Manual D

Metrics and Efficiency Ratings - HVAC Costs pillar

Also known as: duct sizing, Manual-D

ACCA Manual D: the duct-sizing methodology paired with Manual J. Determines duct dimensions and static pressure to deliver the calculated airflow to each room.

Manual D follows Manual J in the ACCA design sequence. Once heating and cooling loads are known, Manual D sizes the supply trunks, branches, and returns to deliver the required CFM at the correct external static pressure. Most retrofit Ontario installs skip Manual D and reuse existing ducts, which is the single largest cause of comfort complaints (uneven temperatures, noisy registers, blower-strain failures). A proper Manual D calculation is 1 to 2 hours of design work.

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