Old Grayton Beach cottages weren't built for central HVAC. Low ceiling lines, shallow attic clearance, crawl-space foundations, and original-growth timber framing make running ductwork either structurally invasive or practically impossible without gutting the house. Window units are the legacy answer. They work, but they're loud, inefficient, vulnerable to theft, and leave large penetrations in the building envelope that compromise both security and moisture control.
This property — a 1,050-square-foot cottage on Defuniak Street — had been running on three aging window units. The owner wanted whole-home cooling with zone control, no visible wall penetrations at eye level, and equipment that could handle the salt-air environment at the Gulf end of Grayton.
Why ductless was the right call
A ductless mini-split system consists of one outdoor condenser and one or more indoor air handlers connected by a refrigerant line set run through a small (typically 3") penetration in the exterior wall. No ductwork. No major framing modification. The line set is covered by a line-set cover on the exterior — paintable, low-profile, and far less visually disruptive than a window unit occupying a full window opening.
Zone control is built in: each indoor head has its own thermostat. In a cottage with a primary bedroom, a guest area, and a main living space, that means each zone runs only when occupied. The energy math is meaningfully better than a central system conditioning a whole house to one temperature all day.
Salt-air considerations
We spec'd equipment with a coastal-rated corrosion-resistant coating on the outdoor condenser fins. Standard aluminum fins in a Gulf-adjacent location show visible oxidation within two to three years; coated fins extend that timeline significantly. We positioned the outdoor unit on the north side of the cottage, shielded from direct Gulf spray by the structure itself to minimize direct salt-spray contact. The line set penetrations were sealed with an exterior-grade, paintable elastomeric caulk rated for coastal use.
The system installed
The installed system is a Mitsubishi MXZ-3C30NAHZ2 multi-zone outdoor condenser with three MSZ-FS12NA wall-mounted indoor heads — primary bedroom, guest room, and main living area. Rated at 20.5 SEER2. Walton County permit pulled before installation; inspection passed on first inspection.
Installation took two days. The three window units were removed and the openings patched and painted to match. The owner has zone-controlled cooling for the first time in the cottage's history.
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