New Construction vs. Replacement Windows
When you decide it is time to upgrade your home's windows, one of the first and most critical decisions you will make with your contractor is the type of installation.
While the glass and the energy efficiency of the windows might be identical, the physical frame of the window and how it attaches to your house will differ based on whether you choose New Construction or Replacement (Retrofit) windows.
What is a New Construction Window?
New construction windows are designed to be installed into a completely raw opening. They have a continuous outer lip called a nailing fin (or nailing flange) that sits flush against the exterior sheathing (wood/OSB) of the house. Nails or screws are driven through this fin to secure the window, and then siding, brick, or stucco is installed over the fin to completely hide and waterproof the edge.
When to use them:
- Building a New Home or Addition: This is the standard choice since the wall studs and sheathing are exposed.
- Major Exterior Renovations: If you are ripping off your old siding or stucco down to the plywood, it is the perfect time to install new construction windows.
- Full-Frame Replacements (Brick-to-Brick): Even on an existing home, a contractor can cut back the exterior siding, remove the entire old window down to the raw 2x4 studs, install a new construction window using the nailing fin, and apply new exterior trim. This is the most robust, weather-tight method but is more expensive and invasive.
What is a Replacement (Retrofit) Window?
Replacement windows (often called "Retrofit" or "Insert" windows) are specifically designed to slip inside the existing frame of your old window without disturbing the surrounding walls, siding, or interior trim.
Unlike new construction windows, they do not have a nailing fin. Instead, they have a smooth, flat outer frame (called a block frame). The contractor removes the old glass and moving sashes, but leaves the original perimeter frame intact. The new retrofit window is slid into this old opening, shimmed, screwed through the sides, and sealed with caulking.
When to use them:
- Updating Old Windows on a Budget: This is the most cost-effective and fastest way to upgrade to energy-efficient glass.
- Preserving Interior/Exterior Trim: If you have beautiful, historic interior wood casings or expensive exterior stucco that you do not want to destroy, retrofit windows allow you to leave the walls untouched.
- The Old Frames are in Great Shape: Retrofit windows must be anchored into solid wood. If your original window frames are completely free of rot and water damage, an insert is a great choice.
Which Should You Choose?
Choose Replacement (Retrofit) if:
- Your primary goal is upgrading the glass for energy efficiency.
- You want a faster, cheaper installation with less mess.
- Your existing window frames are structurally sound and rot-free.
- You want to preserve the surrounding exterior siding and interior drywall/casing.
Choose New Construction (Full-Frame) if:
- You suspect water damage or rot in the walls around your existing windows.
- You are changing the size or shape of the window opening.
- You want to maximize the visible glass area (retrofit windows sit inside the old frame, which slightly reduces the total glass area).
- You are already replacing your home's exterior siding.
The Bottom Line: Discuss both options with your contractor. A good professional will assess the health of your existing frames and your budget to recommend the right installation method for your home.