Three ways a window can open, and three different results in sealing, ventilation, cleaning and size. Here is what actually separates them — and when the American default is still the right call.
Most window comparisons start with frame material or glazing. But the way a sash moves sets a hard limit on how well the window can ever seal, because it determines whether the gasket can be compressed or merely brushed against.
A tilt and turn sash and a casement sash swing clear of the frame, so they can be clamped shut against a continuous gasket. A double-hung sash has to stay free to slide, so it seals against weatherstripping in a track and cannot be clamped. That single mechanical difference is behind most of the performance gap — not the material, and not the glass.
None of which makes the double-hung window a bad window. It has real advantages: no swing clearance at all, a familiar look on traditional façades, and an operation every American occupant already knows. The point is to choose with the trade-off in view.
Same frame material, same glass — the differences below come from the mechanism alone.
| Criterion | Tilt and turn | Casement | Double-hung |
|---|---|---|---|
| How the sash moves | Swings inward, or tilts inward at the top | Swings outward on side hinges | Two sashes slide vertically |
| Sealing principle | Gasket compressed by perimeter cams | Gasket compressed at the hinge side | Weatherstripping in a sliding track |
| Maximum opening | Effectively the full opening | The full opening | Half the window height |
| Ventilation modes | Two — tilt and full open | One | One, adjustable by sash position |
| Cleaning outer glass | From inside, both faces | Reach out, or from outside | Only with tilt-in sashes |
| Insect screen | Outside the frame, stays fixed | Inside the frame | Outside, in the track |
| Security hardware | Multi-point, up to RC3 on request | Multi-point possible | Sash lock, limited by the track |
| Scales to large sizes | Furthest of the three | Limited by hinge leverage | Limited by sash weight |
| Swing clearance needed | Inside the room | Outside the façade | None |
Turn the handle to horizontal and the sash swings fully inward, like a door. Turn it to vertical and the same sash tilts inward at the top, leaving a narrow gap at the head for continuous background ventilation. The tilted position cannot be opened from outside and does not slam in a draught, so a room can be aired while nobody is home. There is no American equivalent to the second mode, and it is the feature most clients notice first.
The default on our systems, and the right answer for most openings in a new or deeply renovated building.
Sensible where the room cannot give up the inward swing but you still want a compressed seal.
The right call on traditional façades and wherever swing clearance simply does not exist.
Both have straightforward answers, and both are worth settling before the drawings are fixed.
Outside the frame. Because the sash opens inward, the screen sits permanently on the exterior and never has to be moved to operate the window — no lifting it out, no storing it for winter. It is specified with the window so the frame accommodates it properly rather than being retrofitted.
It does while fully open, so curtains, blinds and furniture are planned around it. In daily use most occupants leave the window in the tilt position, which projects only a few centimetres at the head. Where the inward swing genuinely cannot work — over a kitchen sink, behind a fitted desk — that opening becomes fixed glazing or a casement, and neighbouring openings stay tilt and turn.
The systems we supply are tilt and turn platforms, and the published performance reflects the compressed seal. Schüco AWS 90.SI+ reaches a frame Uf as low as 0.71 W/(m²·K) and takes triple glazing up to 68 mm; AWS 75.BS.SI+ publishes Uw as low as 0.78 W/(m²·K) for opening elements. Divided by 5.678, that last figure is roughly U-factor 0.14 in US terms. A sliding sash cannot reach those numbers regardless of the glass in it, because the air path around the sash stays open by design. On the other hand, a double-hung window in a mild climate zone on a period façade may be exactly the right specification — the figures only decide the question once the design has left the choice open.
Both are hinged sashes, but they differ in direction and in what a single handle can do. A casement window is hinged at one side and swings outward on friction hinges, operated by a crank or a handle. A tilt and turn window swings inward and adds a second mode: turned to one handle position the sash opens fully inward, turned to another it tilts inward at the top for secure background ventilation. The tilt and turn frame also carries multi-point locking hardware around the full perimeter, which is why it seals and secures better, and why it is the standard opening type across Europe.
Historic continuity more than performance. Double-hung sashes slide vertically within the frame, which suited timber construction, needed no swing clearance inside or outside, and accepted a simple exterior insect screen. That combination made it the American default for well over a century, and the expectation persists in residential design. It is a sound, familiar window — it simply seals against a sliding track rather than compressing a gasket, which puts a ceiling on its air-tightness and thermal performance.
Yes, and the reason is mechanical rather than a matter of quality. A tilt and turn sash closes against a continuous gasket and is drawn tight by multiple locking cams distributed around the perimeter — the seal is compressed. A double-hung sash must remain free to slide, so it seals against weatherstripping in a track and cannot be clamped. Compressed seals achieve lower air leakage, which is why the tilt and turn principle underpins the very low Uw values published for European systems.
Yes. Because a tilt and turn sash opens inward, the screen is mounted on the outside of the frame, where it stays permanently in place and does not have to be moved to operate the window. This is a frequent question from US clients, since the American habit is an interior or track-mounted screen. The screen is specified with the window rather than added later, so the frame accommodates it properly.
Usually yes, and often more easily than a double-hung window. Egress rules set a minimum clear opening width, height and area, plus a maximum sill height. A double-hung window only ever opens half its height, so the clear opening is inherently limited. A tilt and turn sash swings fully clear of the frame, so nearly the whole opening counts. The clear dimensions still depend on the sash and frame size, so every egress opening is dimensioned deliberately rather than assumed.
For large formats none of these three is the right answer — a lift-and-slide door or a fixed pane with a separate ventilation sash is. Within the three, tilt and turn scales furthest: on systems such as Schüco AWS 90.SI+ the hardware carries heavy sashes with triple glazing. Casement windows are limited by the leverage on side hinges and by wind loading on an outward-swinging sash. Double-hung windows are limited by the weight a person can lift, since the sash is moved by hand.
The opposite. Opened inward, the outer face of the glass comes into the room, so both sides are cleaned from inside — which matters on upper floors, where a casement window means reaching out and a double-hung window relies on tilt-in sashes that not every model has. This is one of the more persuasive practical arguments for the type on multi-storey buildings.
To a large extent, yes. Colour, sightline and glazing are specified independently of the opening type. A tilt and turn window can be finished in any RAL colour, given a wood-look surface, divided with astragal bars, or built on a concealed-sash system such as Schüco AWS 75.BS.SI+ where the frame reads as one slim line from outside. What cannot be reproduced is the sliding sash motion of a double-hung window — that is a different mechanism, not a styling option.
Give us the sizes, the floor and what is in front of and behind each window. We will propose an opening type per opening — including the ones where tilt and turn is not the answer.