ARLINGTON, Va. - The Air Conditioning Contractors of America (ACCA) has released a revised and updated version ofManual D - Residential Duct Systems. The book is the industry standard for residential HVAC duct design.

The new version ofManual Dmaintains the popular and accurate procedure of the original manual, but has been enhanced with a number of improvements, including:

• New equivalent length values for flex duct junction boxes.

• Updated guidance, with examples, for variable air volume (VAV).

• Impacts of excess length, sag, and compression in flexible ducts.

Authored by Hank Rutkowski with the oversight of a committee made up of professionals from different sectors of the HVACR industry, the updatedManual Dwas approved as the national standard for residential duct design by the American National Standards Institute (ANSI) on Jan. 22, 2009.

TheManual Dprinciples and calculations can be applied to constant volume systems and zoned variable air volume systems, over a full range of modern construction materials.

Manual Dmay be purchased online (go to ACCA’s online store at and look in “Technical Manuals, Standards & References”) or by calling 888-290-2220.

Publication date:02/16/2009