Home // SIMUL 2025, The Seventeenth International Conference on Advances in System Modeling and Simulation // View article
Authors:
Ankit Bhalla
Mahua Mukharjee
Keywords: Daylight; Window wall ratio; Energy Performance Index; CIE sky
Abstract:
Accurate daylight prediction is critical for designing energy-efficient and visually comfortable indoor environments. Traditionally, daylight simulations rely on the CIE overcast sky model, which serves as a standardized but idealized representation of sky conditions. However, this model does not reflect the dynamic and location-specific nature of real skies, particularly in diverse climatic regions like India. This study investigates the variation in daylight illuminance using the VELUX Daylight Visualizer by comparing results under the overcast sky model and a measured sky model developed from luminance data collected in Gurugram using a sky scanner as per ISO 15469:2004 (CIE Standard General Sky) methodology. A simplified box model with varying Window-to-Wall Ratios (WWRs) (10%, 20%, 30%, 40%) was analyzed. The results show that the overcast model consistently overestimates daylight availability. For instance, in March, 100% of the floor area exceeded 100 lux under overcast conditions for 10% WWR, while only 77% met the same threshold under the measured sky model. This discrepancy demonstrates that relying solely on the overcast model can lead to inflated predictions of daylight performance.
Pages: 72 to 78
Copyright: Copyright (c) IARIA, 2025
Publication date: September 28, 2025
Published in: conference
ISSN: 2308-4537
ISBN: 978-1-68558-300-2
Location: Lisbon, Portugal
Dates: from September 28, 2025 to October 2, 2025