Can improved window insulation prevent condensation on the interior of a window
If this is a single pane window growing to a double or triple pane window will help. To prove thus to yourself put a flash of ice water in the room and a glass of warm water, some may say Duh but a single pane window is the same as the ice water double or triple pane is similar to warm water. A dehumidifier in that room would also reduce the moisture, or things like a vent fan in the bathroom if it doesent have one it will really help. Not sure why the contractor would not think better windows would help unless you already have double pane.