Solar Reflectivity and Glare Compliance Assessment – George Street, Sydney CBD

Shahram Derakhshan
Oct 27
2 min read

Buildings with glazed facades reflecting sunlight, undergoing an assessment for reflectivity and glare.

Project Overview

Deratec was engaged to conduct a solar reflectivity and glare compliance assessment for a new commercial façade development located on George Street, Sydney CBD. The study addressed requirements by Transport for NSW and the City of Sydney Council, ensuring that reflective materials visible from nearby transport corridors would not create glare or safety issues for tram or vehicle operators.

Assessment of solar reflectivity and glare impact on the proposed building façade on George Street, Sydney, visualising solar path and potential reflection angles.

Challenge

The proposed façade featured high-transparency glazing and bronze anodised aluminium cladding, which were architecturally attractive but presented potential glare concerns under high solar exposure from the western orientation. The challenge was to confirm compliance with the ≤15 % visible reflectivity and ≤500 cd/m² veiling luminance limits, while maintaining visual quality and daylight transparency.

Annual direct-sun analysis reveals significant afternoon sunlight exposure on the western façade, highlighting areas of critical heat intensity.

Approach

Deratec applied the Hassall (1991) methodology using advanced Honeybee/Radiance simulation tools within Ladybug for Grasshopper to evaluate façade reflectivity and glare. The analysis considered:

Two tram-driver viewpoints (northbound and southbound) to represent real visibility scenarios
Critical sun positions during the year (summer solstice and equinox) for worst-case reflection
Optical properties of materials (glazing, anodised aluminium, canopies) using manufacturer and simulation data
Calculation of veiling luminance (Lv) and Threshold Increment (TI) to determine compliance

3D simulation in Honeybee/Radiance visualising urban reflectivity and glare impact, highlighting building interactions in a cityscape.

View from the tram-driver’s perspective showcasing urban reflectance levels, with a gradient map indicating high reflectance on the street and varying building surfaces.

Results

Simulation outcomes confirmed that the façade design achieved excellent visual performance:

Viewpoint	Veiling Luminance (Lv)	Threshold Increment (TI)	Compliance
Northbound View	441 cd/m²	11 %	✅ Pass
Southbound View	330 cd/m²	7 %	✅ Pass

False-colour luminance map of an urban scene, showcasing brightness levels in candela per square meter, with vivid colour gradients representing varied light intensities across architectural structures.

Outcome

The analysis confirmed full compliance with TfNSW and City of Sydney glare requirements. Deratec’s modelling demonstrated that the selected façade materials will not produce hazardous glare or excessive reflections, ensuring both visual comfort and public safety while preserving the architectural intent.

Conclusion

The study highlights how simulation-driven reflectivity analysis enables architects and developers to achieve both compliance and design excellence. By integrating Honeybee/Radiance glare modelling early in the design process, Deratec helped ensure that visual comfort, energy efficiency, and regulatory compliance were met in a single, data-backed solution. This project reinforces Deratec’s capability to deliver precise, practical façade assessments for urban developments across Australia.