Correct Installation of a Downdraft Ventilation

What is the length of the vent system?

• The length of vent system and number of elbows should be kept to a minimum to provide efficient performance. 
• The maximum equivalent length of the vent system is 60 ft (18.3 m). Refer to the Installation Instructions of your appliance for specific information.
• For altitudes above 4,500 ft (1372 m), reduce recommended vent run by 20% for best performance.

Was the correct vent material used?

• Use 26-gauge minimum galvanized or 25-gauge minimum aluminum metal vent.
• Poor quality pipe fittings can reduce airflow.
• Flexible metal vent is not recommended. 
• Metal duct may be reduced to 30-gauge galvanized steel or 26-gauge aluminized steel if allowed by local codes. This reduction is based on information in the International Residential Codes Section M1601.1 (2006 edition).

NOTE: Local codes may require a heavier gauge material.

How many elbows were used?  

• Use no more than three 90° elbows. 
• Do not install 2 elbows together.  Make sure there is a minimum of 18" (45.7 cm) of straight vent between the elbows if more than one elbow is used.
  • Elbows too close together can cause excess turbulence that  reduces airflow.
• If an elbow is used, install it as far away as possible from the hood’s vent motor exhaust opening.
• Do not use a 5" (12.7 cm) elbow in a 6" (15.2 cm) or 3¼" x 10" (8.3 x 25.4 cm) system.

Follow the instructions below for best performance:

• Do not reduce to a 5" (12.7 cm) system after using 6" (15.2 cm) or 3¼" x 10" (8.3 x 25.4 cm) fittings.
• Avoid forming handmade crimps. Handmade crimps may restrict airflow.
• Use a vent cap for proper performance. If an alternate wall or roof cap is used, be certain the cap size is not reduced and that it has a back draft damper.
• Use vent clamps to seal all joints in the vent system.
• Use caulking to seal exterior wall or roof opening around the cap.