Glossary

AIRSPACE -- All high performance windows have at least two panes of glass sandwiched together, with an airspace in between. The size of the airspace effects the overall performance of a window. A 1/2" to 3/4" space is considered optimal.

ARGON -- A gas and air constituent used to fill insulating units to increase thermal performance in windows.

AWNING -- A window that hinges at the top, locks on the sides, and projects out from the bottom when in an open position.

BALANCES -- Spring loaded single/double hung vent support system.

BTU -- An abbreviation of British Thermal Units that defines the amount of heat needed to raise the temperature of one pound of water to one degree Fahrenheit.

BUTYL -- Polyisobutylene is a hot melt sealant and is used as the primary seal for dual seal systems.

CAPILLARY TUBES -- A very small metal tube which is factory placed into insulated glass to accommodate air pressure differences. Capillary tubes are not sealed after installation.

CASEMENT -- A window that hinges on the side, locks on the side, and projects out vertically when in an open position.

CAULK -- Material to fill voids around windows and doors.

CONDUCTION -- Refers to heat flow through a solid material such as a window frame or glass. In the winter, the interior surface of a window is warmed by the home's heating system, and that heat is conducted (or transferred) to the cooler outdoors.

DEGLAZE -- Removing the glass from the window frame.

DESICCANTS -- Porous crystalline substances used to absorb moisture and solvent vapors from the airspace of insulating glass units.

DUAL GLAZED UNITS -- Units consisting of two lites of glass and one airspace.

EGRESS -- A fire code that requires entry and exit specifications in bedrooms.

EXTRUSION -- The frame bar from which the window is manufactured.

FOGGED UNIT -- A permanent deposit of contaminates on the interior glass surfaces of an insulating unit.

GRIDS -- A decorative pattern within the insulated unit.

HEADER -- The top portion of the window frame.

HIGH PERFORMANCE WINDOWS -- Windows that have u-values of .40 or lower.

INFILTRATION -- Air leakage which can escape through cracks between the glass assembly and the window frame resulting in heat loss.

JAMBS -- The vertical sides of a window frame.

LAMINATED GLASS -- Two or more lites of glass bonded together with a plastic inner layer.

LOW-EMISSIVITY (LOW-E) -- A coating consisting of a very thin layer of metallic oxide or silver which is applied to the third surface of an insulating glass unit to block radiant heat transfer and ultra-violet rays.

MULLION -- A horizontal or vertical member that holds together two adjacent lites of glass or sashes.

MULTIPLE CHAMBERED FRAME -- Frame members which have hollow core construction to provide strength and insulation.

NFRC -- National Fenestration Rating Council.

PICTURE WINDOW -- A fixed window with no opening members.

PVC -- Polyvinyl Chloride.

R-VALUE -- The resistance of conductive heat energy. The higher the number the greater the insulating capacity. It is the reciprocal of a U-value; R=1/U.

RADIATION -- This refers to the process of heat traveling via infrared or heat rays from a warm object to a cooler object. Radiant heat loss accounts for a large percentage of the heat loss in windows. Radiant heat gains occur when sunlight shines through a window and warms objects inside.

SEAL -- Insulating glass units are sealed at the edges to prevent moisture and dirt from contaminating the interior of the unit. The seal must be durable and usually consists of an aluminum spacer with an exterior sealant.

SILL -- The bottom portion of the window frame.

SINGLE HUNG -- Vertical sliding window.

SLIDER -- Horizontal sliding window.

SPACER -- The aluminum material that separates the two lites of glass in an insulating unit.

TEMPERED GLASS -- Heat strengthened glass used for safety purposes.

U-VALUE -- A measurement that indicates the rate at which the window loses heat through conduction and radiation. The lower the U-value, the more efficient the window. It is the reciprocal of R-value: U-1/R.

VENT -- The sliding or projecting portion of the window.

WEEP HOLES -- Slots of holes in the sill member of the window frame to provide outdoor release of infiltrated water.

XO -- Horizontal sliding window.