This technical paper reviews the HVAC Duct Construction Standards, 2nd edition, 1995, specifications and requirements for zinc coating on galvanized steel ducts. Paragraph and page references from the HVAC-DCS manual are provided along with the text. Commentary in the form of italicized text has been added to clarify the meaning, scope or intent of the manual. In addition, the paper reviews zinc coating thickness variations, as commonly used in trade practice, for sheet, reinforcements, tie rods and fasteners.
Also included in the paper are the burdensome effects of imposing a universal requirement of G-60 and/or G-90 coating for all components. The paper lists the factors to be considered for Rectangular, Round and Oval ductwork, hangers, and service life forecasts. Wide distribution of this technical paper in the construction community is encouraged.