Window Replacement Terminologies: A Guide for Homeowners

Last Updated on March 24, 2022 by Kravelv

 Have you ever experienced trying to buy something in a foreign country where people don’t speak English? It’s hard to explain what you need, and it’s even harder trying to understand what the salesperson is saying. But such scenarios don’t just occur in non-English speaking countries. It can happen right here at home in certain situations. A good example is trying to understand something that you probably know nothing about, like window replacement.

The company’s representative will likely explain to you everything involved in window replacement. But if you know nothing about the terms they’re using, you might end up just nodding your head without understanding a thing they’re saying–even though they’re speaking in perfect English!

The aim of this article is to familiarize you with some of the most common terms used in window replacement projects so when it’s time for you to replace your windows, you’ll understand exactly what’s going on.

I. Types of Windows

KNOW YOUR OPTIONS. Windows come in different style options. By knowing what each looks like and what they offer, makes selecting the right one for your home easier.

Windows come in different types based on the operation. Here are the ones that you’d likely encounter when choosing windows for your home:

  • Double Hung – These are the most common types of windows around. Almost every home has them. Their distinct feature is two glass panels in frames one on top of the other. Double hung windows operate by sliding the two sashes up or down.
  • Casement – These windows are also common. They can easily be identifiable by the location of the hinges that are attached to the sides of the glass frame. Hinges allow the window to open outward and close inward.
  • Bow & bay – These types of windows protrude from the house.
  • Picture – These windows only allow light into the room. They can’t allow air in because they do not open.
  • Sliding – As the name suggests, these windows slide in either direction to open or close.
  • Specialty – These windows are more like works of art than simple windows. They can either stand alone or be paired with other windows of the same type.
  • Awning – These windows are similar to single hung windows but instead of sliding up or down, they open outward.

II. Parts of the Window

ANATOMY OF A WINDOW. By knowing the parts of a window, you can easily tell your window contractor which parts of the window need attention.

The first thing any window manufacturer would need from you is your window preference. It’s a bit difficult to describe what you need if you don’t know the parts of a window. Here are the most frequently used terms:

  • Frame – The window frame is the support structure for the entire window. It’s made up of pieces of wood or metals that surround the entire window.
  • Jambs – The jambs are the vertical sides of the window frame.
  • Mullion – These are heavy vertical and horizontal bars on the glass pane used to separate two windows.
  • Muntins – These are thinner than mullions but act almost the same way. The difference is that they separate adjacent glass panes instead of two windows.
  • Pane – Panes are the large pieces of glass you see in the window.
  • Sash – Window sash are window designs that are made up of several window panes separated by mullion and muntins.
  • Sill – A sill is the lower portion of the window that looks more like a ledge. It’s primary purpose is to keep rainwater from getting in and dripping all over the floor.
  • Stile – The stile is the vertical part of the sash. It is instrumental in allowing the window to move up or down.
  • Opening crank – Some windows, especially casement windows, require a crank mechanism to open and close. These are referred to as an opening crank.

III. Replacement Windows: The Products

Today’s replacement windows are equipped with features that add to their value. Below is a list of terms that you may hear from your window dealer as they explain the advantages of their products.

  • Low-E Glass – Low-e is short for low emissivity. A low-e glass is a type of glass coated with an ultra thin material that is capable of reflecting infrared energy from the sun away from the window pane. This means that heat doesn’t enter the home making it easier to control the temperature inside, thus requiring less energy consumption.
  • Fibrex Material – This is a special type of material used for window frames. It’s a composite material exclusively offered by Andersen Windows and Renewal by Andersen. It is tougher than wood, metal, or PVC, but can also take the appearance of those materials.
  • Argon Gas Fill – Most energy-efficient windows today are made up of two glass panes. There is a very small space between the two panes that is filled with inert gas such as argon. This gas helps in reducing the amount of heat that passes through the window, thus adding to the energy efficiency properties of the window.
  • Energy Star – Energy Star is a program by the Department of Energy that gives information on the energy-efficient properties of windows. If a window has an Energy Star stamp, it means that it has passed the stringent energy efficiency standards of the government.

NFRC LABEL. By checking the ratings on this label, you’ll know whether a replacement window is energy-efficient or not.

  • NFRC label – NFRC, or the National Fenestration Rating Council, is a non-profit organization that monitors the energy efficiency of different products, such as windows, doors, and skylights. If a product has an NFRC label, it means that it has been tested for different energy efficiency indicators, and you can compare its ratings with other energy-efficient products.
  • U-Factor – U-Factor is a way to measure the amount of heat a window prevents from passing through. This means that the lower the measurement is, the more efficient the window is at conserving energy.
  • SHGC – Solar Heat Gain Coefficient is a measurement of how much solar radiation passes through the window. This means that lower figures in this category indicate that the window allows as little heat as possible.
  • VT – Visible Transmittance measures the amount of visible light that can pass through the window. The higher the VT measurement is, the better the window. It means that the window allows the room to become brighter using daylight.
  • AL – Air Leakage rating measures the amount of air that passes through the gaps of a window assembly. Naturally, a low AL rating would mean that less air is leaking through a closed window.

There are certainly more terms involved in window replacement, but the ones listed above should be enough to help you understand whatever a window replacement company representative is trying to tell you.


Author Bio:

Alex Esler serves as marketing manager for Renewal by Andersen, the window replacement subsidiary of Andersen Corporation. Their local, family owned offices in Southern New England, Greater Philadelphia, and Colorado compose the largest replacement window dealership in a network of 100 Renewal by Andersen Dealers. Always eager to help and known to maintain a positive outlook in life, Alex remains driven and inspired by her work and the causes she cares about.


Kravelv is a full time digital marketer and part time furniture and cabinet maker. During his free time he would like to create something out of recycled woods, this varies from toys, furnitures plant boxes etc. Follow him on Twitter | Pinterest | Facebook

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