A gas used to fill the space between glass panes on a double paned vinyl window. Because the gas is denser than air, it acts to resist the passage of outside temperatures through the glass panes. There has been speculation that the gas eventually escapes after a few years, but that hasn't been proven.

Windows that are hinged on top and open outward.

This is the device that holds the single or double hung vertically sliding window sash in the open position. Lower quality windows use a block and tackle system. The better quality windows use a "constant force" system that consists of a titanium coil.

A window hinged on the side that opens outward.They come with the hinge on either the right or left side, depending on buyer's preference.

A window that has two vertically sliding panels. The bottom slides up and the top slides down.

Glass that measures 1/8" thick. Single strength glass measures approximately 3/32". Today, most vinyl window manufacturers use double strength glass in their units.

A safety code that requires a window have a minimum opening large enough for people to get through in case of fire.

ENERGY STAR is a government-backed program helping businesses and individuals protect the environment through superior energy efficiency. CLICK HERE to learn more.

This term describes how the corners of some vinyl windows are connected. The lower grade windows use screws to hold the corners together, called mechanically fastened. Fusion welding involves a process of melting the corners together to essentially form a one piece unit that is far stronger than one held together with screws.

These are vinyl windows with frames shaped differently than the typical rectangle. Examples are octagons, triangles, half round, full round, etc.

Lightweight metal bars placed between two panes of glass to give the appearance of individual square panes of glass, like a french door look.

This is usually two pieces of glass, sometimes three, separated by air space using a spacer on the glass edge. If you know the thickness of each piece of glass and the thickness of the air spacer, you can determine the overall thickness of the IGU.

Left and right verticle parts of a window frame.

Found on vertically sliding single hung or double hung vinyl windows to lift or lower the sash.

Similar to the lift handle, except the protruding lip goes across the entire length of the vinyl window sash.

Glass that has a metallic coating placed on one side. It's always placed on a side of the glass that's between two panes, so it can't be touched. Glass that has a second coating applied is called Low E 2 or Low E squared. For more information on the advantages of lowE Glass CLICK HERE.

Window frames that are fastened at the corners with screws,rather than fusion welded. Found in lower grade windows.

A 1" Protruding fin that goes around a window designed for new construction projects. The fin is used to nail the vinyl window onto the studs.

Glass that obscures ones vision. Used in bathroom windows, there are several types of obscure glass, but probably the most common is P516. That's the stuff that's smooth on one side and little bumps on the other.

Another term for a sliding glass door.

A window without a moving panel.

Used on horizontal sliding vinyl windows to slide the vent panel open and closed.

Same as the pull handle, except the protruding lip goes the entire length of the rail.

A number given to measure a materials resistance to heat penetration. A high R-Value rating means the vinyl window resists heat penetration better than a low R-Value rating.

Found mainly in the western U.S., Retrofit vinyl window frames have a 2" wide lip flush with the exterior of the window frame. This lip fits against the stucco exterior to hide the old aluminum frame that is still attached to the home.

The frame around the glass of the window. On a double hung vinyl window you have an upper sash and a lower sash.

A window that has one vertically sliding panel and one fixed. The lower panel is usually the one that slides.

The downward angle of the outside sill on many old wood windows. The purpose is to aid in water drainage.

A measurement to determine the amount of heat your house gains from the sun. A lower SHGC results in less heat gain from the sun.

The material that creates a space between the panes of glass in an insulated glass unit. This material consistes of aluminum, butyl, or foam. Aluminum is the least efficient spacer material, and foam is arguably the most efficient.

The name given to the lip on a retrofit window. Used mainly on homes with stucco exteriors to hide the old framework .

Glass used in areas where safety is a concern, such as sliding glass doors and any vinyl windows that are at or near ground level. The glass must be cut to proper size before the tempering process. Once tempered, it cannot be cut.

Found on higher quality double hung vinyl windows, it allows you to tilt in the sash so you can clean the outside glass without going outside. This feature is especially handy for vinyl windows on the second floor of a two story home.

This number shows how much heat is able to pass through the vinyl window. Unlike the R-Value, the lower the number,the better the U-Value,because it's measuring how much heat is passing through. So,lower equals better. As of this writing,the ENERGY STAR program requires a U-Value of .40 or lower in order for a vinyl window to qualify for the energy star label.

The portion of a vinyl window that can be opened. In the case of a double hung vinyl window, both portions are vent panels. When you see XO used to describe a vinyl window, the X represents the vent panel and the O represents the fixed panel.

Openings found in the bottom of the vinyl window frame that allow any water that has penetrated the window to drain back outside.