Improved liveability
When replacing windows, one can consider increasing the window size, moving windows to new locations, converting doors to windows or windows to doors, or to install specialty windows such as garden or bow windows. These are all examples of improving the look and feel of a room. Allowing additional light to enter a room will make it feel much larger and brighter, enhancing the overall environment.

Ease of maintenance
Face it, old windows are difficult to clean and dirty windows block a lot of light and obscure the outside view making a room far less appealing. New windows can easily be retrofitted into existing spaces that allow both sides to be cleaned from inside the home. This is especially convenient (and much safer) when installed in a multi-story home!

Window frames constructed of vinyl or fiberglass also add the luxury of never having to be painted or stained and are otherwise virtually maintenance free.

Reduce heating and cooling costs
Wooden windows 25 years old or older tend to have been constructed with marginal regard to energy conversation.These simply constructed windows tend to allow drafts to enter from between the window and frame and from around the frame itself. Depending on construction technique, their tracks may have also become worn, allowing even more drafts to creep into the home.

Aluminum is a very good heat conductor. This is why the heat sink on your computer CPU is likely made of an aluminum alloy. Older, single pane aluminum windows are in this same category and actually act as heat radiators. The aluminum frames try to equalize the temperature between the inside and the outside by conducting the warmer temperature to the cooler side.

Glass too is a good conductor of heat. When only a single pane of standard glass is used in either a wood or aluminum framed window, very little insulation is provided. This condition is marginally improved with the addition of a second aluminum storm window. But the windows then become very difficult to clean, often requiring complete disassembly of the storm window.

Enhance the "Curb Appeal"
When looking to purchase a home, buyers tend to place windows and doors in the same category as roofing, siding, and carpeting. New windows and doors may not excite them, but if they are old and drafty, a buyer may not be as willing to pay the asking price, if they make an offer at all.

Windows and the front door are some of the first things a prospective buyer sees from the street. The window style and their condition is readily apparent and helps set that critical first impression. Old aluminium and crusty wooden windows with layer upon layer of paint tend to hinder that first impression.

Increase the value of the home
The amount of value added to a home and the money realized from the installation of new windows varies across the nation. It's been estimated that the return on investment is typically 76% in the Portland, Oregon region.

Of course this is only an estimate based on historical data and by no means ensures that the market value of any home will increase at this or any other rate as many other factors influence the housing market.