Glossary   Term Description AAMA AMERICAN ARCHITECTURAL MANUFACTURERS ASSOCIATION. THIS GROUP SETS STANDARDS FOR DOORS, WINDOWS AND SKY LIGHTS.   AIR INFILTRATION AIR LEAKAGE INTO AND OUT OF BUILDINGS THROUGH WALL CRACKS AS WELL AS WINDOWS AND DOORS.   AIR LEAKAGE RATING THE RATE OF AIR INFILTRATION AROUND A WINDOW OR SKY LIGHT WITHIN A GIVEN PRESSURE DIFFERENCE. IT IS STATED IN CUBIC FEET PER MINUTE OF EITHER THE SQUARE FEET OF THE WINDOW'S AREA (CFM/SQ FT) OR PER FOOT OF WINDOW PERIMETER LENGTH (CFM/FT). THE LOWEST LEAKAGE RATES ARE THE BEST.   ANSI AMERICAN NATIONAL STANDARDS INSTITUTE; THE REPOSITORY FOR ALL STANDARDS AND SPECIFICATIONS.   ARGON A RARE, INERT AND NON-DANGEROUS GAS USED TO FILL THE AIR GAP BETWEEN SHEETS IN INSULATED GLASS UNITS. THIS GAS SLOWS WARM AIR FROM ESCAPING THROUGH THE INSULATED GLASS UNIT. ARGON MAKES UP @ 9/100THS OF THE AIR WE BREATH DAILY.   ASTM AMERICAN SOCIETY FOR TESTING AND MATERIALS. THEY SPECIFY THE STANDARDS FOR TESTING MATERIALS.   AWNING A WINDOW THAT IS HINGED AT THE TOP; THE BOTTOM SWINGS OUT AS IT IS OPENED.   BAY WINDOW THREE OR MORE WINDOWS, PROJECTING FROM A BUILDING AT 30 OR 45-DEGREE ANGLES, AS ONE UNIT. NORMALLY, THE CENTER WINDOW IS A PICTURE WINDOW AND THE SIDE WINDOWS ARE EITHER VERTICAL SLIDERS (DOUBLE HUNG TILT) OR CASEMENT WINDOWS.   BOW WINDOW FIVE WINDOWS, PROJECTING FROM A BUILDING IN AN ARC, AS ONE UNIT. COMMONLY, THEY ARE OPERATING VERTICAL SLIDER (DOUBLE HUNG TILT) WINDOWS.   BTU BRITISH THERMAL UNIT. THE HEAT NEEDED TO RAISE THE TEMPERATURE OF ONE POUND (SLIGHTLY LESS THAN 1/8TH OF A GALLON) OF WATER ONE DEGREE FAHRENHEIT.   CASEMENT A WINDOW THAT IS HINGED ON ONE SIDE OR THE OTHER; IT MAY SWING IN (FRENCH STYLE) OR SWING OUTWARD (ENGLISH STYLE) DEPENDING ON IT'S DESIGN.   CONDENSATION AIR BORNE WATER VAPOR THAT LAYS ON A COLD INSULATED GLASS UNIT OR THE COLD WINDOW FRAME, CAUSED BY HUMID INDOOR AIR MOVING TOWARD THE COLD. THE GLASS AND FRAME TEMPERATURES WILL BE BELOW THE DEW POINT TEMPERATURE.   CONDUCTION MOVEMENT OF HEAT THROUGH A SOLID OBJECT BY WAY OF MOLECULAR CONTACT. HEAT/WARMTH ALWAYS MOVES TOWARD COOLER TEMPERATURES.   CONVECTION A METHOD BY WHICH HEAT IS TRANSFERRED WHERE THERE IS A DIFFERENCE IN THE DENSITY OF THE AIR GAP BETWEEN THE SHEETS OF GLASS IN AN INSULATED GLASS UNIT AND WHERE GRAVITY INTERACTS WITH IT. THIS SAME EFFECT ALSO AFFECTS HEAT TRANSFER FROM THE GLASS SURFACE TO THE AIR IN THE ROOM.   CRF CONDENSATION RESISTANCE FACTOR. A DECIMAL NUMBER INDICATING A WINDOW'S ABILITY TO RESIST THE FORMATION OF CONDENSATION. A HIGH NUMBER INDICATES THE WINDOW HAS HIGH RESISTANCE TO CONDENSATION.   DEW POINT A TEMPERATURE AT WHICH CONDENSATION WILL FORM AT A CERTAIN AIR PRESSURE AND HUMIDITY.   DOUBLE-GLAZING REFERRING TO ASSEMBLED WINDOWS, TWO CLEAN UNITS OF GLASS, THOROUGHLY DRIED AND TIGHTLY SEALED AGAINST AIR INTRUSION AND THE CHANCE OF CONDENSATION.   DOUBLE HUNG WINDOW A WINDOW WITH TWO SASHES, EITHER OF WHICH CAN BE SLID UP OR DOWN, INSTALLED IN A RECTANGULAR FRAME. ALSO CALLED A VERTICAL SLIDER.   EXTRUSION THE PROCESS OF PRODUCING EITHER VINYL OR ALUMINUM SHAPES BY FORCING HEATED MATERIAL THROUGH A DIE AND SIZERS. ALSO, WHAT ANY EXTRUDED VINYL WINDOW PART IS COMMONLY CALLED.   EYEBROW WINDOW LOW, ARCHED WINDOWS WITH A BASE WIDTH GREATER THAN THEIR HEIGHT RADIUS.   FANLIGHT A HALF-CIRCLE WINDOW WITH RADIATING BARS; USUALLY INSTALLED OVER A WINDOW, SOMETIMES OVER A DOOR.   FENESTRATION THE ARRANGEMENT OF WINDOWS IN A BUILDING. ALSO, A WINDOW WITH IT'S TREATMENT (BLINDS AND SHADES).   FIXED LIGHT REFERS TO BOTH THE OPENING FOR IT AND THE PANE OF GLASS PUT INTO A NON-OPERATING FRAME.   FIXED PANEL THE NON-OPERATING PANEL IN A HORIZONTAL OR VERTICAL SLIDER WINDOW; ALSO THE NON-OPERATING PANEL OF A SLIDING GLASS DOOR.   FIXED WINDOW A WINDOW THAT DOES NOT OPEN OR CLOSE AT ALL.   FLOAT GLASS A HIGH QUALITY GLASS PRODUCED BY FLOATING IT'S MIXTURE ON A BED OF MOLTEN METAL.   FRAME THE VINYL STRUCTURE (HEADER, JAMBS AND SILL) THAT HOLDS AWNING, CASEMENT AND SASH PLUS THE HARDWARE.   GAS FILL AN INERT GAS (ARGON, KRYPTON OR A MIXTURE OF BOTH) THAT FILLS THE AIR SPACE BETWEEN THE GLASS PANES OF AN INSULATED GLASS UNIT. IT IS USED WITH LOW-E GLASS TO LOWER U-VALUES IN INSULATED GLASS UNITS.   GLASS A COMPOSITION OF SAND, SODIUM CARBONATE AND CALCIUM CARBONATE, WITH A SMALL AMOUNT OF OXIDE MATERIAL.   GLAZING THE INSULATED GLASS UNIT (S) OR SINGLE GLASS PANE (S) IN WINDOWS, SKYLIGHTS AND DOORS. ALSO CAN BE PLEXIGLAS OR ANY PLASTIC BASED CLEAR MATERIAL.   GLAZING BEAD A "SNAP-IN" EXTRUDED STOP TO HOLD INSULATED GLASS UNITS THEIR SASHES.   GREEN HOUSE WINDOW ALSO KNOWN AS A "GARDEN WINDOW". IT EXTENDS FROM THE OUTSIDE WALL OF A HOME, HAVING GLAZING ON ALL OUTSIDE SIDES EXCEPT THE BOTTOM. THE BOTTOM SERVES AS A SHELF (OR SEAT), SHELVING MAY BE SUPPLIED FOR THE INTERIOR OF THIS WINDOW.   HEADER THE TOP WIDTH OF A WINDOW FRAME.   HEAT GAIN THE ENTRY OF OUTSIDE HEAT INTO A HOUSE THROUGH THE WALLS, WINDOWS, DOORS AND ROOF. THE HEAT ENTERS BY MEANS OF RADIATION, CONVECTION AND CONDUCTION.   HEAT LOSS THE MOVEMENT OF HEAT THROUGH THE WINDOW, GOING TOWARD THE COLD (OUTSIDE). CONDUCTION, CONVECTION AND RADIATION ARE THE WAYS IT USES TO ESCAPE.   HINGED WINDOWS THESE WINDOWS HAVE A SASH WITH HINGE MECHANISMS ON ONE SIDE. THEY COULD BE AWNINGS, CASEMENTS OR BASEMENT HOPPER TYPES.   HOPPER ON THIS WINDOW, THE SASH IS HINGED AT THE BOTTOM.   HORIZONTAL SLIDER THIS WINDOW HAS A SASH THAT SLIDES TO THE LEFT TO OPEN AND RIGHT TO CLOSE.   INFILTRATION ANY MOVEMENT OF AIR INTO A BUILDING USING CRACKS AROUND WINDOWS AND DOORS. ALSO AIR MOVEMENT INTO A BUILDING WITHIN WALLS, ROOFS AND DOORS.   INSULATING GLASS ONE (1) GLAZING UNIT MADE UP OF TWO (2), SOMETIMES THREE (3) GLASS PIECES, UNIFORMLY SEPARATED FROM EACH OTHER, THEN PRESSURE AND HEAT SEALED. WHEN 2 GLASS PIECES ARE USED, THERE IS ONE (1) AIR SPACE AND THE UNIT IS SAID TO BE DOUBLE GLAZED; BUT, IF 3 GLASS PIECES ARE USED, THERE ARE TWO (2) AIR SPACES AND THE UNIT IS SAID TO BE TRIPLE GLAZED.   INSULATION ANY CONSTRUCTION MATERIAL(S) THAT KEEP OUT THE COLD, HEAT, NOISE AND PROVIDES PROTECTION AGAINST FIRE.   JALOUSIE A WINDOW WITH HORIZONTAL GLASS SLATS THAT ROTATE OUTWARD AS THE WINDOW CONTROL IS OPERATED. WHEN CLOSED, THE SLATS LAY TIGHT AGAINST EACH OTHER. SOME SIMILARITY TO THE ACTION OF A VENETIAN BLIND.   KWH STANDS FOR KILOWATT-HOUR. IT IS THE SAME AS 1000 WATTS PER HOUR AND IS EQUAL TO 3/4 H.P.   LIGHT A WORD WITH MANY MEANINGS. (1) A GLASS PANE IN A WINDOW; (2) A WINDOW ITSELF; (3) THE NUMBER OF SEPARATE PANES OF GLASS IN THE UPPER AND/OR LOWER SASHES. EXAMPLE: 4-OVER-4 LITES.   LOW-E A "SHORT HAND" TERM FOR LOW EMISSIVITY COATED GLASS. IT IS A METALLIC OXIDE COATING APPLIED DIRECTLY TO THE GLASS IN EITHER A SOFT-COAT OR HARD COAT VERSION. THE COATING IS NEARLY INVISIBLE AND EASY TO SEE THROUGH. IT REFLECTS AWAY THE LONG-WAVELENGTH INFRARED RADIATION WHICH CUTS DOWN THE HEAT TRANSFER BETWEEN THE SHEETS OF GLASS.   MUNTINS THE ACTUAL TERM FOR THE GRILLS INSIDE A DOUBLE GLAZED UNIT THAT GIVE THE APPEARANCE OF DIVIDING THE SASH INTO SEPARATE PANES OF GLASS. THEY ARE HERMETICALLY SEALED IN A DOUBLE GLAZED UNIT; SOME SINGLE GLAZED UNITS ARE DESIGNED TO ALLOW THEIR REMOVAL FOR WINDOW WASHING. (SEE "LIGHT").   NFRC ATIONAL FENESTRATION RATING COUNCIL. A NATIONAL ORGANIZATION OF VOLUNTARY MEMBERS, MANUFACTURERS OF WINDOWS AND THEIR SUPPLIERS, CO-OPERATING WITH THE U.S. DEPT OF ENERGY AND E.P.A. THEIR PURPOSE IS TO ESTABLISH ENERGY EFFICIENT THERMAL STANDARDS FOR WINDOWS, DOORS AND SKYLIGHTS IN THE UNITED STATES.   OBSCURE GLASS SIMPLY, GLASS YOU CAN'T EASILY SEE THROUGH. MOST COMMONLY IT IS "FROSTED" , BUT IT ALSO COULD BE ETCHED, GROUND, ETC. MOST OFTEN, IT IS USED FOR PRIVACY, SUCH AS IN BATHROOM/RESTROOM WINDOWS.   OPERATING WINDOW THE OPPOSITE OF A "FIXED WINDOW" (SEE ABOVE); AN OPENABLE WINDOW.   OPERATOR THE MECHANICAL DEVICE WITH CRANK HANDLE THAT OPENS AWNING, CASEMENT AND JALOUSIE WINDOWS.   PANEL REFERS TO THE GLASS UNIT WITHIN A FRAME WORK WHICH IS PART OF A SLIDING DOOR. THE PANEL MAY BE SLIDING OR IT MAY BE FIXED.   PICTURE WINDOW SEE FIXED WINDOW. IT CAN BE USED IN COMBINATION WITH DOUBLE HUNG TILT, SINGLE HUNG TILT, CASEMENT AND AWNING WINDOWS. USUALLY, THIS WINDOW IS MORE WIDER THAN HIGHER. IT DOES NOT OPEN.   PROJECTED WINDOW IT HAS A SASH (OR SASHES) THAT PIVOT OPEN, LIKE A CASEMENT, AWNING OR HOPPER.   PVC ABBREVIATION FOR POLYVINYLCHLORIDE. ALL PVC IS BLENDED TO BE UNPLASTICISED (RIGID); MOLDED OR EXTRUDED INTO FRAME AND SASH MEMBERS FOR VINYL WINDOWS. HAS APPROXIMATELY THE SAME INSULATING (THERMAL) VALUE AS WOOD, YET DOES NOT REQUIRE ANY MAINTENANCE.   R-VALUE A WHOLE OR MIXED NUMBER THAT IDENTIFIES A WINDOW, DOOR , SKYLIGHT OR WALL'S ABILITY TO RESIST THE FLOW OF HEAT THROUGH IT. THE HIGHER THE NUMBER, THE BETTER (EXAMPLE: AN R=2.7 IS BETTER THAN AN R=2.0). R IS EXPRESSED IN UNITS OF HOUR PER SQUARE FEET IN DEGREES FAHRENHEIT OF BRITISH THERMAL UNIT. PROFESSIONALLY, FENESTRATION ORIENTED ORGANIZATIONS USE "U"-VALUE, WHICH THE INVERSE OF "R".   RADIATION THIS IS THE TRANSFERENCE OF WARMTH (OR HEAT) BETWEEN TWO DIFFERENT SURFACES, FROM ONE TO THE OTHER AS ELECTROMAGNETIC WAVES.   RELATIVE HUMIDITY EXPRESSED AS A PERCENTAGE, THIS IS A COMPARISON OF WATER IN THE AIR COMPARED TO THE AMOUNT OF WATER THAT AIR MASS CAN ACTUALLY HOLD. THIS IS ONE OF THE DETERMINANTS OF WHETHER CONDENSATION CAN FORM ON A WINDOW.   RETROFITTING WHEN USED IN REFERENCE TO HOUSES, THIS WORD MEANS THE SAME AS REMODELING. IT IS THE ADDITION OF REPLACEMENT DOORS, WINDOWS, SIDING, VENTS, ETC.   ROUGH OPENING ANY UNFINISHED OPENING IN A WALL INTO WHICH A WINDOW OR DOOR WILL BE PUT IN.   SAFETY GLASS A TEMPERED AND STRENGTHENED GLASS THAT IS LESS LIKELY TO BREAK INTO JAGGED PIECES WHEN IMPACTED ON; INSTEAD, IT IS MORE LIKELY TO BREAK INTO SMALLER, NON-SHARP EDGED PIECES UNDER THOSE CONDITIONS.   SASH THE INSULATED GLASS UNIT (OR FOR OUR STORM WINDOWS, THE SINGLE GLASS PANE) WITH ITS VINYL STILES (SIDES) AND BOTH THE TOP AND BOTTOM WIDTH ATTACHED. THERE MAY BE ONE OR MORE THAN ONE SASHES TO A WINDOW.   SCREEN A METAL FRAMEWORK COVERED BY A WOVEN FIBERGLASS OR METAL MESH. IT FITS INTO A WINDOW SCREEN TRACK WHICH HOLDS IT IN PLACE TO ALLOW VENTILATION OF A ROOM WHEN THE WINDOW SASH IS EITHER RAISED (HUNG WINDOW), TILTED IN (HOPPER WINDOW) OR SWUNG OUT ( EITHER CASEMENT OR AWNING).   SIMULATED DIVIDED LIGHTS AN EFFECT, CREATED IN A LARGE-SINGLE INSULATED GLASS UNIT, THAT LOOKS LIKE IT HAS MANY SMALL PANES OF GLASS SEPARATED BY MUNTINS. ACTUALLY, THE EFFECT IS CREATED BY THE INSTALLATION OF A MUNTIN GRID WORK INSIDE THE INSULATED GLASS UNIT. IF THERE IS 3/16" CLEARANCE BETWEEN THE GLASS AND EACH SIDE OF THE GRID WORK, THE MUNTINS WILL HAVE NO ADVERSE AFFECT ON THE U-VALUE OF THE WINDOW.   SINGLE GLAZING ONE (1) PANE OF GLASS IN A WINDOW OR DOOR. THE U-VALUE IS GIVEN AS EITHER 1.12 OR 1.13 FOR SINGLE GLAZING, INDICATING IT IS NOT GOOD AT STOPPING HEAT LOSS.   SINGLE HUNG WINDOW A HUNG WINDOW WHO'S UPPER SASH IS EITHER AN INTEGRAL PART OF THE FRAME OR AN OTHERWISE IMMOBILIZED SEPARATE SASH AND HAS A BOTTOM SASH WHICH CAN BE RAISED AND LOWERED AND ALSO TILTED IN.   SLIDING GLASS DOOR A TERM APPLIED TO PATIO SLIDING DOORS. USUALLY A DOOR WITH TWO (2) PANELS, ONE (1) OF WHICH SLIDES (OR ROLLS) IN THE TRACK , IN A HORIZONTAL PLANE IN THE FRAME. SLIDING GLASS (PATIO) DOORS ARE MADE USING INSULATED GLASS UNITS.   SLIDING WINDOW A WINDOW WITH EITHER ONE (1) OR TWO (2) SLIDING SASHES. IF THE SASH (OR SASHES) SLIDE UP AND DOWN, THE WINDOW IS A "VERTICAL SLIDER" AND IS OFTEN REFERRED TO A SINGLE HUNG OR DOUBLE HUNG WINDOW. IF THE SASH OR SASHES SLIDE FROM SIDE-TO-SIDE, THIS IS A HORIZONTAL SLIDER; OFTEN, IT WILL BE REFERRED TO AS A "SLIDER". THE SLIDING SASH OR SASHES IN EACH TYPE OF WINDOW MOVE IN THE TRACK FORMED BY THE FRAME.   SOLAR HEAT GAIN CO-EFFICENT THIS IS THE FRACTION OF THE INCIDENT SOLAR RADIATION ENTERING A BUILDING AS HEAT. IT IS COMPRISED OF THE SUM OF THE SOLAR ENERGY TRANSMITTANCE AND THE INWARDLY FLOWING FRACTION OF ABSORBED SOLAR ENERGY ON THE ENTIRE WINDOW. THE VALUE OBTAINED BY THERMAL TESTING IS SOMETHING BETWEEN 0 AND 1. THE LOWER THE VALUE, THE BETTER; FOR EXAMPLE, AN SHGC =0.40 IS MUCH BETTER THAN SHGC= 0.75.   STORM WINDOWS AN AUXILIARY SET OF WINDOWS, USUALLY SINGLE GLAZED, INSTALLED ON THE OUTSIDE OF THE HOME'S PRIMARY WINDOWS. IN SOME INSTANCES, THEY CAN BE INSTALLED ON THE INSIDE OF THE PRIMARY WINDOWS.   TEMPERED GLASS GLASS REHEATED TO ALMOST ITS MELTING POINT, THEN QUICKLY COOLED DOWN. ALTERED BY THIS PROCESS, THE GLASS IS STENGTHENED SUCH THAT IT IS MORE THAN FOUR TIMES STRONGER THAN MOST ANNEALED GLASS. WHEN IMPACTED, IT DOES NOT SHATTER INTO LARGE, JAGGED PIECES; INSTEAD, IT BREAKS INTO SMALL PIECES. IT IS REQUIRED WHERE EVER THERE IS DANGER FROM BROKEN GLASS.   TILT WIINDOW WINDOW WITH ONE (1) OR TWO (2) OPERATING SASHES THAT CAN BE RAISED SLIGHTLY AND INTILTED FOR CLEANING PURPOSES.   TINTED GLASS GLASS WHICH HAS HAD ITS GLASS CHEMISTRY ALTERED BY ADDING A METALLIC OXIDE TO THE GLASS COMPOUND. IRON OXIDES PRODUCE GREEN TINTS; SELENIUM OXIDES PRODUCE BRONZE TINTS AND COBALT OXIDE ADDITIVES WILL PRODUCE A BLUE TINT.   TRANSOM A HORIZONTAL CROSSPIECE THAT SEPARATES A DOOR OR A WINDOW FROM A WINDOW POSITIONED ABOVE IT.   TRANSOM WINDOW SEE TRANSOM (ABOVE). THE WINDOW ABOVE ANOTHER WINDOW OR IMMEDIATELY ABOVE A DOOR.   U-VALUE VERY SIMPLY, IT IS THE RATE OF HEAT TRANSFER THROUGH A COMPLETE WINDOW OR IT'S INSULATED GLASS UNIT. IT IS EXPRESSED IN TERMS OF BTU PER HOUR PER SQUARE FOOT IN FAHRENHEIT DEGREES. THE NUMBER RANGES BETWEEN 0 AND 1.13; THE LOWER THE NUMBER, THE BETTER. A U-VALUE OF 0.30 IS BETTER THAN A U-VALUE OF 0.50.   ULTRAVIOLET LIGHT THIS IS ELECTROMAGNETIC ENERGY EMITTED BY THE SUN, MEASURED BY IT'S WAVELENGTH, EXPRESSED IN NANOMETERS. A NANOMETER = 1 BILLIONTH OF A METER (39.37 INCHES). ULTRAVIOLET LIGHT IS NOT VISIBLE LIGHT; IT RANGES FROM 300 TO ABOUT 380 NANOMETERS. OUR EYES CAN ONLY DETECT LIGHT FROM 380 NANOMETERS TO 760 NANOMETERS. THE SHORTER THE WAVELENGTH, THE MORE ENERGY IS DELIVERED. THIS IS WHY ULTRAVIOLET LIGHT CAN DAMAGE PAINT FINISHES, CARPETS AND FURNITURE FABRICS. IT IS REFERRED TO AS UV.   VENT THE SASH OR THE NON-STATIONARY FRAME OF A WINDOW THAT SWINGS OPEN.   VINYL IN THE FENESTRATION INDUSTRY, THIS IS UNPLASTICISED POLYVINYLCHLORIDE. IT CAN BE EITHER RIGID OR FLEXIBLE. RIGID VINYL IS USED FOR FRAME AND SASH PARTS; FLEXIBLE VINYL IS USED AS PART OF DUAL DUROMETER GLAZING MATERIAL, WHICH IS CO-EXTRUDED AS PART OF THE SASHES. SEE PVC (ABOVE).   VISIBLE LIGHT THE ELECTROMAGNETIC ENERGY EMITTED BY THE SUN, FROM 380 TO 760 NANOMETERS IN WAVELENGTH. IT IS THAT PART OF THE ELECTROMAGNETIC SPECTRUM THAT OUR EYES CAN DETECT. SEE ULTRAVIOLET LIGHT (ABOVE).   VISIBLE TRANSMITTANCE A MEASURE OF THE AMOUNT OF VISIBLE LIGHT TRANSMITTED THROUGH THE GLASS. IT IS REFERRED TO AS VT. IT IS EXPRESSED IN DECIMAL VALUES BETWEEN 0 AND 1.0. THE HIGHER THE VT, THE MORE DAY LIGHT IS TRANSMITTED THROUGH THE WINDOW. CLEAR GLASS WILL LET @ 82% OF LIGHT THROUGH WHILE LOW-E GLASS WILL LET @ 78% OF LIGHT THROUGH. SEE VISIBLE LIGHT ABOVE.   WARM EDGE TECHNOLOGY INSULATED GLASS UNITS POSITION SPACING MATERIAL AT OR VERY CLOSE TO THEIR PERIMETER. IN THE PAST, THIS SPACER WAS USUALLY A HOLLOW, RETACTANGULAR ALUMINUM TUBE WHICH WOULD CONDUCT HEAT OUT THROUGH THE UNIT. NOW, THE SPACER IS USUALLY A VERY LOW CONDUCTING MATERIAL SIMILAR TO BUTYL RUBBER (OR SIMILAR COMPOUND) WITH A THIN-WALL METALLIC STIFFENER. THE INTENT IS TO KEEP WARMTH FROM PASSING THROUGH THE INSULATED GLASS UNIT'S EDGES.   WINDOW A COMPLETE UNIT CONSISTING OF FRAME AND SASH(ES), GLAZING AND HARDWARE NEEDED TO OPERATE IT, INSTALLED IN THE OUTER WALL OF A BUILDING.   WINDOW HARDWARE ANY ITEM THAT COMPRISES A COMPLETE WINDOW OF ANY TYPE OTHER THAN THE VINYL FRAME AND SASHES AND THE GLAZING OF EACH SASH. THIS INCLUDES THE LOCKS, KEEPERS, LIMIT LATCHES, BALANCE SHOES, BALANCES, ALL THE SCREWS, CORNER ANGLES (IF USED), SASH PIVOTS, SLIDER SASH ROLLERS AND THE HARDWARE ASSOCIATED WITH TURN AND SLIDE AND/OR CASEMENT AND AWNING WINDOWS.   © Vinylume Products, Inc. All Rights Reserved Powered & Developed by cboss, Inc.