Explaining the Relationship between Opening Structure and Daylight and Glare Indices in Tall Office Buildings of Tehran: A Case Study of Pars Tower

Nemati Moghaddam, Mehdi; Mousavi, Seyyed Yaser; Masoudi Nejad, Mostafa

doi:10.22034/ijumes.2026.2107626.1413

Explaining the Relationship between Opening Structure and Daylight and Glare Indices in Tall Office Buildings of Tehran: A Case Study of Pars Tower

Document Type : Original Article

Authors

Mehdi Nemati Moghaddam ¹

Seyyed Yaser Mousavi ²

Mostafa Masoudi Nejad ¹

¹ Department of architecture, Ahv.C., Islamic Azad university, Ahvaz, Iran

² Department of Architecture, Ram.C., Islamic Azad university, Ramsar, Iran

10.22034/ijumes.2026.2107626.1413

Abstract

Tall buildings define modern cities, and in office towers, managing daylight penetration and glare is a key design concern. Openings must admit enough daylight for energy efficiency and occupant comfort while preventing the uncontrolled light that causes disabling glare. Moreover, computer simulations cannot fully reproduce real building conditions. This study examines the relationship between opening structure and daylight and glare indices in tall office buildings in Tehran, using Pars Tower as a case study. It also identifies the index that best captures this relationship. This quantitative, applied, experimental study used in-situ measurement. In a selected office unit, five indices were evaluated from calibrated high-dynamic-range (HDR) images: DGP, UGR, DGI, CGI and VCP. The images were captured with a Canon 7D and a fisheye lens and merged in Bracket. They were calibrated in HDRscope against a grey card and a TES-137 luminance meter, then processed with Evalglare. A total of 680 evaluations were conducted over 30 clear-sky days at half-hourly intervals and analyzed using ANOVA. Opening structure was significantly related to all indices in the imperceptible category and to some indices in the perceptible category. It was not significantly related to them in the disturbing or intolerable categories, and glare never reached those levels in the building. DGP showed the lowest dispersion across all categories, making it the most reliable index. Opening structure significantly affects daylight and glare in tall office buildings. DGP is recommended as the most accurate index for explaining this relationship, as recent comparative studies of office spaces also confirm.

Graphical Abstract

Explaining the Relationship between Opening Structure and Daylight and Glare Indices in Tall Office Buildings of Tehran: A Case Study of Pars Tower

Highlights

• The relationship between opening structure and daylight–glare indices are explained through in-situ HDR measurement in a Tehran tall office building (Pars Tower).

• Five indices DGP, UGR, DGI, CGI and VCP were computed from calibrated HDR images across 680 evaluations over 30 clear-sky days.

• Opening structure is significantly related to all indices in the imperceptible glare category, and to some in the perceptible category.

• Glare never reached the disturbing or intolerable levels in the studied building, where openings kept visual comfort within the imperceptible–perceptible range.

• DGP showed the lowest dispersion across all categories and is recommended as the most reliable index for tall office buildings.

Keywords

Daylight Glare Probability

glare indices

High-Dynamic-Range Imaging

opening structure

Pars tower

tall office buildings

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