Description
Chartwell Green uPVC French Casement Window with Mid Rails — Period Character, Centre-Opening Ventilation
The French casement window has a heritage in British domestic architecture that extends far beyond the Channel crossing its name implies. From the wide-opening cottage windows of rural England to the paired casements of Georgian townhouses, the centre-opening casement — two sashes meeting at a central stile and opening outward in opposite directions — has long been one of the most practical and most characterful window forms available to the British homeowner. Our Chartwell Green uPVC French Casement Window with Mid Rails brings this beloved configuration into the present with the addition of a horizontal mid-rail on each casement, full A-rated thermal performance, and the Chartwell Green heritage finish — creating a window that is simultaneously one of the most traditional and most thoroughly specified designs in our entire range.
This is the window for properties where character matters as much as performance — and where the two should never have to be in conflict.
The Centre-Opening French Casement
The defining characteristic of the French casement is the way its two sashes open. Unlike a standard pair of casements where the left sash is hinged on the left and the right sash is also hinged on the left — both opening to the same side in the same direction — the French casement configuration hinges the left sash on the left outer stile and the right sash on the right outer stile. Both sashes therefore open outward from the centre simultaneously, swinging away from each other in opposite directions.
This centre-opening arrangement has a practical consequence that standard casement pairs cannot replicate — when both sashes are fully open, the entire central width of the window between the two outer stiles is completely clear. There is no fixed central mullion interrupting the opening, no fixed frame element in the middle of the clear aperture, and no structural post reducing the width of airflow or view through the open window. The opening is as wide as the window is wide between its outer stiles — and this clear, unobstructed central aperture is what distinguishes the French casement from every other casement configuration.
For rooms where a wide, unobstructed connection to the outside air is the priority — where the window is positioned above a garden terrace, alongside an outdoor seating area, or on an elevation where the view and the ventilation should feel continuous rather than mediated by a fixed central structure — the French casement delivers that connection more completely than any alternative.
In this four-light configuration, the centre-opening mechanism is applied to the lower section of each casement — the active zone below the horizontal mid-rail. When both lower sections swing outward from the centre simultaneously, the full lower width of the window between the outer stiles is open — a wide, clear, bilateral ventilation aperture at mid-to-lower frame height that allows air to enter and exit across the complete width of the opening simultaneously.
The Mid-Rail Divided Character
The horizontal mid-rail that crosses each casement sash at the same height is the element that transforms this French casement window from a functional opening into an architectural statement. In the British domestic tradition, the mid-rail divided casement is most strongly associated with the cottage window — the wide, low casement of the traditional English countryside, with its upper fixed lights and lower opening sections, its simple painted timber frame, and its deep-set position in a thick masonry wall.
In Chartwell Green uPVC, this cottage association is not pastiche — it is a genuine connection to the same proportional logic that made the cottage casement so characteristic and so enduring. The mid-rail at the same height on both sashes creates a continuous horizontal division across the full width of the frame when the casements are closed, giving the window a four-pane grid character — upper left, upper right, lower left, lower right — that reads with immediate clarity on any elevation.
When the lower sections open outward from the centre, the upper fixed lights retain the full structural and visual presence of the frame at head height. The window does not lose its character when ventilating — the two upper lights remain in position above the open lower sections, maintaining the divided-light grid in the upper zone and giving the window a distinctive and characterful open appearance that a casement without mid-rails cannot achieve.
The horizontal mid-rail runs at the same height across both sashes, and when both sashes are closed, it reads as a single continuous horizontal line across the full width of the window — the same visual effect as the continuous rail of a fixed divided-light window, with the critical difference that the section below it is fully operable.
Upper Fixed Lights — The Retained Structure
The upper fixed light in each casement sash sits above the mid-rail as a permanently glazed section that moves with the sash when the casement opens and provides the visual anchor for the upper zone of the window when it closes. Unlike the upper fixed lights in a standard casement-with-top-light configuration — where the upper light is in the fixed outer frame and the casement opens below it — in a mid-rail casement the upper light is part of the sash itself, moving outward with the lower section when the casement opens.
This means that when the French casement lower sections swing outward, each opening sash carries its upper fixed light with it — the full sash height from lower edge to upper edge, including the upper fixed light above the mid-rail, is what swings outward on each side. The upper fixed lights are not left behind in the frame when the sash opens. They travel with the sash, and in the fully open position they flank the clear central aperture on both sides — the left sash with its upper fixed light standing open to the left, the right sash with its upper fixed light standing open to the right, the full central width between them completely clear.
This creates the most distinctive visual characteristic of the mid-rail French casement in the open position — a wide central clear aperture flanked on both sides by fully open casement sashes with their mid-rails and upper fixed lights standing proud of the outer frame at left and right. It is one of the most immediately recognisable and most evocative window configurations in British domestic design.
A-Rated Thermal Performance Throughout
All four panes in this double glazed uPVC window are manufactured to the same A-rated thermal standard. The 70mm multi-chamber uPVC frame, 28mm argon-filled sealed units, soft coat low-E glass, and warm-edge black superspacer bar deliver a U-value of 1.3 W/m²K consistently across the twin upper fixed lights and the twin lower opening casement sections — meeting Part L Building Regulations throughout the complete frame.
The horizontal mid-rail within each sash is a thermally significant element — a continuous frame member crossing the full width of the sash at mid-height with surfaces on the inside and outside of the glazed assembly. Our 70mm multi-chamber profile maintains sealed air chamber thermal resistance at the mid-rail section within the sash, preventing the cold bridge and condensation strip that form at sash mid-rails in single-chamber or thinly profiled alternatives.
The meeting point at the centre of the frame — where the two sashes meet when closed — is manufactured to the same precise thermal standard as the rest of the frame, with the meeting stiles providing consistent compression of the weather seal and consistent thermal resistance at the central junction.
Chartwell Green — The Cottage Connection
In Chartwell Green, the French casement with mid-rails makes its most natural and most compelling appearance. The soft sage heritage tone is the colour most associated with traditional painted timber cottage casements in the British countryside — and in uPVC, it carries that association with none of the maintenance burden that real timber cottage windows impose. No repainting every three to five years. No swelling or shrinking with seasonal moisture changes. No rot at the sill or the bottom rail. Just the Chartwell Green colour, consistently and permanently, in a frame that performs better thermally and in terms of security than any timber alternative.
The fully sculpted 70mm profile gives the mid-rail and the outer frame elements the moulded shadow detail that reinforces the cottage casement character — the shadow lines at the rail and the stile edges catch light the same way that a well-profiled painted timber sash does, giving the window a three-dimensional quality at close range and a genuine period character at building scale.
The Chartwell Green finish is co-extruded into the uPVC profile, backed by a full 10-year profile guarantee against fading, peeling, warping, and discolouration. These uPVC casement windows require no painting, no staining, and no maintenance beyond an occasional wipe with a damp cloth.
Security on Both Opening Sections
Both lower casement sections are independently secured with multi-point locking systems engaging at multiple points along the height of each opening section. Lockable push-button handles are fitted to both lower casements as standard. All four panes across the complete frame are retained by internal glazing beads, preventing glass removal from the exterior on any section. Patented double-action bubble gaskets run the full perimeter of both lower opening sections and the meeting stile junction at the centre, maintaining consistent weathertight and draught-proof seals in all conditions.
The central meeting stile — where the two sashes meet when closed — is secured by the multi-point locking system on both sides simultaneously, providing robust resistance to forced entry at the most vulnerable point of any French casement configuration.
Specification at a Glance
- Energy Rating: A-rated | U-value 1.3 W/m²K
- Configuration: 4-light — twin side-hung French casements each with upper fixed light and lower opening section, horizontal mid-rail on each sash, centre-opening from central fixed mullion
- Frame System: 70mm multi-chamber thermally efficient uPVC
- Glazing: 28mm argon-filled units, soft coat low-E glass, warm-edge superspacer
- Locking: Multi-point locking on both lower opening casement sections
- Handles: Lockable push-button handles on both lower casements
- Beading: Internal across all four panes for maximum security
- Gaskets: Patented double-action bubble gaskets on both opening sections and meeting stile
- Finish: Chartwell Green — guaranteed not to discolour, warp or peel
- Compliance: Part L Building Regulations
- Guarantee: 10-year profile guarantee
Made to Your Exact Measurements
- Frame Width: 415mm – 700mm
- Frame Height: 800mm – 2200mm
Every window is manufactured to order to your precise dimensions. Enter your measurements at checkout for a perfect made-to-measure fit. Our team is available for sizing queries, configuration advice, and handing guidance before you place your order.
When Period Character and Modern Performance Should Come as One
The French casement with mid-rails is the most characterful and most evocative configuration in our entire Chartwell Green range — the window that most directly connects the modern home to the long tradition of British domestic window design. Centre-opening lower sections that clear the full width of the frame when open. Horizontal mid-rails on both sashes that create the classic four-pane cottage grid. Upper fixed lights that travel with the sash and flank the open aperture with architectural presence. And the Chartwell Green frame that gives the whole configuration the heritage colour and sculpted profile quality that make this one of the most visually distinguished, most practically capable, and most authentically British designs in our entire Chartwell Green uPVC window range.
