The problem
Single glazing leaks heat, lets in noise, and sweats with condensation.
A single pane of glass is a thin, conductive barrier. In winter it pulls the warmth straight out of the room, in summer it lets the heat in, and it carries outside noise almost unbroken. When warm indoor air meets that cold glass, it sweats, and the condensation runs down onto sills and frames. Heating and cooling the room harder just sends money out through the glass.