Duct fabrication is the custom construction of metal or fiberglass ductwork components to specifications for residential and commercial HVAC distribution systems. Fabrication includes cutting, bending, and joining sheet metal to create supply and return air paths sized for calculated airflow rates.
Materials and Processes
Galvanized steel typically 26-30 gauge thickness is standard for supply ducts. Return ducts often use 24 gauge. Fiberglass-lined or flex duct serves specific applications. Fabrication requires cutting sheet metal to specified dimensions using shears or plasma cutters, bending using brake machines to 90-degree angles, and joining edges using standing seams, rivets, or screws. Duct sizing follows ASHRAE guidelines, with 400-600 linear feet per minute (FPM) velocity standards to minimize noise and pressure drop.
Quality Standards
All seams must maintain zero-clearance joints preventing air leakage. Rectangular ducts require reinforcement straps every 4-6 feet. Circular ducts are spiral-lock or duct-lock type for strength. Fabricated ductwork must meet SMACNA (Sheet Metal and Air Conditioning Contractors’ National Association) standards for construction integrity. Proper fabrication ensures system efficiency within 5-10 percent of design specifications.