When a duct system is not buried or encased, how far above the ground must it be installed?

When a duct system is not buried or encased, how far above the ground must it be installed?

• A. 2 inches
• B. 4 inches
• C. 6 inches
• D. 8 inches

Answer: (B)

The main idea is keeping exposed ductwork protected from ground moisture and damage. When ducts aren’t buried or encased, they should sit at least four inches above grade. This height helps prevent water, dirt, and splash from reaching joints, reduces the risk of corrosion and pest intrusion, and makes it easier to inspect and service the ductwork. A distance of two inches isn’t enough to shield the duct from moisture, while six or eight inches isn’t required and adds unnecessary cost.

The main idea is keeping exposed ductwork protected from ground moisture and damage. When ducts aren’t buried or encased, they should sit at least four inches above grade. This height helps prevent water, dirt, and splash from reaching joints, reduces the risk of corrosion and pest intrusion, and makes it easier to inspect and service the ductwork. A distance of two inches isn’t enough to shield the duct from moisture, while six or eight inches isn’t required and adds unnecessary cost.