Assess: Storm Windows
Storm windows fit into a window frame next to existing windows and provide extra insulation and protection against air leakage. Storm windows can be installed on the interior or exterior of a window and can be fixed or removable. Interior storm windows are easier to install and later remove for ventilation or cleaning. Storm windows with a low-E (emissivity) coating are more efficient. In cold climates, the coating enhances a window’s ability to trap heat inside. In hot climates, it helps to keep it out.
However, storm windows do not and should not completely close off leaks. Some air must escape to prevent moisture and humid air from being trapped between a storm window and regular window and to avoid condensation on interior surfaces. If you buy low-E storm windows, ensure that the low-E coating is moisture resistant.