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New Construction Windows Vs Replacement Windows

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When buying new windows for your existing home, you may have a choice to make between two types of window installations:  replacement windows and new-construction windows. Let’s take a look at the difference between the two and how you can go about making the right decision for your budget and best for your home. 

All About New-Construction Windows

New-construction windows are meant to fit your home opening with the largest size window from studs to stud and fastened to the outside sheathing of your home with an attached nail fin to the window. Then an Ice and Water Shield would be attached to ensure no water or air infiltration occurs after installation.

If you have siding on the house now, it has to be removed or cut back to give these new construction windows with a nail fin, space to attach and secure to the homes sheathing. If the home or addition has not been built then absolutely-New construction will work best.

Sometimes the cost or ability to remove the siding is not prudent. Sometimes it is the type of siding, sometimes it is the cost. If your home has a stone or brick exterior then new construction can and will not make sense at all. 

Ask the question to your window salesperson, which type of installation makes sense. It will vary depending on the type of window, the type of exterior, the type of existing window coming out, the size of your budget and if you have current issues or problems with the existing window. 

How To Identify

New-construction windows will have nailing or attachment fins, or flanges on the exterior of the window. See picture above right for a type of nailing fin.


New-construction windows are moderately easy to install, if you are installing on a new addition or new  home, though much of the peripheral work of prep work prior and sealing the new construction window, is better left with the professionals. 


New-construction windows are usually easily available and in stock at most home centers and Tom Adams Southampton Outlet. But remember these are usually standard sizes and most home existing windows are never standard, each builder uses different sizes based on the type / style of home and the year it was built. Most windows are custom sized.

Where To Use

New-Construction windows are used when building new structures, extensive remodeling projects that require gutting the space, or repairing badly damaged existing structures. As in homes that need mold remediation.


New-construction windows can be weather-tight when installed correctly. Depending on the quality of the product you choose, they usually carry a lifetime warranty, But replacement windows have the same performance if installed correctly.


Sometimes the cost of just the new-construction window is just a little more than replacement windows and it makes sense to spend the extra money to solve issues or aesthetics. Example: if re-doing your siding, then definitely take advantage of new construction windows, you are already committed to a large majority of costs with the removal and reinstallation of siding.


All About Replacement Windows

Replacement windows replace existing new-construction or older replacement windows in an already constructed space. Replacement windows are great to use especially when removing old existing wood windows. Replacement windows are designed for inserting inside the frame of the wood window after the old wood window is gutted and removed. But remember you will lose a little glass in appearance.

The Replacement Window is inserted into the existing frame so the new replacement sash may be approx. ½” smaller all the way around. If removing new construction vinyl or steel windows the whole window is removed and the new Replacement is installed in the opening and sealant, and aluminum capping is applied to help resistant water and air infiltration. But a New Construction window will have an appearance of a little bit more glass when next to a Replacement Window. When installed by a professional Certified Installation team like Tom Adams Windows Award Winning Teams, you will have a lifetime warranty, including installation- no matter which type of window you want. 

How To Identify

Replacement windows have no nailing fins or flanges and are smooth sided for easier installation.


Replacement windows can be tough for do-it-yourselfers due to exacting tolerances and finishing installation with the correct sealant and installation and bends of capping around the outside perimeter. It is better to let a professional install these windows.


Since they are hard for a homeowner to replace on their own, replacement windows can be hard to find, because of the fact there is NO standard size. So any window you might find will make the glass shown smaller and you need to fill the gaps around the perimeter to stop water and air infiltration. Let the professional order the exact custom size- The cost for custom  is not that much more, it just takes longer.

Where To Use

Replacement windows are used when an existing window and the surrounding area is in good shape. Also based on the type of window you are replacing and the type of wall sheathing you have existing. The other issue is always if you have an HOA that wants existing and replacement windows in your home to be an exact match to everyone else’s home. Replacement windows may look a little different from New construction windows based on size, capping and style. The ability to match new construction, may be the need to buy new construction and pay the extra monies to match, just because your HomeOwners association demands it.


Replacement windows and New-Construction windows carry the same performance of window and glass and can be very energy efficient, especially when compared to the older windows they are replacing. No matter the type of windows – both have lifetime warranty


Can You Mix Window Types? Replacement vs New Construction Windows

Based on the home, the answer is yes you can, but should you. The biggest difference is visual. From the outside you can tell a new construction from a replacement window. Is this what you want for your home? Sometimes cost demands us to accept situations that will not change performance and will fulfill the needs, but athletics will be sacrificed. Ask a Professional at Tom Adams Windows and Carpets. Advice is free just like our estimates. 


Types of Windows: Replacement Windows vs New construction

Here are the common types of new-construction and replacement windows.

Double Hung Windows

Double hung windows are made with a top sash that slides down and a bottom sash that slides up to allow for the best air flow. Their best feature is that both sashes can tilt-in and open. With this design feature, the outside glass is accessible from the inside, making it easy to clean.

Bay windows and bow windows are combinations of picture widows, casements, and double-hung windows that project outward from a home.

They can replace traditional flat windows without cutting a larger hole in a wall to install a window, which means dramatically changing a room without major remodeling. These windows are custom made to fit the opening and have a custom roof or capped to soffit, based on your house needs and design.

Picture Windows

Picture windows are stationary, square, rectangular, or custom-shaped. These windows are non-opening windows that allow large amounts of natural light into the room but no air flow. Picture windows are great to use when you want to feature a large, fixed window or wall of windows that can be combined with double-hung, casement, or shaped windows to accent an opening or create a dramatic appearance in your home.

Where Can I Buy New-Construction and Replacement Windows?

Looking to buy new-construction or replacement windows in Bucks County PA, Montgomery County PA, Lehigh Valley PA, or Philadelphia? At Tom Adams Windows and Carpets, we offer a wide selection, including vinyl, aluminum clad, and fiberglass windows, in various colors, shapes, and styles. All our windows come with a lifetime and glass breakage warranty for your peace of mind.

Explore our range of new construction styles such as double hung, bays & bows, vinyl, wood, fiberglass, casement, picture, and flex screen from top brands like Marvin, ProVia, and Slocumb.

Whether you’re in Bucks County, Montgomery County, Lehigh Valley, or Philadelphia, Tom Adams Windows and Carpets has you covered for all your window needs. Contact us today to start your estimate.


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