A fundamental duct system design manual for commercial and light industrial heating, ventilating and air conditioning systems. System effects for inlets and outlets of fans, noise control in ducts and use of extractors, splinters and dampers are included. New loss coefficients for elbows with 45-degree throats on square and radius heels and radius throats with square heels. Losses compare favorably with elbows with double wall turning vanes in several cases. Structured to offer the designer options in energy-efficient design methods, materials and construction. Includes soft metrics.