CHANTILLY, Va. - The Sheet Metal and Air Conditioning Contractors' National Association (SMACNA) has announced that the fourth edition of theHVAC Systems – Duct Designmanual is available for public review. The manual presents the basic methods and procedures required to design HVAC air distribution systems.

With the growing emphasis on energy conservation, designers must balance duct size with the space allocated and duct system pressure loss, says SMACNA. HVAC Systems – Duct Design provides these guidelines. It contains the basic engineering guidelines for the sizing of HVAC ductwork systems, and also related information in the areas of materials, methods of construction, economics of duct systems, duct system layout, pressure losses, fan selection, duct leakage, acoustic considerations, duct heat transfer, as well as testing, adjusting, and balancing.

The manual is designed to offer both the HVAC system designer and installer detailed information on duct design, materials, and construction methods. Both U.S. and metric units are provided in examples, calculations, and tables.

Although most HVAC systems are constructed to pressure classifications between minus 3 inches water gage (wg) to 10 inches wg, [-750 to 2,500 Pascals (Pa)], the design methods, tables, charts, and equations provided in this text may be used to design other duct systems operating at higher pressures and temperatures. Air density correction factors for both higher altitudes and temperatures are included.

The complete document is available for public review until July 18, 2006 at in the "Technical Papers" section.

Reviewer's comments should reference page, figure, and table numbers, as well as specific paragraphs when dealing with text. All comments should include specific recommendations for improvement.

Send all comments to Peyton Collie, project manager, at SMACNA, 4201 Lafayette Center Drive, Chantilly, VA 20151-1209; fax 703-803-3732; or e-mail

Publication date: 05/08/2006