Mistakes
ExpensiveMistake 05 of 7
Letting the HVAC be sized by rule of thumb
Bigger equipment is not better comfort — it is short cycles and sticky air.
Very hard to spot aloneDifficulty to spot: 5 of 5
Why it happens
- Sizing by square footage is fast and rarely questioned.
- The buyer sees tonnage, never the load calculation behind it.
Warning signs
- No Manual J load calculation exists for your plan.
- The same tonnage is quoted regardless of orientation or envelope options.
- Humidity control is never discussed.
Questions to ask
- May I see the load calculation for my plan and orientation?
- Was my envelope upgrade included in the sizing?
- How is humidity handled in shoulder seasons?
Cost if ignored
$600–$1,500 a year, plus early equipment wear
Oversized systems cool fast, stop, and leave humidity behind — the room feels worse.
Try it
You upgraded insulation and air sealing. The HVAC quote did not change.
What does that most likely mean?