Windows in Charleston are eaten by salt and swollen by humidity. Hardware pits, balances stick, and wood sashes on the peninsula paint themselves shut. Fog between panes is the cooling season plus wet air, on James Island just as in a Summerville ranch. Wind-driven rain finds a joint that looked fine in a still July. Historic openings with wavy glass are a different respect than a builder window in a newer subdivision. A freeze almost never decides this job. The Atlantic does.
Ask whether the work is an insert into the existing frame or a full-frame replacement that opens the wall. Soft sills are ordinary here. An insert on a mush sill keeps the rot and adds a new unit. Full-frame work should expose how the water will leave the opening, who flashes it, and who repairs interior trim and exterior skin. On a house that faces a big wind off the harbor or the marsh, the flange and the fastening are the product. Ask who returns if water enters beside the unit rather than through the glass.
If you want old wood to remain, say so before the conversation becomes a whole-house tear-out. If a storm racked a frame, a pane swap will not square it. One rotten bath window is a small scope. A piazza wall of openings is not. Ask for efficiency figures on the entire unit, and refuse a comfort fable hung on a sticker. Salt will attack uncoated metal. Mention that you are on the coast so the hardware choice matches the air, not a catalog written for a dry inland yard.
Count the units and name rooms. Note crusted locks, sash cords that have failed, or a sill that flakes when you touch it. Old paint on a pre-war window should be named before sanding starts. A single cracked lite with a true frame can stay glass-only. Say that clearly. Street flooding does not by itself mean the upstairs sash failed, but wind-driven rain during the same storm might. Separate those facts.
Bring the count and say peninsula, island, Mount Pleasant, or Summerville. Windows in Charleston fail from salt and sideways rain more than from cold. Call the number on this page.