Glossary Of Replacement Window Terms
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A Glossary of Replacement Window Terms and Definitions – Clean and Clear

Are you considering replacing windows in your home? Does the job seem intimidating? Is there too much to learn? It’s true – there are a lot of terms relating to replacement windows. And if you’re not familiar with them, you may get off-track somewhere in your project. So we’ve put together this glossary of replacement window terms and definitions to clear the air. And the windows, too.

  • Air Chambers
    Air chambers are spaces built into a window frame that make the window stronger and being shaped like a honeycomb, they improve insulation.
  • Air infiltration
    Air infiltration refers to how much air can get through the window frame. It’s expressed as how many cubic feet of air pass through a square foot of the frame, per minute.
  • Air latch
    An air latch keeps a window open at whatever position you set it.
  • Argon gas
    Argon gas is nontoxic, colorless, odorless and tasteless. Since it’s 6 times denser than air, it dramatically reduces heat loss when used between panes of glass in a window.
  • Balance system
    A balance system uses springs or weights to hold a window open at the position you set it.
  • Bay window
    The combination of three windows that stick out from the wall of the house, with the middle window parallel to the house is called a bay window. The other windows are set at 30- to 45-degree angles, connecting the front window to the house.
  • Bow window
    A bow window sticks out from a house like a bay window. The difference is the number of windows – there are 3, 4 or 5, attached at 10-degree angles, creating a semi-circular look.
  • Cam lock and keeper
    A cam lock and keeper is the window handle part that keeps it in the locked position.
  • Casement window
    A casement window is hinged on both sides, allowing for a tighter fit, since the sash closes against the frame. A casement window can be opened outward, allowing for better ventilation.
  • Condensation resistance factor
    The condensation resistance factor tells you how well a window reduces condensation. The higher the number, the better it works.
  • Conduction
    Conduction occurs when two materials contact each other and pass energy between them.
  • Dead-air space
    Dead-air space is the air-space between the two panes of a double- or triple-pane window.
  • Desiccant
    Because of it’s water absorbency, desiccant is used in insulating glass to prevent windows from fogging up.
  • Double-hung window
    A double-hung window is a window that slides or opens up and down.
  • Double-strength glass
    Double-strength glass is about 1/8” thick.
  • Egress code
    The egress code is a law that specifies that a window must be able to open wide enough for a person to get out, or a firefighter to get in.
  • Energy Star®
    When you see an Energy Star® on a product, you know it conforms to energy-efficiency guidelines as set out by the government environmental agency.
  • Fusion-welded
    Fusion-welding melts materials together at 500º or more, thus creating one piece.
  • Glazing
    Glazing is the art of attaching a pane of glass to a frame, then sealing it in place.
  • Grids
    Grids are bars put on a window to divide the larger pane into what looks like smaller panes.
  • Head
    The head is the part of the frame at the top of the window.
  • Hopper
    A hopper is a window that’s hinged on the bottom, allowing it to open inward.
  • I.G. (Insulating Glass) unit
    An I.G. unit is a double- or triple-pane window, with air-space between the panes, and sealed at the edges.
  • Jamb
    The jambs are the parts of the frame on either side of the window.
  • Krypton gas
    Krypton gas is used for the same purpose as argon gas. The difference is that it’s twice as dense as argon, or 12 times denser than air.
  • Laminated glass
    Laminated glass is made by bonding a tough protective layer or polyvinyl butyral (PVB) between two panes of glass under heat and pressure.
  • Lift handle
    A lift handle is simply the handle used to open and close a window.
  • Lift rail
    A lift rail is the same as a lift handle, except it goes all the way across the sash.
  • Low-emissivity (Low-E) glass
    Low-E glass has a special clear coating on it that blocks infrared energy from passing through it.
  • Mechanically-fastened frame
    A mechanically-fastened frame is put together using screws, as opposed to fusion-welding.
  • Muntin bar
    A muntin bar, also known as a grille or a mullion, is a bar that’s used to divide panes.
  • Obscure glass
    Obscure glass is translucent, rather than transparent, and is used for such places as bathroom windows.
  • Picture window
    A picture window is usually very large and has a sash that can’t be moved.
  • R-value
    The R-value of a window refers to the amount of heat loss it allows. The higher the number, the less heat is lost. R-values today can go from 0.9 to 4.0, or even more.
  • Rail
    The rails are the parts of the sash that are horizontal.
  • Sash
    The sash is the part of the window that holds the pane.
  • Sill
    The sill is the bottom part of the frame.
  • Single-hung
    A single-hung window is the same as a double-hung window, except the top sash doesn’t move.
  • Single-strength glass
    Single-strength glass is about 3/32” thick.
  • Slider window
    A slider window moves back and forth, as opposed to up and down.
  • Sloped sill
    A sloped sill is the outside of the window sill, and is sloped downward to allow water to run off.
  • Stile
    The stiles are the parts of a frame that run up and down.
  • Tempered glass
    Tempered glass is specially treated, so that when it breaks, it shatters into little pieces.
  • U-value
    A window’s U-value refers to how much heat passes through the glass. The lower the U-value, the better the insulation.
  • Weep flaps
    Weep flaps are little vinyl-covered holes that let water escape, while keeping bugs out.
  • Weep slots
    Weep slots are holes in the sill that let water run outside.

Now, do you have a clear view? Can you see your way through this project? Everything should fit into place now, and you should be able to get your replacement windows without any grief. And when you’re finished, just relax and pat yourself on the back for a job well done!

Also see: replacement windows.

About The Author

Gareth Marples is a successful freelance writer providing tips and advice for consumers purchasing home replacement windows. His numerous articles offer moneysaving tips and valuable insight on typically confusing topics.

This "Glossary of Replacement Window Terms and Definitions" reprinted with permission.

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