Residential Duct Design Handbook: Sizing, Static Pressure, Friction Rate, and Air Balancing Made Practical for HVAC Contractors, Technicians, and Homeowners

A duct size can be locally correct and still belong to a poor system. The same bedroom can be starved by an undersized branch, a blocked return path, a loaded filter, a restrictive coil, the wrong blower setting, a closed door, or leakage outside the boundary you thought you were testing. Changing the visible part before the whole path has been mapped is how good money gets spent on the wrong fix.

Most residential duct failures are not bad arithmetic. They are a skipped link. A trunk is sized from a guessed tonnage instead of a room load. A fan table is read at the wrong speed or pressure boundary. A filter or coil is counted twice, or not at all. Straight length is mistaken for effective length. Every branch is sized at the same airflow. Flex is selected stretched and installed compressed. The design looks complete while its evidence chain is broken.

The Residential Duct Design Handbook rebuilds that chain in eighteen chapters across five parts, from room load to commissioned system. It treats the duct system as one air circuit joined to a fan, coil, filter, terminals, rooms, and doors, and it shows how loads, exact equipment data, a pressure budget, complete supply and return paths, total effective length, a derived friction rate, section sizing, construction details, control states, and field measurements must all agree before a system is finished.

Inside, you will learn how to:

• Build a safe airflow and static-pressure diagnostic map on one page, separating the homeowner observation lane from qualified measurement work.
• Turn room loads into a reconciled airflow schedule, read blower tables at the right setting, and lock a design airflow the equipment can actually deliver.
• Calculate total external static pressure from signed readings, budget every component loss exactly once, and derive available static pressure without double subtraction.
• Measure developed paths, count fittings by actual geometry, find the critical path, and convert available pressure and effective length into a defensible friction rate instead of a universal rule of thumb.
• Size round, rectangular, flat-oval, and flexible duct at installed conditions, reduce trunk airflow after each takeoff, and check every terminal path against the budget.
• Design returns that work with closed doors, select grilles, registers, and diffusers from throw and sound data, and carry the design through zoning, variable-speed equipment, heat pumps, and ducted mini-splits in every operating state.
• Inspect rough-in by critical path, test leakage, measure airflow and pressure with stated uncertainty, balance proportionally, and hand over a package another qualified person can audit.

Fifty-five worked examples carry every calculation to a boxed answer. Ninety practice problems are solved in full. All 143 numbered equations are collected in one appendix with their variables, units, and boundaries. Ninety-one figures, more than one hundred tables, six project forms, duct sizing tables, a troubleshooting quick reference, and a subject index support work at the desk and in the crawl space. Four complete cases, a new home, an existing home, a zoned heat pump, and a noise complaint, show the method end to end.

Written for HVAC contractors, installers, service technicians, duct designers, commissioning and balancing providers, inspectors, apprentices, and technically engaged homeowners who want to know what qualified work should produce. The workflow follows United States residential practice in inch-pound units with SI equivalents, and an appendix maps units, terminology, and local pathways for Canada, the United Kingdom, Australia, and New Zealand.

Stop guessing at the trunk size and start proving the whole path.

Click the "Buy Now" button to get your copy and begin designing, diagnosing, and balancing residential duct systems.