Windows have evolved to become a bit more complex than just wood and glass . With improvements in technology, windows have not only become easier to use and clean, but significantly more energy efficient, keeping you warmer in the winter and cooler in the summer. In this article, we break it down and explain the anatomy of a standard window.

Window Frame

A fusion welded mPVC frame.

Window frames typically hold the hardware that make operating windows work, whether they’re sliding, twisting, turning or rotating.

The frame of the window is a group of parts that support the entire window system. Window frames typically hold the hardware that make operating windows work, whether they’re sliding, twisting, turning or rotating. The frame is also what is typically secured to the studs in the rough opening to hold the window in place. In Ontario, common frame materials include mPVC, PVC (or vinyl), aluminium, wood, or fibreglass.

Because the frame holds the window’s hardware in place, it’s important that it is built out of quality, strong materials. A properly-installed, strong window frame can help keep your windows functioning smoothly for years to come. The majority of frames that you will see on the market are 3-¼” frames, however some higher-quality and heavier windows may come with deeper profiles, like our own 4-½” frame.

Some common parts of a window frame that you might encounter:

Head : This is the main horizontal member at the top of the window frame

Jambs : These are the main vertical members on the sides of the window frame

Sill : This is the main horizontal member at the bottom of the window frame.

Shopping Tips:

  • Make sure the frame is sturdy. As mentioned, a strong frame can help keep your windows operating smoothly for the life of your windows.

  • Choose frames that are welded or one piece. A well built window frame is a strong defence against the elements, helping to stop drafts and leaks. If made out of many small parts that are screwed or otherwise assembled together, there will always be leaks.

  • The window frame must fit the rough opening right. Having a professional come to measure the window can make a big difference when installation time rolls along. A properly measured opening will ensure that the window is of the right size, with the right clearance for the insulating foam to fill in the available space, while still fitting snugly in the opening. This will prevent water infiltration and air leaks, safeguarding your home against costly damage, and ensuring indoor comfort.

Window Sash

The window sash is the moveable part of the window that is made up of a frame holding in place a piece (or pieces) of glass. Window sashes also often contain minor pieces of hardware that lock or assist in locking the windows shut. Window sashes are typically made from the same material as their frame, and should match in finish and architectural style.

Tremco Spacer.

Nordik Windows use Tremco® EnerEDGE® Technology, a pre-desiccated, ready-to-apply, cellular silicone warm-edge spacer that is suitable for a wide range of insulating glass constructions in fenestration applications.

Thermal Glass Units

The thermal glass units (sometimes referred to as “Thermos”) are typically 2-3 panes of glass separated by a spacer around the edges. The gap between the panes in most modern windows are filled with an inert gas, which acts as a thermal buffer, reducing convection between the panes and the associated heat loss. The gas also offsets water vapour to prevent condensation between the panes. In temperate North America and Europe, you’ll typically see either Argon or Krypton gas filled units.


Glazing refers to the glass that makes up your window unit. The options for window glazing are seemingly endless. From coloured to frosted and etched, glazing can be customized to achieve the look that matches your home. Some glazings also offer thermal properties that can increase the energy efficiency of your home.


Weatherstripping on your window sashes play an important role in keeping out moisture and stopping drafts and leaks. Because the interface between the window sash and window frame is typically two rigid materials there exists an imperfect seal. As the windows age, this imperfect seal becomes increasingly imperfect as the house is moving and shifting, and the studs are expanding and contracting. Weatherstripping is generally made of a flexible material that can adapt to this imperfect interface and create that perfect seal.

Shopping Tips :

When looking at double vs triple, it’s worth noting that more isn’t always better. If you’re in the market for triple-pane windows, make sure that the frames you are getting are sturdy enough to support the extra weight of the triple-pane insulated glass unit. Pay attention to energy ratings on the windows, and ensure they are coming from a reputable source.

Weather Proofing

Weather proofing is an important step in the installation process. While these components aren’t technically part of the window, in most cases their presence is required for a complete, long-lasting installation.


Flashing is a water resistant material that is installed at the gaps between the window frame and the rough opening. Flashing can be made of a range of materials, but is generally aluminum, or some type of plastic-based membrane. Its main purpose is to ensure that any moisture that could accumulate or intrude, runs off on the outside of your home finish material.

Spray Foam Insulation

Spray foam insulation is used to fill any gaps between the window frame and the rough opening. This specially formulated foam is generally applied with an aerosol can, and expands as it reacts with the air. As it expands and dries, the foam turns from a soft material to a stiff material, creating an insulating barrier to protect from drafts and leaks.


Caulking is the water resistant, generally silicone based material that is applied on the exterior of the window frame. Caulking is not meant to fill large gaps, and so it’s used to simply to ensure that no water makes it between the flashing and the window frame.

Shopping Tips :

  • In most cases, all of these weatherproofing techniques are used. If your installer doesn’t, make sure you ask why. There could be a reason why they chose not to use it, or maybe they use something in its place.

  • Ask about the useful life of the caulking when your windows are installed. Changing the caulking may be an easy win in increasing the efficiency and performance of your windows.

Finishing Touches and Hardware


Casing is more less decorative and aesthetic in purpose. This type of finishing is installed on the interior. Typical window and door companies will provide standard casing free of charge with your new windows. If you have a style that you would like to match, often the best move is for you to purchase what you need in advance, and let your installer know that you have your own casing that you would like installed.

Integrated brickmould into window frame.

Added Brickmould cuts down on installation time, guarantees a perfect fit when installing your window, and prevents water infiltration in the walls.


Brickmould is essentially the exterior equivalent of casing. It provides a finishing touch for your windows and lets you install a completely new window into an existing rough opening without disrupting the exterior siding, stucco or brickwork.

Latches, locks and operators

Latches, locks and operators are the components of the window system that likely gets the most wear and tear. Constant opening, closing, locking and unlocking slowly wears down the finishes on these components. Sometimes improper use can bend or damage these components and make them hard to use.

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