Replacement Windows vs. New Construction

There are two general methods when undertaking a home-improvement project involving windows. One method is to purchase replacement or retrofit windows, which fit into the existing window casing. Another method is to use new construction windows, which replace not only the window but the framing of the window as well. Before beginning a window project, it’s important to weigh the options between the two methods of window replacement.

The Facts

Replacement or retrofit windows are generally used in home-improvement projects to provide more energy efficiency than existing windows. New construction windows will be used in situations where the wood studs are accessible so that the metal flange located on the window can be nailed into place. Replacement windows are often less expensive than new construction style windows.


New construction windows can visually be distinguished from replacement windows by the outer metal flange used to nail the window to exposed wood studs. Replacement windows are nailed into the window framing after the existing window panes and any hardware have been removed. Because replacement windows fit into existing window openings, they are visually characterized by smooth sides without protruding nail flanges.


Because of installation methods between new construction windows and replacement windows, consideration should be paid to the condition of wooden sills. Since replacement windows utilize the wooden sills from prior windows, the conditions of the wood will determine the efficiency and longevity of replacement windows. Likewise, insulation concerns should be considered when choosing between window options. New construction windows provide access to the open space in wall studs around window openings, making it easier to add insulation to improve the energy efficiency of the windows.


A common misconception in window replacement is that new construction windows can only be used in new building projects. New construction windows can be used in the replacement of an existing window. When replacing an existing window, the installation of a new construction window requires more time in order to expose the studs necessary to attach the window to the frame of the house. The installation of new construction windows may also increase costs in replacing indoor or outdoor window trims, as well as the costs involved in adding insulation around the window frame.


The installation of replacement or retrofit windows can provide the benefit of energy efficiency, especially in homes with single-pane windows. Replacement or retrofit windows also offer the benefit of faster installation. New construction windows provide the benefit of easily adding additional insulation, as well as the ability to replace wooden sills which may have deteriorated.