John V. Reints is a licensed professional engineer in Illinois who has been using VariTrane duct design software since 1983 for a long list of design-build HVAC systems, all featuring spiral ductwork optimized by static regain computerized calculations. More information is at www.staticregain.net.
In 1948, research by R.G. Huebscher established flow resistance for different shapes of ductwork at equal velocities, which allowed the creation of the duct-sizing calculator or “Ductulator” for picking equivalent sizes of rectangular ducts based on the baseline round duct size.
