Exhaust Duct Summary
Section & Summary
504.3.1 Moisture-Exhaust Ducts
Moisture-exhaust ducts for domestic clothes dryers shall terminate on the outside of the building and shall be equipped with a back-draft damper. Screens shall not be installed at the duct termination.
Ducts for exhausting clothes dryers shall not be connected or installed with sheet metal screws or other fasteners which will obstruct the flow.
Clothes-dryer moisture exhaust ducts shall not be connected to a gas vent connector, gas vent or chimney. Clothes-dryer moisture-exhaust ducts shall not extend into or through ducts or plenums.
504.3.2.1 Domestic Dryer Vent
Domestic clothes dryer moisture exhaust ducts shall be of metal and shall have smooth interior finish.
(Exception) Approved flexible duct connectors not more than 6 feet in length may be used in connection with the domestic dryer exhausts. Flexible duct connectors shall not be concealed within construction.
504.3.2.2 Length Limitation
Unless otherwise permitted or required by the dryer manufacturers installation instructions and approved by the building official, domestic dryer moisture exhaust ducts shall not exceed a total combined horizontal and vertical length of 14 feet, including two 90-degree elbows. Two feet shall be deducted for each 90-degree elbow in excess of two.
(Provided by Fantech)
Typical Airflow: 160 - l80 cfm
Duct Rectangular Velocity Static Pressure *Total Straight Duct
(Dia.) Duct Eqv. (fpm) (Inches per 100) (Horizontal + Vertical)
4 3 ½ x 4 +/- 1800 1.53 14 feet (per code)
5 3 ½ x 7 +/-1175 0.50 21.5 feet
6 3 ½ x 10 +/- 820 0.23 29 feet
7 3 ½ x 14 +/- 650 0.097 36.5 feet
* Includes (2) 90-degree elbows and a flex dryer connector less than 6-0
** Calculations based on 160 cfm of airflow.
Dryer Exhaust Duct Summary_CBC 2007.doc