Acrylic glass or poly(methyl methacrylate), a transparent thermoplastic. Poly(methyl methacrylate) (PMMA) is a transparent thermoplastic often used as a lightweight or shatter-resistant alternative to glass. Although it is not technically a type of glass, the substance has sometimes historically been called acrylic glass.
Aerogel is a synthetic porous ultralight material derived from a gel, in which the liquid component of the gel has been replaced with a gas. The result is a solid with extremely low density and low thermal conductivity. Nicknames include frozen smoke, solid smoke, solid air, or blue smoke owing to its translucent nature and the way light scatters in the material. It feels like fragile expanded polystyrene (Styrofoam) to the touch. Aerogels can be made from a variety of chemical compounds.
Air The common name given to the atmospheric gases used in breathing and photosynthesis is air. By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1%.
Air barriers control air leakage into and out of the building envelope. Air barrier products may take several forms
Air barrier assemblies Combinations of air barrier materials and air barrier accessories that are designated and designed within the environmental separator to act as a continuous barrier to the movement of air through the environmental separator and which has an air leakage rate no greater than 0.20 L/(s•m²) at a pressure difference of 75 Pa when tested in accordance with ASTM E 2357.
Air barrier accessories Products designated to maintain air tightness between air barrier materials, assemblies and components, to fasten them to the structure of the building, or both (e.g., sealants, tapes, backer rods, transition membranes, nails/washers, ties, clips, staples, strapping, primers) and which has an air permeance rate no greater than 0.02 L/(s•m²) at a pressure difference of 75 Pa when tested in accordance with ASTM E 2178. Air barrier components are used to connect and seal air barrier materials and/or air barrier assemblies together.
Air barrier components Pre-manufactured elements such as windows, doors and service elements that are installed in the environmental separator and sealed by air barrier accessories and which have an air leakage rate no greater than 0.20 L/(s•m²) at a pressure difference of 75 Pa when tested in accordance with ASTM E 2357.
Air barrier materials Building materials that are designed and constructed to provide the principal plane of airtightness through an environmental separator, which has an air permeance rate no greater than 0.02 L/(s•m²) at a pressure difference of 75 Pa when tested in accordance with ASTM E 2178. Air barrier materials meet the requirements of the CAN/ULC S741 Air Barrier Material Specification. The air barrier materials are typically the “big” pieces of material used in an air barrier assembly.
Air barrier systems Combinations of air barrier assemblies and air barrier components, connected by air barrier accessories, that are designed to provide a continuous barrier to the movement of air through an environmental separator, which has an air leakage rate no greater than 2.00 L/(s•m²) at a pressure difference of 75 Pa when tested in accordance with ASTM E 779 or CAN/CGSB 149.10 or CAN/CGSB 149.15.
Airflow or air flow In engineering, is a measurement of the amount of air per unit of time that flows through a particular device. The amount of air can be measured by its volume or by its mass. Typically it is measured by volume, but for some applications it is necessary to measure it by mass, as air is a gas and therefore its volume can vary with temperature.
Air leakage is sometimes called Infiltration.
American National Standards Institute (ANSI) private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organization also coordinates U.S. standards with international standards so that American products can be used worldwide. For example, standards ensure that people who own cameras can find the film they need for that camera anywhere around the globe.
Annealing is a process of slowly cooling glass to relieve internal stresses after it was formed. The process may be carried out in a temperature-controlled kiln known as a lehr. Glass which has not been annealed is liable to crack or shatter when subjected to a relatively small temperature change or mechanical shock. Annealing glass is critical to its durability. If glass is not annealed, it will retain many of the thermal stresses caused by quenching and significantly decrease the overall strength of the glass.
ASTM International known until 2001 as the American Society for Testing and Materials (ASTM), is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, and services. The organization’s headquarters is in West Conshohocken, Pennsylvania, about 5 mi (8.0 km) northwest of Philadelphia. ASTM, founded in 1898 as the American Section of the International Association for Testing and Materials, predates other standards organizations such as BSI (1901), DIN (1917), ANSI (1918) and AFNOR (1926).
Atmospheric pressure is the force per unit area exerted on a surface by the weight of air above that surface in the atmosphere of Earth (or that of another planet). In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. On a given plane, low-pressure areas have less atmospheric mass above their location, whereas high-pressure areas have more atmospheric mass above their location. Likewise, as elevation increases, there is less overlying atmospheric mass, so that atmospheric pressure decreases with increasing elevation. On average, a column of air one square centimeter in cross-section, measured from sea level to the top of the atmosphere, has a mass of about 1.03 kg and weight of about 10.1 N (2.28 lbf) (A column one square inch in cross-section would have a weight of about 14.7 lbs, or about 65.4 N).
Awning or overhang is a secondary covering attached to the exterior wall of a building. It is typically composed of canvas woven of acrylic, cotton or polyester yarn, or vinyl laminated to polyester fabric that is stretched tightly over a light structure of aluminium, iron or steel, possibly wood or transparent material (used to cover solar thermal panels in the summer, but that must allow as much light as possible in the winter). The configuration of this structure is something of a truss, space frame or planar frame. Awnings are also often constructed of aluminium understucture with aluminium sheeting. These aluminium awnings are often used when a fabric awning is not a practical application where snow load as well as wind loads may be a factor.
Bay window is a generic term for all protruding window constructions, regardless of height. The most common inside angles are 90, 135 and 150 degrees, though triangular bays formed of two windows set at 120 degrees may be found.
Bow Window or compass window is a curved bay window. Bow windows are designed to create space by projecting beyond the exterior wall of a building, and to provide a wider view of the garden or street outside and typically combine four or more casement windows, which join together to form an arch.
Building A structure that has a roof and walls and stands more or less permanently in one place.
Casement a window sash that is hinged (usually on one side).
Casing The frame or framework for a window or door.
Casement window or casement is a window that is attached to its frame by one or more hinges. Casement windows are hinged at the side. (Windows hinged at the top are referred to as awning windows. Ones hinged at the bottom are called hoppers.) They are used singly or in pairs within a common frame, in which case they are hinged on the outside. Casement windows are often held open using a casement stay.
CFM Cubic feet per minute, a measure of volumetric flow.
Clerestory Are any high windows above eye level. The purpose is to bring outside light, fresh air, or both into the inner space.
Convection is the concerted, collective movement of groups or aggregates of molecules within fluids (e.g., liquids, gases).
Convective heat transfer often referred to simply as convection, is the transfer of heat from one place to another by the movement of fluids. Convection is usually the dominant form of heat transfer in liquids and gases. Although often discussed as a distinct method of heat transfer, convective heat transfer involves the combined processes of conduction (heat diffusion) and advection (heat transfer by bulk fluid flow).
CR Window and frame Condensation resistance (CR), measured between 1 and 100 (the higher the number, the higher the resistance of the formation of condensation)
Degree day is a measure of heating or cooling.
Desiccant is a hygroscopic substance that induces or sustains a state of dryness (desiccation) in its vicinity. Commonly encountered pre-packaged desiccants.
Dew point is the temperature at which the water vapor in a sample of air at constant barometric pressure condenses into liquid water at the same rate at which it evaporates. At temperatures below the dew point, water will leave the air. The condensed water is called dew when it forms on a solid surface. The condensed water is called either fog or a cloud, depending on its altitude, when it forms in the air.
Display window A window of a store facing onto the street; used to display merchandise for sale in the store.
Door a piece of wood, metal, or other firm material pivoted or hinged on one side, sliding along grooves, rolling up and down, revolving, or folding, by means of which an opening into or out of a building, room, or other enclosure is open or closed to passage.
Double glazing a window with two panes of glass and a space between them; reduces heat and noise transmission through the window.
Double-hung window a window having two sashes that slide up and down.
Double-strength glass is sheet glass having a thickness of between 0.118 in. (3.00 mm) and 0.113 in. (3.38 mm).
Egress Window a window which is required in specific locations of a dwelling, which is used for a means of emergency escape. These type of windows must meet specific size requirements meet specific size and requirements to qualify as an egress window. Egress windows are required each room used for sleeping, on every floor and in basements with habitable spaces. An egress window must satisfy all building codes.
Emittance the ratio of radiant flux emitted by a material to that emitted by a blackbody at the same temperature, under the same conditions.
Energy Policy Act (102nd Congress H.R.776.ENR, abbreviated as EPACT92) is a United States government act. It was passed by Congress and set goals, created mandates, and amended utility laws to increase clean energy use and improve overall energy efficiency in the United States. The Act consists of twenty-seven titles detailing various measures designed to lessen the nation’s dependence on imported energy, provide incentives for clean and renewable energy, and promote energy conservation in buildings.
Energy Star power conservation requirements set forth by the Environmental Protection Agency of the U.S. government. In order to display the Energy Star logo, devices such as PCs, monitors and printers must use less than 30 watts of power when inactive
Exfiltration The leakage of room air out of a building, intentionally or not.
Extrusion is a process used to create objects of a fixed, cross-sectional profile. A material is pushed or drawn through a die of the desired cross-section. The two main advantages of this process over other manufacturing processes are its ability to create very complex cross-sections and work materials that are brittle, because the material only encounters compressive and shear stresses. It also forms finished parts with an excellent surface finish.
Eyebrow window a bottom-hinged, inward-opening window in the uppermost level of a house, usually under the front eaves; often one of a series of windows in the frieze of a Greek Revival style building.
Fanlight a semicircular window over a door or window; usually has sash bars like the ribs of a fan.
Fenestration architecture, the arrangement and design of windows in a building.
Fiberglass thread made from glass. It is made by forcing molten glass through a kind of sieve, thereby spinning it into threads. Fiberglass is strong, durable, and impervious to many caustics and to extreme temperatures. For those qualities, fabrics woven from the glass threads are widely used for industrial purposes. Fiberglass fabrics can also be made to resemble silks and cotton and are used for curtains and drapery. A wide variety of materials are made by combining fiberglass with plastic. These materials, which are rust proof, are molded into the shape required or pressed into flat sheets. Boat hulls, automobile bodies, and roofing and ceiling compositions are some of the uses to which such material is put.
Flashing strip of sheet metal placed at the junction of exterior building surfaces to render the joint watertight.
Float glass is a sheet of glass made by floating molten glass on a bed of molten metal, typically tin, although lead and various low melting point alloys were used in the past. This method gives the sheet uniform thickness and very flat surfaces. Modern windows are made from float glass. Most float glass is soda-lime glass, but relatively minor quantities of specialty borosilicate and flat panel display glass are also produced using the float glass process. The float glass process is also known as the Pilkington process, named after the British glass manufacturer Pilkington, which pioneered the technique (invented by Sir Alastair Pilkington) in the 1950s.
Floating mullion is also applied to an interlock profile which is fitted in between a pair of double swing doors.
Forced convection Forced convection is a mechanism, or type of transport in which fluid motion is generated by an external source (like a pump, fan, suction device, etc.
Frame the fixed, nonoperable frame of a window designed to receive and hold the sash or casement and all necessary hardware.
Glass is an amorphous solid (non-crystalline) material that exhibits a glass transition, which is the reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle state into a molten or plastic state. Glasses are typically brittle and can be optically transparent.
Glass–liquid transition (or glass transition for short) is the reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle state into a molten or rubber-like state. An amorphous solid that exhibits a glass transition is called a glass. Supercooling a viscous liquid into the glass state is called vitrification, from the Latin vitreum, “glass” via French vitrifier.
Glazing Bead, glass stop at a glazed opening, removable trim that holds the glass firmly in place.
Headers (Lintels) Structural members in light-frame construction which run perpendicular to floor and ceiling joists, “heading” them off to create an opening.
Heat Gain, (Solar gain also known as solar heat gain or passive solar gain) refers to the increase in temperature in a space, object or structure that results from solar radiation. The amount of solar gain increases with the strength of the sunlight, and with the ability of any intervening material to transmit or resist the radiation. Objects struck by sunlight absorb the short-wave radiation from the light and reradiate the heat at longer infrared wavelengths. Where there is a material or substance (such as glass) between the sun and the objects struck that is more transparent to the shorter wavelengths than the longer, then when the sun is shining the net result is an increase in temperature — solar gain. This effect, the greenhouse effect, so called due to the solar gain that is experienced behind the glass of a greenhouse, has since become well known in the context of global warming.
Heating degree day (HDD) is a measurement designed to reflect the demand for energy needed to heat a building. It is derived from measurements of outside.
HDD or Intel High Definition Audio Honorary Doctor of Divinity, a degree Heating degree day, quantitative indices designed to reflect the demand for energy.
Horizontal sliding window, horizontal slider A window having sashes (in a vertical plane) which slide in horizontal grooves or tracks; when closed, the stiles of the sashes meet and may interlock.
International Code Council ( ICC ) Provides technical, educational, and administrative support to governmental departments and agencies engaged in building codes administration.
International Energy Conservation Code (IECC) is a building code created by the International Code Council in 2000. It is a model code adopted by many states and municipal governments in the United States for the establishment of minimum design and construction requirements for energy efficiency.
Infiltration is the unintentional or accidental introduction of outside air into a building, typically through cracks in the building envelope and through use of doors for passage. Infiltration is caused by wind, negative pressurization of the building, and by air buoyancy forces known commonly as the stack effect.
Infrared (IR) is invisible radiant energy, electromagnetic radiation with longer wavelengths than those of visible light, extending from the nominal red edge of the visible spectrum at 700 nanometers (frequency 430 THz) to 1 mm (300 GHz) (although people can see infrared up to at least 1050 nm in experiments). Most of the thermal radiation emitted by objects near room temperature is infrared.
Insulated glazing (IG), more commonly known as double glazing (or double-pane, and increasingly triple glazing/pane) are double or triple glass window panes separated by an air or other gas filled space to reduce heat transfer across a part of the building envelope. Insulated Glass Units are manufactured with glass in range of thickness from 3 mm to 10 mm (1/8″ to 3/8″) or more in special applications. Laminated or tempered glass may also be used as part of the construction. Most units are manufactured with the same thickness of glass used on both panes but special applications such as acoustic attenuation or security may require wide ranges of thicknesses to be incorporated in the same unit.
Insulation (building construction) Material used in walls, ceilings, and floors to retard the passage of heat and sound. Use of materials or devices to inhibit or prevent the conduction
of heat or of electricity. Common heat insulators are, fur, feathers, fiberglass, cellulose fibers, stone, wood, and wool; all are poor conductors of heat. The use of asbestos, formerly a common insulating material, has been curtailed due to its implication in lung disease. Industrial furnaces are built of brick, which conducts heat so slowly that a high temperature within is barely apparent in the temperature of the outer surface. Steam pipes and water pipes are commonly insulated with thick wrappings of fiberglass pulp. Since insulators prevent the flow of heat in either direction, refrigerators are commonly constructed with double walls separated by an air space (air being a poor conductor) and lined with some insulating material. The use of double walls or hollow tiles in buildings prevents the entrance of heat and its escape. The very effective insulation in a vacuum bottle results almost entirely from the presence of a vacuum between the double walls of the inner flask. In the conduction of electricity from point to point, the conductor acts as a guide for the electric current and must be insulated at every point of contact with its supports to prevent escape, or leakage, of the current. Dry air is a good insulator, or dielectric, so that conductors used for electric-power transmission require insulating material only at their points of contact with the supporting steel structures. Glass and porcelain are commonly used, molded in bell-shaped forms or in rods made up of several segments. Underground conductors are insulated with dry cotton or pulp, rubber, and bitumen. In electrical apparatus, ebonite is widely used. Some other insulators are paraffin, sulfur, resin, and varnishes. Since wet materials can become conductors, insulation must often be waterproof. Ordinary household wires are commonly insulated by a thin rubber or plastic coating; the electric cables passing between house walls frequently have in addition a metal wrapping. Depending upon the application, the insulating material may also need to be resistant to various types of corrosion resulting from exposure to saltwater, oils, or other influences.
Jamb (building construction) The vertical member on the side of an opening, as a door or window.
Laminated glass, safety glass, shatterproof glass Two or more plies of plate glass, float glass, or sheet glass, bonded to a transparent plastic sheet between them to form a shatter-resisting assembly.
Lancet window a narrow window having a lancet arch and without tracery.
Light A flat sheet of glass, cut to fit a window or door or part of a window or door; often of small size, the larger ones usually being called sheets. After installation in a window sash, a pane is often referred to as a light. A window sash may be divided into a number of small lights, often for decorative or stylistic purposes. The configuration of a double-hung window having divided lights is often specified by the number of panes in the upper sash followed by the word over and then the number of panes in the lower sash; for example, a “six-over-three pattern” indicates that the upper sash is divided into six panes and the lower sash is divided into three panes.
Low emissivity (low e or low thermal emissivity) refers to a surface condition that emits low levels of radiant thermal (heat) energy. All materials absorb, reflect and emit radiant energy, but here, the primary concern is a special wavelength interval of radiant energy, namely thermal radiation of materials with temperatures approximately between 40 to 60 degrees Celsius.
Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the chalcogen group on the periodic table and is a highly reactive nonmetallic element and oxidizing agent that readily forms compounds (notably oxides) with most elements. By mass, oxygen is the third-most abundant element in the universe, after hydrogen and helium. At STP, two atoms of the element bind to form dioxygen, a diatomic gas that is colorless, odorless, and tasteless, with the formula O2.
Mullion is a vertical or horizontal element that forms a division between units of a window, door, or screen, or is used decoratively. When dividing adjacent window units, its primary purpose is to provide structural support to an arch or lintel above the window opening. Its secondary purpose may be as a rigid support to the glazing of the window. When used to support glazing, they are teamed with horizontal supporting elements called “transoms“.
Muntin is a strip of wood or metal separating and holding panes of glass in a window. Muntins are also called “muntin bars”, “glazing bars”, or “sash bars”. Muntins can be found in doors, windows and furniture, typically in western styles of architecture. Muntins divide a single window sash or casement into a grid system of small panes of glass, called “lights” or “lites”. Windows with “true divided lights” make use of thin muntins, typically 1/2″ to 7/8″ wide in residential windows, positioned between individual panes of glass. In wooden windows, a fillet is cut into the outer edge of the muntin to “stop” the pane of glass in the opening, and putty or thin strips of wood or metal are then used to hold the glass in place. The inner sides of wooden muntins are typically milled to traditional profiles. In the U.S., the thickness of window muntins has varied historically, ranging from very slim muntins in 19th century Greek revival buildings to thick muntins in 17th and early 18th century buildings. Until the middle of the 19th century, it was economically necessary to use smaller panes of glass, which were much more affordable to produce, and fabricate into a grid to make large windows and doors. However, many considered the division of a window or glazed door into smaller panes to be more architecturally attractive than use of large panes. In the UK and other countries, muntins (typically called “glazing bars” in the UK, or “astragals” in Scotland) were nevertheless removed from the windows of thousands of older buildings during the nineteenth century in favor of large panes of plate glass. Restoration of these buildings in the following century increasingly included reinstatement of the glazing bars, which many now see as an essential architectural element in period buildings. Muntins are often confused with “mullions” (which separate complete window units), and “astragals” (which close the gap between two leaves of a double door). Many companies use the term “grille” when referring to a decorative structure of wood or other material that is put over a single pane of glass to make it look as if there were muntins separating multiple panes of glass. In the UK, the term “grille” tends to be used only when there are bars sandwiched within the insulated glass glazing unit, and not stuck to the outsides of it. Double- or triple-layer insulated glass can be used in place of ordinary single panes in a window divided by muntins, though this reduces the effectiveness of the insulation. Other insulating glass arrangements include insertion of a decorative grid of simulated metal, wooden or plastic muntins sandwiched between two large panels of glass, sometimes adding another grid of simulated wood muntins facing the interior to produce a more convincing divided light appearance.
National Fenestration Rating Council provides accurate information to measure and compare energy performance of windows, doors and skylights.
Obscure glass a glass that has one or both faces acid-etched or sandblasted to obscure vision.
Oeil de boeuf a circular or oval window; 17th or 18th century French architecture.
Operable window a window which may be opened for ventilation.
Pa is a symbol, pascal is the SI derived unit of pressure, internal pressure, stress, Young’s modulus and tensile strength, defined as one newton per square metre. Pressure is a measure of force per unit area. It is named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. Common multiple units of the pascal are the hectopascal (1 hPa ≡ 100 Pa) which is equal to 1 mbar, the kilopascal (1 kPa ≡ 1000 Pa), the megapascal (1 MPa ≡ 1,000,000 Pa), and the gigapascal (1 GPa ≡ 1,000,000,000 Pa). On Earth, standard atmospheric pressure is defined as 101.325 kPa. Meteorological barometric pressure reports typically report atmospheric pressure in hectopascals,  corresponding to about 0.1% of atmospheric pressure. The main corresponding imperial and US customary unit is the pound per square inch (psi); in the context of meteorology, the inch of mercury may also be encountered.
Pane a flat sheet of glass, cut to fit a window or door or part of a window or door; often of small size, the larger ones usually being called sheets. After installation in a window sash, a pane is often referred to as a light. A window sash may be divided into a number of small lights, often for decorative or stylistic purposes. The configuration of a double-hung window having divided lights is often specified by the number of panes in the upper sash followed by the word over and then the number of panes in the lower sash; for example, a “six-over-three pattern” indicates that the upper sash is divided into six panes and the lower sash is divided into three panes.
Panel in Door a distinct section or division of a door, recessed below or raised above the general level, or one enclosed by a frame.
Parting stop a thin strip of wood that separates the sashes in a double-hung window.
Peak load the maximum load carried by a device, system, or structure over a designated time period.
Picture window a large window with a single pane (usually overlooking a view).
Pivoting window a window that opens by pivoting either horizontally or vertically.
Plate glass a high-quality glass sheet having both its flat sides plane and parallel so that it is free of distortions and flaws; has much greater mechanical strength than ordinary window glass; usually formed by a rolling process, then ground and polished, but can also be formed by the float-glass process, in which molten glass floats on a layer of molten metal to smooth out surface irregularities, producing a flat sheet of glass when the temperature of the molten metal is gradually reduced.
Porthole – a window in a ship or airplane.
Pound per square inch or, more accurately, pound-force per square inch (abbreviations: psi, lbf/in2, lbf/in2, lbf/sq in, lbf/sq in) is a unit of pressure or of stress based on avoirdupois units. It is the pressure resulting from a force of one pound-force applied to an area of one square inch.
Projected window a window having one or more rotatable sashes which swing either inward or outward.
PVC Poly(vinyl chloride), commonly abbreviated PVC, is the third-most widely produced polymer, after polyethylene and polypropylene.PVC comes in two basic forms: rigid (sometimes abbreviated as RPVC) and flexible. The rigid form of PVC is used in construction for pipe and in profile applications such as doors and windows. It is also used for bottles, other non-food packaging, and cards (such as bank or membership cards). It can be made softer and more flexible by the addition of plasticizers, the most widely used being phthalates. In this form, it is also used in plumbing, electrical cable insulation, imitation leather, signage, inflatable products, and many applications where it replaces rubber.
R-value a measure of the thermal resistance of a material or component.
Radiation a term applied to the emission and transmission of energy through space or through a material medium and also to the radiated energy itself. In its widest sense the term includes electromagnetic, acoustic, and particle radiation, and all forms of ionizing radiation. Commonly radiation refers to the electromagnetic spectrum which, in order of decreasing wavelength, includes radio, microwave, infrared, visible-light, ultraviolet, X-ray, and gamma-ray emissions. All of these travel through space at the speed of light (c.300,000 km/186,000 mi per sec) but differ in wavelength and frequency. According to the quantum theory, the energy carried in the form of electromagnetic radiation may be viewed as made up of tiny bundles or packets, each bundle being known as a photon. The sun is the source of much radiant energy in the form of sunlight and heat. Heat radiation is infrared radiation. All types of electromagnetic radiation can be reflected and absorbed in the same manner as is visible light. Acoustic radiation, propagated as sound waves, may be sonic (in the frequency range from 16 to 20,000 cycles per sec), infrasonic, or subsonic (frequency less than 16 cycles per sec), and ultrasonic (frequency greater than 20,000 cycles per sec). Examples of particle radiation are alpha and beta rays in radioactivity, and many kinds of atomic and subatomic particles such as electrons, mesons, neutrons, protons, and heavier nuclei (see cosmic rays). Radiation is usually considered to travel from a source in straight lines, but its path may be affected by external factors; for instance, charged particles travel in curved paths in magnetic fields. The Van Allen radiation belts consist of charged particles trapped in the earth’s magnetic field.
Reflective refers to light hitting an opaque surface such as a printed page or mirror and bouncing back.
Reflective glass window glass which has been coated on the outside with a transparent metallic coating to reflect a significant fraction of the light and radiant heat which strikes it.
Refraction in physics, deflection of a wave on passing obliquely from one transparent medium into a second medium in which its speed is different, as the passage of a light ray from air into glass.
Relative humidity A high relative humidity implies that the dew point is closer to the current air temperature. Relative humidity of 100% indicates the dew point is equal to the current temperature and that the air is maximally saturated with water. When the moisture content remains constant and temperature increases, relative humidity decreases.
Retrofitting the process of installing new mechanical, fire protection, and electrical systems or equipment in an existing building; most often required to meet current building code requirements. Also, the process of rethinking a development plan after completion to include newer features, such as green or eco-friendly features.
Rose window large circular window, usually glazed with stained glass, having stone tracery radiating from the center, often with intricate petallike patterns.
Rough opening an opening in a wall, or the framework of a building, into which a doorframe or window frame, subframe, or rough buck is fitted.
Safety glass is glass with additional safety features that make it less likely to break, or less likely to pose a threat when broken.
Sash window or hung sash window is made of one or more movable panels or “sashes” that form a frame to hold panes of glass, which are often separated from other panes (or “lights”) by narrow muntins. Although any window with this style of glazing is technically “a sash”, the term is used almost exclusively to refer to windows where the glazed panels are opened by sliding vertically, or horizontally in a style known as a “Yorkshire light”, sliding sash, or sash and case (so called because the weights are concealed in a box case). The oldest surviving examples of sash windows were installed in England in the 1670s, for example at Ham House. The invention of the sash window is sometimes credited, without conclusive evidence, to Robert Hooke.
Screen for window also known as insect screen or bug screen is designed to cover the opening of a window. The mesh is usually made of metal wire, fiberglass, or other synthetic fiber and stretched in a frame of wood or metal. It serves to keep leaves, debris, insects, birds, and other animals from entering a building or a screened structure such as a porch, without blocking fresh air-flow. Most houses in Australia, the United States and Canada and other parts of the world have screens on the window to prevent entry of disease carrying insects like mosquitoes and house flies. Formerly, screens were required to be replaced by glass storm windows in the winter, especially in regions like the northern United States and Canada, but now combination storm and screen windows are available, which allow glass and screen panels to slide up and down.
Sealant self-leveling silicone firestop system used around pipe through-penetration in a two-hour fire-resistance rated concrete floor assembly. A sealant may be viscous material that has little or no flow characteristics and stay where they are applied or thin and runny so as to allow it to penetrate the substrate by means of capillary action. Anaerobic acrylic sealants generally referred to as impregnants are the most desirable as they are required to cure in the absence of air, unlike surface sealants that require air as part of the cure mechanism that changes state to become solid, once applied, and is used to prevent the penetration of air, gas, noise, dust, fire, smoke or liquid from one location through a barrier into another. Typically, sealants are used to close small openings that are difficult to shut with other materials, such as concrete, drywall, etc. Desirable properties of sealants include insolubility, corrosion resistance, and adhesion. Uses of sealants vary widely and sealants are used in many industries, for example, construction, automotive and aerospace industries. The main difference between adhesives and sealants is that sealants typically have lower strength and higher elongation than do adhesives. Since the main objective of a sealant is to seal assemblies and joints, sealants need to have sufficient adhesion to the substrates and resistance to environmental conditions to remain bonded over the required life of the assembly. When sealants are used between substrates having different thermal coefficients of expansion or differing elongation under stress, they need to have adequate flexibility and elongation. Sealants generally contain inert filler material and are usually formulated with an elastomer to give the required flexibility and elongation. They usually have a paste consistency to allow filling of gaps between substrates. Low shrinkage after application is often required. Many adhesive technologies can be formulated into sealants. Sealants fall between higher-strength adhesives at one end and extremely low-strength putties and caulks at the other. Putties and caulks serve only one function – i.e., to take up space and fill voids. Sealants, on the other hand, despite not having great strength, do convey a number of properties. They seal the substrate at the glue line; they are particularly effective in keeping moisture in or out of the components in which they are used. They provide thermal and acoustical insulation and may serve as fire barriers; sometimes they contain electrical properties. They may also be used for smoothing or filleting. In short, sealants are often called upon to perform several of these functions at once.
Shading coefficient a ratio of the solar energy transmitted through a window to the incident solar energy; used to express the effectiveness of a shading device.
Sheet glass flat sections of glass made by drawing a continuous thin film of glass from a molten bath, then cooling and cutting it; used for common glazing.
Sill for window the lowest part of a window frame. Window sills hold the side pieces in place and slope outward to drain water. In a double hung window, the lower sash rests on the sill; the horizontal piece below a window unit in masonry construction or in wood framing. The window sill of the window frame sits on the window sill of the wall opening; the lowermost, interior trim work on a window;
Single-hung window a window with two sashes, only one of which opens.
Sliding glass door a type of sliding door in architecture and construction, is a large glass window opening in a structure that provide door access from a room to the outdoors, fresh air, and copious natural light. A sliding glass door is usually considered a single unit consisting of two panel sections, one being fixed and one a being mobile to slide open. Another design, a wall sized glass pocket door has one or more panels movable and sliding into wall pockets, completely disappearing for a ‘wide open’ indoor-outdoor room experience.
Sliding window a window that open by sliding horizontally.
Smart glass or Switchable glass also called smart windows or switchable windows in its application to windows or skylights refers to glass or glazing that changes light transmission properties under the application of voltage, light or heat. Smart glass controls the amount of light (and thereby heat) transmission. When activated, the glass changes from transparent to translucent, blocking some (or all) wavelengths of light. Smart glass technologies include electrochromic, photochromic, thermochromic, suspended particle, micro-blind and liquid crystal devices.When installed in the envelope of buildings, smart glass creates climate adaptive building shells, with the ability to save costs for heating, air-conditioning and lighting and avoid the cost of installing and maintaining motorized light screens or blinds or curtains. Most smart glass blocks ultraviolet light, reducing fabric fading; for SPD-type smart glass, this is achieved in conjunction with low emissivity coatings. Critical aspects of smart glass include material costs, installation costs, electricity costs and durability, as well as functional features such as the speed of control, possibilities for dimming, and the degree of transparency.
Solar gain (also known as solar heat gain or passive solar gain) refers to the increase in temperature in a space, object or structure that results from solar radiation. The amount of solar gain increases with the strength of the sunlight, and with the ability of any intervening material to transmit or resist the radiation. Objects struck by sunlight absorb the short-wave radiation from the light and reradiate the heat at longer infrared wavelengths. Where there is a material or substance (such as glass) between the sun and the objects struck that is more transparent to the shorter wavelengths than the longer, then when the sun is shining the net result is an increase in temperature — solar gain. This effect, the greenhouse effect, so called due to the solar gain that is experienced behind the glass of a greenhouse, has since become well known in the context of global warming.
Solar heat gain coefficient (SHGC) an indicator of the amount of solar radiation admitted through and absorbed by a window and subsequently released as heat indoors. SHGC is expressed as a number between 0 and 1; the higher the number, the more solar heat the window transmits.
Solar radiation the full spectrum of electromagnetic energy including visible light from the sun. When solar radiation strikes a solid surface or a transparent medium such as air or glass, some of the energy is absorbed and converted into heat energy, some is reflected, and some is transmitted. All three of these effects are important for effective passive solar design.
Solar screen a nonstructural openwork or louvered panel of a building arranged so as to act as a sun-shading device.
Solar spectrum the spectrum of the sun’s electromagnetic radiation extending over the whole electromagnetic spectrum, from wavelengths of 10-9 centimeter to 30 kilometers.
Sound transmission class, STC a single-number rating of the sound insulation value of a partition, door, or window; it is derived from a curve of its insulation value as a function of frequency; the higher the number, the more effective the sound insulation.
Stack effect is the movement of air into and out of buildings, chimneys, flue gas stacks, or other containers, resulting from air buoyancy. Buoyancy occurs due to a difference in indoor-to-outdoor air density resulting from temperature and moisture differences. The result is either a positive or negative buoyancy force. The greater the thermal difference and the height of the structure, the greater the buoyancy force, and thus the stack effect. The stack effect is also referred to as the “chimney effect”, and it helps drive natural ventilation, infiltration, and fires
Stained-glass window a window made of stained glass.
Storm sash, storm window a window outside an ordinary window to protect against severe weather or winter. Single-pane windows often installed on the interior of the main windows of home to improve insulation. When window replacement is cost prohibitive, adding storm windows can be an alternative for saving energy.
Sunblind a canopy made of canvas to shelter people or things from rain or sun.
Superwindow a window with a very low U-value achieved through the use of multiple glazings, low-E (low-emissivity) coatings, and inert gas fills, usually argon or krypton, placed between sealed panes of glazing in order to provide resistance to heat flow.
Tempered glass or Toughened is a type of safety glass processed by controlled thermal or chemical treatments to increase its strength compared with normal glass. Tempering puts the outer surfaces into compression and the inner surfaces into tension. Such stresses cause the glass, when broken, to crumble into small granular chunks instead of splintering into jagged shards as plate glass (aka: annealed glass) create. The granular chunks are less likely to cause injury. As a result of its safety and strength, toughened glass is used in a variety of demanding applications, including passenger vehicle windows, shower doors, architectural glass doors and tables, refrigerator trays, as a component of bulletproof glass, for diving masks, and various types of plates and cookware. The term tempered glass, in addition to meaning glass that has been heat treated to increase toughness, can refer to glass that has been treated with hydrofluoric acid or other acid. The acid etches away surface scratches and imperfections to increase strength.
Thermal break a component that is a poor conductor of heat and is placed in an assembly containing highly conducting materials in order to reduce or prevent the flow of heat. Also known as thermal barrier.
Thermal expansion the dimensional changes exhibited by solids, liquids, and gases for changes in temperature while pressure is held constant.
Thermal insulation is the reduction of heat transfer (the transfer of thermal energy between objects of differing temperature) between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with specially engineered methods or processes, as well as with suitable object shapes and materials. Heat flow is an inevitable consequence of contact between objects of differing temperature. Thermal insulation provides a region of insulation in which thermal conduction is reduced or thermal radiation is reflected rather than absorbed by the lower-temperature body.
Thermal mass any material or wall that can absorb heat or cold and release it at a later time.
Thermography nanometers or 9–14 µm) and produce images of that radiation, called thermograms. Since infrared radiation is emitted by all objects above absolute zero.
Thermoplastic, or Thermosoftening Plastic is a plastic material, typically a polymer, that becomes pliable or moldable above a specific temperature and solidifies upon cooling.
Threshold a piece of stone, wood, or metal that lies under an outside door.
Tinted glass glass which has been tinted, usually to filter out near-infrared solar energy, thereby reducing the solar heat gain through the glass and reducing the load on the air-conditioning.
Transmittance during absorption spectroscopy, the amount of radiant energy transmitted by the solution under analysis.
U-factor measure of the heat conducted through a given product or material the number of British thermal units (Btu) of heat that move through a square foot of the material in one hour for every 1 degree Fahrenheit difference in temperature across the material. U-factor is the inverse of R-value.
Ultraviolet (UV) light is electromagnetic radiation with a wavelength from 400 nm to 10 nm, shorter than that of visible light but longer than X-rays. Though usually invisible, under some conditions children and young adults can see ultraviolet down to wavelengths of about 310 nm, and people with aphakia (missing lens) can also see some UV wavelengths. Near-UV is visible to a number of insects and birds. UV radiation is present in sunlight, and is produced by electric arcs and specialized lights such as mercury-vapor lamps, tanning lamps, and black lights. Although lacking the energy to ionize atoms, long-wavelength ultraviolet radiation can cause chemical reactions, and causes many substances to glow or fluoresce. Consequently, biological effects of UV are greater than simple heating effects, and many practical applications of UV radiation derive from its interactions with organic molecules.
Uniform Building Code (UBC) a US national building code, prepared and issued by the International Conference of Building Code Officials, 5360 South Workman Mill Road, Whittier, CA 90601-2294. Also see BOCA National Building Code.
Vapor retarder a layer that inhibits vapor diffusion through a building envelope. Examples include polyethylene sheeting, foil facing, kraft paper facing on batt insulation, and low-permeability paints. Most building codes define a vapor retarder as 1 perm or less, with many common vapor retarders being significantly less than 1 perm.
Visible spectrum is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 700 nm. In terms of frequency, this corresponds to a band in the vicinity of 430–790 THz. A light-adapted eye generally has its maximum sensitivity at around 555 nm (540 THz), in the green region of the optical spectrum (see: luminosity function). The spectrum does not, however, contain all the colors that the human eyes and brain can distinguish. Unsaturated colors such as pink, or purple variations such as magenta, are absent, for example, because they can be made only by a mix of multiple wavelengths. Colors containing only one wavelength are also called pure colors.
Water vapor or water vapour or aqueous vapor, is the gaseous phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Unlike other forms of water, water vapor is invisible. Under typical atmospheric conditions, water vapor is continuously generated by evaporation and removed by condensation. It is lighter than air and triggers convection currents that can lead to clouds.
Weatherstripping a narrow strip of material to cover the joint of a door or window to exclude the cold.
Weep hole a weep hole or weeper hole is a small opening left in the outer wall of masonry construction as an outlet for water inside a building to move outside the wall and evaporate. The term was coined by archaeologist C. Leonard Woolley after finding evidence of weep holes in ziggurats. Plastic “weeps” are used in modern masonry construction. Weep holes are located near the base of masonry structures, particularly brick buildings. Raising the grade above weep holes may allow moisture, snakes, insects, and small animals to enter the building. Modern weep holes employ screens, constructed of flexible nylon or plastics. Typically, drain tiles have weep holes, which allow water to enter the tile. Weep holes may also be found in window and door frames.
Window in architecture, the casement or sash, fitted with glass, which closes an opening in the wall of a structure without excluding light and air. It may have a square, round, or pointed head; may be single, double, or grouped; in relation to the wall, it may be flush, recessed, or projected. A projected window is called a bay window if polygonal, a bow window if semicircular, an oriel
if it has corbeled brick or stone supports. A mullioned window is divided by slender bars into panes; when the bars radiate from the center of a circular bar it is called a wheel. It takes the name of rose window when adorned with stained glass or figure design. The long, narrow window of the English Perpendicular Gothic church is called a lancet; a lunette fills a somewhat crescent-shaped space under a vaulted intersection high upon a wall. A fanlight, characteristic of the American Colonial style, is either a semicircular transom, usually over an entrance, or a small attic window (or often a pair flanking the chimney). A French window reaches the floor and has double casements opening as doors; originating in France in the late Renaissance, it was adopted throughout the Continent and in the Southern states in America. The double-hung sashes (sliding up and down within the frame), first used in Renaissance England, attained wide popularity. In Spain windows are frequently ornate, with stone framework, an elaborate head, and a decorative iron grille. In Indian and Byzantine windows a pierced slab of marble or alabaster often substitutes for glass. Muslims also used cement frames in which colored glass was set in brilliant arabesque forms. Carved and turned wood grilles are found in Syria and Egypt. In China and Japan, rice paper, protected by a sliding wooden shutter, often takes the place of glass. Shell, also used in China, was employed by the Romans, as were thin panes of marble, mica, and horn. In modern architecture the use of windows has greatly increased in dwellings and in the exterior walls of factories and commercial buildings.
Window frame the framework that supports a window. The fixed, nonoperable frame of a window designed to receive and hold the sash or casement and all necessary hardware.
Window hardware devices, fittings, or mechanisms for opening, closing, supporting, holding open, or locking the sashes, including such items as catches, chains, cords, fasteners, hinges, lifts, locks, pivots, pulls, pulleys, sash balances, sash weights, and stays.
Window light A flat sheet of glass, cut to fit a window or door or part of a window or door; often of small size, the larger ones usually being called sheets. After installation in a window sash, a pane is often referred to as a light. A window sash may be divided into a number of small lights, often for decorative or stylistic purposes. The configuration of a double-hung window having divided lights is often specified by the number of panes in the upper sash followed by the word over and then the number of panes in the lower sash; for example, a “six-over-three pattern” indicates that the upper sash is divided into six panes and the lower sash is divided into three panes.
Windowpane a pane of glass in a window.