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The sunlight beam index

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journal contribution
posted on 2015-12-07, 15:05 authored by John MardaljevicJohn Mardaljevic, Nicolas Roy
This paper describes a fundamental rethinking of the basis for the evaluation of the sun- light potential of spaces. It provides a robust methodology to answer the question: how much sunlight can enter a room? The measure proposed is the cross-sectional area of beam sunlight that passes through a window. The new measure { called the sunlight beam index { is described, and examples are given for a realistic residential dwelling. The sunlight beam index is determined for a full year on a time-step basis (e.g. every 15 minutes), but it can be aggregated into monthly or yearly totals. The annual total provides a single measure for: one window; a group of windows; or, all the windows for an entire dwelling.



  • Architecture, Building and Civil Engineering

Published in

Lighting Research and Technology


MARDALJEVIC, J. and ROY, N., 2016. The sunlight beam index. Lighting Research and Technology, 48(1), pp.55-69.


© The Authors. Published by SAGE Publications


AM (Accepted Manuscript)

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This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at:

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This paper was accepted for publication in the journal Lighting Research and Technology and the definitive published version is available at