FenestrationMasters key terms

Model code adopted by many jurisdictions that sets minimum requirements for building safety, including structural, fire, egress, and energy provisions that govern fenestration products and their installation.

Model code establishing minimum energy-efficiency requirements for buildings, including fenestration U-factors, solar heat gain coefficients, and air leakage limits by climate zone.

The wind or load pressure, in pounds per square foot, that a fenestration product is rated to withstand in service; used to select products for a specific building location and height.

A single alphanumeric rating assigned to a fenestration product summarizing its tested performance for structural load, water penetration, and air leakage under a standardized rating system.

Glass that has been tempered, laminated, or otherwise treated so it breaks into small pieces or stays in its frame, reducing injury risk in hazardous locations such as doors, sidelights, and low windows.

Glass heat-treated to develop high surface compression so that, when broken, it fractures into small blunt fragments rather than sharp shards; it cannot be cut or drilled after tempering.

Glass heat-treated to a lower surface compression than tempered glass, giving it greater strength than annealed glass but breaking into larger, more angular fragments; not classified as safety glazing.

Ordinary float glass cooled slowly under controlled conditions, leaving low internal stress; it is the base product from which tempered, heat-strengthened, and laminated glass are made.

Two or more glass plies bonded to a plastic interlayer that holds fragments in place when broken, providing safety, security, and acoustic or impact resistance depending on the interlayer.

The plastic sheet, commonly polyvinyl butyral or ionoplast, placed between glass plies in laminated glass to bond them and provide post-breakage integrity, sound damping, or solar control.

A microscopically thin metallic or metal-oxide film applied to glass that reflects long-wave infrared radiation, lowering U-factor and reducing heat loss or solar gain depending on coating type.

A low-emissivity coating deposited off-line by sputtering and typically used on the interior surface of an insulating glass unit; it offers lower emissivity but is less durable than hard-coat coatings.

A low-emissivity coating applied on-line during float glass manufacture by pyrolytic deposition; it is durable, handleable, and often used on exposed surfaces but has higher emissivity than soft-coat products.

The overall rate of heat transfer through a fenestration assembly, including frame and edge effects, expressed in Btu/(h·ft²·°F); lower values indicate better insulating performance.

The fraction of incident solar radiation admitted through a fenestration product as heat gain, including both directly transmitted and absorbed-then-inward-released heat; values range from 0 to 1.

The fraction of visible light in the solar spectrum that passes through a glazing product, expressed from 0 to 1; used to compare daylighting potential and perceived darkness of glass.

The ratio of visible transmittance to solar heat gain coefficient, indicating how much daylight a glazing admits relative to the solar heat it lets in; higher values mean better daylighting per unit of heat gain.

An assembly of two or more glass panes separated by a sealed spacer and gas space, designed to reduce heat transfer and condensation; the edge seal is critical to long-term performance.

The component that separates glass panes in an insulating glass unit, contains desiccant, and provides the primary sealant bed; its design strongly affects edge-of-glass thermal performance.

A hygroscopic material, usually in granular or matrix form inside the spacer, that absorbs residual moisture in the sealed air or gas space of an insulating glass unit to prevent internal condensation.

A spacer made of low-conductivity material, such as stainless steel, silicone foam, or plastic hybrids, that reduces heat flow at the IGU perimeter and raises interior edge temperatures to limit condensation.

A low-conductivity element, typically polyamide or polyurethane, separating interior and exterior metal frame sections to reduce heat conduction through aluminum framing.

Window, door, and curtain wall framing made from extruded aluminum profiles; strong and durable but highly conductive, so thermal breaks are usually needed to meet energy code requirements.

A non-load-bearing exterior wall assembly that carries its own weight and wind loads and is attached to the building structure, typically glazed and designed to resist air and water infiltration.

A framed glazing system, usually aluminum, used for ground-floor commercial frontage; it is typically limited in height and spans between the floor and a header rather than the full building envelope.

A vertical or horizontal framing member that divides and supports adjacent lites of glass in a window, curtain wall, or storefront system and transfers loads to the surrounding structure.

The pressure or suction exerted on a building envelope by wind, determined by factors including basic wind speed, exposure category, building height, and topography; drives structural design of fenestration.

The test pressure applied to a fenestration specimen during structural performance testing, typically 1.5 times the design pressure, to verify it can withstand loads without failure.

A fenestration product's ability to resist water leakage under specified test conditions of pressure and water application rate, expressed as the highest pressure passed without uncontrolled leakage.

The design strategy of shedding, draining, and flashing exterior water away from the building envelope, including sloped sills, weep systems, and proper sequencing of weather barriers.

Sheet or formed material installed to direct water away from joints and openings, typically integrated above and below window and door openings to prevent moisture intrusion behind cladding.

A small opening in the sill or frame of a fenestration product that allows accumulated water in the drainage track or sill pan to escape to the exterior.

A preformed or site-fabricated watertight tray installed under a window or door sill to collect and drain any water that reaches the rough opening, protecting the wall below.

The volume of air passing through a fenestration assembly per unit area or length of crack under a specified pressure difference, typically reported in cubic feet per minute per square foot.

Unintentional airflow through building envelope gaps, cracks, and fenestration joints driven by pressure differences from wind, stack effect, and mechanical systems; increases energy use and can cause condensation.

A resilient strip, bulb, or fin installed in operable fenestration frames to seal the gap between sash and frame, reducing air infiltration and water entry when the unit is closed.

A single-number rating of how well a building element attenuates airborne sound across speech frequencies; higher values indicate greater sound isolation from exterior noise.

A single-number rating of a facade assembly's sound attenuation emphasizing lower frequencies such as traffic and aircraft noise; often more relevant than STC for exterior fenestration.

A relative rating of how well a fenestration product resists the formation of condensation on interior surfaces, influenced by frame U-factor, spacer type, and glazing surface temperatures.

Glazing designed to withstand windborne debris impact, typically laminated glass or glass with a protective film, used in hurricane-prone regions and tested to standardized missile-impact criteria.

A non-profit organization that develops standardized procedures for rating and certifying fenestration energy performance, producing labels that report U-factor, SHGC, VT, and air leakage.

A label affixed to a fenestration product summarizing its certified performance ratings, such as U-factor, SHGC, VT, and air leakage, issued under a recognized rating and certification program.

Performance testing conducted on installed fenestration assemblies at the building site, commonly for air and water infiltration, to verify that field installation matches laboratory-rated performance.

Laboratory or on-site testing of a full-scale representative assembly of fenestration and adjacent wall construction to evaluate structural, water, and air performance before or during construction.

The gap between two building components filled with an elastomeric sealant to accommodate movement and prevent air and water passage; joint design must account for width, depth, and expected movement.

A compressible foam rod inserted into a sealant joint to control sealant depth, support the sealant bead, and prevent three-sided adhesion that would restrict movement.

A tape or coating applied to the bottom of a sealant joint to prevent the sealant from adhering to the joint base, allowing the sealant to stretch and compress freely.

A membrane or sheet installed over wall sheathing to resist water and air penetration while allowing vapor to escape, integrated with flashing and fenestration to maintain continuity of the enclosure.

Flat glass produced by floating molten glass on a bath of molten tin, yielding uniform thickness, parallel surfaces, and a fire-polished finish free of distortion.

The framed opening in a wall into which a window or door unit is installed, sized to allow shimming, insulation, and flashing while accommodating the unit's frame dimensions.

A thin spacer, usually wood, plastic, or composite, placed under or beside a fenestration unit during installation to level, plumb, and square it while transferring loads to the structure.