Section SPS 322.39 - Ventilation and moisture control(1) GENERAL. Design and construction shall prevent deterioration from moisture condensation and ice damming.(2) VENTED ATTICS. (a)1. Except as allowed under subd. 6., where air-permeable ceiling or attic insulation is installed in a horizontal position, ventilation shall be provided above the insulation in accordance with this paragraph.2. At least 50% of the net free ventilating area shall be distributed at the high sides of the roof.3. The remainder of the net free ventilating area shall be distributed in the lower half of the roof or attic area.4. If more than 50%, but less than 75% of the net free ventilating area is provided at the high sides of the roof, the total net free ventilating area shall be a minimum of 1/300 of the horizontal area of the ceiling.5. If 75% or more of the net free ventilating area is provided at the upper sides of the roof, the total net free ventilating area shall be at least 1/150 of the horizontal area of the ceiling.6. Ventilation is not required for separated roof areas, such as dormers, bump-outs or bays that cover a floor area of 40 ft2 or less.(b) Engineered systems that provide equivalent ventilation to that required under this subsection may be used.(c) Insulation shall not block the free flow of air.(3) CONDITIONED ATTICS. Attic spaces are not required to be vented where air-impermeable insulation is attached directly to the underside of the roof deck and all of the following conditions are met: (a) No interior vapor retarders are installed between the living space and the conditioned attic.(b) The temperature in the attic space is maintained high enough to prevent any moisture condensation on the insulation. Note: Maintaining the interior surface temperature of the insulation at or above the dew point temperature of the interior air will minimize condensation. Maintaining at least 45°F on the surface of the insulation will minimize condensation on the surface when the interior air temperature is 70°F and the interior relative humidity is 45%.
(4) CATHEDRAL CEILINGS. Air-permeable insulation in a cathedral ceiling assembly shall fill the entire cavity space unless an air barrier separates the top of the insulation from the ventilation space.(5) MECHANICAL VENTILATION. Outdoor air intakes and exhausts shall have automatic or gravity dampers that close when the ventilation system is not operating.(6) CLOTHES DRYERS. Clothes dryers shall be vented to the outside of the structure.Wis. Admin. Code Department of Safety and Professional Services § SPS 322.39
CR 08-043: cr. Register March 2009 No. 639, eff. 4-1-09. See s. SPS 323.14 for vent material requirements.