Glossary of Roofing and Replacement Window Terms 

Glossary of Roofing and Replacement Window Terms 

Air Chambers
Small honeycomb spaces within the sash and frame, which help to insulate and strengthen the window.

Air Infiltration
The amount of air that passes between a window sash and frame. In windows it is measured in terms of cubic feet, or air per minute, per square foot of area. The lower the number, the less air the window lets pass through.

Air Latch
Latch mechanism on the interior face of the sash that retains the window in a partially open position for ventilation.

Angled Exterior
A sloped extension from the frame that adds an aesthetically-pleasing dimension to the exterior of the window.

Inside flat trim member, which is used under the stool at the bottom of the window.

Argon Gas
An odorless, colorless, tasteless, non-toxic gas, which is six times more dense than air. It is used to replace air between the glass panes to reduce temperature transfer.

A bituminous waterproofing agent applied to roofing materials during manufacturing.  Asphalt plastic roofing cement:  An asphalt-based cement used to bond roofing materials.

The center member of a double door, which is attached to the fixed or inactive door panel.

Awning Window
A top-hinged window that swings outward for ventilation.

Back Surfacing
Fine mineral matter applied to the back side of shingles to keep them from sticking.

Balance covers
Covers the balance cavity holding the coil-spring balance system inside the jamb.

Balance System
Device for holding vertically sliding sash in any desired position through the use of a spring or weight to counterbalance the weight of the sash.

Base Flashing
The portion of the flashing attached to or resting on the deck to direct the flow of water onto the roof covering.

Bay Window
A composite of three windows, usually made up of a large center fixed unit and two flanking units at 30°,45° or 90° degree angles to the wall.

This architectural term refers to a narrow, half-round molding that spans the edge of the siding.

Beveled Exterior
An angled extension from the frame that adds an aesthetically-pleasing dimension to the exterior of the window.

Block Frame Window
Used when replacing the wood sash of an old double hung wood window.

Bow Window
A composite of four or more window units in a radial or bow formation.

Brick mold
Outside casing around window to cover jambs and through which nails are driven to install the window.

A package of shingles. There are 3, 4 or 5 bundles per square.

Butt Edge
The lower edge of the shingle tabs.

A rubber material that seals the glass to the spacer, creating an airtight and water-tight IG unit. Butyl has the lowest gas permeability of all rubbers.

Cam Lock and Keeper
The mechanisms, which pull the sash together when placed in the locked position.

Capillary Tubes
Small hollow tubes, which penetrate the spacer system of an insulating glass unit. They allow pressure equalization between manufacturing locations, shipping, and installation locations. Since the insulating glass unit is not permanently sealed, the air space cannot be filled with Argon gas.

Casement Window
A window unit in which the single sash cranks outward, to the right or left.

Molding of various widths, thicknesses, and shapes applied to the framework of window and door units.

A mastic compound for filling joints and sealing cracks to prevent leakage of water and air, commonly made of silicone, bituminous, acrylic, or rubber-based material.

To fill a joint with mastic or asphalt cement to prevent leaks.

Check rail
On a double-hung window, the bottom rail of the upper sash and the upper rail of the lower sash, where the lock is mounted.

A generic term referring to any of a variety of window units with one or more curved frame members, often used over another window or door opening.

A thin, narrow board with one edge thicker than the other, used as siding. CertainTeed siding brands offer clapboard-style siding in different exposures, several different textures, and even different panel projections.

A window near the top of an outside wall.

Pre-formed flange placed over a vent pipe to seal the roof around the vent pipe opening. Also called a vent sleeve.

Energy transfer from one material to another by direct contact.

Heat transfer by currents that flow from a warm surface to a colder one.

Cottage double-hung
A double-hung window in which the upper sash is shorter than the lower sash.

Coved Exterior
An arced extension from the frame that adds an aesthetically-pleasing dimension to the exterior of the window.

The short 2″ x 4″ members used to frame under the sill or above the header in a rough opening for a window in a frame wall.

A watertight wall or frame used to raise slope glazing above the surface of the roof as a preventive measure against water leakage from melting snow or rain run-off.

The surface installed over the supporting framing members to which the roofing is applied.

Dead-air space
The space between the panes of glass of an I.G. Unit.

A piece of glass or IGU with a sash profile around it; not set within the main frame of a window unit.

A material used in insulating glass to absorb water vapor which causes fogging.

Design Pressure
A numerical value that defines the structural wind loading requirements (in pounds per square foot) for a building and the components and cladding of a building.

A space, which protrudes from the roof of a house, usually including one or more windows.

Double glazing
Use of two panes of glass in a window to increase energy efficiency and provide other performance benefits.

Double-hung Window
A window unit that has two operable sashes, which move vertically in the frame.

Double rafter
The doubling (side by side) of the roof members to reinforce an opening in the roof for a slope-glazing installation.

A pipe for draining water from roof gutters. Also called a leader.

Drip Cap
A molding placed on the top of the head brickmold or casing of a window frame.

Drip Edge
A non-corrosive, non-staining material used along the eaves and rakes to allow water run-off to drip clear of underlying construction.

Dry glazing
An alternative method of placing glass in a door or window. No glazing mastic is used. Dry glazing is recommended whenever reflective coatings are glazed to first surface.

Double or Dual Glazing
Use of two panes of glass in a window to increase energy efficiency and provide other performance benefits.

A beveled-edge siding panel that was popularized by early American settlers.

The horizontal, lower edge of a sloped roof.

Egress window
A window large enough, as defined by local building codes, for exit or entry in case of an emergency. Typically required in bedrooms.

The relative ability of a surface to radiate heat.

ENERGY STAR® is an independent U.S. government program establishing a standard set of guidelines to recognize the energy efficiency of various products. ENERGY STAR® guidelines are used in conjunction with a variety of building materials, including windows and patio doors. Over the past ten years, ENERGY STAR® guidelines have helped double the efficiency of windows they endorse.

The width of each “board” of siding. Also called a reveal.

A form produced by forcing material through a die. Most window frames are clad with extruded vinyl or aluminum.

Architecturally, “fascia” refers to a flat, horizontal band. A flat board that runs horizontally along the eaves of a roof, typically capping the ends of the roof rafters to give the roof edge a more finished look and provide a base for attaching gutters.

An architectural term referring to the arrangement of windows in a wall. From the Latin word, “fenestra,” meaning window.

A composite material made by embedding glass fibers in a polymer matrix. May be used as a diffusing material in sheet form, or as a standard sash and frame element.

A means of joining individual pieces of wood together to form longer lengths. The ends of the pieces are machined to form a set of interlocking fingers, which are then coated with adhesive and meshed together under pressure.

Refers to the texture (and sometimes the gloss level) of a siding panel. For fiber cement, this refers to the coating used to finish the siding. Usually an opaque paint; solid or semi-transparent stain.

Fixed Window
Non-venting or non-operable window. Also known as picture window.

A thin strip of metal or synthetic material that diverts water away from a window or skylight.

The enclosure in which window sash or door panels are mounted.

French hinged door
Hinged door(s), which have wider panel members around the glass.

French sliding door
A sliding door, which has wider panel members around the glass, giving the appearance of a French hinged door.

The horizontal member connecting the top of the siding with the soffit.

In house construction, the portion of the roof above the eave line of a double-sloped roof.

Gable Roof
A type of roof containing sloping planes of the same pitch on each side of the ridge. Contains a gable at each end.

Gambrel Roof
A type of roof containing two sloping planes of different pitch on each side of the ridge. The lower plane has a steeper slope than the upper. Contains a gable at each end.

A pliable, flexible continuous strip of material used to effect a watertight seal between sash and frame of roof windows much like the seal around a refrigerator door.

Glass in a window or door; the act or process of fitting with glass.

Glazing Bead
A plastic or wood strip applied to the window sash around the perimeter of the glass.

Glazing compound
A pliable substance applied between the window sash and the lites of glass to seal against the elements and sometimes to adhere the glass to the sash.

Glazing Stop
The part of the sash or door panel which holds the glass in place.

The trough that channels water from the eaves to the downspouts.

Flat strap that is installed under the roofing material that holds up the horizontal section of the gutter.

The main horizontal member forming the top of the window or door frame.

Head board
A flat board cut to fit the contour of a bow or bay window and installed between the head jambs and the flat wall surface to finish off that area, which would normally be ceiling.

A horizontal framing member placed over the rough opening of a window to prevent the weight of a wall or roof from resting on the window frame.

Head expander
A vinyl shape cut the width of a product and placed on the head, fitting over it snugly. This piece is used as a filler to expand or lengthen the unit from the head and take up the gap in the opening between the unit and the opening in the unit.

A window unit in which the top of the sash swings inward.

I.G. Unit (Insulating Glass Unit)
Two or more lites of glass separated by a spacer and hermetically sealed at the glass edges.

Ice Dam
Condition formed at the lower roof edge by the thawing and re-freezing of melted snow on the overhang. Can force water up and under shingles, causing leaks.

Impact Resistant Glass
Single or double pane construction made up of laminated glass containing a .090 interlayer.

Insulating Glass
A combination of two or more panes of glass with a hermetically sealed air space between the panes of glass. This space may or may not be filled with an inert gas, such as argon.

Integral extension on the outside of a new construction window that eases installation on siding applications.

Jack stud
Framing members, generally 2″ x 4″s, which form the inside of the window or door rough opening. They run from the sole plate to the header, which is supported by them.

The main vertical members forming the sides of a window or door frame.

Jamb liner
Metal or plastic covering the inside surface and head jambs of sliding windows.

The protruding, hook-shaped part of a casement window lock, which is mounted on the inside surface of the sash stile.

Molding of various widths used to trim door and window openings at the jambs. Also referred to as:  box post, window and door surround.

A handle or grip installed on the bottom rail of the lower sash of a double-hung window to make it easier to raise or lower the sash.

Light or Lite
Glazing framed by muntins and/or sash in a window or door.

Light shaft
An insulated shaft built to direct the light from a roof window or skylight through the attic to the room below.

A horizontal member above a window or door opening that supports the structure above.

Lock Rail
The horizontal section of the sash where the cam lock is attached.

Lock Stile
The vertical section of the sash where the cam lock is attached.

Low-E Glass
A common term used to refer to glass, which has low emissivity due to a film or metallic coating on the glass or suspended between the two lites of glass to restrict the passage of radiant heat.

Main Frame
The head, sill, and jamb sections of a window.

Masonry Opening
The space in a masonry wall left open for windows or door.

Mechanically Fastened Frame
Refers to frames fastened with screws.

Meeting Rail
The horizontal section of a pair of sashes that meet when the sashes are closed.

Meeting Stile
The vertical section of a pair of sashes that meet when the sashes are closed.

Fabric made of either fiberglass or aluminum, used in the making of screens.

An ornamental exterior trim around the perimeter of a frame.

A slot or rectangular cavity cut into a piece of wood to receive another part.

A strong wood joint made by fitting together a mortise in one board and a matching projecting member (tenon) in the other.

A wood or metal part used to structurally join two window or door units.

Applies to any short or light bar, either vertical or horizontal, used to separate glass in a sash into multiple lites. Also called a windowpane divider or a grille.

Muntin Bar
Any small bar that divides a windows glass.  Also called a grille or windowpane divider.

National Fenestration Rating Council® – a non-profit organization that provides fair, accurate, and credible energy performance ratings for windows and doors.

Nail Hem
The top edge of a siding panel, where it is nailed to a wall.

Obscure Glass
Glass that has been made translucent instead of transparent.

A metal arm and gear, which allows for easy operation or closing of projecting windows.

A window with the meeting rail located off center of the frame. Most oriels have a 60/40 configuration.

Outer frame member
The exterior protruding portion of a window frame which has no exterior casing.

That portion of the roof structure that extends beyond the exterior walls of a building.

Palladian window
A large, arch-top window flanked by smaller windows on each side.

A framed sheet of glass within a window.

Panel Projection
The section of siding that projects from the wall. As a rule of thumb, a larger panel projection creates a more pronounced shadow line.

Passive solar collector
Any glazed area in the walls or roof of a building pointed to the south to take maximum advantage of the sun’s heat without a mechanical (or active) method of storage or distribution of the heat.

Patio door
A glass door that slides open and close on adjustable tandem rollers. Available in 2- or 3-lite configurations with the operable panel available in any position.

Non-venting or non-operable window. Also know as a fixed window.

Picture frame casing
The use of casing on all four sides of the interior of a window, replacing the stool and apron at the sill. Also known as full-bound casing.

Picture Window
A window that has no moveable sash.

The degree of roof incline expressed as the ratio of the rise, in feet, to the span, in feet.

A mode of operation for ventilating windows, which generally means the sash pivots on a central axis and turns 90º or more.

Pivot Alignment System
An exclusive hinge-type system used on hung windows. This system attaches the sash to the balance, creating perfect alignment between the sash and frame, while allowing the sash to tilt inward for cleaning.

Side view of a siding or soffit panel.

Pull Handle
A handhold for sliding the sash back and forth. Handle implies that the handhold is not continuous across the sash.

Pull rail
A handhold for sliding the sash back and forth. Rail implies that the handhold is continuous across the sash.

Pull Stile
A handhold for sliding the sash back and forth. Stile implies that the handhold is continuous across the sash.

Resistance a material has to heat flow. The higher the R-value, the greater the resistance.

Wave energy transmitted directly from one object to another through the atmosphere, or through transparent or translucent materials. The energy radiated is either transmitted, absorbed, reflected, or a combination of all three.

Structural members of a roof that support the roof load and run from the ridge to the eaves (overhang).

The top and bottom horizontal members of the framework of a window sash.

Raised Exterior
An angled extension from the frame that adds an aesthetically pleasing dimension to the exterior of the window.

Trim members that run parallel to the roof slope and form the finish between the wall and a gable roof extension.

Relative Humidity Condensation Point
The relative humidity level at which visible water vapor or other liquid vapor begins to form on the surface of the sash or frame, based on an inside temperature of 70° F and an outside temperature of 0° F. The higher the percentage, the more moisture the air can hold before condensation will occur.

The uppermost, horizontal external angle formed by the intersection of two sloping roof planes.

The vertical distance from the eaves line to the ridge.

Rough Opening
The framed opening in a wall into which a window or door unit is to be installed.

Rough sill
The horizontal rough framing member, usually two inches by four inches, which forms the bottom of the rough opening. It is toe-nailed into the jack studs and is supported by cripples.

A single assembly of stiles and rails made into a frame for holding glass.

Sash Alignment System
An exclusive hinge-type system used on hung windows. This system attaches the sash to the balance, creating perfect alignment between the sash and frame, while allowing the sash to tilt inward for cleaning.

Sash balance
A system of weights, cords, and/or coiled springs, which assist in raising double-hung sash and tend to keep the sash in any placed position by counterbalancing the weight of the sash.

Sash cord
In double-hung windows, the rope or chain that attaches the sash to the counter balance.

Sash Lift
A protruding handle screwed to the inside bottom rail of the lower sash on a double-hung window.

Sash lock
Generally, a cam-action type lock applied to the check rails of a sliding window, or at the open edges of a projecting window, to pull the check rails tightly together, or to seal the sash tightly to the frame, both for security and weathertightness.

Sash weights
In older double-hung windows, the concealed cast-iron weights that are used to counterbalance the sash.

Seat Board
A flat board cut to fit the contour of a bow or bay window and installed between the sills and the flat wall surface, providing a seat or shelf space.

Shading Coefficient
The ratio of solar heat that is transferred through a glazing material relative to the solar heat transferred through 1/8″ clear glass. The lower the number the more efficient the window is at reducing solar heat gain.

Shadow Line
The shadow pattern cast by a particular siding in the sunlight. Shadow line is influenced by the style and panel projection of the siding.

Wood wedges (often wood shingles) used to secure the window or door unit in the rough or masonry opening in a square, level, and plumb position during and after installation.

Narrow fixed units mulled or joined to door units to give a more open appearance.

The main horizontal member forming the bottom of the frame of a window or door.

Sill Extender
An extrusion that is attached to the bottom of the window to cover the gap between the sill and the rough opening.

Simulated Divided Lite
A method of constructing windows in which muntins are affixed to the inside and outside of a panel of insulating glass to simulate the look of true divided light.

Single Glazing
Use of single panes of glass in a window. Not as energy-efficient as double glazing.

Single-hung Window
A double-hung type of window in which the top sash is fixed or inoperable.

Slider Window
Both sashes slide horizontally in a double-sliding window. Only one sash slides in a single-sliding window. Ventilation area can vary from a small crack to an opening of one-half the total glass area. Screens can be placed on the exterior or interior of the window unit.

The degree of roof incline expressed as the ratio of the rise, in inches, to the run, in feet.

Slope glazing
Any glazed opening in a sloped roof or wall, such as a stationary skylight or fully operable roof window.

Sloped sill
The sill of the window that has a downward slope to the outside. This sill has sufficient degree of slope to aid in water runoff.

Usually the underside of an overhang or eaves.

Solar Heat Gain
The percentage of heat gained from both direct sunlight and absorbed heat. The smaller the number, the greater the ability to reduce solar heat gain.

Sole plate
The bottom horizontal member in a frame wall. Usually either single or double 2″ x 4″s. It is nailed to the deck or rough floor and the studs are nailed into it.

Material placed between two or more pieces of glass in order to maintain a uniform width between the glass and prevent sealant distortion.

Stepped Sill
An exclusive triple-stepped, sloped sill design.

The main vertical members of the framework of a sash.

Protects the jamb from the hardware latch on a door. Covers the latch and deadbolt.

Unit of measure for siding equal to 100 square feet (or a 10-foot by 10-foot wall section).

An interior trim piece on a window which extends the sill and acts as a narrow shelf.

A wood trim member nailed to the window frame to hold, position, or separate window parts. The stop is often molded into the jamb liners on sliding windows.

Stop Molding
A molding used to hold, position, or separate window parts.

Stucco Fin
An extrusion used in stucco home installations that is attached to the main frame to create a smooth, finished look for both the window and the stucco.

Vertical wood framing members, which form a frame wall. In normal construction these are eight foot-long 2″ x 4″s.

Tempered Glass
Glass with a surface compression of not less than 10,000 psi, or an edge compression of not less than 9,700 psi. When broken, the glass breaks into pebbles instead of shards.

A rectangular projection cut out of a piece of wood for insertion into a mortise.

Thermal Break
The addition of a thermal insulating material between two thermally conductive materials.

The bottom part of the door frame, i.e. the area you step on when entering or exiting through the doorway.

Tilt Latch
Mechanism that unlocks the sash and allows it to tilt in from the main frame.

Tilt-in/lift-out sash
A sash that can be tilted to the interior, removed for cleaning, and is manufactured by welding.

Total Unit U- and R-values
The U- and R-values of the window calculated from the average of the center of glass, edge of glass and frame U- and R-values. It is the reciprocal of the R-value.

A small window that fits over the top of a door or window, primarily for additional light and aesthetic value.

Triple glazing
A sash glazed with three lites of glass, enclosing two separate air spaces.

True Divided Lite
A term which refers to windows in which multiple individual panes of glass or lites are assembled in the sash using muntins.

Asphalt saturated felt used beneath roofing to provide additional protection for the deck.

Amount of heat transferred through a material. The lower the U-value, the slower the rate of heat flow and the better the insulating quality.

UV Block
The percent of ultraviolet rays blocked from being transmitted through the glass. The higher the number the lower the percentage of ultraviolet rays transmitted through the window.

Unison lock
A casement locking system, which secures the window at two locking points by operation of one handle.

The internal angle formed by the intersection of two sloping roof planes.

Vapor barrier
A watertight material used to prevent the passage of moisture into or through floors, walls, and ceilings.

Any outlet for air that protrudes through the roof deck such as a pipe or stack. Any device installed on the roof, gable, or soffit for the purpose of ventilating the underside of the roof deck.

Latch mechanism on the interior face of the sash, which retains the window in a partially open position for ventilation.

Vent Unit
A window or door unit that opens or operates.

Vertical Siding
Also referred to as “panel siding”, this rectangular shaped siding is typically manufactured in 4 x 8, 4 x 9 or 4 x 10 sizes. Vertical siding is never overlapped. Solid vinyl soffit can also be used as vertical siding.

A plastic material used for cladding or entire window units.

Visible Light Transmittance
The percentage of light that is transmitted through glass in the visible light spectrum (380 to 720 nanometers). The higher the number the higher the percentage of visible light transmitted through the window.

Wind Born Debris Region
Areas within hurricane-prone regions within one mile of the coast where the basic wind speed is 110mph or greater, or where the basic wind speed is equal to or greater than 120mph, or Hawaii.

A material or device used to seal the openings, gaps, or cracks of venting window and door units to prevent water and air infiltration.

Weep flaps
A weep hole that is covered with a vinyl flap that allows water to escape, while keeping insects out.

Weep Holes
Small openings designed to allow water to escape that might otherwise accumulate in a window’s sill.

Weep Slots
Slots or holes in the sill (bottom) member of the sash frame that provides an outdoor release of infiltrated rainwater.

Wet Glazing
A silicone-based substance used to secure and seal the glass to the sash.

Force exerted on a surface by moving air.

Windowpane divider
A short bar used to separate glass in a sash into multiple lites. Also called a muntin or a grille.

Wood blocks
Pieces of plywood that come in different thicknesses, depending on the depth of the hook of the frame. They are used to make the window flush with the opening it is filling. They are also used to assist in pre-mulling windows together and give the screw more to bite into when joining the windows.

Wood jamb strips
Strips of wood that run along the jamb used to shim up the window.