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- Carreau du Temple, Paris
A Monument Historique that hides solar cells in its lanterns — invisibly, precisely, irreversibly well
Heritage and innovation meeting not in compromise — but in a gradient of solar cells across 19th-century glass
Invisible solar energy in a listed cast-iron market hall — no visible wiring, no visual disruption
Built in 1863, Le Carreau du Temple is one of Paris’s last surviving cast-iron and glass market halls, officially listed as a Monument Historique. When studioMilou architecture undertook its renovation between 2011 and 2014, the challenge was precise: embed measurable renewable energy generation into the structure’s three rooftop lanterns — the lanternons — without a single visible wire, fixing or disruption to the building’s historic rhythm and luminosity.
ISSOL® answered with 465 m² of made-to-measure semi-transparent BIPV glazing installed in the three lanterns. The silicon cells are arranged in a pixelated pattern that subtly fades towards the top of each lantern, following the building’s own light gradient. On the north-facing slopes — where cells would generate little — an identical pattern was reproduced in enamelled glass without active cells, preserving perfect visual symmetry. Heritage authorities and architects saw the same roofscape. Only the lanterns themselves knew which panes were working.
Monument Historique oversight, fully concealed cabling, and a gradient that had to earn approval
- Monument Historique classification: every detail — cell pattern, glass tone, fixing method — reviewed by France’s architectural preservation authorities; no standard BIPV approach acceptable
- Fully concealed cabling: all wiring absorbed into the steel framing profiles; zero visible conduit or junction boxes anywhere in the lanterns
- Gradient cell pattern: density fades towards the lantern apex, harmonising with the building’s structural rhythm and natural light play; custom-designed for each of the three lanterns
- North-facing panes: active cell pattern reproduced in enamelled glass — no PV cells, identical appearance — maintaining the visual balance the monument required
- Thermal, acoustic and waterproofing standards all met within the double-glass laminate construction; reversible mounting system designed for long-term maintenance
- Delivered alongside 48 m² of thermal solar collectors as part of an integrated energy strategy targeting HQE certification and ~20% primary energy reduction vs. RT2005 baseline
Why it fits: ISSOL® Square’s pixelated cell pattern — tunable in density and arrangeable in a gradient — gave studioMilou and heritage authorities a BIPV solution that looks like a design decision, not an engineering concession. The glass-glass double laminate meets the thermal, acoustic and waterproofing requirements of a 19th-century roof structure in a single product. Fully concealed cabling within the steel profiles meant the most demanding constraint of the brief — zero visible wiring — was answered structurally, not cosmetically. The enamelled-glass north panes completed the symmetry. Carreau du Temple remains the benchmark for BIPV in heritage-sensitive contexts across Europe.
Parameters for rapid evaluation
| Parameter | Value | Notes |
|---|---|---|
| Application | BIPV rooftop lanterns | Three lanternons (lanterns); fully integrated in existing cast-iron steel frames; Monument Historique |
| ISSOL® solution | ISSOL® Square | Double-glass semi-transparent PV laminate; silicon cells in pixelated gradient pattern; custom per lantern |
| BIPV surface | 465 m² | Active PV glazing across three lanterns |
| Installed capacity | 28.56 kWp | Total system output |
| Annual yield | ~30,000 kWh/yr | Powers building lighting and ventilation systems |
| Cell pattern | Pixelated gradient | Density fades towards lantern apex; custom gradient per lantern; harmonises with structural rhythm |
| North-facing panes | Enamelled glass (non-active) | Identical pattern to active panes; no PV cells; preserves full visual symmetry of the monument |
| Cabling | Fully concealed | All wiring integrated within steel framing profiles; zero visible conduit |
| Mounting | Reversible system | Designed for long-term maintenance and panel replaceability |
| Energy strategy | BIPV + 48 m² thermal solar | Combined: ~20% less primary energy vs. RT2005 baseline |
| BIPV consultant | Ecotemis | Energy consultancy; integration strategy |
| Metalworks | Loison | Steel frame fabrication and BIPV installation |
| Engineering | Bollinger + Grohmann · Batiserf · Inex · Tribu | Structural, services and environmental engineering |
| Project budget | €58 million | Full renovation and extension of Le Carreau du Temple |
| Completed | 2014 | Paris, 3e arrondissement (2011–2014) |
“Heritage and innovation are not mutually exclusive. At Carreau du Temple, the past and future meet not in compromise, but in harmony — through solar glass crafted with precision, purpose and profound respect.”
Le Carreau du Temple — Paris, 3e arrondissement, 2014
Three lanterns, 465 m² of solar glass — invisible to heritage authorities, unmistakable in performance
