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C402.5 Air Leakage—Thermal Envelope (Mandatory)
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The thermal envelope of buildings shall comply with Sections C402.5.1 through C402.5.8, or the building thermal envelope shall be tested in accordance with ASTM E 779 at a pressure differential of 0.3 inch water gauge (75 Pa) or an equivalent method approved by the code official and deemed to comply with the provisions of this section when the tested air leakage rate of the building thermal envelope is not greater than 0.40 cfm/ft2 (2.0 L/s • m2). Where compliance is based on such testing, the building shall also comply with Sections C402.5.5, C402.5.6 and C402.5.7.
A continuous air barrier shall be provided throughout the building thermal envelope. The air barriers shall be permitted to be located on the inside or outside of the building envelope, located within the assemblies composing the envelope, or any combination thereof. The air barrier shall comply with Sections C402.5.1.1 and C402.5.1.2.
Exception: Air barriers are not required in buildings located in Climate Zone 2B.
The continuous air barrier shall be constructed to comply with the following:
- The air barrier shall be continuous for all assemblies that are the thermal envelope of the building and across the joints and assemblies.
- Air barrier joints and seams shall be sealed, including sealing transitions in places and changes in materials. The joints and seals shall be securely installed in or on the joint for its entire length so as not to dislodge, loosen or otherwise impair its ability to resist positive and negative pressure from wind, stack effect and mechanical ventilation.
- Penetrations of the air barrier shall be caulked, gasketed or otherwise sealed in a manner compatible with the construction materials and location. Sealing shall allow for expansion, contraction and mechanical vibration. Joints and seams associated with penetrations shall be sealed in the same manner or taped. Sealing materials shall be securely installed around the penetration so as not to dislodge, loosen or otherwise impair the penetrations' ability to resist positive and negative pressure from wind, stack effect and mechanical ventilation. Sealing of concealed fire sprinklers, where required, shall be in a manner that is recommended by the manufacturer. Caulking or other adhesive sealants shall not be used to fill voids between fire sprinkler cover plates and walls or ceilings.
- Recessed lighting fixtures shall comply with Section C402.5.8. Where similar objects are installed that penetrate the air barrier, provisions shall be made to maintain the integrity of the air barrier.
A continuous air barrier for the opaque building envelope shall comply with Section C402.5.1.2.1 or C402.5.1.2.2.
Materials with an air permeability not greater than 0.004 cfm/ft2 (0.02 L/s • m2) under a pressure differential of 0.3 inch water gauge (75 Pa) when tested in accordance with ASTM E2178 shall comply with this section. Materials in Items 1 through 16 shall be deemed to comply with this section, provided that joints are sealed and materials are installed as air barriers in accordance with the manufacturer's instructions.
- Plywood with a thickness of not less than 3/8 inch (10 mm).
- Oriented strand board having a thickness of not less than 3/8 inch (10 mm).
- Extruded polystyrene insulation board having a thickness of not less than 1/2 inch (12.7 mm).
- Foil-back polyisocyanurate insulation board having a thickness of not less than 1/2 inch (12.7 mm).
- Closed-cell spray foam having a minimum density of 1.5 pcf (2.4 kg/m3) and having a thickness of not less than 11/2 inches (38 mm).
- Open-cell spray foam with a density between 0.4 and 1.5 pcf (0.6 and 2.4 kg/m3) and having a thickness of not less than 4.5 inches (113 mm).
- Exterior or interior gypsum board having a thickness of not less than 1/2 inch (12.7 mm).
- Cement board having a thickness of not less than 1/2 inch (12.7 mm).
- Built-up roofing membrane.
- Modified bituminous roof membrane.
- Fully adhered single-ply roof membrane.
- A Portland cement/sand parge, or gypsum plaster having a thickness of not less than 5/8 inch (15.9 mm).
- Cast-in-place and precast concrete.
- Fully grouted concrete block masonry.
- Sheet steel or aluminum.
- Solid or hollow masonry constructed of clay or shale masonry units.
Assemblies of materials and components with an average air leakage not greater than 0.04 cfm/ft2 (0.2 L/s • m2) under a pressure differential of 0.3 inch of water gauge (w.g.)(75 Pa) when tested in accordance with ASTM E2357, ASTM E1677 or ASTM E283 shall comply with this section. Assemblies listed in Items 1 through 3 shall be deemed to comply, provided that joints are sealed and the requirements of Section C402.5.1.1 are met.
- Concrete masonry walls coated with either one application of block filler or two applications of a paint or sealer coating.
- Masonry walls constructed of clay or shale masonry units with a nominal width of 4 inches (102 mm) or more.
- A Portland cement/sand parge, stucco or plaster not less than 1/2 inch (12.7 mm) in thickness.
The air leakage of fenestration assemblies shall meet the provisions of Table C402.5.2. Testing shall be in accordance with the applicable reference test standard in Table C402.5.2 by an accredited, independent testing laboratory and labeled by the manufacturer.
Exceptions:
- Field-fabricated fenestration assemblies that are sealed in accordance with Section C402.5.1.
- Fenestration in buildings that comply with the testing alternative of Section C402.5 are not required to meet the air leakage requirements in Table C402.5.2.
MAXIMUM AIR LEAKAGE RATE FOR FENESTRATION ASSEMBLIES
| FENESTRATION ASSEMBLY | MAXIMUM RATE (CFM/FT2) | TEST PROCEDURE |
| Windows | 0.20 a | AAMA/WDMA/CSA101/I.S.2/A440 or NFRC 400 |
| Sliding doors | 0.20 a | |
| Swinging doors | 0.20 a | |
| Skylights — with condensation weepage openings | 0.30 | |
| Skylights — all other | 0.20 a | |
| Curtain walls | 0.06 | NFRC 400 or ASTM E283 at 1.57 psf (75 Pa) |
| Storefront glazing | 0.06 | |
| Commercial glazed swinging entrance doors | 1.00 | |
| Power-operated sliding doors and power-operated folding doors | 1.00 | |
| Revolving doors | 1.00 | |
| Garage doors | 0.40 | ANSI/DASMA 105, NFRC 400, or ASTM E283 at 1.57 psf (75 Pa) |
| Rolling doors | 1.00 | |
| High-speed doors | 1.30 |
For SI: 1 cubic foot per minute = 0.47 L/s, 1 square foot = 0.093 m2.
- The maximum rate for windows, sliding and swinging doors, and skylights is permitted to be 0.3 cfm per square foot of fenestration or door area when tested in accordance with AAMA/WDMA/CSA101/I.S.2/A440 at 6.24 psf (300 Pa).
In Climate Zones 3 through 8, where combustion air is supplied through openings in an exterior wall to a room or space containing a space-conditioning fuel-burning appliance, one of the following shall apply:
- The room or space containing the appliance shall be located outside of the building thermal envelope.
- The room or space containing the appliance shall be enclosed and isolated from conditioned spaces inside the building thermal envelope. Such rooms shall comply with all of the following:
- 2.1. The walls, floors and ceilings that separate the enclosed room or space from conditioned spaces shall be insulated to be not less than equivalent to the insulation requirement of below-grade walls as specified in Table C402.1.3 or C402.1.4.
- 2.2. The walls, floors and ceilings that separate the enclosed room or space from conditioned spaces shall be sealed in accordance with Section C402.5.1.1.
- 2.3. The doors into the enclosed room or space shall be shall be fully gasketed.
- 2.4. Water lines and ducts in the enclosed room or space shall be insulated in accordance with Section C403.
- 2.5. Where an air duct supplying combustion air to the enclosed room or space passes through conditioned space, the duct shall be insulated to an R-value of not less than R-8.
Exception: Fireplaces and stoves complying with Sections 901 through 905 of the International Mechanical Code, and Section 2111.14 of the International Building Code.
Doors and access openings from conditioned space to shafts, chutes stairways and elevator lobbies not within the scope of the fenestration assemblies covered by Section C402.5.2 shall be gasketed, weatherstripped or sealed.
Exceptions:
- Door openings required to comply with Section 716 of the International Building Code.
- Doors and door openings required to comply with UL 1784 by the International Building Code.
Stairway enclosures, elevator shaft vents and other outdoor air intakes and exhaust openings integral to the building envelope shall be provided with dampers in accordance with Section C403.7.7.
Cargo door openings and loading door openings shall be equipped with weatherseals that restrict infiltration and provide direct contact along the top and sides of vehicles that are parked in the doorway.
Building entrances shall be protected with an enclosed vestibule, with all doors opening into and out of the vestibule equipped with self-closing devices. Vestibules shall be designed so that in passing through the vestibule it is not necessary for the interior and exterior doors to open at the same time. The installation of one or more revolving doors in the building entrance shall not eliminate the requirement that a vestibule be provided on any doors adjacent to revolving doors.
Exceptions: Vestibules are not required for the following:
- Buildings in Climate Zones 1 and 2.
- Doors not intended to be used by the public, such as doors to mechanical or electrical equipment rooms, or intended solely for employee use.
- Doors opening directly from a sleeping unit or dwelling unit.
- Doors that open directly from a space less than 3,000 square feet (298 m2) in area.
- Revolving doors.
- Doors used primarily to facilitate vehicular movement or material handling and adjacent personnel doors.
- Doors that have an air curtain with a velocity of not less than 6.56 feet per second (2 m/s) at the floor that have been tested in accordance with ANSI/AMCA 220 and installed in accordance with the manufacturer's instructions. Manual or automatic controls shall be provided that will operate the air curtain with the opening and closing of the door. Air curtains and their controls shall comply with Section C408.2.3.
Recessed luminaires installed in the building thermal envelope shall be all of the following:
- IC-rated.
- Labeled as having an air leakage rate of not more 2.0 cfm (0.944 L/s) when tested in accordance with ASTM E283 at a 1.57 psf (75 Pa) pressure differential.
- Sealed with a gasket or caulk between the housing and interior wall or ceiling covering.
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