M1501.1

Section M1501.1 is titled 'Outdoor discharge' and covers requirements for mechanical systems. The location for exhaust systems to be discharged is established. The purpose of this section is to prevent interior air contamination and excessive moisture which can prematurely degrade wood-based products and facilitate mold growth. This section has an exception which allows for whole-house ventilation-type attic fans to discharge into private attics. The purpose for this exception is to allow for air which is less likely to be contaminated or high in moisture content to be moved to the attic through a centralized exhaust fan specifically intended for interior air-comfort purposes.

The model shows a bathroom fan which is alternating between being compliantly exhausted to the exterior and non-compliantly exhausted into the attic.