Fixed window with top light, made to measure

This window splits into two fixed panes: a small one at the top and a larger one below. Neither opens — it is the fixed window raised into a taller, narrower shape. That suits a stairwell, a hallway, or a strip of wall next to a door that already lets in enough air, where you're mainly after height and light rather than ventilation.

The standard size is 1,000 × 1,800 mm, with the top pane taking a quarter of the height and the lower pane the rest. If you do want to ventilate in exactly that spot, the fixed window with tilt-in top light — the same two-part window with a bottom-hung sash instead of the fixed top light — is the form that provides for it, without the look changing.

The transom at a quarter of the height isn't a decorative choice; it follows from the proportion between the two panes: a small top light above a larger main pane keeps the weight of the glass low, where the frame supports it. Put the transom in the middle and the construction carries two equal, heavier panes instead of one light and one heavy pane — that is possible, but it is a different split from the standard here.

This layout is the simplest of three windows with the same split: alongside the fixed window with top light there are the fixed window with tilt-in top light (a bottom-hung sash instead of the fixed top light) and the tilt and turn window with tilt-in top light (a bottom-hung sash above a full tilt and turn window). All three share the same proportion between upper and lower pane, with a standard width of 1,000 mm here and 1,100 mm for the other two; the difference is purely in how much of the two panes can move, and so in how much hardware and price come with it.

For your order, measure the full height of the opening in one go, from sill to head — the configurator handles the split between the two panes as soon as you have entered the height. Because both panes are fixed, no clear space is needed for a swinging sash; that makes this window easy to fit even right next to a wall, a door frame or a stair rail.

Because both panes are fixed, this window needs the least maintenance of all the two-part windows in this group: no hinge, no tilt mechanism, no locking hardware, just glass and frame. Colour and finish follow the same chart as any other pane — any RAL colour on aluminium, a foil or through-colour on uPVC. Because the top light and the lower pane form one unbroken area of colour in the standard size, this layout gives a tall, calm window with no difference in hardware or sash joint between the two parts.

When a stairwell or a tall hallway is renovated, this window often replaces a single tall window that no longer met current insulation standards, without the position or the opening changing — only the glass and the frame are renewed. In a new build this form is often fixed early in the design, because the proportion between the top light and the main pane affects how high the actual opening in the elevation needs to be.

For break-in resistance, both panes of this window are fixed and so harder to force than an opening pane — there is no hinge or locking point anywhere to get a grip on, only the glass. On the ground floor, laminated or safety glass is where you gain any extra resistance.

Because both panes are fixed, you can use the heaviest, best-insulating glass in both the top light and the main pane with no consequences for hardware. That makes this window a logical choice if you want to get the most insulation out of a particular spot without giving up on the shape.

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