Architecture
HVAC Load — Simplified Manual J
A quick BTU/h estimate for heating + cooling loads. This is NOT ACCA Manual J — it's a sizing-ballpark version. Get a real Manual J before buying equipment.
⚠ This is a simplified estimate, not Manual J
Real ACCA Manual J takes 30+ inputs (orientation, duct loss, infiltration, internal gains, occupant load). Use this for early concept sizing. Engage an HVAC engineer or use Wrightsoft / CoolCalc for permit-ready loads.
FAQ
What's a 'ton' of cooling? +
12,000 BTU/h. So a "3 ton" AC is 36,000 BTU/h. A 2,000 sf code-built house in zone 4 typically lands at 2.5-3 tons.
Why does 'oversized' equipment hurt? +
An AC that's too big cycles on/off rapidly without removing humidity. A furnace that's too big short-cycles and wastes fuel. Right-sizing is critical — bigger isn't better.
Why do most contractors oversize anyway? +
Lazy rules of thumb (1 ton per 500 sf) ignore envelope quality. A well-insulated house needs much less. Always demand a real Manual J calc.