Flow Box

Proper bathroom ventilation is essential for controlling humidity, preventing mold growth, and maintaining good indoor air quality. Exhaust fans work by pulling air out of the bathroom and expelling it outside, with modern models offering features like humidity sensors and timers for improved efficiency. However, many existing fans are outdated, noisy, and ineffective. The ASHRAE 62.2 standard sets national guidelines for indoor air quality, including minimum exhaust fan flow rates. In Maine, building codes follow this standard, specifying a minimum flow rate of 50 CFM for bathroom fans. During energy audits, we use a flowbox (pictured here) to measure and verify that these standards are met.