Window types
Every residential window type: mechanism, history, standard sizes, performance, cost, and the design situations each is right for. The definitive reference.
Windows define how a room feels more than any other wall fixture. Where they go, how big they are, and what type they are control four critical things: daylight (brightness and direction), view (what you see and how much), ventilation (whether the window opens and how much air it admits), and aesthetic (the window is one of the largest visible details on any building facade).
Residential window types have been engineered for at least 2,000 years. Roman glazed windows used small bronze-framed panes; medieval European windows used leaded glass in iron frames with hinged (casement) operation; the sash window — the single- or double-hung type that dominated American housing for 200 years — was invented in 17th-century England. Modern American residential construction added the horizontal slider (mid-century California), the awning (commercial / industrial heritage), and the picture window (post-war suburban). Today the residential market offers all of these plus several specialty types.
This page is the complete guide to residential window types — what each is mechanically, where it came from historically, when it's appropriate, and how it performs. For deeper dives on specific bay and corner-bay variations, see bay windows and corner bay windows. For the fixed-vs-sliding comparison, see fixed vs sliding windows. For dimensions reference, see standard window sizes.
In this guide
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Fixed (picture) windows — no operation
Mechanism. Glass mounted permanently in a frame. No sash, no operation, no opening. The window is sealed in place — usually with structural silicone or weatherstrip — and remains closed for the life of the installation. History. Predates operable windows. Roman glazed windows were small fixed panes set into bronze or wood frames. The modern 'picture window' — a single very large fixed pane in a residential setting — emerged in post-WWII American suburbia around 1950, driven by the availability of large-pane plate glass and the desire for views in ranch and split-level houses. Standard sizes. - Width: 24–96+ inches. 36, 48, 60, 72 are most common. - Height: 24–96+ inches. 36, 48, 60 are most common. - Common 'picture window' size: 60×48, 72×60 (the classic large suburban living-room window). - Modern walls of glass: 96×96 inches or larger, sometimes 144+ inches. Materials. Same as operable windows — vinyl, wood, aluminum, fiberglass, wood-clad. Cost is generally lower than equivalent operable windows because there's no operating mechanism. Performance. Best seal of any window type (no operating gaskets to fail). Best thermal performance per square foot of glass area. Highest light transmission (no sash bars or operating hardware to obstruct). When to use. - Living-room picture windows for view. - Transoms (above doors or other windows). - Anywhere ventilation is provided elsewhere in the room. - Modern minimalist architecture where the wall is mostly glass. When NOT to use. - Bedrooms (egress requirements — bedroom windows must operate and provide minimum opening dimensions for emergency escape). - Rooms with no other ventilation source (the room needs SOME operable window). - Bathrooms (often require ventilation; check local code).
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Single-hung and double-hung windows
Mechanism. Two sashes (window panels) stacked vertically in a single frame. One or both sashes slide up and down in tracks within the frame. - Single-hung: Only the bottom sash operates; the top is fixed. - Double-hung: Both sashes operate. Either can be raised or lowered independently. Counterweights (historical) or spiral balances (modern) hold the operable sash in any position. History. Invented in mid-17th-century England as a refinement of the sliding casement. By 1700, double-hung windows had spread across English residential architecture and into American colonial construction. They dominated American residential housing from the late 18th century through the mid-20th century. Sash-window manufacturing was industrialized in the 19th century; Andersen Windows (founded 1903) and other manufacturers produced standardized double-hung windows in catalog sizes from about 1910 onward. The term 'sash window' is sometimes used for these — the operable panel is called a 'sash'. Standard sizes. - Width: 24–48 inches. 30, 32, 36 are common. - Height: 36–72 inches. 48, 60, 72 are common. - Common configurations: 30×48 (bedroom), 30×60, 36×60. Glazing. Modern double-hung windows use dual-pane IGU; older houses may have single-pane glass that's been retrofitted with storm windows or upgraded to dual-pane. Performance. Mid-range thermal performance. Weatherstripping at the meeting rail (where the two sashes meet in the middle of the frame) is a critical seal point. When to use. - Traditional and Federal architecture. - Bedrooms (egress requirement satisfied). - Anywhere a vertical-sliding window matches the architectural style. - Historic preservation projects. When NOT to use. - Mid-century modern architecture (which prefers horizontal sliders or large picture windows). - Modern minimalist (where casement or sliding is more appropriate).
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Casement windows
Mechanism. Hinged on one side, opens outward like a door (sometimes inward, rare). Operated by a crank handle (modern) or a sliding rod (historical). History. The oldest operable window type in European architecture. Medieval European houses used casement windows almost exclusively — leaded glass in iron frames, hinged on iron pivots. The form dominated European residential architecture from the medieval period through the 18th century and remained common in continental European housing through the 20th century. In American architecture, casement windows are common in Tudor, English Cottage, Craftsman, and Prairie School styles. They fell out of fashion in mid-century American construction but remain dominant in European housing and have been revived in contemporary American architecture. Standard sizes. - Width: 18–36 inches (each casement; pairs run 36–72 total). - Height: 36–72 inches. - Common: 24×48, 30×60. Operation. Crank handle at the side or bottom of the window. Turning the handle moves a small arm (operator) that pushes the sash outward to the desired opening angle. Performance. Excellent thermal performance — the sash compresses against the perimeter weatherstripping when closed, sealing tightly. Often the best-sealing operable window type. Excellent ventilation — opens 90% of the window area. When to use. - Tudor, English Cottage, Craftsman, Prairie School, traditional European-inspired architecture. - Maximum ventilation requirements. - Best thermal performance among operable types. - Bedrooms (egress requirement well-satisfied). - Hard-to-reach windows (the crank operator allows opening without physically reaching the window). When NOT to use. - Locations where the outward opening would conflict with adjacent objects (decks, walkways). - Architectural styles that don't include casement vocabulary (mid-century modern primarily uses sliders). - Strong wind exposure (the opened sash catches wind and stresses the operator).
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Awning windows
Mechanism. Hinged at the top, opens outward from the bottom (the bottom swings out, the top stays in place). Operated by a crank handle, similar to casement. History. Industrial and commercial origin in the late 19th century — used in factories, schools, and other institutional buildings where ventilation was needed without rain ingress. Migrated into residential use in mid-20th-century American housing, especially in basements and bathrooms. Standard sizes. - Width: 24–48 inches. - Height: 18–36 inches (awning windows are typically shorter than wide). - Common: 30×24, 36×24, 48×30. Operation. Crank handle at the bottom of the window. Turning opens the sash outward at the bottom, creating an awning-like overhang. Performance. Excellent thermal performance (similar to casement). Excellent rain shedding — the open sash forms an awning that prevents rain from entering even when the window is open. When to use. - Bathrooms (high humidity, frequent ventilation needs). - Basements (low to grade, often shorter than wide). - Above other windows (creating a layered window assembly). - Anywhere ventilation is wanted even in light rain. - Climates with frequent rain. When NOT to use. - Where the outward opening would conflict with adjacent objects. - Egress (awning windows don't meet egress dimensional requirements for bedroom emergency escape).
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Hopper windows
Mechanism. Hinged at the bottom, opens inward (or outward) from the top. Essentially an inverted awning window. History. Industrial origin. Used in basement and lower-level applications where the window sat below grade and the inward-tipping sash didn't conflict with anything outside. Standard sizes. Similar to awning: 24–48 inches wide × 18–36 inches tall. Performance. Good thermal performance. Some rain ingress with inward-opening hoppers in wind-driven rain. When to use. - Basement windows below grade. - Window wells. - Bathrooms. - Anywhere a top-tilting sash is appropriate. When NOT to use. - Standard above-grade applications (awning is usually a better choice).
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Sliding (horizontal slider) windows
Mechanism. Two or more sashes in horizontal tracks; at least one sash slides past the others. Same principle as sliding glass doors but in a window-sized frame. History. Mid-20th-century American residential introduction. The form emerged in post-WWII California ranch architecture alongside sliding glass patio doors. Mid-century modern, ranch, split-level, and contemporary architecture all use horizontal sliders extensively. Standard sizes. - Width: 36–96 inches. 48, 60, 72, 96 are common. - Height: 24–60 inches. - Common: 60×36, 72×48. Effective opening. Half the total width on a two-panel slider (same as sliding glass doors). Performance. Good with modern construction; older aluminum sliders are thermal disasters. Modern thermally broken vinyl or fiberglass sliders match double-hung or casement thermal performance. When to use. - Mid-century modern, ranch, contemporary architecture. - Bedrooms (egress dimensions usually adequate). - Anywhere a wide horizontal-proportioned window is appropriate. - Quick access to a wide vent area. When NOT to use. - Traditional or formal architecture. - Maximum sealing applications (casement seals better).
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Bay, bow, and corner bay windows
Bay window. A window assembly projecting outward from one wall, with three or more panels at angles to each other, creating an interior alcove. See bay windows for the comprehensive deep-dive. Bow window. A bay window with four or more panels in a smooth curve rather than angular panels. See bay window styles angled box bow for the style comparison. Corner bay window. A bay window spanning two adjoining exterior walls at the building's corner. See corner bay windows. All three are major architectural features. They project outward; they create interior alcoves; they cost significantly more than flat windows; they're a defining residential design feature when used.
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Transom windows
Mechanism. A small window mounted above another window or above a door. Usually fixed (non-operable); occasionally operable as an awning, hopper, or hinged transom. History. Common in Federal, Colonial, and Victorian architecture as a daylight transfer feature above front entry doors. The 'fan transom' (semicircular with radiating muntins) is a Federal-era signature. Modern interior transoms transfer light between rooms. Standard sizes. - Width: Matches the door or window below (24–72 inches typically). - Height: 12–18 inches. When to use. - Above front entries to bring daylight into entry halls. - Above interior doors for borrowed daylight between rooms. - Between a room and a hallway when full privacy isn't needed. - Above other windows to gain extra daylight in tall walls. When NOT to use. - Where ceiling height is too short for the transom.
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Clerestory and skylights
Clerestory windows. High windows positioned above eye level, typically near the ceiling. Used for daylight without view (the view is sky) and without privacy concern. Common in mid-century modern, contemporary, and modernist architecture. Standard sizes. Variable; typically 18–24 inches tall × 24–96 inches wide. Often configured as a continuous ribbon along the upper wall. When to use. Modern and contemporary architecture; rooms that need daylight but not view; rooms where privacy or wall use below makes lower windows undesirable. Skylights. Windows installed in the roof, providing overhead daylight. Various operating types: fixed, vented (manually crank-operated), motorized. Standard sizes. Manufacturer catalogs (Velux, Sun-Tek, Solatube): 14×46, 21×46, 22×27, 30×30, 30×46, etc. When to use. Bathrooms (for ventilation without privacy compromise), interior rooms without exterior walls (kitchens with attached garages, hallways, walk-in closets), modern architecture, attics converted to living space. Performance considerations: - Daylight: highest light-to-area ratio of any window type. - Heat gain: significant solar heat gain in summer; specify low-e and consider shades. - Leakage: more vulnerable to leaks than wall windows; require proper flashing.
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Specialty types
Jalousie (louver) windows. Multiple horizontal glass slats that pivot together. Common in 1960s–1970s American beach houses and tropical climates. Poor thermal performance; rarely used in modern construction. Used now mostly in tropical climates where ventilation matters more than insulation. Glass block. Hollow glass blocks set in mortar or steel framing. Provides light transmission with privacy. Used in bathrooms, basements, and decorative wall sections. Common in art deco and 1980s-1990s residential. Tubular skylight (sun tunnel). A small skylight that channels daylight through a flexible reflective tube from roof to ceiling-mounted diffuser. Brings daylight to interior rooms without exterior wall access. Compact (10–14 inch diameter typical). Garden window. A small bay-like window with shelves and shelving for plants; typically over a kitchen sink. Common in 1980s residential. Egress window. Any window meeting building code requirements for emergency escape from a bedroom or basement living space (minimum opening width 20 inches, height 24 inches, area 5.7 sq ft, sill height max 44 inches). Most operable bedroom windows qualify. Storm window. A secondary exterior window mounted outside the primary window. Provides additional weather protection and thermal performance for older single-pane windows.
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Window configurations and combinations
Windows are often combined in configurations rather than used singly. Side-by-side pairs. Two windows mounted next to each other with a narrow mullion (frame divider) between them. Used in living rooms, bedrooms, and dining rooms where a single window would be too small. Each window operates independently. Picture window with flanking casements. A large fixed picture window centered, with smaller casement windows on either side that open for ventilation. Common configuration: picture window centered on a living-room wall flanked by 24-inch casements. Transom above a window. A fixed transom (12–18 inches tall) mounted above an operable window. Adds daylight area without affecting operation. Half-circle or semi-elliptical transom. A decorative transom in Federal, Colonial, or transitional architecture. Fan-style with radiating muntins. Ribbon windows. A horizontal band of continuous windows; common in mid-century modern, ranch, and prairie school architecture. Floor-to-ceiling glass. Walls of windows from floor to ceiling; common in contemporary architecture. Bay window with side casements. A bay window's center panel is a fixed picture; the side panels (at angles) are operable casements. Mulled units. Multiple windows joined into a single frame at the factory. Reduces field installation work and provides cleaner appearance than field-installed multiple windows.
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In Room Sketch 3D
Room Sketch 3D's Build Panel → Windows section provides four tiles covering the most common residential types: 1. Window — standard fixed or operable window. The default; covers picture, double-hung, casement, slider, awning, and hopper variants. Set width and height in the Inspector. 2. Sliding Window — horizontal slider variant. Distinct tile because of the configurable panel count. 3. Bay Window — projecting bay assembly with configurable style (angled, box, bow). See bay windows. 4. Corner Bay Window — corner-spanning bay. See corner bay windows. For specialty types (transoms, clerestory, skylights), use the standard Window tile and adjust dimensions and position to match. The 3D View renders all windows as transparent glass panels in the wall, with frames and (where applicable) muntins.
Tips
Match window type to architecture
Bay windows on a Victorian; sliders on a mid-century ranch; double-hungs on a Colonial; casements on a Tudor. Putting the wrong type on the wrong house reads off immediately. The architectural language determines the appropriate window vocabulary.
Sizing rule of thumb: 10–20% of floor area
Total glazing area should be 10–20% of the room's floor area for typical daylight. Below 10% feels dark; above 20% feels glass-heavy and risks thermal performance issues.
Egress in every bedroom
Every bedroom in the US needs at least one window meeting egress dimensional requirements (opening 5.7 sq ft, opening dimensions, sill height max 44 inches). Plan this in design — basements and small bedrooms are common compliance failures.
Mind the sill height
Window sill height affects views (low sills enable seated views; tall sills enable standing-only views) and safety (low sills with children require window guards or tempered glass). Standard sill: 36 inches for living rooms; 28–30 inches for dining; 24–30 for bedrooms with views.
Don't block windows with tall furniture
Tall furniture (bookcases, armoires) blocking windows wastes the daylight investment. Plan tall furniture on solid walls; reserve windowed walls for low furniture (sofas with backs below window sills, beds, ottomans).
Common confusions
Picture window in a bedroom
Fixed picture windows don't meet egress requirements. Bedrooms need operable windows of adequate dimensions for emergency escape. Use casement, double-hung, or operable slider instead.
Casement that opens into a deck path
Casement windows open outward. If the window is above a deck, walkway, or porch where it would conflict, use a double-hung or slider instead.
All-fixed windows in a bathroom
Bathrooms need ventilation. At least one operable window (or a properly-vented exhaust fan) is required by most codes.
Mid-century modern with double-hung windows
Period-incorrect. Mid-century modern uses sliders, casements, picture windows, and ribbon windows — not double-hungs.
Frequently asked questions
What window types are in a typical house?
The dominant types vary by architecture and era. Pre-1950 American: double-hung, casement, transom. Mid-century modern: horizontal slider, picture, casement, ribbon. Contemporary modern: large picture, casement, slider, floor-to-ceiling. Traditional new construction: double-hung, casement, bay. Most houses use 2–4 window types together.
What's the difference between casement and double-hung windows?
Casement: Hinged on one side, opens outward like a door, crank-operated. Double-hung: Two sashes sliding vertically in tracks within the frame. Casements seal better and provide more ventilation; double-hungs are more traditional and don't conflict with adjacent objects.
Are bay windows energy-efficient?
Less efficient than flat windows of equivalent glass area. More glass surface, more frame area, more thermal bridging, and the small roof and apron conduct heat. Modern bay windows with dual-pane low-e and proper construction: U-factor 0.30–0.40 typical. For comparison: flat windows of equivalent area: 0.25–0.35.
What's an egress window?
Any window meeting code requirements for emergency escape from a bedroom or basement living space. Typical US requirements: minimum opening 5.7 sq ft (or 5.0 at grade level), minimum opening width 20 inches and height 24 inches, maximum sill height from floor 44 inches. Required in every bedroom and most basement living spaces. Verify local code.
Where do I add a window in Room Sketch 3D?
Build Panel → Windows. Four tiles: Window (fixed or operable), Sliding Window, Bay Window, Corner Bay Window. Click the tile, then click the wall. Set width, height, position, and (for bay) projection and configuration in the Inspector.
What's the most energy-efficient window type?
Casement windows seal best because the sash compresses against the perimeter weatherstripping when closed. Followed by awning, hopper, double-hung, slider. Fixed windows are technically the most thermal-efficient (no operating gaskets to fail) but provide no ventilation.
How many windows does a room need?
Total glazing area should be 10–20% of the room's floor area for adequate daylight. A 200 sq ft room needs 20–40 sq ft of glazing. Distributed across one large window or multiple smaller ones depending on architecture. Bedrooms need at least one operable egress window.
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