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New Construction Vs Replacement Windows: What Are The Differences?

New Construction Vs Replacement Window Ft Img

New construction and replacement windows are two types of windows that can be bought and installed when having glazing fitted. Although they serve the same purpose, and can look and be built from identical materials, they have very different purposes, and the choice of which you require is almost a definite answer.

Homeowners choose replacement windows when they are replacing existing windows while new construction windows are used in new builds. However, there are some exceptions: times when you are replacing a window but may be better served with a new construction installation, rather than replacement.

Read on to find out more about these two types of windows and to determine which of the two is best for your project.

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Overview of New Construction Windows:

New construction windows are, as the name suggests, built for new constructions. They have a special frame feature called a nail-fin frame. The frame can be nailed directly into the property’s frame and this feature is not found on replacement windows.

New construction windows may have a lower ticket price than replacement windows, but once you take the cost of replacing the frame and repairing the surrounding property frame, they are more expensive. They require a lot of additional use, but they are necessary in new builds. They also come in the same variety of styles, shapes, colors, and materials as replacement windows.

two window installers
Image By: Yuriy Golub, Shutterstock


The fin around the new construction window is used to hold the window frame firmly in place but it also offers waterproofing and protection against bad weather. It is an essential part of the new window installation, although it is the only real difference between new construction and replacement windows.

It is not usually safe to remove moulded pins, but an increasing number of manufacturers are using removable pins. This means that if you are looking for a replacement and you find a new construction window cheaper, the fin can be safely removed. However, you do need to ensure this is the case before sawing the nail fin away.

In any case, installation of a new construction window requires that there is no window frame in the wall. The stud wall or sheathing needs to be displayed, because this gives something for the nail to secure to.


The most obvious and common use for new construction windows is in newly constructed buildings. However, there are other uses. If you are having an extension built, there will not have been a window before so this will require a new construction.

Similarly, if you are adding a window to a wall that did not previously have one, this needs a new construction window. If an existing window frame and surrounding area are badly damaged, and need repair before the window can be fitted, this will usually require this type of window as well.

  • May be cheaper than replacement windows
  • Suitable for new constructions
  • Can be used in extensions and where there was no window before
  • Comes in a full range of materials, colors, and styles
  • Difficult to install
  • Not suitable in most renovation or window replacement projects

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Overview of Replacement Windows:

Replacement windows are those that we most often think of when talking about new windows in an existing house. They replace the original new construction windows, and they are also used to replace other replacement windows. They do not have the nail fin and they simply slide into the window hole horizontally.

They do not cause any changes or damage to any other elements of the window or surrounding wall. Their lack of aa wall fin means that they should not be used for a new construction or where no window has been before.

man installing window
Image Credit: ronstik, Shutterstock


Replacement windows do come with a window frame, but they slide into the hole left behind by the previous window. They are installed in this way so that you do not need to damage or otherwise alter the walls or the stud to install them. As a result, they are easier to install than new construction windows and their installation costs less, although the windows themselves may cost a little more to purchase.


You should not use replacement windows in a new build, but you will want to use them when replacing existing glazing, if the wall and surrounding area is still in good condition. You may also use a replacement window if a new construction partially uses an existing wall and existing window hole.

  • Easy to install
  • Do not cause damage to the wall
  • Available in all materials, sizes, and styles
  • Cannot be used on a new build
  • Usually unsuitable for extensions

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Choosing Window Type

Choosing the right type of window will depend entirely on the type of installation and the type of building or refurbishment project you are undertaking.

Windows For New Houses

You should never use a replacement window when building a new house. This is the very reason that new construction windows exist.

Windows For an Extension or Addition

Similarly, if you are having a brand-new extension or an additional building added to your home, you will, in the majority of cases, use new construction windows. The only time you can consider using replacement windows is if there is an existing partial wall that is being built on.

Replacing a Damaged Window

If the window, siding, drywall, and studs around a window are badly damaged, it is likely that they will need repairing once the old, damaged window is out. In these cases, new construction windows are the right choice. However, if it is only the window and its frame that is damaged, and everything else is structurally sound, you can opt for replacement windows.

man removing old window
Image Credit: Africa Studio, Shutterstock

Replacing An Existing Window

Replacement windows are used when old windows are removed, the wall has already been built and it should not be disturbed or damaged in any way. The new window simply slides in and leaves all other elements intact.

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Replacement windows are used, as the name suggests, to replace existing windows, assuming that other elements like the siding and drywall remain undamaged. Otherwise, if the wall is new or if there has never been a space for a window before, the new construction window is the best option. Typically, there is only one correct option of which type of window to choose, and it should never purely come down to a question of cost or ease of installation.

Featured Image Credit: Left: New Construction Windows (Dmitry Kalinovsky, Shutterstock), Right: Renovation Windows (Andrew Angelov, Shutterstock)


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