Casement windows remain the most specified operable aluminum window across residential and light commercial projects worldwide. Builders, architects, and distributor brands choose casement configurations for their superior airtightness, unobstructed sightlines, and flexibility in meeting regional performance requirements. This guide compares five core casement window types — single, double, French, push-out, and top-hung awning — with size ranges, hardware specifications, design pressure ratings, and typical project applications so you can match the right configuration to your next development.
1 Single Casement Windows: The Standard Configuration
The single casement is the most common aluminum casement window type. One sash is hinged on either the left or right side and swings outward, controlled by a crank-operated multi-point locking mechanism or a manual lever handle. Because the single sash creates only one continuous weatherseal perimeter, this configuration achieves the highest airtightness values of any operable casement variant.
Single casement windows are engineered to DP50 design pressure ratings when built with 6063-T5 aluminum profiles of at least 1.6mm wall thickness, multi-chamber thermal break profiles, and multi-point stainless steel locking hardware. This makes them suitable for coastal residential projects, mid-rise apartment buildings, and most commercial applications where wind load performance is critical.
Standard Size Ranges
| Parameter | Minimum | Standard Maximum | Custom Maximum |
|---|---|---|---|
| Width | 400 mm | 900 mm | 1,200 mm |
| Height | 500 mm | 1,800 mm | 2,400 mm |
| Frame Depth | 70 mm | 80 mm | 120 mm (thermal break) |
| Glass Thickness | 5 mm single | 4-12-4 IGU | Triple 4-12-4-12-4 |
Typical Hardware Configuration
- Multi-point lock with 3–5 locking points (standard for DP50 projects)
- Friction stay arm or butt hinge in 304 stainless steel
- Handle options: crank operator (North America), tilt-back handle (Europe), or locking lever
- Adjustable friction stay to control sash opening angle (0–90 degrees)
For B2B buyers specifying single casement windows, the key decision is hinge side and swing direction. Most markets require outward swing for casement windows to maximize interior floor space, but some jurisdictions (particularly high-density urban areas) restrict outward swing onto public walkways. Always confirm local building code requirements before finalizing your hardware specification.
2 Double & French Casement: Wider Openings, No Mullion
Double casement windows use two sashes meeting at a central vertical mullion, with each sash hinged on the outer jamb and swinging outward. This configuration doubles the clear opening width compared to a single casement, making it the preferred choice for living rooms, master bedrooms, and hospitality projects where wider ventilation and egress are required.
French casement windows are a variant of the double casement that eliminates the fixed central mullion entirely. Instead, a floating astragal bar attaches to one sash and seals against the other when closed. When both sashes open, the result is a fully unobstructed clear opening — ideal for projects where maximizing the view and natural light is a priority. The trade-off is that French casements require tighter manufacturing tolerances on the astragal seal, which can slightly reduce airtightness performance compared to a fixed mullion double casement.
Double vs French Casement Comparison
| Feature | Double Casement | French Casement |
|---|---|---|
| Central mullion | Fixed aluminum mullion | None (floating astragal) |
| Clear opening width | Up to 1,600 mm | Up to 1,800 mm unobstructed |
| Airtightness (Class) | Class 3–4 (EN 12207) | Class 3 (EN 12207) |
| Typical Uw value | 1.0–1.3 W/m²K | 1.1–1.4 W/m²K |
| Max DP rating | DP50 | DP40–DP50 |
| Best for | Bedrooms, living areas, mid-rise residential | Premium villas, hospitality, panoramic views |
Both configurations support multi-point locking hardware. Double casements typically use two independent multi-point locks (one per sash), while French casements use a single multi-point lock on the active sash plus shoot bolts on the passive sash that engage into the head and sill. The French configuration requires additional engineering attention to wind load deflection because the central meeting stile lacks a fixed mullion for structural support.
3 Push-Out Casement: European-Style Hardware
Push-out casement windows replace the crank operator with a simple lever handle. The user pushes the sash outward directly, and a friction stay arm holds the sash at the desired opening angle. This hardware style originated in European residential architecture and has gained popularity in premium North American and Australian projects for its clean aesthetic and tactile operation.
Push-out hardware is best suited for windows up to 900 mm wide and 1,500 mm tall. Beyond these dimensions, the sash weight makes manual pushing difficult and wind load on the open sash can exceed the friction stay holding force. For larger openings, crank-operated multi-point locking hardware remains the engineering recommendation.
Push-Out vs Crank-Operated Casement
| Specification | Push-Out Hardware | Crank-Operated Hardware |
|---|---|---|
| Max sash size | 900 x 1,500 mm | 1,200 x 2,400 mm |
| Max sash weight | 45 kg | 80 kg |
| Opening mechanism | Direct push, friction stay | Scissor arm or chain operator |
| Locking points | 1–2 (lever handle) | 3–5 (multi-point lock) |
| Recommended DP rating | Up to DP40 | Up to DP50+ |
| Aesthetic | Minimalist, European | Traditional, North American |
Push-out casement windows pair well with European-style tilt & turn systems, allowing architects to specify a consistent hardware language across a facade. When specified with concealed friction stays and slimline lever handles, push-out casements achieve the narrowest visible frame width of any casement variant — often as low as 60mm visible face width. This makes them particularly attractive for passive house and low-energy projects in Germany, Austria, and Scandinavia, where Uw values below 1.0 W/m²K are standard requirements.
4 Top-Hung Awning Casement: Ventilation + Rain Protection
Top-hung awning casement windows hinge at the head and swing outward from the bottom, creating a sloped awning effect when open. This configuration provides two distinct advantages: it allows ventilation during rainfall, and the outward-projecting sash creates a natural rain shield. Awning windows are commonly used in bathrooms, kitchens, basements, and high-level clerestory positions where controlled ventilation is needed without direct weather exposure.
From an engineering perspective, top-hung awning casements use scissor-arm operators similar to crank-operated casements, but mounted at the sill. The sash weight is supported by the top hinge, which must be engineered for both static dead load and wind-induced dynamic load. For this reason, awning casement sizes are typically limited to 1,200mm wide and 1,200mm tall — wider than tall.
Awning Casement Performance Characteristics
- Ventilation pattern: Directs airflow downward and inward, reducing drafts at occupant height
- Rain protection: Sash projects outward at 15–30 degrees, shedding rain away from the opening
- Privacy: Sloped sash blocks direct sightlines from outside, ideal for bathrooms
- Common sizes: 600–1,200mm wide, 400–1,200mm tall (landscape orientation)
- Max DP rating: DP30–DP40 (lower than side-hung casement due to top-hinge load)
- Hardware: Scissor arm operator with locking handle, 2–3 locking points
Awning windows are frequently combined with fixed or casement windows in a single frame assembly to create composite window units. A common residential configuration places an awning window above a large fixed picture window, providing ventilation without sacrificing the view. For commercial projects, awning windows in clerestory positions allow continuous fresh air intake while maintaining the facade’s clean horizontal lines.
5 Spec Comparison Table: Which Type Fits Your Project
The final selection of casement window type depends on project-specific requirements including opening size, wind load zone, ventilation strategy, aesthetic preference, and budget. The following consolidated comparison table provides a quick reference for builders and architects during the specification phase.
| Casement Type | Max Size (W x H) | Max DP Rating | Typical Uw (W/m²K) | Hardware Style | Best Application |
|---|---|---|---|---|---|
| Single Casement | 900 x 1,800 mm | DP50 | 1.0–1.3 | Crank or lever | Bedrooms, apartments, coastal homes |
| Double Casement | 1,800 x 1,800 mm | DP50 | 1.0–1.3 | Dual multi-point lock | Living rooms, master suites |
| French Casement | 1,800 x 2,000 mm | DP40–DP50 | 1.1–1.4 | Multi-point + shoot bolts | Premium villas, hospitality |
| Push-Out Casement | 900 x 1,500 mm | DP40 | 0.9–1.2 | Friction stay + lever | European residential, passive house |
| Top-Hung Awning | 1,200 x 1,200 mm | DP30–DP40 | 1.1–1.4 | Scissor arm operator | Bathrooms, kitchens, clerestory |
For projects targeting specific regional performance standards, the following guidelines apply. North American coastal projects engineered to DP50 typically use single or double casement with crank-operated multi-point hardware. European passive house projects targeting Uw 0.8 W/m²K or lower generally specify push-out casement with triple-glazed units and thermal break profiles. Australian projects designed to meet AS2047 wind load requirements favor single or double casement configurations with reinforced sash sections. Always verify local building code requirements and engage engineering support early in the specification process.
Frequently Asked Questions
Q: Which casement window type is best for high-wind coastal projects?
A: Single casement with multi-point locking hardware is the most common choice for DP50 coastal projects because the single sash reduces air infiltration paths and the multi-point lock resists cyclic wind load. Top-hung awning variants are also used where rain protection during ventilation is required.
Q: What is the difference between French casement and double casement?
A: Double casement uses a fixed or removable mullion in the center to support two sashes. French casement removes the mullion entirely and uses a floating astragal bar attached to one sash, creating an uninterrupted clear opening when both sashes are open.
Q: Are push-out casement windows suitable for commercial buildings?
A: Push-out casement hardware is generally used for low-rise residential and light commercial projects where opening force requirements are modest. For high-rise or high-wind commercial facades, crank-operated multi-point locking hardware provides better wind load resistance and is the recommended choice.
Download Free Casement Window Spec Sheet Full size charts, hardware options, DP ratings, and Uw performance data for all five casement types. Includes CAD detail drawings and test specimen configurations. Download Resource →
