Mich. Admin. Code R. 408.30533 - [Effective 8/29/2025] Frost closure
Rule 533. Section P3103.2 of the code is amended to read as follows:
P3103.2. Frost closure. To
prevent frost closure, every vent extension through a roof shall be not less
than 3 inches, 76 millimeters, in diameter. Any increase in the size of the
vent shall be made inside the building with a minimum of 1 foot, 305
millimeters, below the roof or inside the wall.
Notes
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