HVAC Load Calc: Manual J

Saved jobs and a one-page PDF report, so you can hand the customer the numbers instead of a screenshot. Subscription required, free trial.

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.

Every subscription starts with a free trial. After the trial, HVAC Load Calc requires a subscription, and everything described below is a subscriber-only feature.

ENTER THE HOUSE

• Floor area, ceiling height, and stories
• Climate from the site ZIP code: it picks the nearest weather station, anywhere in the US. Search by town instead, or enter your own design temperatures.
• 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

KEEP THE JOB

• Save a calculation under the job name and reopen it later with every input intact
• The list shows each job's loads and tonnage, so you can find one without opening it
• Everything stays on the device. There is no account to create.

HAND OVER A REPORT

• A one-page PDF: design loads, equipment size, and every input behind them
• Look at the page before you send it, then share it like any other file

ON IPAD

• The form and the report sit side by side and update as you work

WHERE THE NUMBERS COME FROM

• Textbook ASHRAE heat transfer: envelope conduction, infiltration, solar and internal gains. This is the same basis as the ACCA Manual J block load.
• Design temperatures from the ASHRAE tables, and from fifteen years of hourly NOAA records everywhere else.
• Every assumption is on screen and you can change it.

Cancel anytime in Settings.

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

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