Home Renovation Glossary .
Renovations can be overwhelming and confusing — especially if you're unfamiliar with some of the industry lingo that experts use. So, we’ve compiled a list of terms that will help you better understand the renovation process and start building your dream home.
Home Improvement Glossary
- A -
American Architectural Manufacturers Association. A national trade association that establishes voluntary standards for the window, door, storefront, curtain wall and skylight industries.
The amount of air leaking in and out of a building through cracks in walls, windows and doors.
A window with wood construction covered with aluminum sheet that have a factory-applied finish (to provide a longer maintenance-free life).
The molded frame or ornament surrounding a window, door or other rectangular opening.
An inert, nontoxic gas used in insulating glass units to reduce heat transfer.
American Society of Heating, Refrigerating & Air Conditioning Engineers, Inc.
The ASTM (American Society for Testing and Materials) is an organization that creates standards and procedures for testing materials. These standards are used to ensure consistency and quality in the manufacturing, testing, and use of a wide range of materials, from metals and plastics to textiles and building materials. The ASTM works with industry experts, academics, and government agencies to develop these standards, which are widely used in various industries, including construction, aerospace, and manufacturing. The ASTM's goal is to promote safety, quality, and innovation in the development and use of materials through its standards and testing methods.
An interior molding is affixed to one of a set of doors or side-hinged windows to prevent excessive swinging; it is also utilized with sliding doors to enhance the tightness of their fit where they meet. This feature is frequently present on older casements or swinging screens.
A window that is hinged at the top and swings outward for ventilation.
- B -
A flat material used on the face of the house, between the studs and the siding, to provide a nailable surface for the siding.
A snap in covering that conceals the EvenForce™ block and tackle balance system within the window frame, helping to keep dirt and dust out of the chamber.
A basement sash or cellar sash is a type of window sash that swings inward and is typically made of wood or metal. It is hinged either at the top or the bottom, allowing it to be opened for ventilation or access to the basement or cellar area.
An angled combination of three windows that project out from the wall of the home. The windows are usually positioned at 30- or 45-degree angles.
Some Alside windows feature a unique fusion-welded design that accommodates differing installation methods and architectural styles. It is the angled portion of the masterframe profile that adds a three dimensional appearance to the exterior of the window.
Block and Tackle Balance System
The block and tackle system utilizes a high-density nylon cord pulley action which is attached to a moveable block that travels up and down within a metal chamber. Tension from a heavy duty coil spring at the top of the block creates the proper resistance necessary for smooth operation of the window sash.
An angled combination of windows in 3-, 4- or 5-lite configurations. As the windows are joined to each other, they combine to form an arch shape that projects from the wall of the home.
A hollow mullion between two double-hung windows to hold the sash weight.
A standard milled wood.
B.T.U. – (Btu)
An abbreviation for British Thermal Unit, commonly shown as “Btu”; the heat required to increase the temperature of one pound of water one degree Fahrenheit, about the heat from burning one wooden match.
The bottom edge of a siding or soffit panel, or accessory piece, opposite the nailing slots, which locks onto the preceding panel.
A rubber material that seals the glass to the spacer, creating an airtight and water-tight insulated glass unit.
- C -
Cam-action lock and keeper
The mechanisms, which pull and secure the sashes together when placed in the locked position.
A window sash that is hinged on the side and swings open is commonly referred to as a casement window. In-swinging casement windows are of French origin, while out-swinging ones are believed to have originated in England. They both have their advantages and disadvantages.
A window with a side-hinged sash that opens and closes outward by a crank handle mechanism. Available in continuous mainframe, with multi-lite configurations.
Trim refers to the decorative or functional molding or framing that is used to cover the gap between a window or door frame/jamb and the adjacent wall, either on the inside or outside of the building. Its purpose is to provide a finished look and protect the edges of the opening from wear and tear. Trim can be made of various materials such as wood, PVC, composite, or aluminum and comes in different styles and sizes to match the design of the building.
A type of sealant used to fill gaps and cracks between surfaces to prevent the leakage of air or water. It is typically made of a mastic compound that can be applied to surfaces such as windows, doors, and siding to improve energy efficiency and weather resistance. Caulking is commonly made of silicone, bituminous, acrylic, or rubber-based materials, depending on the specific application and the surfaces being sealed. It is typically applied using a caulking gun and can be smoothed out with a tool to ensure a proper seal. Caulking is an important part of building maintenance and can help to prevent water damage and energy loss.
A centigrade scale of temperature measurement based on 0° as the freezing point and 100° as the boiling point of water. Abbreviated °C.
The area of the accessory trim or corner post where siding or soffit panels are inserted. Channels also refer to the trim itself, and are named for the letters of the alphabet they resemble (e.g., J-channel, F-channel, etc.).
(Meeting Rail) – (Lock Rail) – The horizontal members (of a double-hung window) which come together.
A chemical treatment that when applied to glass, helps to create a smoother surface that won’t attract or hold dirt and dust. Established by PPG Industries.
A clerestory (also spelled clearstory) is a type of window that is located in the upper part of a lofty room, typically above eye level. It is designed to admit natural light into the interior of the room, often at the center of the space. Clerestory windows can be found in a variety of architectural styles, from traditional to modern, and are often used in large public buildings such as churches, museums, and galleries, as well as in residential homes. They can be fixed or operable and can be made of various materials such as glass, wood, or metal. Clerestory windows are an effective way to bring natural light into a room while maintaining privacy and minimizing glare.
The brand name for the insulated glass unit that is present in Alside’s insulating glass packages. A ClimaTech unit will contain either two or three panes of glass, with one or two of those panes being a Low E surface. It will utilize the SST warm edge spacer system and contain either argon or krypton gas.
A window glass with an outside surface provided with a mirror reflective surface; the shading coefficient ranges from 20% to 45%.
An architectural style associated with an early American period; Early American style c. 1730.
A type of window design that features small rectangular panes of glass known as divided lites. These windows are often referred to as 12-lite, 16-lite, or other variations, depending on the number of panes used. Colonial windows were popular during the Colonial era of American history, from the 17th to the 18th century, and are still commonly used today in traditional or historic architecture. The divided lites in Colonial windows are typically arranged in a symmetrical pattern, with larger panes at the bottom and smaller panes at the top. They are often paired with shutters to provide privacy and security. The small panes of glass in Colonial windows can be made of various materials, including wood, metal, or vinyl, and can be single or double-glazed for insulation..
Combination Window Unit
(Combination Storm Sash and Screen) – A window assembly containing a half screen and two glass storm panel; in frame, exposing the screen panel.
A voluntary set of rules and regulations covering quality of product (or installation), method of testing, rating of the product, certification, and labeling of manufactured products.
The deposit of water vapor from the air on any cold surface whose temperature is below the dew point, such as a cold window glass or frame that is exposed to humid indoor air.
See Natural Convection and Forced Convection. A heat transfer process resulting from the circulation or movement of fluids, such as air.
A row of panels, one panel wide, running the length of the house from one side to the other, or, in the case of vertical siding, from top to bottom.
Coved glazing beads
A contoured piece of vinyl that holds the glass in place within the sash and adds an elegant, finished look.
Trim molding with a concave face.
The total length of the crack around a sash through which outdoor air could leak into the room. In a double-hung window, the total crackage is 3 times the width plus 2 times the height of the sash.
- D -
A rectangular slot or groove (with 3 surfaces) cut across the grain of a wood member, into which another board is fitted.
A measure of heating demand, based on the difference between the mean daily outdoor temperature and 65°F. Cumulative totals for the month or heating season are used by engineers for estimating heating energy requirements.
Design Heat Loss
It refers to the calculated values, typically expressed in Btu per hour (Btuh), of the heat transmitted from a warm interior to a cold outdoor condition, based on prescribed extreme weather conditions. This information is used in selecting appropriate heating equipment and estimating seasonal energy requirements for a building. Design heat loss takes into account various factors such as building size, insulation, windows, doors, ventilation, and air leakage. Infiltration heat loss, which occurs when outside air enters the building through cracks, gaps, or unsealed openings, is a part of the overall design heat loss. By accurately calculating design heat loss, building designers and HVAC professionals can ensure that heating systems are appropriately sized and optimized for energy efficiency.
A drying agent, such as silica gel, used by some manufacturers between the panes of insulating glass to prevent fogging between the panes.
Dew Point Temperature
The temperature of the air at which the water vapor in the air starts to condense in the form of liquid or as frost.
A window that has two vertical operating sashes.
Double Channel Lineal
A siding accessory that joins two soffit panels.
Sheet glass with a thickness between 0.115″ to 0.133″ (3 to 3.38mm).
Double Windows – (Double Glazing)
Two windows, such as a regular window plus a storm sash; also an insulating window with air space between panes.
Two windows separated by a mullion, forming a unit. Also called a coupled window.
Drip Cap/Head Flashing
An accessory installed with vertical siding to ensure that water drips away from panels and does not infiltrate them; it is also used as a vertical base.
A form of glazing in which the glass is secured in the frame with a dry gasket, wood stops, or metal stops, instead of by a glazing compound.
- E -
Brand name for specially coated, operating hardware that helps to resist oxidation and corrosion.
The minimum opening of a window for people to exit or firefighters to enter a building/dwelling. Different states or regions have different code requirements.
Emergency Exit Window
(Egress Window) – Fire escape window; large enough for a person to climb out; each bedroom should be provided with exit windows.
The Energy Star program is a joint venture between the US Environmental Protection Agency (EPA) and the US Department of Energy (DOE) designed to encourage homeowners to purchase energy-efficient products. Using less energy in our homes reduces the amount of CO2 emissions released into the atmosphere from burning fossil fuels such as coal, oil and natural gas. The advanced components and design in the ClimaTech™ insulated glass package exceed all performance criteria required by the Energy Star program.
Alside’s brand name for its block and tackle balance system. A balance system is a device for holding the vertically sliding sashes in any desired position within the window mainframe.
An extension jamb, also known as jamb lining or jamb extender, is a board used to increase the depth of a window frame's jambs to fit a wall of any given thickness. It is typically made from wood and is attached to the existing window frame's jambs to extend them outward. Extension jambs are used when installing a window in a wall that is thicker than the frame's standard depth, and they help to ensure a proper fit and seal around the window. They are commonly used in retrofitting or remodeling projects where the wall thickness has changed due to the addition of insulation or other materials.
- F -
Refers to the side of a siding or soffit panel that is showing once the panel has been installed.
The action of fastening directly onto the “face” side of a panel (instead of using the nail hem slot). This practice is generally not used in siding installation.
A board attached to the ends of the rafters between the roofing material and the soffit overhang. Fascia cap is the covering around that board.
Devices for jointing two parts together, such as screws nails and bolts.
The placement of window openings in a building wall, one of the important elements in controlling the exterior appearance of a building. Also, a window, door or skylight and its associated interior or exterior elements, such as shades or blinds.
(Finish Trim) – Interior trim boards around a window unit.
(Emergency Exit Window) – Window which opens onto fire escape; window designed for emergency exit.
A pane of glass installed directly into non-operating framing members; also, the opening or space for a pane of glass in a non-operating frame.
An inoperable panel of a sliding glass door or slider window.
A window with no operating sashes.
A thin, flat material, usually aluminum, positioned under or behind J-channels, corner posts, windows, etc., to keep draining water from penetrating the home.
(Window Glass) – (Plate Glass) – (Float Glass) – (Rolled Glass) – (Cylinder Glass)
– Glass sold in flat sheets and named according to the method used in its manufacture.
Smooth glass formed on the top of molten tin surface; a flat glass sheet.
French patio doors
A two panel glass door where both panels operate and swing either inward or outward.
Two casement sash hinged on the sides to open in the middle; the sash extends to the floor and serves as a door to a porch or terrace.
A heat transfer process, aided by mechanical circulation of a liquid (such as water) or a gas (such as air). This applies to natural wind flow over a window.
A wooden or steel framing material, usually 1″ x 3″, used to provide an even nailing base. To
“fur” a surface means to apply these strips.
The process of joining materials by melting them together with extreme heat (in most cases over 500°F), resulting in the materials combining into a one-piece unit.
- G -
Designed much like a bay or bow window, a garden also extends from the wall to the exterior of the home. It is built in a square or rectangular shape at right angles. The two side lights often operate for added ventilation.
A gas other than air, usually argon or krypton, placed between window or skylight glazing panes to reduce the U-factor by suppressing conduction and convection.
An elastic transparent material composed of silica (sand), soda (sodium carbonate), and lime (calcium carbonate) with small quantities of aluminum, boric, or magnesia oxides.
Glazing refers to the glass or plastic panes used in windows, doors, or skylights. It is the transparent or translucent material that allows natural light to enter a building while providing a barrier against the elements. Glazing can be made from various types of glass or plastic, such as tempered, laminated, or insulated glass, depending on the desired performance and application.
Glazing bead is a type of molding or stop that is used around the inside of a window frame to hold the glass in place. It is typically made from wood, vinyl, or metal and is designed to provide a secure and tight fit for the glass pane. Glazing bead can be used on various types of windows, including single and double-hung windows, casement windows, and sliding windows, and is an important component of a window's overall performance and energy efficiency..
A groove cut into the sash for the mounting of glass.
Optional horizontal or vertical lineals installed between the glass panes help to create the appearance of a divided window design.
A long, narrow cut on the face of a wood member; a groove across the grain is a Dado; one parallel with the grain is a Plough. A groove exposes three surfaces, in contrast with the two surfaces exposed in a Rabbet or Notching.
- H -
Mounting a sash in its frame.
(Hung Sash) – Sash hung on a cord connected to a counterweight.
The top or upper member of any element or structure; in windows, it refers to the top of the frame, as in Round Head Window.
All of the horizontal members at the top of the window frame.
(Lintel) – (Beam) – Supporting member or beam above window opening which transfers building weight above to the supporting wall structure on each side of the window. The term header is generally in reference to a wood beam, whereas Lintel often refers to a steel beam.
(Tinted Glass) – Window glass containing chemicals (with gray, bronze, or blue-green tint) which absorb light and heat radiation, and reduce glare and brightness. Shading coefficient of this glass varies from about 50% to 70%.
Heat Transfer Coefficient
(U-value) – A value indicating the rate of heat flow through a building construction, expressed in units of ‘Btuh per square foot of surface per degree F. difference between indoor and outdoor air temperature.’ This is numerically equal to the ‘inverse of the sum of R-values’ for the construction.
A movable joint enabling a window to swing open.
Hinged patio doors
A two panel glass door where one panel is stationary or fixed, while the other operates and swings either inward or outward.
(Hopper Vent) – (Hopper Ventilator) – Inward opening sash hinged at the bottom.
A bottom-hinged sash window that opens inward for ventilation.
Horizontal Sliding Window
(Horizontal Slider) Windows which slide horizontally.
Window with one or more hanging sashes.
The ability to ‘give off’ and ‘take on’ moisture, as in wood exposed to changes in relative humidity of air.
- I -
(Window Screen) – (Screen) – Woven mesh of metal, plastic, or fiberglass stretched over a window opening to permit air to pass through, but not insects.
(Interior Casing) – (Interior Finish) -(Interior Trim) – The inside visible molding surrounding the interior of the window frame
Insulating air chambers
Various chambers within the sash and masterframe, which help to insulate and strengthen the window.
Double- or triple-glazing with an enclosed, dehydrated, and hermetically sealed air space between the panes; the space is commonly from 3/16″ to
A window with multiple glazing that provides one or more air spaces between layers of glazing.
The fusion-welding process of some Alside windows.
Glazing installed from inside of building.
Interior Mullion Casing
The inside trim between adjacent windows.
- J -
(Awning Window) – Window with several out-swinging, awning-type windows that pivot near the top of the glass and operate in unison.
A vertical member at the side of a window frame or the horizontal member at the top of the window frame, as in head jamb.
Width of the window frame from inside to outside.
- K -
Not assembled; parts for a window frame pre-manufactured for assembly at a later date on the job site.
An inert, nontoxic gas used in insulating windows to reduce heat transfer.
- L -
To overlap the ends of two siding panels or accessory pieces to allow for expansion and contraction of the vinyl product.
(Catch) – (Lock) – A device which holds a window shut, such as the latch at the meeting rail of a double-hung window or one mounted on the stile of casement windows, often referred to as a lock.
(Lead Glazing) – (Stained Glass) – Window with small panes of glass set in grooved rods of cast lead (or came). The glass can be clear, color, or stained.
for raising the lower sash in a double-hung window. Also called sash lift.
Horizontal member (wood, steel, or stone) over a window opening to support the weight of the wall above.
A unit of glass in a window.
A fastening device in which a bolt is secured and can be operated by a key. Commonly used to refer to Latches or Catches.
The vertical member (stile) of a casement sash which closes against the surrounding frame.
Low E (Emissivity) Glass
Microscopically thin, virtually invisible, metal or metallic oxide layers deposited on a window or skylight glazing surface primarily to reduce the U-factor by suppressing radiative heat flow. A typical type of low-E coating is transparent to the solar spectrum (visible light and short-wave infrared radiation) and reflective of longwave infrared radiation.
The raised “ears” or tabs on a siding panel, created by a snaplock punch, which can be used to lock a siding panel into place when the nailing hem has been removed.
A crescent-shaped window framed by moldings or an arch.
- M -
The combination of the head, sill and jamb sections of a window.
The part of a sliding glass door, a sliding window or a hung window where two panels meet and create a weather barrier.
Any structural part of a window, such as a rail, stile, or lintel.
Window sash and other wood products made in a wood-working plant.
To make a diagonal cut, beveled to a specific angle (usually 45°). Sometimes miter cuts are made into an overlapping siding or soffit panel surface, to provide a neater appearance.
Two members joined at an angle, commonly 45 degrees.
(Vapor Barrier) – A material which retards the passage of water vapor from one space to another. Polyethylene sheet is commonly used as a vapor retarder.
Percentage of dry weight of material which is composed of water, such as in wood.
(Molding) – A relatively narrow strip of wood used to conceal a joint or to emphasize ornamentation of a structure.
(Moulding) – British spelling of mold, and molding.
Vertical member between window units.
(Sash Bar) – (Window Bar) – (Glazing Bar) – a secondary framing member (horizontal, vertical, or slanted) to hold the window panes in the sash. This term is often confused with Mullion.
Wood, plastic, or metal grilles.
A sash divided into many lites.
A weatherstripping material that is present where the sash frame meets the masterframe. Adds increased resistance to air infiltration.
- N -
Nailing Hem (or Flange)
The section of siding or accessories where the nailing slots are located.
A heat transfer process involving motion in a fluid (such as air) caused by difference in density of the fluid and the action of gravity This is an important part of heat transfer from the glass surface to room air.
National Fenestration Rating Council.
A rectangular cut across the grain of the wood member at the end of the board.
- O -
Glass that has been made translucent instead of transparent.
Crank-operated device for opening and closing casement or jalousie windows.
A window projecting from the wall and carried on brackets, corbels, or a cantilever. Unlike a Bay Window, the projection of an Oriel does not extend all the way to the ground.
The placement of a room, window, or building with respect to sun, wind, earth, access, or view.
The virgin uPVC vinyl used in all Alside windows. The material’s low thermal conductivity makes it the best choice for window manufacturing. Will not rot, peel, blister, swell or deteriorate from corrosion or pitting.
(Outside Facing) – (Outside Trim) – (Exterior Casing) – That portion of the window frame which is exposed to the outdoors.
Glazing installed from the outside.
- P -
A sheet of glass for glazing a window. After installation, the pane is referred to as a ‘light’ (lite) or ‘window light.
A major component of a sliding glass door, consisting of a light of glass in a frame installed within the main (or outer) frame of the door. A panel may be sliding or fixed.
(Parting Strip) – (Parting Stop) – A vertical strip on each jamb that separates the sashes of a double-hung window.
One or both surfaces of glass with a rolled design; used for privacy and light diffusion.
Weight of water vapor in air divided by weight of vapor contained in saturated air, expressed as a percentage.
A picture window that does not move or operate.
Artificial substances made of organic polymers that can be extruded or molded into various shapes, some of which have been adapted to windows. The material is commonly stiffer than rubber.
(Plow) – A rectangular groove or slot (with 3 surfaces) cut parallel with the grain.
A position or measurement that is truly and exactly vertical, 90° from a level surface.
Area below the nailing hem that the buttlock locks into.
The balanced or moving sash of a window unit.
Window with single or multiple glazing to which storm sash may be installed.
Describes the design of the panel (Clapboard, Dutch lap, Triple 3, etc.)
An awning-type window that swings either inwards or outwards at the top or the bottom. The ‘PIB’ or ‘project in at bottom’ window can be cleaned from the inside.
A chart which shows dry bulb and wet bulb temperatures used to determine the relative humidity of air and the dew point temperature. Other engineering data referring to moisture in air are also shown.
(Polyvinylchloride) – An extruded or molded plastic material used for window framing and as a thermal barrier for aluminum windows.
- No Glossary Entries For “Q” -
- R -
The transfer of heat in the form of electromagnetic waves from one separate surface to another. Energy from the sun reaches the earth by radiation and a person’s body can lose heat to a cold window or skylight surface in a similar way.
A rectangular notch (consisting of two surfaces) cut parallel with the grain of wood along the edge.
The joint formed by two boards with rabbetted ends, as in some window frames.
(Head Rail) – (Top Rail) – (Bottom Rail) – (Meeting Rail) – Horizontal member of a window sash.
Window glass coated to reflect radiation striking the surface of the glass.
A plastic or wood molding placed in a concrete or masonry opening to provide a uniform groove for a spline-type gasket to hold window glass.
Weight of water vapor in air divided by the weight of water vapor in completely saturated air at the same temperature, expressed as a percentage.
R-value is a measure of the thermal resistance of a material, such as a glazing material or fenestration assembly, to heat flow. It is the inverse of the U-factor (R = 1/U) and is expressed in units of hr-sq ft-°F/Btu. The R-value indicates how well a material can resist the transfer of heat through it, with a higher R-value indicating greater resistance to heat flow and a higher insulating value. In the context of windows, a high-R-value window has a greater ability to resist heat flow through its glazing and frame, which can help to reduce energy loss and improve thermal comfort inside a building. R-value is an important factor to consider when selecting windows for energy efficiency and can help to reduce heating and cooling costs over the lifetime of a building.
- S -
A strengthened or reinforced glass that is less subject to breakage or splintering, such as glass for storm doors and some windows.
Separate from the masterframe, the portion of the window that contains the glass.
A device for counter-balancing a sash of a double-hung window to hold it in the up position.
Sash and Frame
A window and its casing frame.
Sash limit locks
A feature that allows a window to be safely raised to a certain height.
A molding that covers the joint between window sash and the jamb.
Running a utility knife blade, a sharpened awl, scoring tool, or other sharp implement across a soffit or siding panel face without cutting all the way through the panel. This weakens the vinyl surface in a specific area and allows the panel to be bent and broken off cleanly.
(Wire Cloth) – A close-mesh woven screening material of metal, plastic, or fiberglass for a window screen, to block the entry of insects but permit light, air, and vision through the screen.
A compressible plastic material used to seal any opening or junction of two parts, such as between the glass and a metal sash, commonly made of silicone, butyl tape, or polysulfide.
Sealed Double Glass
Two panes separated by a sealed space.
(Sun Screen) – A specially fabricated window screen of sheet material with small narrow louvers formed in place to intercept solar radiation striking a window; the louvers are so small that only extremely small insects can pass through. Also, an awning with fixed louvers of metal or wood construction.
A decimal value which is the solar gain of a window, divided by the solar gain for a clear single-glass window of the same size. The shading coefficient of clear, double-glazing is about 0.85 to 0.9.
(Laminated Glass) – Two sheets of glass with a transparent plastic sheet sandwiched between to form a pane resistant to shattering.
(Margin Light) – A fixed, often narrow, glass window next to a door opening (or window).
(Silicone Sealer) – An enduring sealing agent that resists water.
The horizontal, bottom section of the masterframe.
A window that is similar to a double-hung window except that the top sash is stationary.
Glass with thickness between 0.085 to 0.100″ (2.16 mm to 2.57 mm).
Sliding patio doors
A combination of fixed and sliding glass door panels that operate solid brass roller trucks. Available in 2-, 3- or 4- lite configurations with the operable panel available in any position.
A measuring instrument with two thermometers (dry-bulb and wet-bulb) used for determining the dewpoint and relative humidity of air; its relation to windows is ascertaining the point at which moisture will condense on the inside surface of the glass.
(Sliding Windows) – A window which moves horizontally in grooves or tracks.
A window in which the sashes move horizontally. Available in a 2- or 3-lite configurations.
Material used to enclose the horizontal underside of an eave, cornice, or overhang. Some soffit panels may also be used as vertical siding.
Solar Heat Gain Coefficient (SHGC)
The fraction of solar radiation admitted through a window or skylight, both directly transmitted and absorbed and subsequently released inward. The solar heat gain coefficient has replaced the shading coefficient as the standard indicator of a window’s shading ability. It is expressed as a number between 0 and 1. The lower a window’s solar heat gain coefficient, the less solar heat it transmits and the greater its shading ability. SHGC can be expressed in terms of the glass alone or can refer to the entire window assembly.
A building placed on a lot so that the long dimension faces south and a majority of the windows are south-facing.
(Sound-Resistive Glass) – Double glass fixed on resilient mountings and separated so as to reduce sound transmission.
An object placed between two or more pieces of glass which helps to maintain a uniform width between the glass, and prevent sealant distortion.
A rectangular strip of wood or metal inserted between two boards, which have been slotted to receive it.
A fastener for holding the sash in a fixed location by means of a spring-loaded bolt in the stile entering a hole in the jamb.
A measurement of siding. One square equals 100 square feet (10 x 10 wall).
SST non-metal spacer
A solid silicone foam spacer covered with Mylar. It is sealed to the edge of the glass and then sealed with butyl for greater energy efficiency.
Stacked Window Units
A combined grouping of awning, hopper, casement, or non-operative windows to form a large glazed unit.
Stained Glass Window
A window with a painted scene or pattern that has been fired into the glass. Windows with plain colored glass set in lead are also called stained glass.
A fixed sash; also referred to as a picture, studio, vista, or view sash.
The vertical-edge members of a window sash.
A shelf-like board of the interior part of the window sill, against which the bottom rail of the sash closes.
(Bead, Side Stop, Window Stop, Parting Stop) – The molding on the inside of the window frame against which the window sash closes, or in the case of a double-hung window, the sash slides against the stop.
(Storm Window) – An extra window on the outside to protect an existing window, but mainly to increase the thermal resistance of the window.
A flexible framing material used to even a surface prior to installation.
An accessory applied directly to the surface of the building and used to secure the first course of siding to the home.
A sash fastener located at the meeting rails of a double-hung window, which rotates and clamps the two rails closer together.
- T -
Special heat-treated, high-strength safety glass which shatters into pebble-sized particles but not into slivers.
In technical usage, the term is a convenient measure of heating value, namely 100,000 Btu. One therm is roughly equivalent to the heating value of 100 cubic feet of natural (methane) gas.
(Thermal Break) – A material of high thermal resistance placed between two metal sash, or installed between adjoining metal framing of metal windows, in order to reduce thermal conduction from indoors to outdoors.
Heat transfer through a material by contact of one molecule to the next. Heat flows from a high temperature area to one of lower temperature.
Thermal Conductivity –
Heat transfer property of materials expressed in units of ‘Btu per hour per inch of thickness per square foot of surface per one degree F. temperature difference.’ Referred to by the letter ‘k.’
Same as Thermal Conductivity except thickness is ‘as stated’ rather than one inch. Referred to by the letter ‘C.’
A material that resists heat flow. Material having a high R-value.
(R-value) – A property of a substance or construction which retards the flow of heat; one measure of this property is R-value.
(Transom Bar) – A horizontal member separating a door from a window panel above the door, or separating one window above another.
(Transom Window) – The window sash located above a door.
Visible molding surrounding a window opening.
Triple glazing refers to a type of window that has three panes of glass with two air spaces in between them, typically filled with an insulating gas such as argon or krypton. The purpose of triple glazing is to provide improved insulation and energy efficiency compared to traditional double-glazed windows. The additional pane of glass and air space helps to reduce heat loss and improve sound insulation, making it an ideal choice for colder climates or areas with high levels of noise pollution.
Triple glazing can be installed in several ways, including as a separate storm sash or as an insulating window in a single frame. When installed as a separate storm sash, the triple-glazed unit is mounted outside the existing window, providing an extra layer of protection against the elements. Alternatively, when installed as an insulating window in a single frame, the triple-glazed unit replaces the existing window, providing improved insulation and energy efficiency without the need for a separate storm sash.
A term generally referring to any tripartite group of windows with square heads. These are frequently found on Colonial Revival houses; they suggest Palladian Windows but are less expensive to build.
TrueCapture™ Sloped Sill
The sill of some Alside double-hung windows that has a downward slope toward the outside with a capture dam that helps to keep water from infiltrating the base of the bottom sash. Sloped sill assists water drainage to the exterior of the window.
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Weather-resistant material placed under vinyl siding panels.
UV (Ultraviolet light)
The invisible rays of the spectrum that are outside of the visible spectrum at its short-wavelength violet end. Ultraviolet rays are found in everyday sunlight and can cause fading of paint finishes, carpets and fabrics.
Extremely short wave length invisible radiation, which is a component of solar radiation, and merges into the visible spectrum; attributed as a source of skin sunburn and color fading of draperies and carpeting.
The percentage of ultraviolet rays being blocked rather than being transmitted through the window’s glass unit. The higher the number, the lower the percentage of ultraviolet rays being transmitted through the window.
A measure of the rate of non-solar heat loss or gain through a material or assembly. It is expressed in units of Btu/hr-sq ft-°F (W/sq m-°C). Values are normally given for NFRC/ASHRAE winter conditions of 0°F (18° C) outdoor temperature, 70° F (21° C) indoor temperature, 15 mph wind and no solar load. The U-factor may be expressed for the glass alone or the entire window, which includes the effect of the frame and the spacer materials. The lower the U-factor, the greater a window’s resistance to heat flow and the better its insulating value.
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(Vapor Retarder) – A membrane or coating which resists passage of water vapor from a region of high vapor pressure to low pressure, more accurately called a Vapor Retarder.
Vertical Sliding Window
One or more sashes that move in a vertical direction.
The portion of the electromagnetic spectrum that produces light that can be seen. Wavelengths range from 380 to 720 nanometers.
That portion of the total radiation that is visible to the human eye and which lies between the ultra-violet and the infra-red portions of the electromagnetic spectrum. The colors associated with the visible spectrum range from violet, indigo, blue, green, yellow, orange, through red.
Visible transmittance (VT)
The percentage or fraction of the visible spectrum (380 to 720 nanometers) weighted by the sensitivity of the eye that is transmitted through the glazing.
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The use of low-conductance spacers to reduce heat transfer near the edge of insulated glazing.
Weatherstripping is a type of material used to cover the gap between a window sash and frame to prevent air leaks and keep water from entering a building. It is a strip of resilient material, typically made of rubber, foam, or other synthetic materials, that is installed around the perimeter of a window or door to provide a seal against the elements. The weatherstripping material is designed to compress when the window or door is closed, creating a tight seal that helps to prevent drafts and reduce energy loss. Weatherstripping can be installed on various types of windows, including casement, double-hung, and sliding windows, as well as on doors. It is an effective and affordable way to improve energy efficiency and comfort in a building, and can help to reduce heating and cooling costs.
Sealed to prevent entry of air and precipitation into the structure.
Openings cut into siding or accessories to allow for water runoff.
A glazed opening in an external wall; an entire unit consisting of a frame, sash and glazing, and any operable elements.
The fixed frame of a window, which holds the sash or casement as well as hardware.
Various devices and mechanisms for the window including: catches, cords and chains, fasteners and locks, hinges and pivots, lifts and pulls, pulleys and sash weights, sash balances, and stays.
A complete window with sash and frame.
The pressure produced by stopping the wind velocity; the main cause of air infiltration.