Repairing or replacing a broken window pane is usually not very costly on an individual basis, unless the window is one of unusual design or a large thermal pane with double or triple glazing.
During a windows inspection, check all windows for cracked and broken panes that require replacement. If the window is covered by a storm pane, BB holes or small cracks in the corner of a pane may be overlooked. If the putty around the pane is cracked, dry, chipped or missing, the window joints should be re-puttied. Check the window frames and exterior sills for any cracked and rotten sections. If the windows have metal frames, check for peeling or flaking paint or disintegrating sections of plaster near the window frame.
When conducting a windows inspection, pay particular attention to steel casement windows, because they are usually a problem. Steel casement windows rust easily and must be painted every few years to prevent deterioration. In addition, they often do not close properly, a problem generally caused by a sprung frame or excessive layers of paint around the joints. Moreover, almost invariably you will find cracked panes. Casement windows are usually crank-operated, so check the hardware as well to make sure the cranking mechanism is operational.
Open and close all windows to make sure they operate relatively easily, without sticking or binding. Double-hung windows should not rattle in the channel, but stay in a fixed position when opened partially or fully. When it comes to older double-hung windows, most of them use a counterweight to hold the sash in a fixed open position. The weight is usually tied to a sash by a cord or a chain, so you should also check the cord and make sure it is not broken. Broken cords are relatively common and should be replaced. If the cord is frayed, replace it before it breaks.
When inspecting the windows, check to see whether the glazing is a single pane or a thermal pane, i.e. two pieces of glass separated by a sealed air space. You can determine the type by looking at the thickness of the joint between the pane and the frame. A single pane will be no more than 3/16-inch thick, while a thermal pane is usually about ⅜ to one inch thick. You can also tell by looking very closely at the pane. Dust or dirty spots on the opposite side may reveal the thickness of the pane.
In some cases, fixed-pane windows and sliding glass doors have thermal panes, although the windows that can be opened throughout the house have only a single pane. Thermopane, commonly referred to as insulating glazing, is a popular type of thermal glass. Each manufacturer has its own term for it, but you can usually find the manufacturer’s name in the corner of the window pane.
Such thermal-pane windows are manufactured by hermetically sealing dry air on an inert gas between the panes, in order to eliminate the possibility of future condensation problems between the panes. If the seal breaks, water vapor can enter the space between the panes. During your windows inspection, check the windows for any signs of a faulty seal. If a portion of the window seems cloudy or there are water droplets between the panes, it means the seal has been broken.
The insulating properties of a thermal-pane window with a faulty seal are still at least as good as a storm window, however this condition is not desirable from a cosmetic point of view. If the seal has broken, the window requires replacement. Fortunately, reputable window manufacturers offer a 20-year warranty on the seal of these windows.