Supply ducts deliver conditioned air from the furnace or air handler to individual rooms and spaces throughout the building. They distribute heated or cooled air to maintain desired temperature and comfort levels. Proper sizing and sealing of supply ducts prevent energy loss and ensure adequate conditioning of all occupied spaces.
Design Specifications
Supply ducts must be sized based on airflow requirements, typically delivering 300 to 400 CFM per ton of cooling capacity. Duct diameter ranges from 4 inches for small branch runs to 12 to 24 inches for main supply trunks. Supply ducts operate at positive pressure, requiring proper insulation and sealing to prevent heat gain or loss.
Installation Standards
Supply ducts should be routed as directly as possible to minimize pressure drop and turbulence. All seams and connections must be sealed with duct mastic or metal tape to prevent air leakage. Ducts in unconditioned spaces require R-6 to R-8 insulation. Proper duct support, clearance from obstacles, and access for maintenance are essential installation requirements.