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A Glossary of Replacement Window Terms and Definitions
you considering replacing windows in your home? Does the job seem intimidating?
Is there too much to learn? It's true that 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.
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!
- 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
A bay window is a combination of three windows that stick out from the wall
of the house, with the middle window parallel to the house. The other
windows are set at 30- to 45-degree angles, connecting the front window to
- 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
- 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 occurs when two materials contact each other and pass energy
- Dead-air space
Dead-air space is the air-space between the two panes of a double- or
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
Fusion-welding melts materials together at 500° or more, thus creating one
Glazing is the art of attaching a pane of glass to a frame, then sealing it
Grids are bars put on a window to divide the larger pane into what looks
like smaller panes.
The head is the part of the frame at the top of the window.
A hopper is a window that's hinged on the bottom, allowing it to open
- 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.
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
- 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
- Muntin bar
A muntin bar, also known as a grille or a mullion, is a bar that's used to
- 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.
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.
The rails are the parts of the sash that are horizontal.
The sash is the part of the window that holds the pane.
The sill is the bottom part of the frame.
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.
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.
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.
About the author: Gareth Marples is a successful
copywriter who enjoys working from home. His numerous articles offer moneysaving tips and
valuable insight on typically confusing topics.
"Glossary of Replacement Window Terms and Definitions" reprinted with
© 2004 - Net Guides Publishing, Inc.
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