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Received an Innovative Commercialization Grant
from the U.S. Department of Energy in 1991

Glossary of Terms

Argon Gas: This is an inert gas that is inserted into the space between the glass. The gas is less dense than air and therefore transmits heat and sound at a slower rate. This adds to the sound proofing of the window and to the insulation value. Over time, this gas dissipates, losing its value.

Bi-Glass System: This is a window renovation system in which the single-pane glass is replaced with insulated glass, while retaining the original sash. A vinyl jambliner system replaces the old weight and pulley or friction balance system.

Hidden Balances: These are balances that are cut into the side of the sash and attach to the jamb so that they remain hidden from view at all times.

Infiltration: This refers to the air that leaks around the sash and works its way into the weight pocket area in the wall. The infiltration makes up 2/3 of the heat loss in a standard, single-pane window.

Insulated Glass: This is two pieces of glass that are bonded together using aluminum, foam, or butyl spacers. They do not have a vacuum between the glass, but have either air or argon gas. They come in different thicknesses, depending upon the application.

Jambliner: The jambliner consists of a vinyl unit that has spring balances installed into it in order to balance the window sash in its operation. This replaces the old weight and pulley system. They have a foam backing to prevent infiltration and weatherstripping to prevent air leakage at the meeting rails.

Low-E Glass: A major cause of winter cold spots and drafts is window glass. Here is what happens: When it's 0 degrees outside and 70 degrees inside, the inside surface of the glass in a single-pane window is a very chilly 14 degrees! You feel a cold spot next to the window. The cold spot interacts with the warm air, setting up currents which cause cold drafts. Under the same winter conditions with "Comfort-E" low-E glass, heat reflected by the glass warms the inside pane of the double-pane windows to about 56 degrees. Cold spots are drastically reduced, so there is little opportunity for convection currents to develop or for condensation to form. Low-E glass is glass with a coating of tin oxide applied to the surface of the interior pane. The coating also contributes to the R-value, helping to increase the insulation value of the glass by up to 10%. The coating also reflects approximately 60% of the ultraviolet rays out of the house, thereby reducing the fading of carpets, floors, and furniture.

Meeting Rails: The meeting rails are the horizontal parts of the sash that meet each other in the center of the sash.

Muntin: A muntin is the grid work that separates the panes of glass in a sash.

Rail: The rails of the sash are the horizontal pieces.

R-Value: This refers to the resistance to heat loss of any object. It is the measuring system used to specify and grade insulated glass. Single-pane glass has virtually no R-value while insulated panels 7/16" to 3/4" thick, range from 1.87 to 2.9 in R-value.

Sash: This is the wooden operable part of the window that holds the glass in place.

Sash Locks: There are a variety of locks for window sash. The standard is a cam lock with a modern look. Reproduction brass locks are also available.

SDL/Simulated Divided Lights: This is a term used to describe a sash that is no longer truly divided (many individual pieces of glass in one sash), but has muntins applied permanently to the interior and exterior. In some cases, there is a spacer grid placed between the glass panels in the insulated glass that match the muntin pattern.

Silicone Bulb Weatherstripping: This type of weatherstripping is a silicone product that is used to seal the horizontal joints of a window sash. It has virtually no memory, therefore it retains its shape even after being compressed all winter long.

Stile: The stiles of a window sash are the two vertical pieces of the sash.

Tape Balance: Tape balances have been used for over 100 years and take the place of the weight and pulley system. They are mounted in the pulley holes and have a flat spring tape that replaces the sash cord. This system is good for large windows where vinyl is not an option.

Vinyl Windows: Windows made completely of extruded vinyl.

Weight Pockets: These are the pockets the weights are housed in. They are filled with insulation when the weights are removed.