Considered as one of the greatest masterpieces of gothic architecture, the Cathedral of Strasbourg revels in newfound splendour. The precise and sensible work of lights and shadows creates now a highly balanced, quiet surround. Designed by the French studio Acte Lumière, the lighting design project of the Cathedral of Strasbourg won the 1st Prize of the Codega Awards 2017 for “the classic setting of the project with a perfect application of lighting technics. The result represents an elegant and conservative approach of the architectural principles.”

The lighting design project in short

One of the biggest challenges was to keep a global and uniform quality of light, and to create/respect shadows in the center of the city.

600 LED projectors creating warm accent lighting and highlights which contrast beautifully with the cast and modeled shadows, resulting in an overall glow and a peaceful illumination.

The «Sandstone» is the keyframe of the project. Mostly stripped brow and yellow, the stone include a deep and rich gradient of red and purple. The Studio worked on splitting and positioning the flood sources for regular modeled and cast shadows, and accompanied the impressive elevation (142m). The quality and consistence of quality despite all the differents size and chape of floodlight was a challenge for the project.

To protect the building (about 14 km of cables and 500 light-sources are installed on the building), all the installation is made without any hole drilled on the Stone but only the stone joints. Clamping sleeves, collars, and fixture corset was created on-demand and adapted to each needed, projectors got onsite painting to with the color of stone.
The consumption is about 10kW, after adjustment of the dynamic white and dimming.

Harmony and perfect balance

For the setting of light of the cathedral of Strasbourg, Acte Lumière built a balanced project, respectful all in smoothness and subtlety, in order to accompany the pertaining to worship range and symbolic parts of the building.

The four pillars of the project:
1. A precise work on the color rendering quality to reveal the chromatic wealth of Sandstein.
2. A balance between the writing of the “flood” of light which hem the architecture of gradient of shades and outline its extraordinary verticality, with the succession of small beam of highlighting which them, underlines the work of depth and the thickness of the successive layers of stone lace.
3. A search of esthetics and composition of luminous contrasts of architectureand sculptures with a very smooth gradients of tones.
4. A perfect balance between the various distances from perception.

This harmony is ensured by the combination of two effects of lighting. The ambient luminescent: qualitative, it is the results of the installation of lighting at a battery of strategic points giving a direction to the light and cast shadows on the whole of the frontage of the western façade. The focal glow and hightlights: the separation of the beams by levels and spans makes it possible to illuminate the buttresses at a slightly lower intensity. The depth is ensured by the implementation of dynamic white light (able to produce various tonalities and intensities of white in more or less hue) fitted between the different layers of architecture. The lighting devices (embedded in the ground, projectors and linear), are concealed in the architecture and are set to reveal its strucutral depths, and interior volumes.

An evolutionary nightime highlighting

The evolution in various luminous states makes it possible to slightly change perceptions and to offer new way of reading the building through three night-times.

First time: Expressed like a kind of continuity of the colours from the last solar rays. This first time developing the global perception of the volume and the precise reading of iconographics (details of architecture, scuptural Works, interior volumes).
Second time: Under the same lighting of volume (slightly lower), the iconographic detail are reduced and blurred, to enhance the rising of the eyes in the levation and in the glance in the night.
Third time: Only the upper part of the Cathedral Tower and Roofs is highlighted, immutable and comforting remains emergent throughout the night above the urban area and of the territory.

A 100% LED project

The lighting of the Cathedral integrates the challenges of energy saving and an easy maintenance. The light produced 100% by Light Emitting Diodes, which constitutes a first in France on a patrimonial building of such a size. As of the design of the new illuminations and their implementations, the optimization of the energetic performances of the installation was one of the strongest challenges of the project. The use of the lastest LED technologies makes it possible to better target the elements to be lit and thus to reduce total consumption for a more effective lighting. The installed LED have a very long lifetime and reduced maintenance.

Technical elements

The «Sandstone», mostly stripped brown and yellow, include a deep and rich gradient of red and purple (corresponding on the R8 – R9 CRI, the weakest color rendering quality of diodes). The studio measured and determinated a Color temperature 2700K, dominant length wave (582nm) and chromatic distortion ( > 2 macadams ellipts) to ensure the quality of light. We have worked on splitting and positioning the flood sources for regular modeled and cast shadows, and accompanied the impressive elevation (142m).

Consumption and Modulation

The installation is made up of 580 lighting devices, including 30 periphery projectors, 60 devices embedded in the ground, 490 projectors or linear on the building, divided into 8 families of devices (from 3W to 250W). Every projector is dimmable for the perfect quantities of light. These elements are DMX controlled by 9 electrical power boxes permitting to tune the luminous power and the color temperature. The total power of the installed equipment is 15 kW.

After adjustment of the dynamic white and modulation of the devices between 60 and 80% of initial flow, the consumption is about 10kW ( 18 kW for the previous installation).

A discrete integration

No devices (except thoses recessed in the grounds) are visible from the exterior of cathedral, This results in a balanced, quiet, « chiseled light » and a magnificent poetic glow of the building. This completely reversible project used 14 km of cables and 400 light-sources (of 600) installed on the building. All the installation is made without any hole drilled on the stone but only on the stone joints. Clamping sleeves, collars, and fixture corsets were created on-demand and adapted to each needed, projectors were painted on site to match the stone color. Everything can be removed without damage to the building (program initial request).

Place: Place de la Cathédrale, Strasbourg
Date: Octobre 2016
Photo credits:  X. Boymond – JY Soetinck

Watch the video of the Cathedral of Strasbourg – Project

Watch the video of the Cathedral of Strasbourg – Men at work


You may also be interested in this articles:
Codega Awards 2017 winners