Building Tips

Difference Between New Construction and Replacement Windows

What is the difference between new construction and replacement windows? And which one is the right choice for your project? These are questions that we had to ask as we planned our flip house project. Part of the project included a large addition. We also needed to replace and relocate several existing windows. So we decided that the best option was to go with new construction windows for the addition and the same windows for the existing part of the house, but with no nailing fin.

The nailing fin is the biggest difference between these two types of windows. A new construction window has a nailing fin and the replacement window does not. The nailing fin is what is placed against the framed opening and nailed or screwed to the framing. When replacing a window, this should already be in place to protect against water and air filtration.

When Do I Use New Construction Windows?

New construction windows are used mostly on new constructions, new additions, or on a damaged structure. New construction windows are used on homes with clear openings and no siding and trim in place. With this type of situation, you have no choice because there is not an existing window in place to replace it. The only time you would need to use a replacement window is if you have an already existing wall within a new addition that includes windows.

When Do I Use Replacement Windows?

Replacement windows are used on homes or structures that already have existing windows. If the area around the window is in good shape, these windows will work perfectly. The existing window will be measured and the replacement window will be ordered to fit. If you are changing the window size to a bigger or smaller area, you would then look at new construction windows.

Keep in mind, when installing a replacement window it is very important to remember that these windows need to be weatherproofed. This will allow for no heat or air to escape or come in.

Cost Difference

The difference in cost is not normally from the window itself, it’s mostly from the installation process. If you were to compare the price of the window itself, the replacement window may seem a little cheaper. It is important to make sure you get an estimate based on your particular job because each situation is different.

For instance, installing a new construction window in a newly framed house is less labor-intensive than replacing a window. Also, replacing a window that is a different size requires a lot more work than replacing one with the same size window.


In general, most new construction windows are pretty easy to install. Replacement windows can be a little tricky to install. In fact, Henry and my dad installed several on the flip house recently. They do require a little extra work when changing the window size to either smaller or larger. Changing the rough openings can be challenging especially when you are also dealing with a brick exterior.

Now that you know the difference between new construction and replacement windows, you should be able to make the right choice for your building project.

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