Evaluation of SBI and SBI-Airmass as Indicators for Sunlight Access
(2026) AEBM01 20261Division of Energy and Building Design
- Abstract
- The assessment of sunlight access in buildings is constrained by methods that rely on simplified point-based evaluation. EN 17037 sunlight exposure evaluates sunlight at a single point on the aperture under restricted temporal conditions. This limits the representation of how sunlight interacts with the aperture over time. These characteristics reduce its applicability at early design stages. The resulting evaluation does not capture the distribution of direct sunlight across the aperture.
This study examines the aperture-based indicators Sunlight Beam Index (SBI) and SBI-airmass as geometry-driven measures of direct sunlight access. A custom computational workflow was developed in Rhino–Grasshopper using Python to calculate these... (More) - The assessment of sunlight access in buildings is constrained by methods that rely on simplified point-based evaluation. EN 17037 sunlight exposure evaluates sunlight at a single point on the aperture under restricted temporal conditions. This limits the representation of how sunlight interacts with the aperture over time. These characteristics reduce its applicability at early design stages. The resulting evaluation does not capture the distribution of direct sunlight across the aperture.
This study examines the aperture-based indicators Sunlight Beam Index (SBI) and SBI-airmass as geometry-driven measures of direct sunlight access. A custom computational workflow was developed in Rhino–Grasshopper using Python to calculate these metrics at the aperture level based on time-resolved solar position data. The analysis combines a parametric study using a reference “shoebox” model with an evaluation of existing buildings in their urban context. The results are examined in relation to SBI and SBI-airmass as well as EN 17037 sunlight exposure, Annual Sunlight Exposure (ASE), and Annual Sunlight Hours (ASH), using correlation analysis, distribution analysis, relationship modelling, and variable importance assessment.
The results show that SBI varies in proportion to aperture area, with orientation, obstruction, and aperture configuration influencing the outcome. SBI-airmass keeps the geometric basis of SBI but adds an airmass factor to account for the reduced strength of low-elevation sunlight. Comparisons with EN 17037 sunlight exposure, ASE, and ASH show that these metrics produce different outcomes under the same conditions due to differences in spatial definition and temporal scope. The relationships between them show a pattern at lower and upper ranges, while variation is observed within intermediate values.
The findings indicate that aperture-based indicators provide a continuous, geometry-dependent description of sunlight access that can be evaluated without interior definition. This allows the assessment of sunlight conditions at stages where only building form and spatial context are defined. SBI and SBI-airmass extend the evaluation of sunlight access by connecting geometric configuration to time-integrated exposure, while remaining distinct from existing methods in both formulation and output. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/student-papers/record/9232786
- author
- Aral, Tural Doruk LU and Gebura-Tetiurka, Agnieszka Malgorzata LU
- supervisor
-
- Niko Gentile LU
- organization
- course
- AEBM01 20261
- year
- 2026
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- SBI, SBI-airmass, EN 17037, ASE, ASH, direct sunlight exposure, solar access indicators, aperture-based indicators.
- language
- English
- id
- 9232786
- date added to LUP
- 2026-06-09 11:48:49
- date last changed
- 2026-06-09 11:48:49
@misc{9232786,
abstract = {{The assessment of sunlight access in buildings is constrained by methods that rely on simplified point-based evaluation. EN 17037 sunlight exposure evaluates sunlight at a single point on the aperture under restricted temporal conditions. This limits the representation of how sunlight interacts with the aperture over time. These characteristics reduce its applicability at early design stages. The resulting evaluation does not capture the distribution of direct sunlight across the aperture.
This study examines the aperture-based indicators Sunlight Beam Index (SBI) and SBI-airmass as geometry-driven measures of direct sunlight access. A custom computational workflow was developed in Rhino–Grasshopper using Python to calculate these metrics at the aperture level based on time-resolved solar position data. The analysis combines a parametric study using a reference “shoebox” model with an evaluation of existing buildings in their urban context. The results are examined in relation to SBI and SBI-airmass as well as EN 17037 sunlight exposure, Annual Sunlight Exposure (ASE), and Annual Sunlight Hours (ASH), using correlation analysis, distribution analysis, relationship modelling, and variable importance assessment.
The results show that SBI varies in proportion to aperture area, with orientation, obstruction, and aperture configuration influencing the outcome. SBI-airmass keeps the geometric basis of SBI but adds an airmass factor to account for the reduced strength of low-elevation sunlight. Comparisons with EN 17037 sunlight exposure, ASE, and ASH show that these metrics produce different outcomes under the same conditions due to differences in spatial definition and temporal scope. The relationships between them show a pattern at lower and upper ranges, while variation is observed within intermediate values.
The findings indicate that aperture-based indicators provide a continuous, geometry-dependent description of sunlight access that can be evaluated without interior definition. This allows the assessment of sunlight conditions at stages where only building form and spatial context are defined. SBI and SBI-airmass extend the evaluation of sunlight access by connecting geometric configuration to time-integrated exposure, while remaining distinct from existing methods in both formulation and output.}},
author = {{Aral, Tural Doruk and Gebura-Tetiurka, Agnieszka Malgorzata}},
language = {{eng}},
note = {{Student Paper}},
title = {{Evaluation of SBI and SBI-Airmass as Indicators for Sunlight Access}},
year = {{2026}},
}