San Antonio Windows Term Dictionary
Making the right design choices for your home can be complicated even when you understand all the factors that go into those decisions, but purchasing windows takes that to a whole different level. You would think it’d be simple, but the diversity of terms and ideas can be challenging even for professionals. But we’re here to help! Use this dictionary of window terms to assist you in your home improvement adventure.

Air Leakage, also known as air infiltration. This can give buyers a sense of the window’s impermeability. You want your window to be as immune to air leaks- both inwards and outwards- as possible because you want the temperature of your internal environment to remain as unaffected by the outside weather as possible. This rating is measured by how many cubic feet of air penetrate through compared to the square footage of window area. The lower this number is, the better!
Awning Window, which is a window that opens outward via a hinge located at the top. These are typically found in basements.
A Casement Window is a window that swings outward from hinges on the side.
Composite Windows are made from more than one material, such as fiberglass, wood, or recycled plastic.
A Double-Glazed Window consists of two panes of glass separated by a space. With energy-efficient windows, this space can be filled with a gas (such as krypton) that can limit UV rays, but overall a space between two panes of glass limits temperature transference.
Double Hung Window: a window with sashes which open from the top and bottom.
A Fixed Window doesn’t open but can be amazing for allowing light to enter and adding to the aesthetic of an open-floor design.
Gas-Filled Windows are energy-efficient windows containing two or three panes of glass with gases inserted between them, which increases insulative performance because these gases are denser than oxygen. While Argon is the most common, these windows can contain Argon, Krypton, or Xenon which are listed from least dense to most dense respectively.
Low-E (Low-emissivity) Windows possess a coating that creates greater resistance to temperature transmission because it improves the reflective properties of the glass. This essentially traps heat on whichever side of the glass it originated from.
R-Value measures how well a material resists the flow of heat. A low R-Value is ideal because this indicates that the substance your windows are made from is not a good conductor and therefore does not allow heat to transfer in or out easily.
A [Window] Sash is the framework that holds the glass in place.
Single Hung Windows are similar to double hung windows, but only the bottom sash opens and closes while the top sash is fixed.
Tempered Glass is a material your windows can be made of so that they are more difficult to break.
The Visible Transmittance Rating is determined by the quantity of light which passes through the glass, with higher numbers showing a larger light transmission.