1.57 lb/ft2) (0.02 L/s·m2 under a pressure differential of 75 Pa) when tested in accordance with ASTM E2178. These materials comply with this requirement when all joints are sealed and the above section on characteristics are met:
1. Plywood—minimum 3/8 in. (10 mm)
2. Oriented strand board—minimum 3/8 in. (10 mm)
3. Extruded polystyrene insulation board—minimum 3/4 in. (19 mm)
4. Foil-back urethane insulation board—minimum 3/4 in. (19 mm)
5. Exterior or interior gypsum board—minimum 1/2 in. (12 mm)
6. Cement board—minimum 1/2 in. (12 mm)
7. Built up roofing membrane
8. Modified bituminous roof membrane
9. Fully adhered single-ply roof membrane
10. A Portland cement/sand parge, or gypsum plaster minimum 5/8 in. (16 mm) thick
11. Cast-in-place and precast concrete
12. Fully grouted concrete block masonry
13. Sheet steel
b. Assemblies. Using assemblies of materials and components that have an average air leakage not to exceed 0.04 cfm/ft2 under a pressure differential of 0.3 in. water (1.57 lb/ft2) (0.2 L/s•m2 under a pressure differential of 75 Pa) when tested in accordance with ASTM E2357 or ASTM E1677. These assemblies comply with this requirement when all joints are sealed and the above section on characteristics are met:
1. Concrete masonry walls coated with:
a. one application of block filler and two applications of a paint or sealer coating, or
b. a Portland cement/sand parge, stucco or plaster minimum 1/2 in. (12 mm) thick.
c. Building. Testing the completed building and demonstrating that the air leakage rate of the building envelope does not exceed 0.4 cfm/ft2under a pressure differential of 0.3 in. water (1.57 lb/ft2) (2.0 L/s•m2under a pressure differential of 75 Pa) in accordance with ASTM E779 or an equivalent approved method.