Glossary
Windows, doors & siding vocabulary — 173+ terms explained in plain language.
A
Air Barrier
A system of materials designed to control airflow between the conditioned interior and unconditioned exterior of a building, reducing energy loss and drafts.
Air Leakage Rating
A measure of the rate of air infiltration through a window assembly, expressed in cubic feet per minute per foot (cfm/ft²). Lower values indicate a tighter seal.
Aluminum
A lightweight, strong metal used for window and door frames, siding, and . Naturally corrosion-resistant; requires a for good insulation.
Aluminum Siding
Metal cladding made from lightweight sheets. Durable and fire-resistant, but can dent easily and may fade or oxidize over time.
Argon Gas Fill
An inert, colorless gas injected between glass panes in an IGU to reduce heat transfer. Argon is denser than air and a poorer conductor of heat.
Astragal
A vertical moulding strip attached to the edge of one door in a double-door system, covering the gap between the two doors when closed.
Awning Window
A window hinged at the top that swings outward from the bottom, allowing ventilation even during light rain.
B
Backer Rod
A cylindrical foam strip inserted into wide gaps or joints before applying , providing a surface for the sealant to bond to and controlling joint depth.
Balance
A mechanical device, usually a spring or weight system, concealed in the window that counterbalances the weight of the for smooth operation.
Batt Insulation
Pre-cut panels of fiberglass or mineral wool insulation designed to fit between wall studs, ceiling joists, and floor joists.
Bay Window
A window that projects outward from the exterior wall, typically consisting of a large center fixed pane flanked by two operable windows set at 30° or 45° angles.
Bi-Fold Door
A door system with panels that fold against each other accordion-style to create a wide opening, popular for connecting indoor and outdoor living spaces.
Blown-In Insulation
Loose-fill insulation (cellulose or fiberglass) mechanically blown into wall cavities or attic spaces, conforming to irregular shapes for complete coverage.
Board and Batten
A siding style using wide vertical boards with narrow strips (battens) covering the joints between them, creating a traditional farmhouse aesthetic.
Bow Window
Similar to a but composed of four or more equal-sized windows arranged in a gentle curve to create a rounded appearance.
Brick Opening
The measured opening in a brick or masonry wall where a window or door will be installed, typically measured from brick edge to brick edge.
Brickmould
A wide, decorative exterior (trim) around a window or door, commonly used on homes with brick, stucco, or masonry exteriors.
Building Envelope
The physical barrier between the conditioned interior and unconditioned exterior of a building, including walls, roof, windows, doors, and foundation.
Building Permit
An official authorization from the local municipality required before starting construction, renovation, or certain replacement work to ensure compliance with building codes.
C
Cam Lock
A lock commonly used on double-hung and sliding windows that rotates to pull the sash tightly against the , improving seal compression.
Capillary Break
A gap or feature designed to interrupt the capillary action of water, preventing it from being drawn through tight joints or between overlapping materials by surface tension.
Casement Window
A window with a hinged on one side that swings outward like a door, operated by a crank mechanism. Offers excellent ventilation and a tight seal when closed.
Casing
The trim or moulding that covers the gap between the window or door and the wall, providing a finished appearance.
Caulk Maintenance
Periodically inspecting and replacing exterior around windows, doors, and siding joints to maintain a weathertight seal and prevent moisture intrusion.
Caulking
A flexible applied around window and door frames, siding joints, and trim to create a waterproof and airtight seal.
Cedar Shake Siding
Siding made from split or sawn cedar shingles that provide a rustic, textured appearance. Naturally resistant to decay and insects but requires periodic treatment.
Centre-to-Centre (O.C.)
A measurement from the center of one structural member (stud, joist, rafter) to the center of the next, typically 16" or 24" apart in residential framing.
Clad Frame
A wood window or door covered with an exterior layer of or vinyl to protect the wood from weather while retaining the warm interior wood appearance.
Composite
A material made by combining two or more different materials (e.g., wood fibers and plastic resin) to achieve properties superior to either component alone.
Condensation
Water droplets that form on window surfaces when warm, moist indoor air contacts a cooler glass or surface. Indicates humidity levels or insufficient insulation.
Condensation Resistance (CR)
A rating from 1 to 100 indicating how well a window resists the formation of on its interior surface. Higher numbers mean better resistance.
Corner Post
A vertical trim piece installed at the inside or outside corners of a building to provide a finished transition between siding panels on adjacent walls.
Crank Operator
A hand-operated crank mechanism used on casement and awning windows to open and close the smoothly and precisely.
CSA Group (Canadian Standards Association)
A standards organization that develops codes and standards for building materials, including windows and doors (e.g., CSA A440 for ).
D
Daylight Opening
The visible glass area of a window or door when viewed from the interior — the actual area through which light passes, excluding and material.
Deadbolt
A lock mechanism that extends a solid metal bolt into the door , providing security beyond a standard latch. Single-cylinder deadbolts use a key outside and thumb turn inside.
Design Pressure (DP)
A rating indicating the maximum wind load a window or door can withstand without failure. Higher DP ratings mean greater structural strength.
Door Knocker
A decorative metal fixture mounted on the exterior of an , used by visitors to announce their presence.
Door Lite
A glass panel or insert within a door. Available in various sizes and decorative styles, from full-lite to half-lite to small sidelite inserts.
Door Sweep
A strip of flexible material attached to the bottom of a door to seal the gap between the door and the , blocking drafts, moisture, and pests.
Double-Hung Window
A window with two vertically sliding sashes that can both move up and down independently, allowing ventilation from the top, bottom, or both.
Double-Pane Glass
An consisting of two glass panes separated by a sealed air or gas-filled space, significantly improving thermal performance.
Drip Cap
A Z-shaped installed above windows and doors to divert water away from the top of the trim and prevent moisture intrusion behind the siding.
Drip Cap (Flashing)
Z-shaped metal installed above a window or door to divert water over the exterior and away from the unit.
Dry Fit
The practice of placing a window or door into the without fasteners to verify proper fit, alignment, and clearance before final installation.
Dutch Door
A door divided horizontally so the top half can open independently of the bottom half, allowing air and light in while the lower portion stays closed.
E
Eavestrough Cleaning
Removing leaves, debris, and sediment from gutters and downspouts to ensure proper water drainage away from the home's foundation and prevent overflow damage.
Egress Window
A window large enough to serve as an emergency exit, required by building codes in bedrooms and finished basements.
EnerGuide
A Canadian labeling program that provides standardized energy-efficiency ratings for windows, doors, heating systems, and other products.
Energy Rating (ER)
A Canadian performance metric that balances heat gain from the sun, heat loss through the and glass, and air leakage. Higher ER values indicate better overall energy performance.
ENERGY STAR
A certification program that identifies windows, doors, and other products meeting strict energy-efficiency criteria set by Natural Resources Canada or the US EPA.
ENERGY STAR Canada
An international symbol identifying energy-efficient products. Windows and doors must meet zone-specific performance criteria to earn the label in Canada.
Engineered Wood Siding
Siding manufactured from wood strands, fibers, and resins bonded under heat and pressure. Offers the appearance of real wood with improved resistance to moisture and insects.
Entry Door
The main exterior door of a home, designed for security, insulation, and curb appeal. Available in steel, fiberglass, and wood.
F
F-Channel
A trim piece shaped like the letter F, used to attach siding edges to other surfaces.
Fenestration
A broad term encompassing all openings in a , including windows, doors, skylights, and curtain walls.
Fiber Cement Siding
A durable cladding made from a mixture of cement, sand, and cellulose fibers. Resists fire, rot, and termites; can mimic wood grain or smooth textures. James Hardie is a leading brand.
Fiberglass (FRP)
Fiber-reinforced polymer used for window frames, doors, and some siding. Extremely strong, dimensionally stable, and paintable with very low thermal expansion.
Fiberglass Door
An with fiberglass skins over a foam-insulated core. Can realistically mimic wood grain, resists denting, cracking, and warping.
Fixed Window
A non-operable window designed solely to let in light and provide an unobstructed view. Also called a .
Flashing
Thin pieces of waterproof material (metal or membrane) installed around window and door openings to direct water away from the wall structure and prevent leaks.
Flashing Tape
A self-adhesive waterproof membrane applied around window and door openings before installation to direct moisture away from the wall structure.
Frame
The outer structural of a window unit that holds the , glass, and hardware in place and attaches to the wall opening.
French Door
A pair of hinged doors with full-length glass panels that swing inward or outward, offering wide access and abundant natural light.
Full-Frame Installation
A window replacement method where the entire window — including the — is removed down to the , allowing for new insulation, , and a completely new unit.
Furring Strip
A thin strip of wood or metal attached to the wall to create a flat, even surface or an air gap for siding installation on uneven walls.
G
Garden Door
A pair of outswing hinged doors, similar to French doors, but without the center when open, providing a clean, unobstructed opening.
Garden Window
A small bay-style window that projects outward and features a glass top, often used in kitchens to create a mini greenhouse shelf.
Glass Replacement
The process of removing and replacing a damaged or failed insulated glass unit within an existing window or .
Glazing Bead
A strip of material (wood, vinyl, or ) that holds the glass in place within the or .
Grille
A decorative grid pattern applied to or between the glass panes of a window to create the appearance of multiple smaller panes.
H
Handle Set
A matching set of exterior and interior handles for an , often including a lever, grip, and lock cylinder.
Hardware Adjustment
Tightening, realigning, or replacing window and door hardware (locks, , rollers, operators) to restore proper operation and seal compression.
Header
The horizontal structural beam above a window or door opening that supports the weight of the wall above.
Hinges
Pivoting hardware that attaches a door to its and allows it to swing open and closed. Exterior doors typically use three or more heavy-duty hinges.
Hopper Window
A window hinged at the bottom that tilts inward from the top. Often used in basements and bathrooms for ventilation.
Housewrap
A synthetic weather-resistant barrier (e.g., Tyvek) installed over wall beneath the siding to block water and air infiltration while allowing moisture vapor to escape.
I
Ice Damming
A ridge of ice that forms along the roof edge when heat escaping from the attic melts snow, which then refreezes at the eave, potentially causing water to back up under shingles.
Insulated Glass Unit (IGU)
A factory-sealed assembly of two or more glass panes separated by a spacer and filled with air or inert gas, designed to reduce heat transfer.
Insulated Vinyl Siding
backed with a layer of , improving the wall's thermal performance, impact resistance, and reducing panel waviness.
J
J-Channel
A J-shaped trim piece used to receive and conceal the edges of siding panels where they meet windows, doors, or other surfaces.
Jamb
The vertical side pieces of a window or door that form the sides of the opening.
K
Krypton Gas Fill
A denser inert gas than argon used between glass panes for superior thermal insulation, especially in triple-pane units with narrow spacers.
L
Laminated Glass
Two or more layers of glass bonded with a plastic interlayer (PVB or EVA). If broken, the glass fragments adhere to the interlayer, providing safety and sound reduction.
Lap Siding
Horizontal siding where each board overlaps the one below it. Also called clapboard or bevel siding. The most common siding installation pattern.
Level
Perfectly horizontal. The and head of a window or door must be level to prevent operational issues and water intrusion.
Lockset
The complete door lock mechanism including the knob or lever, latch, and lock cylinder, responsible for securing the door.
Low-E Glass
Glass with a microscopically thin metallic coating that reflects infrared heat while allowing visible light to pass through, improving energy efficiency.
Low-E² / Low-E³
Advanced Low-E coatings applied to multiple surfaces within a multi-pane unit. Low-E² has two coated surfaces; Low-E³ has three, further reducing heat transfer.
Low-Expansion Foam
A spray foam that expands gently, used to fill gaps around window and door frames without exerting excessive pressure that could warp the unit.
Lubrication
Applying silicone spray or light oil to window and door tracks, rollers, , and lock mechanisms to ensure smooth operation and prevent premature wear.
M
Minimum SHGC / U-Factor Requirements
Building-code mandated maximum or minimum values for Solar Heat Gain Coefficient and based on the climate zone in which the building is located.
Mullion
A vertical or horizontal bar that divides a window into separate sections or panes, providing both structural support and visual detail.
Multi-Point Lock
A locking system that engages the door at three or more points along its edge simultaneously, greatly improving security and seal compression.
Multi-Slide Door
A system of large glass panels that slide and stack behind one another or into a pocket, creating an expansive opening to the outdoors.
Muntin
A thin strip of wood or other material that divides the glass within a single into smaller panes, often decorative in modern windows (simulated divided lites).
N
NAFS
North American Standard — a unified standard for rating the performance of windows, doors, and skylights across Canada and the US.
Nail Fin
A flat flange extending from the window or door , providing a surface to nail or screw the unit directly to the wall during new construction installation.
National Building Code of Canada (NBC)
The model building code developed by the National Research Council of Canada, providing minimum standards for safety, health, and energy efficiency in buildings.
O
Obscure Glass
Textured or frosted glass that allows light in while providing privacy. Common in bathroom windows and sidelights.
Ontario Building Code (OBC)
The provincial building code governing construction standards in Ontario, including requirements for windows, doors, insulation, and structural elements.
Operating Force
The amount of force required to open, close, or lock a window or door. Building codes set maximum limits to ensure accessibility.
Operator
The crank, lever, or handle mechanism used to open and close casement and awning windows.
OSB (Oriented Strand Board)
An engineered wood panel made from compressed layers of wood strands bonded with resin. Used as wall beneath siding and as roof decking.
P
Paint Touch-Up
Applying matching paint to scratched or chipped areas on painted wood, steel, or fiber cement surfaces to prevent moisture penetration and maintain appearance.
Passive Solar Design
An architectural approach that uses the building's orientation, window placement, and thermal mass to capture and store solar heat in winter and minimize it in summer.
Patio Door
A wide door providing access to an outdoor area. Can be a sliding, hinged (French), or folding design.
Peephole / Door Viewer
A small wide-angle lens installed in an that allows the occupant to see who is outside without opening the door.
Picture Window
A large that does not open, designed to a view and allow maximum natural light into a room.
Plumb
Perfectly vertical. A window or door must be plumb (using a ) during installation to ensure proper operation and weathertight performance.
PVC Trim
Cellular PVC boards used as exterior trim around windows, doors, and corners. Completely moisture-proof, paintable, and will not rot, split, or attract insects.
R
R-Value
A measure of thermal resistance — the inverse of . Higher R-values mean better insulation and less heat transfer through the window.
Retractable Screen
A that rolls into a hidden housing when not in use, providing an unobstructed view. Available for windows and patio doors.
Retrofit (Insert) Installation
A window replacement method where the new window is inserted into the existing , which remains in place. Faster and less expensive but may slightly reduce the glass area.
Rigid Foam Insulation
Stiff insulation boards (EPS, XPS, or polyiso) applied to exterior walls beneath siding to add continuous insulation and reduce .
Rough Opening
The framed opening in the wall where a window or door will be installed. It is typically ½" to 1" larger than the unit on each side to allow for and insulation.
Rough Opening (RO)
The width and height of the framed wall opening, measured between the studs (width) and from the plate to the (height), before the window or door is installed.
S
Sash
The movable framework that holds the glass pane in a window. In a , both the upper and lower sash can move.
Sash Lift
A handle or grip attached to the bottom rail of a single- or to assist in raising the sash.
SB-12 (Supplementary Standard)
An Ontario energy-efficiency supplementary standard within the OBC that sets performance requirements for components including windows and doors.
Screen
A mesh panel fitted over a window opening to allow airflow while keeping insects out. Available in fiberglass or mesh.
Screen Door
A door with a mesh instead of solid panels, allowing airflow while keeping insects out. Often paired with a solid entry or .
Screen Repair
Patching holes or replacing damaged mesh in window and door screens to maintain their ability to keep insects out while allowing airflow.
Seal Failure
The breakdown of the seal in an insulated glass unit, allowing moisture or air to enter the space between panes, resulting in foggy or hazy glass.
Sealant
A flexible compound (silicone, polyurethane, or latex) applied to joints and seams around windows, doors, and siding to prevent water and air infiltration.
Seasonal Inspection
A periodic check of windows, doors, and siding for damage, wear, seal integrity, and proper operation — ideally conducted in spring and fall.
Shake & Shingle Siding
Siding resembling traditional hand-split shakes or machine-cut shingles. Available in wood, vinyl, or fiber cement for a classic, textured look.
Sheathing
Structural panels (plywood, OSB, or foam board) attached to the exterior wall studs, providing a base for siding attachment and lateral bracing.
Shimming
Using tapered wedges (shims) to and a window or door within the before securing it with fasteners.
Sidelight
A narrow, fixed or operable glass panel flanking one or both sides of an , adding light and visual interest to the entryway.
Siding Washing
Cleaning exterior siding with water, mild detergent, and a soft brush or low-pressure washer to remove dirt, mildew, and stains without damaging the surface.
Sill
The horizontal bottom piece of a window , designed to shed water away from the wall below.
Sill Pan
A waterproof tray installed at the bottom of a window or door to catch and drain any water that penetrates past the unit.
Single-Hung Window
A window with two sashes where only the bottom slides upward while the top sash remains fixed in place.
Single-Pane Glass
A window with one layer of glass. Offers minimal insulation and is largely replaced by double- or triple-pane units in modern construction.
Skylight
A window installed in the roof or ceiling to bring natural light into interior spaces. Can be fixed or operable.
Sliding Patio Door
A door with one or more panels that glide horizontally on a track, popular for patios and decks because they don't require swing clearance.
Sliding Window
A window with one or more sashes that slide horizontally along a track. Common in modern homes for wide openings.
Solar Heat Gain Coefficient (SHGC)
The fraction of solar radiation admitted through a window, expressed as a number between 0 and 1. Lower SHGC reduces cooling costs; higher SHGC is better for passive solar heating.
Sound Transmission Class (STC)
A rating that measures how well a window reduces sound transmission. Higher STC ratings indicate better noise reduction.
Spray Foam Insulation
Liquid polyurethane that expands into a solid foam when applied, filling gaps and cracks around windows, doors, and wall cavities for an airtight seal.
Square
When a window or door has 90° corners. Checked by comparing diagonal measurements — if both diagonals are equal, the frame is square.
Starter Strip
A narrow piece of trim installed at the bottom of the wall to lock the first course of siding panels into place and establish the correct angle.
Steel (Door)
Cold-rolled or galvanized steel used for skins. Offers excellent security and durability; foam-filled steel doors provide strong insulation values.
Steel Siding
Metal cladding made from galvanized or coated steel panels. Extremely durable and resistant to impact, fire, and insects. Heavier than .
Storm Door
A secondary exterior door installed in front of the main to provide additional insulation, ventilation, and protection from the elements.
T
Tempered Glass
Safety glass that has been heat-treated to be four to five times stronger than regular glass. When broken, it shatters into small, blunt pieces instead of sharp shards.
Thermal Break
A material of low thermal conductivity inserted between two conductive materials (e.g., inside an window ) to reduce heat transfer.
Thermal Bridging
Heat transfer through a more conductive material (like a wood stud or metal ) that bypasses the surrounding insulation, creating a weak spot in the .
Threshold
The bottom component of a door that bridges the gap between the interior floor and the exterior surface, providing a seal against air, water, and pests.
Tilt Latch
A spring-loaded mechanism on double-hung windows that releases the from the , allowing it to tilt inward for easy cleaning of the exterior glass surface.
Tilt-and-Turn Window
A European-style window that can tilt inward at the top for ventilation or swing fully inward like a door for easy cleaning.
Tinted Glass
Glass with color added during manufacturing to reduce solar heat gain and glare. Common tints include bronze, gray, and green.
Transom (Door)
A window panel above a door, either fixed or operable, that allows additional light into the entryway.
Transom Window
A narrow window placed above a door or larger window, often decorative or used to let additional light into a space.
Triple-Pane Glass
An IGU with three layers of glass and two insulating air spaces, offering superior thermal and acoustic insulation for cold climates.
U
U-Factor
A measure of how well a window prevents heat from escaping. Lower U-factor values indicate better insulating performance. Measured in W/m²·K or BTU/hr·ft²·°F.
Unit Size
The overall exterior dimensions of a window or door, including the . This is the measurement manufacturers use for ordering.
Utility Trim
Also called undersill trim, a channel that locks the cut top edge of the last siding panel under a windowsill, eave, or other horizontal surface.
V
Vapour Barrier
A material (typically polyethylene sheeting) installed on the warm side of insulation to prevent moisture-laden indoor air from condensing within the wall cavity.
Vertical Siding
Siding panels or boards installed vertically rather than horizontally, providing a modern or farmhouse aesthetic depending on the profile used.
Vinyl (PVC)
Polyvinyl chloride — a durable, low-maintenance synthetic material widely used for window frames, siding, and trim. Resists moisture, rot, and insects; never needs painting.
Vinyl Siding
Lightweight, low-maintenance exterior cladding made from PVC. Available in a wide range of colors and profiles, it resists rot and insects but can crack in extreme cold.
Visible Transmittance (VT)
The fraction of visible light that passes through the glazing, rated from 0 to 1. Higher VT means more natural daylight enters the room.
W
Warm-Edge Spacer
A low-conductivity spacer bar placed between glass panes in an IGU to reduce heat transfer at the edges and minimize .
Weatherstrip
A strip of compressible material (foam, rubber, vinyl) applied around windows and doors to seal gaps and prevent air and water infiltration.
Weep Hole
A small opening at the bottom of a window or door that allows any accumulated water within the frame to drain to the exterior.
Wind-Driven Rain
Rain propelled at an angle by high winds, increasing the chance of water penetrating siding joints, window seals, and other openings.
Window Blinds (Built-In)
Mini blinds sealed between the panes of a double- or triple-pane window, offering tilt or raise/lower control without exposure to dust or damage.
Window Hardware
All mechanical components that allow a window to operate, lock, and tilt, including locks, handles, crank operators, , and tilt latches.
Wood (Frame)
A traditional material for window and door frames. Offers natural beauty and excellent insulation but requires regular maintenance to prevent rot, swelling, and paint failure.
Wood Siding
Natural wood boards or shingles used as exterior cladding. Prized for its authentic beauty and warmth, but requires regular maintenance (painting or staining) to prevent rot and decay.
WSIB (Workplace Safety & Insurance Board)
An Ontario organization providing workplace insurance. Reputable contractors carry WSIB coverage to protect homeowners and workers during window, door, and siding projects.
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