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, as a revised industry standard.


The 30-day ANSI public review period will be from July 4, 2025, with a comment deadline of Aug. 3, 2025.

This is the 3rd public review for proposed revisions to Manual D – 2016, and only involves the addition of three missing pages that were inadvertently omitted from the two previous public review drafts. The missing pages in Section N4: Fitting Equivalent Lengths are unchanged from the 2016 edition.

Manual D provides requirements and calculations for sizing residential HVACR duct systems, including return and supply ducts and registers, to distribute the correct amount of heating and cooling to each room based on the ACCA Manual J load calculation results.

Below is a copy of the three missing pages. To share comments, fill out the form at the same link.

ACCA ANSI Public Response Form - Proposed Revisions to Manual D.