What is the intermittent bathroom ventilation requirement with a switch in cubic feet per minute (CFM)?

The intermittent bathroom ventilation requirement is set at a minimum flow rate of 50 cubic feet per minute (CFM). This standard is established to ensure adequate air exchange and to effectively remove moisture, odors, and contaminants from the bathroom, thereby promoting a healthier indoor environment and reducing the risk of mold and mildew growth.

In bathrooms, which are typically smaller and more prone to humidity due to bathing activities, a higher ventilation rate helps quickly clear the space of excess moisture. A flow rate of 50 CFM is deemed appropriate for intermittent operation, meaning the ventilation fan can be manually operated via a switch as needed to control humidity levels during and after bathing activities.

In contrast, lower flow rates, such as the other options listed, may not sufficiently reduce humidity in the space, potentially leading to issues with air quality and structural integrity over time. Therefore, 50 CFM is recognized as the baseline requirement for effective ventilation in residential bathroom settings.