What is the primary advantage of a dual duct system?

• A. It reduces energy use by removing reheat.
• B. It uses only a single duct for all zones.
• C. It eliminates the need for outdoor air.
• D. It serves multiple spaces and allows for independent supply and return flows.

Answer: (D)

Dual-duct systems carry two separate supply airstreams—hot and cold—into the building, with zone dampers that blend these streams to satisfy each space’s temperature setpoint. The main advantage is the ability to serve multiple spaces with independently controlled supply conditions. Because each zone can receive a different mix of hot and cold air, you can accommodate varying loads and desired temperatures across zones without one zone’s settings affecting another. This level of per-zone control and flexibility is what sets dual-duct systems apart, whereas a single-duct approach can’t provide the same degree of independent zone conditioning.