ACCA's Updated Manual D®, Residential Duct Systems, Out for ANSI Public Review

Alexandria, VA (February 23, 2024) – The Air Conditioning Contractors of America Educational Institute (ACCA-EI) Standards Task Team (STT) announces an American National Standards Institute (ANSI) public review period for proposed revisions to ANSI/ACCA 1 Manual D® – 2016, Residential Duct Systems. The 45-day public review period starts on February 23 with a comment period deadline of April 8. 

The proposed revisions are to the four “Normative Sections” of Manual D® which contain the minimum requirements for conducting a residential duct system design. Revisions include:

  • N1: General Requirements and Definitions
  • N2: Manual D Procedure
  • N3: Maximum Air Velocity and Transfer Air Tables
  • N4: Fitting Equivalent Lengths

Manual D® uses heating and cooling loads to determine space air delivery requirements for residential applications. The Manual D® procedures match duct system resistance (pressure drop) to blower performance (as defined by the manufacturer’s blower performance tables). This delivers appropriate airflow to the rooms and spaces while ensuring that system airflow is compatible with the operating range of the HVAC equipment. The capabilities and sensitivities of the Manual D® procedures are compatible with single-zone and multi-zone systems. The primary equipment may feature single-, multi-, or variable-speed blowers.

Manual D® is also referenced by the ICC International Residential Code (IRC) and IAPMO Uniform Mechanical Code (UMC).

Comments, along with a copy of the proposed Normative Sections can be obtained by contacting David Bixby, ACCA manager of codes and standards, at

For more information, please contact Kate Wessels, ACCA vice president of communications, marketing, and partnerships at or 703-824-8864.