MEP
Ductwork
The network of metal or flexible conduit used to distribute conditioned air from HVAC equipment throughout a building.
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In the Field
Sheet metal rectangular duct is used in main runs; flex duct connects to diffusers. Flex duct must not be kinked — bends greater than 45 degrees significantly increase resistance and reduce airflow. Support flex duct every 4 feet maximum with proper saddle supports, not wire.
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Rule of Thumb
Each 90-degree elbow in ductwork adds the equivalent of 10–15 feet of straight duct in friction loss. Design duct runs with as few elbows as possible to maintain system efficiency.