afst.bundel 8 MEI 07 - Technische Universiteit Eindhoven

Figure 2 Model rectangular building
Figure 3 Model bubble
Both models were simulated in Radiance and this resulted in
the conclusion that regarding the overall daylighting quality
none of the buildings is significantly better than the other one.
The daylight distribution is better in the bubble, due to the
possibility of the different placement of the openings.
In a simulation with a sunny sky with sun glare occurs in both
buildings in the compared north-facing viewpoints, caused by
reflections on the wall, on the floor or on reveals. In the southfacing
viewpoints glare is also caused by the sky.
From the simulations with the overcast sky is concluded that
glare will occur at a free field luminance of 14024 lux in the
bubble and of 14937 lux in the rectangular building. Regarding
the luminances, these are variable depending on the sky used in
the simulation and the position of the window. None of the buildings
is distinctively better in this criterion.
Regarding the luminance ratios it is depending on the type of
sky which building is better. In an overcast sky situation the
luminance ratios are lower in the bubble; in a situation with a
sunny sky the rectangular building gives lower luminance ratios.
But in both situations with the north-facing viewpoints the
requirement is exceeded, due to low luminances on the wall.
The vertical illuminance turned out to be too complex to make a
fair comparison.
In the end some recommendations are made regarding
solutions for the problems concerning daylighting quality and
regarding interesting additional research. Solutions for the glare
in the north-facing positions are changing the angle under
which the window is placed and increasing the absorption factor
of the reveals. A solution for the problems concerning the
luminance ratio is to increase the luminances on the wall by
artificial lighting. Furthermore the suggestion is done to create a
tool for designers to make them aware of the influence of the
sun in order to make the right decision regarding the
positioning of the openings during the design process.
In order to find a way to suppress brightness in an architectural
acceptable way in buildings with curved glazing an overview is
made of existing glare protection and sun-shading systems.
These systems are divided into four groups: external systems,
glass systems, systems in the cavity of the glazing and internal
systems. A selection of these systems was made based on their
applicability to double curved glazing. The selected systems are
judged based on seven criteria: the influence on the indoor
climate, the adjustability of the system, maintenance, the
manufacturing procedure, the light transmission, the costs and
whether the system is active or passive. This resulted in the so
called switchable systems being the most suitable systems for
double curved glazing. Switchable systems are photochromic,
thermochromic, thermotropic and electrochromic glass and
gas-chromatic systems. Of these systems electrochromic glass is
chosen to evaluate its influence by implementing it in the
simulation models.
Electrochromic glass has, even in a clear state, a significantly
lower transmittance than normal clear glass. This has a transmittance
of 0.8, while the transmittance of electrochromic glass
is 0.5 in clear state and 0.15 in shaded state. This resulted in a
large decrease of the amount of light entering the building.
Where in the original situation the building was qualified in an
overcast sky situation as being well lit by daylight, the
qualification in case of clear electrochromic glass degraded to
moderately lit and in case of shaded electrochromic glass to
dark. Nevertheless, the exceeding of the luminance ratios still
occurred in the overcast sky situation, because the luminance on
the wall also decreased due to the smaller amount of light entering
the building.
The recommendations regarding glare protection and sun-shading
in buildings with curved façades are to develop shading
scenarios for different times and days. In these scenarios only
the windows for which shading is necessary at that time are
shaded. Concerning further research it is recommended to look
at the implementation of double curved glass in the
manufacturing procedures of glare protection and sun-shading
systems.
afstudeerbundel faculteit bouwkunde
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