Windows are one of the most important features of any house. They allow you to experience the outdoors from the comfort of your living room, making windows a source of natural light and scenery. While most people look past the making of a window and focus on the sights through them, there are various parts to a home window’s anatomy that make that possible.
Every window has several parts that are crucial to the whole assembly. While most people focus on the glass itself, the panes would not be in place if there were no frames, jambs, heads and sills to hold everything together. In the window industry, key parts of a house window include:
In a window assembly, glass is the principal component. Glass is the material comprising the window panes and allowing homeowners to see outside.
Glass is made from quartz, a mineral composed of oxygen and silicone. During the production stages, glass formulas are mixed in a hot liquid form and then poured at exact quantities into shaping containers, which then enter ovens for hardening. Window panes are constructed this way, as are bottles, vases and various other glass products.
Glass is a strong material that can withstand the elements for many seasons. Thanks to the material’s combination of transparency and hardness, you can watch a raging storm from the comfort of your living room without the risk of flying debris or interior leakage, all due to the protective qualities of glass. Glass can warp over time, but this is generally a rare sight because most of today’s homeowners replace their windows approximately every 20 years.
In window assemblies, glass panes are placed within the frames that hold the left, right, upper, and lower sashes. In modern windows, double panes are often used for extra strength and insulation.
2. Upper Sash (Upper Panel)
In a hung (vertical) window assembly, the upper sash is the panel that contains the top pane of glass and its surrounding frame. The majority of hung window assemblies are known as single-hung windows because the upper sash is stationary and serves as the backbone of the assembly, whereas the lower half can be manually raised or lowered along the moving tracks.
Though the height of a single-hung window can vary, the upper sash typically sits above eye level. As such, the upper sash facilitates the entrance of natural light while the lower sash provides a view to the outside.
While the majority of hung window assemblies are of the single-hung variety, there is an alternative option known as the double-hung window. In a double-hung design, the upper sash can also be lowered and raised along the tracks. As such, double-hung windows allow you to lower the top panel and raise the lower panel.
In the summer months, double-hung windows increase air circulation because the ambient air is allowed to travel in and out through two openings. The double-hung window is an advanced design that is popular among homeowners in warmer climates.
3. Lower Sash (Lower Panel)
The lower sash in a hung window assembly is the bottom panel that can be opened at the owner’s discretion for air circulation. In a typical living room layout, the lower sash sits between hand and eye level, making the panel easy to raise and lower according to the user’s preference. A lower sash can be opened to any height between the bottom and middle of a hung assembly. When fully opened, the lower sash covers the upper sash from the inside.
In a single-hung window, the lower sash is typically found open during the spring and summer months. Homeowners often keep the lower sash raised for air circulation in times of warm weather. Screens are usually placed on the outside of the lower sash to block out bugs and debris. In select homes, a raised lower sash will serve as a placement holder for a window air conditioner. Homeowners who do not use window air conditioners will sometimes seat fans on the ledge in front of an open lower sash.
As with the upper sash, a lower sash can consist of either a single pane or multiple panes. In the latter design, the panes are divided by decorative grids that divide the pane into four or six panels. On older homes, grids are a common feature of hung windows, whereas apartments and office buildings typically feature single-hung windows without grids.
The grids in a window assembly are the pieces that divide the panes into four or more panels. Grids commonly appear in windows of older homes and are also popular among owners of lavish properties. You typically see them on window assemblies with wood framing. However, you can see them on select window designs that incorporate vinyl or fiberglass framing materials.
Grids give each window pane a more decorative appearance. For windows at ground or street level, multiple grids can enhance privacy by reducing the level of transparency from the outside. Grids are common on single-hung and double-hung window designs, but can also be found on sliding windows. In most cases, grids feature on the bay and bow window assemblies that are more common in lavish homes.
Grids can be used to divide a pane into any given number of panels. The most common designs consist of four, six or eight panels. On some windows, the panes physically divide the glass into separate mini panes, as seen on many older homes. These days, most grids are placed on the inside and outside of a solid double-pane of glass to create the illusion of multiple panels.
Window assemblies are equipped with hardware components that allow for safe operation and security. For opening panes, the most important feature in this regard is the locking mechanism, which allows you to shut and lock or unlock and open the window at your own discretion. On single-hung windows, locks usually sit at the top of the lower sash. On sliding windows, the lock sits along the edge of the opening pane.
On hung windows, the lock will usually consist of a switch that you push left to fasten and pull right to unlock. On sliding windows, the lock will sometimes consist of a clamping mechanism. Window locks are usually made of metal. On bay and bow windows, a turning lever gets placed on the far panels that allow those panes to open outward at angles.
In addition to the locking mechanisms, windows come with metal tracks that allow the opening panes to slide up and down or left and right, depending on the design of the assembly.
For maximum protection against wind drafts, window assemblies come with weatherstripping along the opening edges. Each piece of weatherstripping is a protective strip, typically made of rubber, and placed along the upper and lower edges of the lower sash on a single-hung window. On bay windows, weatherstripping lines the outer opening panels. Weatherstripping protects insulation and seals out air drafts that could otherwise form along the opening edges of a window.
Weatherstripping helps to extend the life of a window assembly by locking in air and keeping out wind, heat and the elements. Though it can wear out over time, weatherstripping is one of the easiest features to replace on a window.
Within a window assembly, the frames around each sash are known as jambs. Essentially, the jambs are the inner frames of the window assembly that attach directly to the glass panes. The jambs move within the tracks of the outer frames that attach to the surrounding wall. Jambs get placed along the top, bottom and sides of each window sash.
Depending on the window design, the jambs can serve as decorative features that draw attention to the window. On wood-framed windows, jambs can be varnished or coated with a clear vinyl layer for a natural lumber look.
The side of a window is a self-explanatory feature, whether you talk about the jambs or the outer frame. On the jambs of a sliding or hung window, the sides would be the left and right jambs of each sash. On the outer frame that attaches the window to the wall, the sides would be the left and right vertical frames.
Sides can be one of the decorative features of a window assembly. On a wooden frame, you could have a natural, varnished wood look or paint the sides in a color that complements your interior scheme.
The head of a window is the top-most horizontal part that attaches the upper-edge of the window assembly to the surrounding wall. Within the framework of a window assembly, the head joins at each underlying end with two vertical boards that form the left and right sides of the outer frame. The head is mirrored at the bottom of the window by the sill, which connects the bottom-most portion of the window assembly to the wall.
As with the jambs and sides, the head of a window can be a decorative feature. On most modern windows, the head is painted or coated white, though some homeowners prefer light hues or rich colors.
Beneath the panes and side-frame components of each window assembly is the sill, which connects the underlying portion of a window to the surrounding wall. From a structural standpoint, the sill is one of the most important features because it fastens and balances the window assembly into the corresponding wall slot.
On wooden window assemblies, the sills are usually varnished and treated with protective vinyl for long-term moisture and stress resistance. The sills on windows made with acrylic or fiberglass framing material are usually white or neutral colored.
Products that undergo evaluations by the National Federation Ratings Council (NFRC) are affixed with labels that show performance ratings. The NFRC label allows you to compare the ratings of various products and determine the best performing product in a given category.
What Is a NFRC Label?
NFRC labels are a group of color-coded number ratings that can be found on select products. Each label rates the product in four different categories with a number that indicates the product’s performance in a specific area. The four basic categories under the NFRC rating label concern:
- Insulation – Divided into two rating categories: U Factor (orange) and Solar Heat Gain Transmittance (purple).
- Visible transmittance – Indicates the window’s ability to bring light into a home.
- Air leakage
What Is NFRC Certification?
Products certified by the NFRC have undergone a series of tests for performance quality in several key areas that pertain to energy efficiency. Based on the numbers assigned on a product’s NFRC label, you can determine whether the product will allow you to lower your energy consumption. On a new window, the NFRC label would indicate whether the window would reduce your reliance on heat, air conditioning and artificial light.
What Is a Good U Factor?
On NFRC labels, the U Factor indicates the insulating qualities of the product in question. On a window set, the U Factor number would indicate the window’s ability to prevent the passage of air between the interior and exterior of a room. Products are given a U Factor in the range of 0.20 to 1.20. Low numbers in this spectrum are positive and indicate an air-tight product, whereas a number at 1.00 or above would suggest a product with poor insulation qualities. The U Factor is most important during fall and winter when cold weather hits and you need to trap as much warmth within your living quarters as possible.
What Is a Good SHGC Rating?
On NFRC labels, the Solar Heat Gain Coefficient (SHGC) notates a product’s resistance to heat gain. On a window set, the SHGC would indicate the window’s ability to block the entrance of heat from the outside. SHGC numbers are assigned on a range of 0 to 1. The lower the number, the more effectively the window will block out heat from your living quarters. The SHGC number is most critical during the more humid months when cool, refreshing air is at a premium.
Buy New Energy Efficient Windows
Knowing all the basic window terms, you can confidentially shop for new casement windows and other designs. At Homespire Windows, we sell a range of energy-efficient windows that block air drafts, boost insulation and offer maximum security. Contact Homespire today to learn more about how our windows can transform the look and comfort of your home.