Windows in South Carolina rot, fog, and seize for different reasons in the foothills and on the harbor. Salt air along the Lowcountry and the Strand pits balances and swells wood until the sash is painted shut. Inland sun and a long cooling season fog the insulated glass. An Upstate mill house may still have old wood units that leak winter air. A new subdivision window may only have a failed seal. Name the coast or the interior with the symptom.
Ask if you are buying an insert that leaves the old frame or a full-frame job that opens the wall. Soft sills from condensate and blown rain are common, and an insert on mush is a leak you kept. Full-frame work should say who flashes the opening and who repairs trim inside and out. Hurricane wind on the coast makes the installation the product. A pretty unit with a careless flange fails in the first hard blow. Ask who stands behind water at that joint.
Historic wood on a coastal street and vinyl on a sandhills ranch should not be sold with the same sentence. If the glass is original and wavy and you want it to stay, say that. If a storm racked the frame, glass-only will not square it. Ask for efficiency figures on the whole unit, and do not accept a comfort promise dressed up as a lab sticker. One bath window with a rotten sill is a small call. A wall of units facing the water is not.
Count the openings. Note fog between panes, hardware that has crusted, or a room that whistles when a storm comes off the water or across a piedmont field. Old flaking paint on a pre-war sash should be mentioned before anyone sands. A single cracked pane with a true frame can stay a glass repair. Say which you have so the call does not swell into a whole-house order you did not need.
Bring a count and the town. Windows in South Carolina are a salt problem, a sun problem, or both, and the first sentence should pick one. Call the number on this page.