What is the minimum nominal diameter required for a clothes dryer exhaust duct?

The minimum nominal diameter required for a clothes dryer exhaust duct is 4 inches. This specification is outlined in the mechanical codes to ensure adequate airflow and effective venting of moist air, lint, and other byproducts produced during the drying process. A 4-inch diameter duct strikes a balance between ensuring efficient exhaust flow and minimizing the risk of clogs or insufficient ventilation.

Using a smaller diameter duct could lead to reduced airflow, increasing the risk of dryer malfunction or fire hazards due to lint accumulation. Larger diameters, while they could theoretically allow for better airflow, may not be practical or necessary for standard residential dryers, which are designed to operate efficiently with a 4-inch exhaust duct. Following this standard helps maintain the safety and performance of the dryer while promoting good installation practices.