Introduction: Reflective facades in modern architecture
The newly constructed skyscraper at 20 Fenchurch Street in London, nicknamed the “Walkie Talkie,” gained notoriety in 2013 for an unusual phenomenon. Its concave south-facing facade reflects sunlight into a concentrated beam, reportedly capable of melting cars, damaging shopfronts, and even frying eggs. This “death ray” effect highlights the challenges of modern architectural glazing and the need for advanced simulation tools to predict and prevent such issues. Using Ocean™ software, we conducted a study to simulate and analyze this phenomenon.
The challenge of reflective facades
Modern buildings frequently feature glass facades to enhance aesthetics and improve energy efficiency. These facades often use double-glazed panels with reflective coatings to control solar heat. However, the interplay between facade curvature, material imperfections, and environmental lighting can lead to unintended consequences, such as glare or concentrated reflections. Such effects pose safety and design challenges for architects and building material professionals.
How Ocean™ simulates reflective phenomena
Ocean™, a high-performance light simulation software, is designed to predict visual appearance and illumination in complex CAD models. By modeling the Walkie Talkie’s facade, we aimed to understand the factors contributing to the “death ray” effect and explore potential solutions. Below is an outline of our simulation process.
Modeling the scene with SketchUp
We started with a standard urban test scene, incorporating two small detailed buildings and blocks, and added a 90-meter-high, 38-meter-wide concave skyscraper to the north. The facade consisted of 2.5m x 2.5m double-glazing panels with a 100m curvature.
A “Fryscraper” quickly modeled with sketchup
Setting facade glass materials
Modern glass facades are made of double glazing. The outer glass pane is generally coated with a thin film that reflects solar heat outside of the building, in order to reduce air-conditioning costs and improve comfort.
The simulation here has been conducted with:
- Outer Pane: PPG Solarban R100, a high-performance reflective coating that reflects 32% of visible light and 41% of solar heat.
- Inner Pane: Standard float glass.
Imperfections were added to simulate real-world conditions:
- Roller-wave distortions: 0.1mm to 0.2mm variations.
- Glazing misalignment: ±0.25°, corresponding to ±2.5mm tolerances.
Adding reference probes
We added two 30cm white boards to the scene. One is on the building wall, another laying on the floor. They are modeled with a perfectly neutral lambertian material with 18% reflectance.
These probes, placed in a neighboring street facing the problematic building, will allow us to calculate the amount of light incoming on the scene by measuring its luminance. We could also have set up a “lightmap” instrument in Ocean™, but this would have required a separate simulation to render the image and measure the falling light.
Modeling sunlight
The simulation used the Preetham skylight model with a clear sky (low turbidity : 2) and an extended wavelength range (295-2500nm), encompassing both visible and infrared light. Ocean™’s fully spectral capabilities allow precise analysis of lighting conditions beyond the visible spectrum. The sun’s elevation was set to 41°, simulating conditions in London on September 5th, one hour after solar noon. See our dedicated article on Ocean™’s Sky Importer feature, which demonstrates its ability to incorporate real-world weather data.
Results: quantifying the "Death Ray" effect
Reference Image (Direct Sunlight)
A reference image is simulated, with the sun hitting the building at the same incidence of 41°.
- Vertical Probe Measurements:
- Luminance: 13,700 cd/m²
- Illuminance: 76,300 lx
- Radiance: 121 W/m²
- Irradiance: 676 W/m²
- Horizontal Probe Measurements:
- Luminance: 13,300 cd/m²
- Illuminance: 74,000 lx
- Radiance: 118 W/m²
- Irradiance: 660 W/m²
These are classical values for direct sunlight.
Reference image with direct sunlight exposure.
1/160s, f/16, 200ISO
Death ray simulation
With the concave skyscraper added, reflected sunlight intensified dramatically:
- Vertical Probe Measurements:
- Luminance: 61,800 cd/m²
- Illuminance: 343,600 lx
- Radiance: 668 W/m²
- Irradiance: 3,708 W/m²
- Horizontal Probe Measurements:
- Luminance: 51,500 cd/m²
- Illuminance: 286,200 lx
- Radiance: 558 W/m²
- Irradiance: 3,102 W/m²
The energy values were 5.5 times higher than direct sunlight, equivalent to over 4.9 kW/m² at normal incidence—enough to partially replicate the heating power of a cooking device.
Simulated skyscraper death-ray image
1/160s, f/16, 200ISO
Insights for building design
Ocean™ performancesin simulating reflective phenomena
This study demonstrates Ocean™’s ability to accurately simulate reflective phenomena in architectural glazing thanks to:
- Its unbiased algorithm ensuring that the simulated beam is the exact solution of geometry optics for the given model.
- The full spectral calculations allowing a precise estimation of light and energy amounts in the scene, even with high-performance coated glass.
Study findings for predicting skyscraper glare
The findings of this study suggest that:
- High-performance solar control coatings significantly influence the intensity of reflections.
- Imperfections in glass flatness and alignment reduce rays focusing but do not eliminate the risk.
To go further, Ocean™ can help architects design shading structures or select appropriate materials to mitigate glare and heat concentration. Discover light simulation for building materials and ensure safety from reflective glare with Ocean™
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Q&A
What causes skyscraper glare?
Skyscraper glare is caused by the reflective properties of glass facades, often compounded by their curvature and material imperfections. When sunlight hits a concave or angled facade, it can focus light into a concentrated beam, resulting in intense heat and luminance. This phenomenon, sometimes called the “death ray effect,” can damage nearby objects and pose safety risks.
How does Ocean™ simulate reflective phenomena?
Ocean™ uses advanced light simulation algorithms to predict how light interacts with complex materials and geometries. Its fully spectral capabilities enable precise analysis of light behavior across visible, ultraviolet, and infrared wavelengths. By incorporating environmental conditions, material properties, and real-world imperfections like roller-wave distortions and glazing misalignments, Ocean™ provides highly accurate simulations of reflective phenomena, such as glare and concentrated heat. Additionally, Ocean™ can handle fully detailed CAD models with several million polygons, eliminating the need to create simplified models for light engineering, thereby saving time and ensuring precision.
Why is spectral simulation important in architectural design?
Spectral simulation considers light beyond the visible spectrum, including ultraviolet and infrared wavelengths. This approach is essential for accurately predicting heat generation and energy reflection in building materials, helping architects select appropriate glazing options and coatings for energy efficiency and safety. Ocean™’s spectral analysis ensures reliable insights for material performance in diverse lighting conditions.
Can Ocean™ help prevent glare in building design?
Yes, Ocean™ can be used to evaluate and optimize architectural designs to mitigate glare risks. By simulating various facade materials, curvatures, and coatings, architects can identify potential problem areas and implement solutions, such as shading structures or high-performance coatings. These insights help ensure safe and efficient building designs.
How does Ocean™ incorporate real-world weather data?
Ocean™ can simulate lighting conditions based on real-world weather data using its Sky Importer feature. This tool allows users to input specific weather conditions, such as sky turbidity and sunlight angles, for accurate and context-sensitive simulations. By integrating this data, architects can assess building performance under different environmental scenarios.
What are some examples of buildings affected by glare?
Notable examples include the Walkie Talkie skyscraper at 20 Fenchurch Street in London and the Vdara Hotel in Las Vegas. Both buildings experienced concentrated sunlight reflections due to their concave facades, leading to property damage and safety concerns. Such cases highlight the importance of simulating and addressing glare in architectural design.
How can architects get started with Ocean™?
Architects can start using Ocean™ by contacting Eclat Digital for a demo or consultation. Our virtual prototyping software offers powerful simulation tools for predicting light behavior, improving facade designs, and ensuring energy efficiency. Eclat Digital also provides licensing options and optical simulation services to support professionals in the building materials industry.
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