Theoretical Impact of Building Façade Thickness on Daylight Metrics and Lighting Energy Demand in Buildings: A Case Study of the Tropics

Rizki A Mangkuto,Brian Yuliarto,Atthaillah Atthaillah,Mochamad Donny Koerniawan

doi:10.3390/buildings11120656

Rizki A Mangkuto, Brian Yuliarto + Show 2 more

Open Access

https://doi.org/10.3390/buildings11120656

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Abstract

In daylighting design, variation of building façade thickness (f) will result in variation of the daylight opening areas, which in turn will modify the values of daylight metrics within the space. However, studies dedicated to investigating the impact of varying f on indoor daylight metrics are relatively scarce. This study, therefore, aims to assess the theoretical impact of various façade thicknesses on various daylight metrics and lighting energy demands in a reference office space. Analytical calculations are performed using an outdoor diffuse illuminance profile of a tropical city. The building façade thickness values are varied within 0–0.50 m, at window-to-wall ratios (WWR) of 25%, 50%, and 75%. Based on sensitivity analysis, it is found that variation of f yields different impacts on the observed metrics, with sDA300/50% being the least influenced. Among all metrics in the central calculation point, DA300, UDI-a, and UDI-a′ yield relatively small coefficients of variation, and thus, have the lowest uncertainty with respect to f. Among all metrics for the entire room, sDA300/50% and sUDI-a50% have the lowest uncertainty, with interquartile ranges of no more than 0.4%. Overall, the contribution of this study is providing insight into the impact of façade thickness on various daylight metrics in indoor spaces, particularly in the worst-case scenario under the standard CIE overcast sky.

Highlights

Over the past two or three decades, there has been a large body of research highlighting the physical, physiological, and/or psychological benefits of daylight admission in buildings
The room is assumed to sit under the standard CIE overcast sky, which is rotationally symmetrical so that the façade orientation is irrelevant for the calculation
Analytical daylighting calculations have been performed to predict the theoretical impact of non-zero façade thickness f (0 < f ≤ 0.50 m) on various daylight metrics and annual lighting energy demand in a reference office room under the standard CIE overcast sky, taking the case of the annual daylighting profile of a tropical city in Indonesia

Summary

Introduction

Over the past two or three decades, there has been a large body of research highlighting the physical, physiological, and/or psychological benefits of daylight admission in buildings. Among many relevant design parameters, the opening area or window-to-wall ratio (WWR) is arguably the one most discussed due to the potential conflict that may arise between the resulting thermal, energy, and lighting performances of the indoor space (e.g., [11,13,14,15,16,17]). Another daylighting design parameter that may reasonably influence the building performance is the façade or opening wall thickness. This has been well reflected in the literature (e.g., [18,19,20,21,22,23,24])

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