Field tools · Calculator

Manual J Load Calculator

Punch in the structure, envelope, climate, occupants, and infiltration. ChillFlow resolves a heating + cooling load in BTU/hr and a ballpark equipment size — furnace or heat pump stage in kBtu/hr, cooling in tons with a ±0.5-ton band.

Mixed-humid

ACCA ballpark · first pass

Punch in the envelope and climate. ChillFlow returns a heating + cooling load in BTU/hr and a ballpark equipment size. Share-by-URL: every input you change is encoded into the link, so a coworker opens it with the exact same view.

Structure

Conditioned area (sqft)

step ±100

Ceiling height (ft)

step ±0.5

Total window area (sqft)

step ±20

Envelope

Wall insulation

Ceiling insulation

Floor insulation

Window pane

Climate

Hot-humid

High latent load · favor larger blower / dehumidification.

Heat: 35°F · Cool: 95°F

Hot-dry

Sensible-dominant cooling · wide indoor/outdoor delta.

Heat: 25°F · Cool: 105°F

Mixed-humid

Both heating and cooling loads are meaningful.

Heat: 22°F · Cool: 92°F

Mixed-dry

Lower humidity · SHGC on west glass dominates cooling.

Heat: 15°F · Cool: 90°F

Cold

Heating-dominant · verify slab-edge heat loss.

Heat: 5°F · Cool: 88°F

Very-cold

Heating-dominant · design for sub-zero envelope load.

Heat: -10°F · Cool: 85°F

Marine

Mild year-round · verify latent load during shoulder seasons.

Heat: 28°F · Cool: 80°F

Heating design (override, optional) (°F)

step ±5

Cooling design (override, optional) (°F)

step ±5

Leave overrides blank to use the pre-baked climate defaults.

Loads

Occupants (people)

step ±1

Infiltration (ach)

step ±0.1 ACH

Heating load

31190BTU/hr

30 kBtu/hr nominal · band 25–35 kBtu/hr.

Walls: 7689 · Ceiling: 4320
Floor: 11782 · Windows: 3888
Infiltration: 6912 · Internal gains subtracted: 3400
Delta-T (heat): 48 °F

Cooling load

22368BTU/hr

2.0 tons nominal · band 1.5–2.5 tons. Sensible + latent combined.

Walls: 2610 · Ceiling (×1.4): 2053
Floor (×0.4): 1600 · Windows +SHGC: 2400
Infiltration (sens+lat, ×3): 9504
Occupants + appliance: 4200
Delta-T (cool): 22 °F

This is a first-pass ACCA-bent estimate — not a substitute for full ACCA Manual J software or an engineer's room-by-room load calc. Use it for the pre-quote walk-around and the disconnect-side sanity check, then verify against the OEM design specs before final equipment selection.