Replacement Windows 101 – Everything You Need To Know

Photo: Andersen Windows

Windows come in all styles, types, shapes and sizes. However, unless you are building a new home, all of the above options are largely predetermined. There are of course some exceptions. Perhaps a previous home owner replaced the original windows with units that are historically inadequate or inferior. (Historic window styles are available today from manufacturers like Andersen.) Or you could add a family room in the back of the house where it would be okay to deviate from the double hanging windows in the front. You can use wings in this situation. Sometimes a homeowner wants to enlarge or reduce the window being replaced. However, if you’re like most homeowners, the real choices have more to do with energy saving features and ease of maintenance.

Replacement window glazing

In terms of energy saving, you should first focus on the glazing. Efficient windows usually have two layers of glass and are known as double pane or double pane. The small gap between the glass layers forms a barrier for the flow of heat, which can be reinforced by an additional glass layer (two separate insulating chambers). In this case, it is called triple-glazed. The gap or gaps between the glazing layers are often filled with a gas that further reduces the flow of heat by conduction. Argon and krypton or a combination thereof are commonly used gas fillings.

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Reflective films, shades and coatings

Reflective films, shades, and low-emission (Low-E) coatings are some of the other ways window manufacturers are using to improve window performance.


Reflective films block much of the radiant energy hitting a window, keeping occupants cooler. However, they also block most of the visible light. Not only do they give the windows a mirror-like appearance, but they also often result in occupants using more electric light to compensate for the loss of daylight.


Bronze and gray tinted glass reflect radiant energy and reduce the cooling load without reducing the visible light entering the house. A visual transmittance (VT) of 60% (versus 90% for clear glass) is common.


Low-E coatings are more versatile than reflective films or shades, and are virtually invisible. Microscopic metal or metal oxide particles suppress the radiant heat flow out of the window and can be formulated in such a way that different degrees of solar radiation enter. In climates where warming is the main concern, low E coatings can be used to prevent the transmission of radiant heat from the window while maintaining high solar heat gain. In climates where both heating and cooling are required, Low-E coatings can reduce radiant heat loss while allowing moderate heat gain. In climates where cooling is the primary concern, Low-E coatings are mainly used to reduce solar heat gain. It is even possible to optimize solar thermal gain by choosing a low-E coating with a high solar thermal gain coefficient (SHGC) for south-facing windows and a lower coefficient for other orientations.

Replacement window

Replacement window construction

The material that the window frame is made of also significantly affects its efficiency. Insulated-filled vinyl frames and fiberglass perform better than wood, wood paneling, and vinyl that is not insulated. Aluminum and steel perform worse than any of the above.

There are three approaches to replacing windows: sash only, insert window, and replace full window.

  • Replacement kits for grand pianos only Add new wing and post liners for improved operation. They are easy to install, but should only be used in windows that are otherwise in good condition.
  • Retrofit windows (also called inserts) fit into the existing window frames. Only the window remains and old sashes have to be removed. Existing molded parts inside and outside are not affected. Installing inserts is only an option if the old window frame is in good condition, rot-free, and square. The inserts can be installed with less labor, lower cost, and less dirt than replacing full frames. They are usually tailored specifically to the size of your openings and the angle of your existing threshold. The advantage of retrofit windows is that they are available with tilt cleaning.
  • Full window (full screen) replacement Typically, the entire existing window must be removed, including the casing, frame, sash and exterior cladding. This method can be used to correct situations where the old window frame has deteriorated, is not square, or when a different window style or size is desired. While replacing full frames requires more work, expense, and glitch, you can do this to better insulate the window frame, and often energy leaks. With the siding removed, you can spray closed cell foam insulation between the window frames and the cleats. The exchange of full-size windows can usually be done with standard window sizes, but can also be ordered according to customer specifications. Another bonus: with full screen replacement, unlike insert replacement, no glazing area is lost.

Save money on replacement windows

Replacing old windows with new, energy efficient windows offers several benefits. However, don’t expect drastic savings on your heating bill. Most replacement windows have R values ​​of 4 or 5 compared to 2 for single glazed windows with storm windows. Given that the window area is a fraction of the total wall area, it would make more sense to first invest in attic and wall insulation, sealing strips and sealants such as caulking, duct mastic or even insulating window treatments. Most likely, more heat enters and / or escapes from your home through attics, skylights, recessed lighting, chimneys, and other penetrations in the envelope of your home than through your windows.

Related: Know Your Window Styles: 10 Popular Designs

When to replace your Windows

Wooden windows that have deteriorated due to water infiltration and rot are prime candidates for replacement. Or maybe your windows are no longer working properly and are expensive to repair. You may also want to update your windows for easier maintenance. It’s no fun climbing ladders to wash the exterior of the window, but today’s new window designs allow you to access the exterior glazing from your home. Aesthetics can also play a role when replacing windows. Many homes of historic importance have been negatively affected by the installation of inappropriate window styles and storm windows. Replacing them with the right style storm-free windows will improve the look and value of your home.

Are you considering a window replacement?

Find licensed window installers near you and get free, no-obligation estimates for your project.

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