A spandrel panel is the opaque section of a curtain wall or window wall that spans between the vision glass of one floor and the next, hiding the floor slab edge, ceiling space and services behind it. It is usually spandrel glass (opacified or with a backpan and insulation) or an infill metal panel.
What a spandrel panel hides
On a glass building, the band between the head of one window and the sill of the next lines up with the slab edge, the perimeter beam, the ceiling plenum and often perimeter heating. The spandrel covers that zone so the facade reads as continuous glass or panel, while insulation and fire protection go behind it.
Types of spandrel panels
| Type | How it works | Watch for |
|---|---|---|
| Opacified spandrel glass | Glass made opaque with a ceramic frit or silicone coating, usually on the inside face | Must be heat-strengthened or tempered; coating must be compatible with sealants |
| Insulating glass (IGU) spandrel | An IGU with an opaque inner coating, used to match the look of the vision units | Colour match to vision glass changes with light; check on a mockup |
| Shadow box | Clear or tinted glass with a backpan set behind it, giving depth like vision glass | Heat build-up and condensation in the cavity; needs a sealed or vented design |
| Metal panel | Aluminum plate or insulated metal panel glazed into the curtain wall pocket | Oil-canning, joint alignment with mullions |
| Stone, terracotta or other infill | Heavier panels set in the frame or hung from the structure | Weight and anchorage; coordinate with the curtain wall engineer |
Typical spandrel build-up
- Spandrel glass or panel on the outside face of the frame.
- An air space.
- A sealed sheet-metal backpan, which usually forms the air and vapour barrier at the spandrel.
- Insulation, typically mineral wool, fixed to the backpan.
- Perimeter fire barrier (safing) and smoke seal between the slab edge and the curtain wall, tested as a system (ASTM E2307 in the US).
Spandrel vs vision glass
Vision glass is the transparent area you see through; spandrel glass is opaque. Matching them is harder than it looks, because vision glass has an interior behind it and spandrel glass doesn’t, so the same tint can read differently. Most projects approve spandrel colour on a full-size mockup in daylight.
Design and site tips
- Spandrel glass absorbs heat with nowhere to dump it, so it is normally heat-strengthened or tempered. Ask the glass supplier for a thermal stress check.
- Inspect the slab-edge firestop and backpan seals before the interior is closed in. They can’t be seen afterwards. Our firestopping guide covers inspection.
- Keep insulation tight to the backpan with no gaps at mullions.
- Label and protect coated glass; scratches and incompatible sealant on the coating show through.
Other meanings of spandrel
- Architecture: the roughly triangular wall area between the curve of an arch and the frame around it.
- Spandrel beam: the perimeter beam at the slab edge behind a spandrel.
- UK timber frame: prefabricated triangular “spandrel panels” form gables and party walls in a pitched roof.
Related terms
- Curtainwall
- Mullion
- Low Iron glass
- Mockup
Related templates and guides
- Curtainwall Quality Control Checklist
- Interface Guidelines for Curtainwall
- Insulated Metal Panels: The Basics
- Basics of Building Envelope Construction
Frequently asked questions
What is a spandrel panel on a window?
It is the opaque panel in a window wall or curtain wall that sits between the vision glass of one floor and the next. It hides the slab edge, beam and ceiling space, and has insulation and fire protection behind it.
Is spandrel glass tempered?
Usually it is heat-strengthened or tempered. Spandrel glass absorbs solar heat with little ability to shed it, and annealed glass can crack from thermal stress. The glass supplier normally confirms the treatment with a thermal stress analysis for the project.
What is a shadow box spandrel?
A shadow box uses glass that looks like the vision glass, with a backpan set some distance behind it to create depth. It gives the most consistent look across the facade but needs careful design for heat build-up and condensation in the cavity.
What is the difference between spandrel and vision glass?
Vision glass is transparent and lets people see out and light in. Spandrel glass is opaque and hides the structure and services between floors. They are often specified as a matched pair but rarely look identical, so a mockup is used to approve them.
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