A lantern is a glazed structure set on the top of a dome, a roof or a tower, intended to admit daylight and sometimes to exhaust air. It is a small, self-contained construction — circular, octagonal or square — with a roof of its own.
Types
- Dome lantern — sits on the oculus, the opening at the crown of a dome. Renaissance and Baroque churches use it as their crowning feature.
- Roof lantern — a structure on a flat roof above a hall, stairwell or atrium.
- Tower lantern — an open, louvred stage high in a church tower, with sound openings that let the bells be heard.
- Crossing lantern — the lantern above the crossing of nave and transept.
Why light from above?
Daylight entering from above is considerably more effective than the same area of glass in a wall. The light is distributed far more evenly through the space, and no neighbouring building takes it away. A lantern also works as a heat outlet: warm air gathers under the highest point and can escape through opening lights. That stack effect is the basis of natural ventilation in large halls.
Points to watch
- The roof junction is where it leaks. Work with a sufficiently high upstand — a common rule of thumb is at least 100 to 150 mm above the finished roof covering — and carry the waterproofing layer up against it without interruption.
- Overheating. Glass high in a space catches the sun from above. Without measures the space beneath becomes unbearable in summer. Solar control glass helps; external shading helps considerably more.
- Condensation. A cold lantern above a warm space is a classic condensation point. Thermally broken profiles, insulating glazing and a carefully continued vapour control layer are needed; otherwise it drips from above in winter.
- Access for maintenance. Glass at a high level has to be cleanable and the opening lights have to stay reachable. Design that in rather than discovering it later.
- Wind load. A lantern projects above the roof plane and catches more wind than the rest of the roof; the fixing of the upstand deserves attention.
Related terms
- Dome
- Rooflight
- Upstand
- Sound opening
- Lantern of the dead
- Crossing tower
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