What is the nominal size diameter of domestic clothes dryer exhaust ducts?

The nominal size diameter of domestic clothes dryer exhaust ducts is commonly standardized at 4 inches. This dimension has been adopted because it provides an optimal balance between facilitating adequate airflow for moisture and lint expulsion while minimizing the risk of overheating or blockage.

A 4-inch diameter duct helps to ensure that the dryer operates efficiently, as it allows for smooth passage of exhaust without excessive resistance. If the duct were smaller, it might lead to increased back pressure, causing the dryer to work harder, potentially leading to overheating and reducing its lifespan. Conversely, larger ducts may be unnecessary and cumbersome, which could complicate installation and require more space without significantly benefiting performance.

In residential settings, this standard 4-inch duct size has become the norm for most dryers, aligning well with manufacturers' specifications and building codes related to dryer venting systems.