Fixed window with tilt-in top light, made to measure

This window splits its height in two: a small bottom-hung sash at the top that tilts inward for ventilation, and a larger fixed pane below that doesn't move. It is the same split as the fixed window with top light, but with an opening in the upper pane instead of fixed glass. That suits a bathroom, WC or stairwell where you want to air the room now and then without a sash swinging open at eye level.

The standard size is 1,100 × 1,800 mm, with the tilt-in sash taking a quarter of the height and the fixed pane the rest. If in that same spot you do want full ventilation and the option of cleaning the glass from inside, the tilt and turn window with tilt-in top light — the same window with a tilt and turn sash instead of the fixed lower pane — is the broader choice.

You usually operate the top sash with a long pole, because it sits at or above the reach of a standing adult. That is exactly the idea: you ventilate without a sash standing open at eye level, and the large fixed pane below stays clean, uncluttered glass with no gap to let in a draught. In a steamy bathroom or a WC without an extractor fan, that is often enough to keep the air fresh without leaving the door open.

Of the three two-part windows (the fixed window with top light, this one, and the tilt and turn window with tilt-in top light), this sits in the middle for hardware and so for price: more than an all-fixed window, less than the version with a complete tilt and turn window below. Choose it precisely when you do want to air the room up high, but would rather keep a large, unbroken pane of glass below than a pane you also have to operate and clean.

For this layout, measure the full height of the opening in one go; the configurator handles the split between the tilt-in sash above and the fixed pane below as soon as you enter that height. When deciding where it goes, also think about the operating rod for the top sash: it has to be reachable from the floor or from a fixed spot in the room without a cupboard, a curtain rail or a light fitting in the way.

Maintenance on this window is limited to the top sash: its hinge and the operating rod are worth checking now and then, while the fixed pane below needs as little maintenance as a plain fixed window. Colour and finish follow the same chart as any other pane, with any RAL colour on aluminium and a foil or through-colour on uPVC. Because the top sash is small compared with the fixed pane below, any colour difference between inside and outside is less noticeable here than on a window where both panes are the same size.

In a bathroom or WC renovation, this window often replaces an old window that had no separate ventilation position, so you add a tilt-in sash without making the opening larger. In a new build this split is often fixed in the design, so the layout of the tiling or a bathroom unit below can allow for the fixed pane that doesn't move.

For break-in resistance, the fixed pane is the harder of the two to force; the tilt-in sash above usually sits too high to be an attractive target. If in doubt, ask about a stronger locking cylinder on the top sash if the spot can be reached after all, for example from an extension roof or a canopy.

In the fixed pane you can use the heaviest glass with no consequences for hardware; in the tilt-in sash, weight does count for the hardware carrying it. The configurator checks this as soon as you enter the size and glass for this window.

Still not sure? Use the comparison with the other layouts in this group above to see which arrangement suits your situation best.