Manual D is the ACCA standard for residential duct design. It uses the results of the Manual J load calculation to size and lay out the ductwork that delivers conditioned air throughout the home.
Properly designed ductwork does two things: it delivers the right amount of air to each room, and it does so quietly and efficiently. Poorly designed ductwork — too small, too long, or poorly routed — leads to uneven temperatures, noisy registers, and systems that work harder than they should.
Manual D accounts for the available static pressure, the length and fittings in each duct run, and the airflow each room needs. The result is a duct system sized to the actual design, not improvised in the field.
For custom homes and remodels with complex layouts, good duct design is often what separates a comfortable home from a frustrating one.
Manual D duct design is part of our complete residential and custom home mechanical plan sets.