Retrofit vs. New Construction Windows

Published May 3, 2022
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Lake Washington Windows

When the time comes for a homeowner to install new windows in their home, one major question inevitably arises. What’s the difference between retrofit and new construction windows? While each window type serves a unique purpose, the decision depends on the window replacement project’s circumstances. This article will describe the difference between these two types of windows to help readers understand which window type to choose for which project.

What is a new construction window?

New construction windows are used when installing new windows into a newly built home or adding windows during a major home renovation. New construction windows can be ordered in hundreds of standard window sizes depending on the design preferences of the homeowner.

The primary difference between retrofit or replacement windows and new construction is the nailing fin surrounding the perimeter of the window unit. This nailing fin secures the window unit directly onto the studs of the rough opening. Once installed, professional window installers weatherproof the window and then install the house’s exterior siding, interior drywall, and window trim over the exposed nail fin.

What is a retrofit (replacement) window?

A retrofit window, commonly known as a replacement window, involves installing new energy-efficient glass into an existing window frame without needing to touch the surrounding framing, drywall, siding, or trim. Whereas homeowners can order new construction windows in any shape or size, retrofit windows must fit the size of the existing frame.

The beauty of replacement windows is the installation process is straightforward and they are compatible with nearly any existing window. There are times where the existing window frame is not plumbed to the wall or has warped over time, in which case the installation process will be more complex. Even when this happens, replacement windows generally require less effort compared to the installation process of new construction windows.

When to use new construction windows

The choice between installing new construction or retrofit windows boils down to the circumstances surrounding the window replacement. Each window type serves a different purpose in certain circumstances. Here are some of the reasons a homeowner would choose new construction windows:

Remodeling, Renovation, and New Home Projects

If a homeowner is planning a major remodeling or renovation project involving changes to exterior walls, such as adding a home extension or additional rooms, installing new construction windows will be the only choice available. Likewise, during the initial construction of a house, new construction windows are the appropriate window type to install, hence their given name.

Installing a larger or different shaped window

Perhaps a homeowner doesn’t want to complete an extensive renovation or remodeling project but wants to replace old windows with larger windows to provide one room with better lighting or a nicer view. In this case, new construction windows are the obvious choice because the homeowner is choosing to change the size of the entire window frame.

Rotting or damaged window frames

Another circumstance that may require new construction windows is if the surrounding window frame is damaged. Over time wooden framing materials can be exposed to moisture and insects, leading to rot and decay. Additionally, the shape of the wood can warp due to moisture and temperature changes, and if the warping is significant enough, replacing the frame might make the most sense when installing new windows.


When to use replacement windows

Replacement windows are quick and easy to install into an existing window opening with no need for substantial repairs or damage to the surrounding frame, drywall, or exterior siding. Retrofit windows are the best choice when considering a window replacement project in many circumstances. Here are some of the reasons that make retrofit windows the best window replacement option:

Unchanged window frames in good condition

Replacement windows are an excellent choice if the existing window frames remain in good condition and there are no plans to change the size of the old windows. Installing retrofit windows is a much simpler process than installing new construction windows, and the extra effort required often doesn’t make sense in terms of finances or convenience.

Low-cost window efficiency improvement

Suppose a homeowner is looking for a way to improve the energy efficiency of their home with no desire to undertake a larger construction project. In that case, replacement windows are the best choice. Likewise, suppose a window is leaking, drafty, or rattling due to an issue with the frame, sashes, or rails. In that case, replacement windows will solve the problem instead of the labor-intensive alternative.

Quick, non-invasive solution

Another situation where choosing replacement windows makes the most sense is when a homeowner is looking for a quick way to improve the comfort, curb appeal, and resale value of a home they plan to sell. Retrofit windows can be installed quickly and make a home more attractive to prospective buyers.

Are new construction windows more expensive than replacement?

New construction window units can actually be cheaper than replacement window units, especially when purchased in volume. However, the entire installation process of a new construction window is significantly more expensive, often costing 50% to 100% more than replacement windows due to the labor involved.

Are retrofit windows as good as new construction windows?

The primary benefit of new construction windows is they are one integral unit that the contractor can install, plumb, and square to ensure maximum weather protection without difficulty. Whereas with retrofit windows, problems may arise if the existing frame isn’t plumb and square. That being said, an experienced window installation team should be able to make any necessary adjustments to ensure a replacement window is air-tight, no matter the circumstance. Make sure to know the difference between builder grade windows and high quality replacements. That is a common mistake we see homeowners make.

What do retrofit windows look like?

Retrofit windows and new construction look almost identical. The only difference between the two is the nail fin surrounding the perimeter of a new construction window that does not exist on a retrofit window.

Is retrofit the same as replacement?

Yes, the terms retrofit and replacement are used interchangeably when referring to replacement windows.

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Written by Lake Washington Windows

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