If a window in your home is cracked or has an obvious hole in it, then of course it's time to have that window repaired. However, not all damage to window glass is as noticeable as an outright crack or chip.
Window frames also need to be properly maintained, as frames that are in poor condition can be letting out your heating and air conditioning, while allowing in insects and humidity. This moisture gets absorbed by your home's framework, potentially leading to water damage and mould growth. To ensure your home's windows and window frames are always in good condition, note when it might be time to invest in window repairs.
Never assume that windows are naturally difficult to open and close, as this sticking often means that a window frame has become misshapen or otherwise shifted out of position. Sticking might happen most often with wood window frames, as wood will absorb humidity and then dry out, causing the material to cup and bow over time. As a house settles and shifts, this can also cause windows to pull away from the home's framework so that the window is uneven and begins to stick. When this happens, have the windows repaired as needed so that they move freely.
You feel excessive heat or cold near the windows
If you can feel hot or cold air around the windows, this often means that the glass has become etched and scratched, or the window frame may have pulled away from a home's framework, creating gaps. The windows may also need a fresh line of caulk around the glass panes. If you feel heat or cold around the windows but not an actual draft, this could signal that the glass has gotten thin over time and needs repair or replacing.
Condensation forms when water is extracted from warm air and then clings to a cool surface. This condensation should never form on a home's windows, as window glass and its surrounding caulk should be strong enough to insulate those windows from these extremes in temperature. If you notice condensation on your home's windows, the glass may have gotten thin, or the caulk could be breaking away from the window frame. There could also be small leaks in the window glass that are allowing the transfer of cold and warm air through the window. Whatever the cause, have the windows repaired or replaced when you notice condensation clinging to either side of the glass.