HVAC Load Calc: Manual J

Whole-house heating and cooling load in seconds — Manual J block method, sensible and latent, straight to the tonnage. No spreadsheets.

Right-size any residential system in seconds. HVAC Load Calc runs a whole-house block load (the Manual J method) from a few envelope inputs — no spreadsheets, no guesswork.

ENTER THE HOUSE

• Floor area, ceiling height, and climate (built-in design temps for major US cities)
• Insulation presets for walls, ceiling, and floor — or your own U-values
• Window area and glazing type, air tightness, and occupants

GET THE LOAD

• Design HEATING load (BTU/h)
• Design COOLING load, split into SENSIBLE and LATENT (BTU/h)
• Recommended equipment TONNAGE, with a sanity check that flags oversizing

BUILT ON REAL PHYSICS

• Textbook ASHRAE heat transfer: envelope conduction, infiltration, solar and internal gains — the same basis as ACCA Manual J block load.
• Transparent assumptions you can adjust, not a black box.

Free to download and try. Pro unlocks unlimited calculations with a 7-day free trial, then renews yearly — cancel anytime in Settings.

Engineering reference only — a whole-house block load, not a substitute for a certified room-by-room Manual J or professional engineering judgment.

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