ZEMCH 2019 International Conference Proceedings April.2020 | Page 325
1. Introduction
Highly glazed office buildings in Chile are strongly exposed to solar radiation. Shading devices
are essential for ensuring thermal and visual comfort inside these buildings. Especially if the shading
devices are positioned outside, they considerably reduce the solar heat gains through the façade, thus
limiting the increase of the indoor temperature and improving the thermal comfort of the occupants [1‐
2]. They also contribute to the improvement of the visual comfort by reducing the excess of daylight,
by adapting the level of light to the task to be performed, and by limiting the risk of glare [3‐6]. On the
other hand, when they are opaque, the shading devices notably affect the visual contact with the outside.
The view through a solar protection device is a characteristic that is generally sought and contributes
to the visual comfort of the occupant. It depends on the optical properties of the different layers of the
glazed façade and on the external illuminance conditions [7, 8]. The rate of perforations and the color
of the solar protection device are clearly two major factors. Very few studies investigated the view
clarity through shading devices in general. Konstantzos et al. [7] developed a new metric, the so‐called
View Clarity Index, based on a field study (questionnaires) realized with 18 people for evaluating the
view clarity through 14 internal roller blinds (fabrics). European standard EN 14501 [8] defines several
performances classes for solar shading devices related to the thermal and visual comfort. The
performances of the shading device in terms of the visual contact with the outside are classified in five
classes (0=very low; 5=very good) according to the normal‐normal and normal‐diffuse transmittance
factors of the shading device. The standardized classification does not consider the impact of the
external illuminance conditions on the view clarity.
To the best of authors knowledge, no study about the view clarity has been realized on perforated
curved louvers. The present work aims to evaluate in outdoor test cells the view to the outside of several
products of different types of external shading devices (fabrics, perforated louvers, …), characterized
by different light properties. The methodology is based on questionnaires realized on a relatively high
number of persons (about 60 per investigated product), complemented by measured illuminance data.
Based on the collected data, it is evaluated whether the degree of vision to the outside can be
satisfactorily correlated with known optical properties of the solar shading devices and to what extent
the outdoor illumination conditions influence the results. The few metrics described in the literature
will be evaluated and new ones will be proposed if necessary. This paper includes only preliminary
results of the first campaign realized on nine fabrics of different colors and openness factors and is
based on the observations of fourteen human subjects.
2. Materials and Methods
2.1. Solar shading devices
During the first phase of the project (winter 2019), nine external solar shading devices were
examined. All of them are fabrics (roller blinds) coming from the same collection, with the same
thickness and weave configuration. They were supplied by the same manufacturer. These fabrics were
selected in order to cover a wide range of light properties, with different openness factors (OF), light
transmittance factors (Tv) and light reflectance factors (Rv), as shown in Table 1. They correspond to
products frequently installed in offices in Chile. Three colors were chosen (2 light colors and 1 dark
color) and three different openness factors (1%, 3% and 10%), generating a total of 9 combinations.
Other types of shading devices, such as perforated curved louvers and innovative external solar
shading devices will be evaluated during the second phase of the project (2020‐2021).
Table 1. Selected fabrics with their light properties
ID
N1
N2
Color
White
Grey‐white
OF (%)
1
1
Tv (%)
11
6
Rv (%)
80
62
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