While clean windows don't automatically increase home value, they make your home look more attractive from the outside, and since the exterior is the first thing a potential buyer will see, it can help make a good first impression that paints the rest of your home in a positive light. Educated homebuyers will see that your home is well cared for if they see clean window tracks and sparkling window glass, which can contribute to an overall positive opinion of your property. Clean windows give the impression that the rest of the home—including systems and appliances—is probably well-kept, too.

If your windows are drafty, fogging up between panes, or hard to open or close, it might be time for a replacement. Unexplained increases in your energy bills, rotting frames, broken seals, and noticeable noise from outside can also indicate it’s time for new windows. In addition, if you find yourself frequently needing to repair your windows, it’s probably more cost-effective in the long run to replace them.

When your double-hung window upper sash keeps falling down, it means you could be letting out warm air in the winter or cool air from the AC in the summer. That means your HVAC system works harder to warm or cool the house, costing you extra on electric bills.

If the lower sash continues to fall down, it means when you’ve popped open the window for fresh air, it could slam shut. In addition to being inconvenient, this could be dangerous if you have small kids, children, or pets that like to hang out by the window.

Whether or not you need permission to change the windows in your house depends on your local laws. If you’re enlarging an opening or installing a new window and need to make structural changes to the house, you’ll need a permit. In most locations, you won’t need permission if you’re just replacing a window with another window of the same size. The window installation company you work with will be able to help you navigate any planning permits you may need.