A while back, we did a post about the different parts of a window to help homeowners learn their window anatomy and better understand how windows work. However, that post was mostly geared towards hanging windows as a baseline.
Other window types, like casement windows, vary significantly from hanging windows in their parts, operation, and even care.
So, let’s do a new set of blogs about window anatomy, starting with a focus on casement windows: their parts, how they work, and some general care tips:
Window Anatomy for a Casement Window
A casement window has two main components: the frame that attaches the window to the window opening and the sash that rests in the frame and holds the insulated glass unit (IGU).
However, these are just the most basic, large-scale pieces of the window that can be identified from the outside. On the frame and sash are many additional components that allow the window to be operated and keep it securely shut.
Casement Window Anatomy: The Frame
The frame of a casement window serves as the connection between your window and the surrounding window opening. The frame consists of multiple components, including:
- Stops (Bottom, Top, and Sides). The portions of the frame that the sash will stop on or rest against while shut.
- Operator Handle & Cover. This handle is what you would turn to open or close the casement window. The cover goes over the mechanical portions of the crank that connect it to the armature mechanisms to protect them from dirt, dust, and other hazards.
- Armature/Arm Operator. The mechanism that moves the casement window sash so it swings outward from the window frame. Often made from steel or aluminum for durability and strength.
- Lock Handle. The portion of the locking mechanism that users can operate from inside the home to lock the window in place.
- Interior Locking Mechanism. The actual mechanism connected to the lock handle which moves to secure the window sash in place when the lock is engaged.
- Head. The top of the window frame.
- Sill. The bottom of the frame on the window’s exterior.
- Stool, an interior ledge on some casement windows that can be used as either a shelf or a purely aesthetic detail.
- Jambs. The sides of the frame that connect to the window opening around the frame.
- Casing. Molding on the exterior of the frame that connects and seals it to the outside of the home.
In Florida, the most ideal material for the exterior frame of a casement window is PVC (polyvinyl chloride). This is because it provides the right combination of thermal insulation, resistance to chemicals commonly affecting coastal homes, and durability against common impacts.
A popular alternative is aluminum. However, while aluminum is much stronger than vinyl, it also has a high thermal conductivity. According to IRB Fraunhofen, aluminum has a thermal conductivity of around 160 W/m°K. Compare this to PVC, which has a thermal conductivity of just 0.17 W/m°K.
In short, aluminum conducts heat into your home 940 times faster than vinyl does. This is a major problem for energy efficiency, as it means your air conditioner will have to work that much harder to maintain a stable temperature in your home.
Another benefit of a vinyl frame on casement windows is that they don’t show scratches as readily as painted aluminum or wooden window frames do. That’s because they’re typically extruded in all one color. So, if a scratch occurs, the underlying material is the same color as the top layer, helping hide minor scratches.
Casement Window Anatomy: The Sash
The sash is the portion of the window that contains the insulated glass unit and swings out of the way of the frame when the window is opened.
The parts of a casement window sash include:
- The Insulated Glass Unit. In impact windows, the IGU consists of at least two panes of glass separated by an air gap between them. In the gap, there is a separator and butyl sealant that keeps the IGU airtight. Some high-efficiency windows may have an argon gas fill in this gap to further inhibit the transfer of heat between the interior and exterior of the home. Some windows may also have grilles installed in between the panes of glass in the IGU.
- Stiles. The vertical sides of the window sash.
- Rails. The horizontal parts of the sash at its top and bottom.
- Grille(s). Decorative bars that are set either on or inside of the window sash. May be removable depending on the grille type.
- Sash Bracket(s). Hardware that connects the sash to the window frame when closed. A single sash may have several brackets to keep it from being forced open.
- Sash Keeper. Stationary piece of the sash that receives the window lock. When the handle is flipped or turned, the locking mechanism hooks into the keeper.
Pros of Casement Window Anatomy
By design, casement windows have a few advantages going for them over other window types.
First, and foremost, they offer great air flow when open. That’s because of how they open. Where sliding windows and hanging windows still obstruct part of the window opening, casements move the sash almost completely out of the way of the frame. This allows for greater air flow from the same size window opening compared to hanging or sliding windows.
Another benefit of casement windows is that they provide a large, uninterrupted viewing area from the inside. A casement sash typically takes up the whole of the window frame with one contiguous piece of glass, so they’re a good fit for large windows with vista views.
Third, casements are incredibly difficult to force open. This is thanks to their multiple locking points when shut. It is tough for someone to leverage a casement open from the outside. When combined with impact-rated safety glass, a casement window can easily frustrate even experienced break-in artists.
For some, casements may be easier to open, even if they open more slowly than hanging or sliding windows. The cranking mechanism and the operator arms do the ‘heavy lifting’ for you. This is a good fit for homeowners who have mobility issues or live with others who might struggle to lift their arms above their head due to age, illness, or injury.
Cons of Casement Windows
So, why don’t all homeowners use casement windows for every opening? There are a few reasons that homeowners might cite.
One of the biggest ones has to do with the cranking mechanism used to open and close the window. It’s comparatively easy for the crank to fail if used incorrectly or not properly cared for over time.
Another issue is that there are more moving parts in a casement compared to a sliding or hanging window, which not only increases the casement’s comparative cost, but the chance of mechanical failure (especially if not correctly installed in the first place).
Some homeowners prefer hanging windows to casements simply because hanging windows are faster to open and close. With hanging windows, you just disengage the lock and lift the window in a second or two.
Finally, casement window mechanisms, like the armature, are made of metal. Metal which may be exposed to salty ocean air if you live in a coastal area. This increases the risk of rust and other issues that may make it difficult to open and close the casement window.
Basic Casement Window Tips
If you have a casement window, there are a few things you can do to ensure that it lasts for as long as possible without you needing to replace it:
- Keep Your Window Closed on Days with Strong Gusts. While an open casement window is great for air flow, the window sash catches wind like a boat’s sail when open. If there are strong winds coming through your area, it’s best to keep the casements in your home shut. While resistant to hurricanes when closed, winds pushing on the open sash can pull on the mechanical arms, deforming them or the window frame.
- Periodically Clean Armature Mechanisms. Check your casement’s armature for signs of rust or corrosion and clean it off. Start by vacuuming off loose dirt, wipe it down with a soft cloth soaked with soapy water (dish soap), dry it off with another cloth, then apply lubricant while moving the window to keep the operating armature working smoothly.
- Check That the Window Sash Seats Neatly Against the Frame Stops. When opening and closing your casement window, keep an eye on the sash to see if it swings open and shut smoothly or if it catches on the edge of the window frame. If the sash is scraping the inside of the frame, it may be out of alignment and in need or repair or replacement. The sooner you can catch a misalignment, the better.
Need Expertly-Installed Casement Windows?
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Reach out today to request a free in-home consultation! We’ll take a look at your home’s window openings and help you identify the best type of window for each one.
