How Replacement Windows Will Affect Your Renovation Project

New windows are easy to open, close, and clean. They provide enhanced energy efficiency and heightened curb appeal to your building or home.

Replacement Windows

Replacement Windows Massachusetts keep cold air out during chilly winters and hot air out, reducing the workload on your furnace and AC unit. They also reduce noise, making your home a quieter place to relax.

A window’s frame is the primary structural component, which also holds the sash (operating or non-operating). Window frames are usually made of wood or vinyl. They may be clad with aluminum, PVC or other factory-applied finishes for protection from the elements and enhanced aesthetics. Frames are often insulated to enhance energy efficiency.

The type of material used for a frame’s construction and its insulation properties will influence the final product’s performance. Wood frames and sash provide superior thermal resistance, but require regular maintenance and are subject to rot. Vinyl and fiberglass are durable, low-maintenance options with good thermal performance. Those with a foam core perform even better.

In general, the frame will determine how well a replacement window performs. It is therefore important to understand the difference between insert and full-frame replacement windows before you make a purchase.

An insert replacement window fits within the existing frame and preserves the original interior and exterior trim. This limits disruption and offers a quick solution without the need to remove existing sash, operating hardware or covers.

For this reason, it is often a simpler option for homeowners to undertake as a do-it-yourself project. However, if the frame is rotted or otherwise damaged, it may be a more complex task than expected.

A full-frame replacement window installs a new head jamb, sill and side jambs that create an entirely new opening for the replacement window. This is the only option if the old frame, sill or jambs are rotting or soft and cannot support a new window.

A full-frame replacement is the best choice if you want to upgrade your existing windows for improved performance and aesthetics, or if you need to replace a window in an area of your home with poor air and water insulation. It’s also the best option if your current frames are made of wood, which provide the highest level of performance but require a high degree of care to protect against the elements. Full-frame replacement windows are available in a wide range of materials, including fiberglass, vinyl and wood clad, to suit your aesthetic preferences and budget.


Many homeowners choose to replace a window because their current one has broken glass or is in poor condition. They may also want to upgrade the window style, increase efficiency or let in more natural light. It is important to understand the different styles, types and sizes of replacement windows available, and how they will affect your renovation project.

When a replacement window is installed, it forms a tight seal to reduce cold drafts and hot spots in your home. It can also help keep moisture out to avoid mold and mildew. It is a good idea to install replacement windows that are ENERGY STAR certified, which will help save money on energy costs in the long run.

A window frame is composed of the head, jambs and sill that form an exact opening (the frame) for a window sash. A sash is the moving part of a window that lifts or lowers to allow air to circulate.

The sash is supported by vertical and horizontal rails that run the full length of the window. Usually, they are made of wood or metal, but they can be made from other materials, such as vinyl or fiberglass. Depending on the style of window, the number and placement of rails will determine the operation and appearance of the window.

Before installing a new window, it is necessary to remove the existing sash and trim. Then, apply elastomeric caulking to the inside of the window opening and blind stops around the outside. Bore 3/8-inch holes in the sash weight pockets, and spray foam into them. Finally, apply a layer of glazing compound to the grooves of the window pane and install new compound points with the tip of a putty knife every 10 inches.

Some modern windows have insulated glass units (IGUs) with two or more panes of tempered or laminated glass with a spacer between each. This spacer is filled with a noble gas, such as argon or krypton, to improve the window’s energy efficiency. If you’re replacing an IGU, be sure to pay close attention to its NFRC label that shows U-factor and solar heat gain coefficient figures. The lower the numbers, the more efficient the window.

Muntins & Mullions

Whether you’re planning to restore windows in an historic home or want to upgrade the style of your new home with new replacements, the details matter. Understanding the differences between mullions and muntins will help you choose the right components for your project.

Mullions are vertical dividers that separate glass panes in a window frame. They’re often referred to as “dividers” or even “grille bars,” but they differ from muntins in that mullions channel the weight of the windows vertically instead of horizontally. Historically, builders used mullions to support windows, but they’re now primarily used for aesthetics and decoration.

Aesthetics: Decorative elements like a grid pattern can be added to single-pane windows to add detail and eye appeal. When paired with a distinctive color, they can create an elegant focal point for the window. Mullions also allow homeowners to bring new functionality to single-pane windows. With a track, hinges, and an operator installed to the mullion, a single-pane window becomes a casement window that can be opened and closed.

Historically, mullions were essential to supporting large windows, as the walls of homes couldn’t handle the load of large pieces of glass. They’re still a popular choice for bringing visual accuracy to period renovation projects and new constructions that want to capture the spirit of a particular historical style.

Function: When combined with a grid pattern, mullions help block out sunlight and reduce the amount of heat that enters a space. Modern mullions can be ornate and decorative, but they can also be streamlined and minimalist to provide the same structural integrity for smaller windows.

Modern muntins aren’t as ornate and decorative as their traditional counterparts, but they’re a great option for homeowners who don’t want to sacrifice energy efficiency for the look of classic windows. They’re a great alternative to traditional, fixed window grids and are available in a wide range of patterns that match a variety of home styles and decorating preferences, from the classic grid designs of Colonial-style homes to the Victorian style of curved or arched windows and even a modern, minimalist design for farmhouse-style homes.


Depending on the type of window chosen, installation could take several weeks. Insert replacement windows, for example, are typically custom-made to fit existing openings. While some professionals scoff at this method, many homeowners find that carefully installed insert windows perform quite well for years.

Before starting any work, carefully examine the frame and sill for signs of rot or other damage. If there is, the project should be put on hold until repairs are made. It is also important to ensure that the frame is square, or plumb, and is sound and dry.

The first step in a standard replacement window installation is to remove the interior trim from around the window opening. Carefully pry out the inside stop, sash, and parting stops using a sharp utility knife or nail nippers. Once the old windows are removed, save the interior stop moldings (or cut new ones to size with a miter saw) to reattach to the new window when it is installed.

With the new window positioned in the opening, use wood shims to keep the reveal even at the jambs. Be sure to place the shims behind each screw hole so as not to loosen the screws that hold the window in the frame. With the shims in place, open and close the window to be sure that it is sliding smoothly and aligning correctly where the top and bottom sashes meet in the middle.

If the window is sliding smoothly and aligning properly, install the rest of the screws and apply caulk to seal the joints between the new and existing frames. Use a water-resistant latex caulk for this, and be sure to follow the manufacturer’s instructions on how much caulk to use — too little or too much can cause problems.

In addition to caulking the joints between the new and existing frames, you should also caulk the exposed edges of the exterior frame itself. This helps to reduce air infiltration and condensation, as well as helping the window look neater. Finally, if the sash weight pockets are hollow, spray them with expanding foam insulation to fill the spaces and help the window to seal better.