An Approach for Lighting Calculations in Indoor Mirrored Facilities Based on Virtual Twin-Spaces

The presence of walls with different reflectance in indoor facilities is a problem when designing their lighting installations. This problem becomes more serious when one or more walls are mirrors, a common situation in medical, sport, educative and many other indoor facilities. Even if some programs can work with different approaches, the results are far from exact and, in many cases, designers ignore the mirrors and work by eye, with results that are frequently excessive in terms of illuminance on the working planes, glare and energy consumption and use of materials. These deviations from the intended results are due to the direct or indirect estimation of reflectance remarkably lower than 1 in the mirrored walls. In this framework of uncertainty, this work is presented with the objective of developing an intuitive theoretical model based on the consideration of virtual twin-spaces behind the mirrors. This proposal is not just an approach, but a useful tool providing the input for any kind of calculation ranging from the lumen method, used in quick pre-dimensioning, to the most complete calculations with computational methods. In addition, apart from calculating the number of luminaires and photometric parameters, the use of virtual twin-rooms also takes into account the extended field of vision of the users, including objects behind, and virtual luminaries. This advantage has no precedent in the literature up to date.

Automated summary

The presence of walls with different reflectance in indoor facilities, especially when the walls are mirrors, is a problematic issue in lighting design. Existing methods are not accurate and designers often neglect the mirrors, resulting in excessive illuminance, glare, energy consumption, and material usage. This study proposes an intuitive theoretical model based on virtual twin-spaces behind the mirrors, which can be applied to various calculation methods. Additionally, the model takes into account the users' extended field of vision and virtual luminaries, providing an advantage that is not found in existing literature.