The house was eight months old when the owner called. 3,400 square feet, new construction, Gulf views on two elevations. The AC ran nearly continuously in July and August, never quite reaching setpoint on the hottest days, and the humidity indoors sat uncomfortably high even when the temperature was close. The builder's response when the owner flagged it was: "It's a beach house. They're harder to cool."
That's not wrong, exactly. But it's also the answer a contractor gives when they don't want to look at their own work.
The diagnostic
We ran a Manual J load calculation — the ACCA-standard method for sizing residential HVAC equipment. Manual J accounts for the actual envelope: square footage, ceiling height, window area and orientation, insulation R-values, infiltration rate, internal heat gains, and local design temperatures. It is not a square-footage rule of thumb.
The calculation came back at 4.5 tons for the structure. The installed system was a 2.5-ton unit. That's a two-ton gap — roughly 44% of the required capacity. The system wasn't failing. It was doing everything it could do. It was simply not built for the house.
We also found the refrigerant charge 14% low — a common new-construction issue when the installing contractor doesn't verify charge with gauges after pulling vacuum. And two of the supply runs to the Gulf-facing rooms had visible duct leakage at the boot connections, confirmed with smoke pencil testing.
The correction
We replaced the system with a 4.5-ton Lennox XC20 variable-speed system, sealed the duct leakage at all boot connections with mastic, and re-balanced the register airflow for the corrected capacity. We pulled the Walton County permit. The new system was commissioned with full refrigerant charge verification, static pressure measurement at the air handler, and room-by-room airflow measurement against the Manual J targets.
The owner's first full summer on the corrected system: setpoint reached quickly even on the hottest days, indoor humidity consistently below 55%, and energy bills down roughly 27% from the previous two summers, per the owner's utility statements.
If you moved into a new Inlet Beach home and the AC has never felt right, it's worth a diagnostic before you spend another summer accepting it. The most common causes are an undersized system, a low refrigerant charge, or duct leakage — all findable and all fixable. Call us.