Hidden Sash Windows
nothing on the glass

A hidden sash window is a window whose operable sash sits behind the outer frame instead of in front of it. From outside you see frame and glass, with no second aluminum line around the opening leaf - so an operable window looks identical to a fixed pane beside it. Inside, the sash is there and works normally. The European system providers call it hidden sash, concealed sash, or hidden vent depending on the brand.

A concealed or hidden handle is window hardware that does not sit on the face of the sash. The version I quote most is Cortizo's Arch Invisible: the handle is integrated into the sash profile and operated from the side of the leaf, so from the front the window shows no lever at all. It is a separate option from the hidden sash itself, and only some systems offer both together - which is the specific combination most of my clients are asking for when they say they want a window with nothing on it.

The Arch Invisible handle is Cortizo's invisible handle for hidden sash windows. Rather than mounting on the face of the sash, it is built into the sash profile and actuated from the lateral side, which leaves the interior face completely clear. It works with side-hung, tilt & turn, and turn-tilt leaves, and it is the reason the COR 70 Hidden Sash is the system I point people to when both the sash and the hardware need to disappear.

Hidden sash aluminum windows fall in the normal aluminum range - about $45 to $95 per square foot supplied, before duty and freight - and the Cortizo COR 70 Hidden Sash is one of the lower-priced aluminum systems in my estimator. Against the same provider's standard sash, the concealed profile adds a premium mostly on operable units. Clad Hidden Sash in timber is quoted from drawings.

Smaller than a standard sash, and this is the constraint that decides most projects. Typical limits are around 4 ft 3 in wide by 7 ft 10 in high on standard hardware, or 3 ft 11 in by 11 ft 6 in on heavy-duty side-hung hardware, with sash weights to about 350 lbs. Large openings get split into a fixed pane plus a smaller operable leaf - which is exactly the look the system is designed for anyway.

That depends on the size of the operable leaf, not on the hidden sash detail itself. Because the maximum sash is smaller than a conventional one, egress openings need to be checked position by position rather than assumed. Tell me which openings are egress on your plan set and I will size those leaves first and build the rest of the elevation around them.

The concealed-sash systems are built primarily around inward-opening leaves - side-hung, tilt & turn, and bottom-hung. If your project needs outswing sash with interior screens, that usually means a different system, and I would point you at the outward-opening European casement lines instead. Ask early, because this decision drives the whole package.

The same way they work on any inward-opening European window: the screen mounts on the exterior side of the opening, in a slim frame or a cassette with a roller. It sits outside the sash swing, so the window still operates normally. Worth planning at the drawing stage rather than after delivery.

Several European aluminum system providers make hidden sash windows - Cortizo, Reynaers (Hidden Vent) and Aliplast (SU) among them - and in timber there is Clad Hidden Sash, an aluminum-clad wood line. What matters is whether the handle can be concealed too, how deep the glazing rebate is, and how large the sash may get. I quote across providers.

For standard aluminum hidden-sash orders, plan around 9-16 weeks from approved shop drawings to on-site delivery, including production, freight and customs. The selected glass, finish, hardware and destination can change that schedule, so I confirm the date for each order. Aluminum-clad wood is quoted with a separate order-specific lead time.