Window Coverings Glossary
This glossary, which is drawn from our own research, contains descriptions of terms comonly found in the window coverings industry.
- 2-D adjustable
Any window covering that can be adjusted in two ways, either top-down & bottom-up for a shade or up-down/open-closed for a louvered blind.
The portion of radiant energy that is absorbed by a material (radiant energy can be absorbed, transmitted, or reflected).
- adjustable slats
Refers to any louvered or slatted window covering in which the slats or louvers can be adjuisted or angled to allow different levels of indirect lighting, privacy, and weather protection. The couterpart to fixed slats.
Synonyms: adjustable slat
- air infiltration
Air leaking into a building (can account for 25 – 40% of total cooling/heating energy in a home).
- air tightness
How well a window covering resists air infiltration with lower infiltration representing greater energy efficiency and comfort.
Synonyms: airtightness Airtightness
- applied film
Most commonly, flexible plastic sheet applied directly and permanently to glass to improve the window’s optical and/or thermal performance. Often called applied film to distinguish it from seasonal film (which is applied to window trim, not the window glass). Many variations exist for additional desired performance including: glare reduction, privacy, security,and winter thermal performance.
Synonyms: surface film surface-applied film window film surface-applied window film applied films Surface film
Interior window trim at bottom of the window, sometime also called a “skirt” (see Window Parts diagram in Overview).
Term referring to window coverings that have a pivoting action, such as a blind, and generally referring to louvered window coverings.
- automated operation
Control and adjustment of window covering settings by sensors, timers, or programming. Motorization is a key element of automation but motorization alone requires active user involvment in setting the window covering.
An exterior shading window covering, either fixed or retractable.
Most commonly, louvered window covering with stacked vanes that can be both tilted and raised/lowered.
- bottom rail
Horizontal part of the window sash at the sill (see Window Parts diagram in Overview).
Most often interior adjustable window coverings that operate or adjust by raising the covering from the bottom up.
Abbreviation for British Thermal Unit, about the heat content of a stick match.
Window type hinged on the side, most commonly swinging out.
window trim (covers space between framed opening and window unit).
- cellular shade
Most commonly, window covering made of pleated fabric that is “honeycombed” and can be raised and lowered. Their adjustability adds elements balancing view, privacy, glare control, and daylighting. Also called insulated cellular shade.
Synonyms: cellular shades insulated cellular shade insulated cellular shades
- check rail
The sash frame parts of a hung window where the two sashes meet; also called the meeting rail (see Window Parts diagram in Overview).
- clear rigid polymer
Transparent sheet material used most often in interior window panels in place of glass.
Synonyms: acrylic rigid plastic plastic
Any windows high on a wall designed to daylight most or all of a room.
- condensation resistance
How well a window, or combined window and covering, resists liquid water accumulating by condensation on the innermost surface of the prime window (as represented by an NFRC number resulting from a standardized test for this property).
Heat moving through solids, always from warmer to colder materials (the three ways that heat moves are conduction, convection, and radiation).
Heat moving in fluids (liquids and gases); hot air rises/cold air falls and energy can be lost or gained through convective loops (the three ways that heat moves are conduction, convection, and radiation).
Interior fabric window covering hanging from a rod, often paired in a window and hanging in loose folds; similar to and often including drapes.
- dark color
- Any color on the visible spectrum other than white or very dark shades of all colors that absorb most of the sun’s heat energy.
- daylighting control
How well a window covering manages daylight while accomodating other functions, such as view, privacy, solar heat gain.
- Opaque or translucent films that depict scenes or other images and obscure any direct view and provide privacy.
Temperature at which the moisture in air condenses into a liquid.
- divided light
Window glass separated by small frames within the sash (see Window Parts diagram in Overview).
- DIY installation
- Degree of skill, length of time, and tools required to install a window covering yourself.
- double pane
Window unit with two panes of glass sealed into a glazing unit; gas between the panes is trapped (also called an insulated glazing unit – IGU).
- Double Pane Clear
Double Pane Clear provides strong thermal performance: good resistance to heat loss, high solar heat gain, and high visual transmittance.
- Double Pane with Low-e
Double Pane with Low-e glass provides high resistance to heat loss and can be tuned for solar gain but with some loss of visual transmittance.
- double-hung window
Rectangular window with top and bottom sashes that slide up and down within the window frame.
For storm windows and window panels, three panels—two glass and one insect screen—with the top panel being fixed in place and the lower glass panel and insect screen operating in tracks in the frame.
Interior fabric window covering most commonly hung from a rod; typically differs from a curtain by hanging well below the bottom of the window it covers.
- Drapes and curtains
Drapes and curtains are primarily used as decorative elements. Their adjustability combines some level of solar and glare control with privacy. Insulating versions improve wintertime comfort.
- durability – service life
How long a window covering typically lasts, with a warranty serving as a proxy for this attribute.
Synonyms: Durability - Service Life Durability - service life Durability - Service life
- Efficient Windows Collaborative (EWC)
Sister organization providing fair, rational, and comprehensive information on window performance and window selection.
Glass that changes from clear to darkened (and back) based on electrical current (versus thermochromic or photochromic).
How readily the surface of a material gives off heat by radiation. Many common building materials have “high” emissivity (around 0.9 out of 1.0 being a perfect emitter), while materials or objects with metallic coatings or surfaces have “low” emissivity (around 0.15 or less).
- Ext. louvered shutter
Exterior louvered shutters protect existing windows from weather and improve security and privacy. Certain types also provide excellent solar heat gain control.
Synonyms: exterior louvered shutter Exterior louvered shutter Exterior louvered shutters Ext. louvered shutters
- Ext. roller shade
Exterior roller shades cover and protect existing windows from weather and provide solar heat gain control. Their adjustability adds elements of view, privacy, and glare control but can reduce existing window protection.
Synonyms: Exterior roller shade Exterior roller shades Ext. roller shades
- Ext. solar screen
Exterior solar screens provide good solar heat gain control while reasonably maintaining view.
Synonyms: Exterior solar screen Exterior solar screens Ext. solar screens
- Exterior storm
Exterior window panel (tracked/operable or fixed/inoperable) covering and protecting existing windows from weather, improving energy performance (including air-tightness), while maintaining view. Low-e coatings in cold climates and low solar gain coatings in hot climates increase their energy performance.
Synonyms: Exterior storms storm window storm windows
- face mount
Any window covering installed on to the face of window trim (versus inset mount).
Windows and doors or their placement in buildings.
Window, any glass panel, or awning that is not operable (can’t be opened).
- Fixed awning
Fixed awnings provide good solar heat gain and glare control while reasonably maintaining view.
Synonyms: Fixed awnings
- fixed slats
Refers to any louvered or slatted window covering in which the slats or louvers are set at a fixed angle, generally an angle that allows indirect lighting and some privacy, but no adjustment. The couterpart to adjustable slats.
Synonyms: fixed slat
- gas fill
Argon, xenon, or krypton gas sealed between the panes of insulated glazing units (IGU). These gases are used because they exhibit less convective heat transfer than air.
- glare control
How well a window covering shields from direct, bright, harsh light—light that obscures occupant view of items such as TV and monitor screens.
Surface-mounted plastic cosmetic grids simulating the muntins in true divided lite windows.
- high solar gain low-e
There are generally two types of low-e coatings that improve energy performance, with the high solar gain (HSG) coatings designed for colder climates. Although currrently these coatings are applied mainly to glass, they can be applied to clear plastic polymer panels as well.
Synonyms: high solar gain low-e polymer
- horizontal slats
Refers to any louvered or slatted window covering with vanes or slats parallel to the floor, or horizontally-oriented, operating up and down.
High Solar Gain
- hung window
Any window with sash(es) that move up and down and that resist gravity/make adjustment easier by being “balanced” or “hung” using counterweights or springs.
- infrared (IR)
Invisible heat wave energy (far red) often used as shorthand for an infrared camera, which produces images that represent surface patterns of temperatures of objects.
- inset mount
Any window covering installed between the jambs of the prime window (versus face mount).
Getting the window covering or attachment in place. Installation can be either do-it-yourself or professionally done, with some coverings and attachments better suited to one or the other.
- insulated glass unit (IGU)
Window unit with two panes of glass sealed into a glazing unit; gas between the panes is trapped (also called double-glazing).
- Referring to window coverings specifically designed to reduce heat loss and gain (generally with insulating materials and greater air tightness).
How well a window covering resists heat loss/gain, usually measured with R-value.
- Int. louvered shutter
Interior louvered shutters provide solar heat gain control. Their adjustability adds elements of view, privacy, glare control, and daylighting.
Synonyms: Interior louvered shutter Interior louvered shutters Int. louvered shutters
- Int. roller shade
Interior roller shades provide solar heat gain control. Their adjustability adds elements of view, privacy, and glare control. Shades are available in a wide range of fabric, affecting many aspects of roller shade performance.
Synonyms: Interior roller shade Interior roller shades Int. roller shades
- Int. solar screen
Interior solar screens provide solar heat gain control while reasonably maintaining view. Roller versions add all the advantages of adjustability.
Synonyms: Interior solar screen Interior solar screens Int. solar screens
- Interior panel
Interior Panels primarily reduce winter heat loss and improve air-tightness while maintaining view. Low-e coatings further improve their insulation properties.
Synonyms: Interior panels
Parts of window frame facing into the window opening, at sides and top (see Window Parts diagram in Overview).
- light color
- Any color on the visible spectrum other than black or very dark shades of all colors that reflects most of the sun’s heat energy.
- Louvered blinds
Louvered blinds provide solar heat gain control. Their adjustability adds elements balancing view, privacy, glare control, and daylighting.
Synonyms: Louvered blind
- louvered shutter
Exterior or interior hinged window covering most commonly with louvers fixed providing shade and privacy with some daylighting.
Synonyms: louvered shutters
- low solar gain low-e
There are generally two types of low-e coatings that improve energy performance, with the low solar gain (LSG) coatings designed for warmer climates. Although currrently these coatings are applied mainly to glass, they can be applied to clear plastic polymer panels as well.
Nearly invisible metallic coating on inside surface of double-pane glass, storm windows, and interior window panels that improves the energy efficiency of the window and the thermal comfort of occupants.
- manual operation
- Operation by hand (versus motorized operation).
- meeting rail
The sash frame parts of a hung window where the two sashes meet; also called the check rail (see Window Parts diagram in Overview).
Mechanical adjustment of the covering. User does not have to adjust by hand but the setting is accomplished by user/occupant.
Most commonly, the location or structural/finish detail where two window separate window units are joined or “ganged.”
- Cellular shades with more than one cell in cross section.
The window part that divides panes or lites within a window sash (see Window Parts diagram in Overview).
National Fenestration Rating Council, which leads the window industry in evaluating window performance based on standardized testing and reporting.
- noise control
How well a window covering keeps outside noise from being heard inside.
- Referring to window attachments designed primarily for security and storm protection (exterior) or privacy (interior), which lack insulating materials and are not particularly airtight.
- Referring to window attachments not rolled around a spindle and typically affixed to the primary window with magnetic strips, snaps or other fastener.
Material that does not directly transmit light (versus transparent or translucent).
- open weave
- Referring to the degree of openness in the fabric of solar screens, shades and awnings, open weave lets more light and air (ventilation) through than closed weave fabrics.
- openness factor
In reference to solar shades or screens, the % visible light that gets through the window covering.
Any window covering or attachment that can be adjusted or set in different operating positions.
sheet of glass in a window (see Window Parts diagram in Overview).
- parting stop
A strip of solid material that holds another part of the window or window covering in place; also called a parting bead (see Window Parts diagram in Overview).
Glass or glazing that changes from clear to dark based on sunlight levels (versus electrochromic or thermochromic).
- Pleated Shade
Pleated shades provide solar heat gain control. Their adjustability adds elements that balance view, glare control, and daylighting.
Synonyms: Pleated Shades pleated shade pleated shades
- prime window
This is the existing window to which window coverings are added to improve overall performance.
Synonyms: prime windows
- prime window protection
How well an exterior window covering protects the prime window from the weather and traumatic damage.
How well a window covering obscures view into a building, either during the day or night, or both.
- pro installation
- Installation by someone you pay, often with greater skill, and sometimes certified specifically for the type of installation.
Insulating value of any component of an outside wall. Window coverings can increase R-value of a window (R-1) to R-2 to R-5 (R-value is the reciprocal of U-value).
Heat moving through empty space by energy wave (the three ways that heat moves are conduction, convection, and radiation).
horizontal element of the sash frame (see Window Parts diagram in Overview).
The portion of radiant energy that is reflected by a material (radiant energy can be absorbed, transmitted, or reflected).
Computer modeling program used to estimate the energy performance of windows and window coverings in homes.
- Retractable awning
Retractable awnings provide good solar heat gain and glare control while maintaining view. Their adjustability improves qualities such as privacy and glare control.
Synonyms: Retractable awnings retractable awning retractable awnings
Refers to any adjustable window attachment or covering that winds or stores around a pin-hung cylinder or roller.
- Roller shutters
Roller shutters protect existing windows from weather, including severe weather, and improve security and privacy. They also provide excellent solar heat gain control. Insulated versions substantially improve resistance to heat loss in cold climates.
Synonyms: Roller shutter roller shutter roller shutters
- Roman shade
Roman shades provide solar heat gain control and limited insulation. Depending on fabric type, they can also provide good sound absorption. Their adjustability adds elements that balance privacy, view, glare control, and daylighting.
Synonyms: Roman shades roman shade roman shades
- roof window
Any window mounted on a roof rather than in a wall; same as skylight.
The glass and its frame in any window, not including the window frame in which the sash is installed (see Window Parts diagram Overview).
- seasonal film
A temporary, clear, plastic sheet fastened or adhered to interior window trim to improve the airtightness of drafty prime windows (in contrast to window film).
Synonyms: clear flexible polymer
- Referring to window attachments that improve the security of the primary window.
- Material that transmits some light and energy but no view.
Most commonly an adjustable, fabric, window covering on a roller.
Term meaning translucent fabric and applied to any of the following—blinds, curtains, drapes, shades—but most commonly referring to horizontal shades that are creased or stack in folds.
- Sheer shade
Sheer shades provide solar heat gain control. Their adjustability adds elements that balance view, glare control, and daylighting.
Synonyms: Sheer shade sheer shade sheer shades
- side track
Any slotted or notched window covering that rides in a track on the vertical sides, increasing separation of the interior from light, sound, temperature to the exterior of the window covering.
Synonyms: side tracks
The bottom horizontal element of the window frame, often sloped outward for drainage (see Window Parts diagram in Overview).
- single hung
Any window or window covering with two sashes or glass panels and only the bottom of the two operable.
- Single Pane Clear
Single Pane Clear, commonly found on older homes, provides the weakest thermal performance but highest visual transmittance.
Synonyms: clear glass
- Cellular shades with one cell in cross section.
- solar heat control
How well a window covering blocks the sun’s heat or infrared energy.
- solar heat gain
Term used to describe how much of the sun’s energy makes it past the window/window covering. High solar gain means much of the sun’s energy makes it past; low solar gain means little of it does.
- solar screen (shade screen)
Course-woven fiberglassor polyester-based screen designed to block sun/maintain view (interior and exterior; fixed frames and roller)
Synonyms: solar screen solar screens solar shade
- solar spectrum
Full range of radiant energy from the sun, mainly: ultra-violet (UV), visible, infra-red (IR).
- sound absorption
How well an interior window covering deadens inside sounds.
Synonyms: Sound Absorption Sound absoprtion
- spectrally selective
low-e coatings and tints on windows and clear window coverings that favor keeping heat in or keeping it out.
vertical member of the sash frame (see Window Parts diagram Overview).
Shelf-like interior, bottom-of-the-window trim sometimes incorrectly called the sill (see Window Parts diagram Overview).
- summer comfort
A quality combining a window covering’s insulation, air tightness and most importantly solar heat control; a measure of how comfortable it is to locate close to a window in summer.
- thermal break
Any part of a window covering that is designed to overcome a thermal bridge in the prime window.
- thermal bridge
Any part of a window or window covering made of materials that readily conduct heat and therefore represent a weak point in the assembly’s thermal performance.
Glass that changes from clear to dark based on temperature (versus electrochromic or photochromic).
- tight weave
- Referring to the degree of openness in the fabric of solar screens, shades and awnings; tight weave lets less light and air (ventilation) through than open weave fabrics.
Referring to applied films when they are darkened to reduce direct sunlight and glare. Tints are available as either low or high solar gain.
Synonyms: tint low solar gain tint high solar gain tint
Most often interior window coverings that operate or adjust from the top down. Usually top-down adjustment is in addition to bottom-up adjustability.
Interior window coverings that can be adjusted by raising the bottom and/or lowering the top of the window covering.
Material that obscures clear vision but lets significant visible light through (versus opaque—no light transmitted—or transparent (all in nearly all visible light transmitted).
The portion of radiant energy that is transmitted by a material (radiant energy can be absorbed, transmitted, or reflected).
Material that lets all or nearly all visible light through; clear vision (versus opaque or translucent).
- triple pane
Three panes of glass with two sealed gas spaces.
Synonyms: triple glazing
For storm windows and window panels this is three panels—two glass and one insect screen—that operate (up and down) inside tracks in the frame.
- U-factor (U-value)
The reciprocal for R-value, a measure of how readily heat transfers through a material or component. This is also one of the three performance properties reported on a window’s NFRC rating.
Wavelengths of energy too short to be visible but with enough energy to degrade materials, particularly finishes, fabrics, and carpets.
A measure of how a window covering allows outside air/breezes through an open primary window.
- vertical slats
Refers to any louvered or slatted window covering with vanes or slats perpendicular to the floor, or vertictally-oriented, operating side to side.
Synonyms: vertical slat
How well a window covering gives visual access to the outdoors, with different window coverings using different approaches to maintaining view while performing other functions: awning, solar screens, louvered blinds.
- visible light
In the solar spectrum, light energy we can see: red through violet (the solar spectrum is primarily made up of UV, visible, and IR).
- visible transmittance (VT)
A performance property of glass/windows that is measure by standardized testing and reported in NFRC window ratings.
- weep (weephole)
A small space intentionally designed into the bottom rail of any exterior window covering to allow condensate to drain and not accumulate.
- window attachment/covering/treatment
Each of these three terms is used differently but all mean any component added to the prime window to improve its performance.
- window panel
A tracked-operable or fixed-inoperable glass window installed on the interior to supplement the performance of the prime window.
Synonyms: window panels
- window quilt
Multi-layered fabric window covering—either adjustable on a roller or fastened in place with snaps or magnetic tape—used primarily in cold climates to improve thermal performance.
Synonyms: window quilts Window quilt Window quilts
- window retrofit
Any change to an existing window including window replacement, window repair, and the addition of window coverings.
Synonyms: window retrofits
- winter comfort
A quality combining a window covering’s insulation and air tightness; a measure of how comfortable it is to locate close to a window in winter.