uPVC Combination Windows: Fixed Glazing, Opening Sashes, One Frame

A combination window is a single frame containing more than one type of panel — fixed glazing alongside opening sashes, arranged to suit what the opening actually needs to do.

It is the answer to a problem most large openings have: you want the light, but you do not need every square foot of it to open.

Why a wide opening rarely wants to be all sliding

Take a living room opening four or five metres wide. Specified as a multi-track sliding window, every panel is operable — which sounds like flexibility and is mostly cost.

Every operable panel needs its own track, rollers, interlocking sections and hardware. Each also has a seal that is necessarily less airtight than a fixed pane, because it has to move. So an all-sliding wide opening is more expensive to build and seals less well than one where only part of it opens.

In practice most households open one or two panels and leave the rest closed permanently.

A combination unit makes that explicit. The panels people actually use are operable; the rest is fixed glazing — cheaper per square foot, better sealed, and with a slimmer sightline because it carries no hardware.

Common arrangements

Fixed centre, opening sides

A large fixed pane in the middle with casement or sliding sashes either side. Maximum uninterrupted glass where the view is, ventilation from both edges. The standard approach for a living room facing a garden or balcony.

Fixed lower, opening upper

Fixed glazing at sill level with a smaller opening section above. Useful where furniture sits against the wall, or where ventilation is wanted without a fully opening sash at low level.

Opening centre, fixed sides

The reverse arrangement, used where the opening panel needs to align with something — a door beyond, a walkway, a particular sightline.

Corner combinations

Two runs of glazing meeting at a corner within a continuous frame arrangement. Visually striking, structurally more demanding, and needing careful specification of the corner post.

Fixed panels are not a compromise

Worth stating plainly, because fixed glazing is often treated as the cheap option rather than the right one.

A fixed pane has no tracks, no rollers, no hardware and no moving seal. It is the cheapest configuration per square foot, the best sealed against air and water, and it gives the slimmest frame profile because it carries no opening mechanism.

Where an opening exists to bring in light rather than air, fixed glazing is simply the better answer. The only real question is whether that pane will ever need cleaning from outside, and on upper floors that is a genuine consideration.

Choosing what opens

The useful discipline is to work out how the room is actually ventilated rather than making everything operable by default.

• Cross-ventilation needs two openings on different walls, not two panels beside each other. Two sashes in the same frame ventilate far less effectively than one sash here and one on the opposite side of the room.
• Casement sashes seal better than sliding ones, so in a combination unit the operable portion is worth specifying as casement where the room is air-conditioned or faces a road.
• Reachability matters. An opening panel behind a sofa or above a kitchen counter will not get used. Put the operable section where someone can actually reach the handle.
• Cleaning access. Fixed panels on upper floors can only be cleaned externally. On a high floor that may argue for making a panel operable purely for access.

What holds a wide unit together

The structural element in a combination window is the mullion — the vertical member separating panels — and the transom, its horizontal equivalent.

These carry the load of the glazing on either side and resist wind pressure across the whole opening. On a wide unit they are doing real structural work, which means the profile depth and steel reinforcement matter more here than in a single small window.

This is why wide combination units are typically specified in a deeper series. An 80mm or 88mm section carries the loads that a 60mm section, adequate for a standard bedroom window, would not.

Ask specifically whether reinforcement is included in the mullions and transoms, not only the outer frame. It is the item most often omitted, and its absence shows up as a unit that bows visibly under wind load.

What Eumax offers in this configuration

Combination units can be built across the sliding and casement systems, in profile depths from 50mm through to 108mm depending on the span and the loads involved.

The laminated series is available in the same configurations, so a combination unit can be specified in Walnut, Golden Oak, Metallic Grey, Dark Oak or Black with the finish bonded to the profile before fabrication rather than applied afterwards.

Glass is specified and procured separately according to the project requirement — Eumax manufactures and supplies the profiles, frames and hardware.

Specifying one properly

A combination window is a designed unit rather than an off-the-shelf product, so the specification conversation matters more than usual.

1. Decide the panel layout from how the room works — where people stand, where furniture goes, where air needs to move — before deciding proportions.
2. Choose the profile depth for the span, not for consistency with the rest of the house. Wide units need deeper sections.
3. Confirm mullion and transom reinforcement in writing.
4. Match the opening type to the room. Casement where sealing matters, sliding where space does.
5. Think about cleaning before committing large fixed panels on an upper floor.

Done well, a combination unit costs less than an equivalent all-operable window, seals better, and looks less cluttered because fewer panels carry hardware. Done without thought, it produces a beautiful window with the only opening panel somewhere nobody can reach.

Frequently asked questions