C402.5 Air Leakage — Thermal Envelope
The continuous air barrier shall be constructed to comply with the following:
The completed building shall be tested and the air leakage rate of the building envelope shall not exceed 0.25 cfm/ft2 at a pressure differential of 0.3 inches water gauge (2.0 L/s × m2 at 75 Pa) at the upper 95 percent confidence interval in accordance with ASTM E779 or an equivalent method approved by the code official. A report that includes the tested surface area, floor area, air by volume, stories above grade, and leakage rates shall be submitted to the building owner and the code official. If the tested rate exceeds that defined here by up to 0.15 cfm/ft2, a visual inspection of the air barrier shall be conducted and any leaks noted shall be sealed to the extent practicable. An additional report identifying the corrective actions taken to seal air leaks shall be submitted to the building owner and the code official and any further requirement to meet the leakage air rate will be waived. If the tested rate exceeds 0.40 cfm/ft2, corrective actions must be made and the test completed again. A test above 0.40 cfm/ft2 will not be accepted.
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:
All 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. For the purposes of this section, "building entrances" shall include exit-only doors in buildings where separate doors for entering and exiting are provided.
Interior and exterior doors shall have a minimum distance between them of not less than 7 feet (2134 mm). The exterior envelope of conditioned vestibules shall comply with the requirements for a conditioned space. Either the interior or exterior envelope of unconditioned vestibules shall comply with the requirements for a conditioned space. The building lobby is not considered a vestibule.
Exception: Vestibules are not required for the following: