Screening sheet · not Manual J

Size the room, then the duct.

Planning numbers only. Not a Manual J or Manual D permit calculation.

Input values to calculate

Floor area, square feet

Ceiling height, feetPeople in the room

IECC climate zoneInsulationGlassSunAdd a 4,000 BTU/h kitchen allowance

Cooling temperature difference, °FCFM override, blank uses the load

Design friction, in. w.g. per 100 ftWhere this duct runsMax rectangular aspect ratio

Cooling

6,800

0.57 tons · suggested 1.0 tons

Supply air

315

CFM at 20°F

Round duct

10 in

578 fpm · 0.058 in. w.g./100 ft · rectangle 10 × 8 in

Velocity is inside the limit used for this run type.

You enter the room: floor area, ceiling height, climate zone, insulation, glass, sun, and how many people.
The sheet screens a cooling number from those choices. It is a planning number, not a full room-by-room load.
It turns that cooling number into supply air. Airflow is the cooling load divided by 1.08 times the temperature difference you set.
It sizes a round duct for that air at the friction rate you set, then a rectangle that moves the same air.
If the air is moving too fast for that kind of run, the note tells you to go up one size.