Civil Engineering Reference
In-Depth Information
3.1.2 Natural Lighting and Shading
Good daylight levels are essential for comfort of users and for this reason regula-
tions and standards in Europe mandate either minimum daylight levels, or dimen-
sions of windows relating to size of rooms, or maximum distances of workplaces
to windows. Good levels of natural lighting inside the building not only save elec-
tricity for artificial lighting but reduces the related internal gains.
The issue of natural lighting needs to be gauged against the ingress of solar
energy that may be beneficial in terms of winter heating, but may also lead to glare
(especially in workplaces) and to summer overheating, especially in buildings with
high internal gains such as offices and schools.
As summer temperatures rise throughout Europe (Rubel and Kottek cit.), the
control of solar radiation becomes crucial for homes; this is not only in Southern
countries where traditional architecture has always been facing this problem. It is
thus necessary to spread the use of effective shading systems that control heat gain
and glare (adjustable systems allow for precise control in different conditions)
while letting natural light in for visual comfort. Solutions range from glazing-inte-
grated shading to complex, adjustable systems that rely on indirect reflections to
spread light in rooms. This sort of shading can be very useful also in refurbish-
ment operations, when lighting levels need to be improved. Shading systems may
also be an effective surface for energy generation (e.g., PV panels or vacuum
tubes), since they typically receive a high amount of solar radiation.
Natural light is even more desirable in difficult conditions such as deep-plan
buildings and urban canyons. Solutions that allow transportation of light deep into
the building can range from bespoke architectural features such as light shelves
to less visible ones such as light pipes (tubes with highly reflective coating), glass
fibres, or heliostats (horizontal or vertical). These are also suitable for improving
natural lighting levels in existing buildings.
Examples of efficient shading, light control and light transportation are shown
below.
Light shelves
A light shelf is an architectural element that allows daylight to penetrate deep into a build-
ing, while providing a degree of shading according to latitude and orientation. It is pos-
sible to obtain a light shelf placing a horizontal light-reflecting overhang above eye-level.
This element should have a high-reflectance upper surface, reflecting daylight onto the
ceiling and deeper into a space. Light shelves are generally made of an extruded alumin-
ium chassis system and aluminium composite panel surfaces, but any reflecting surface
can work correctly.
Light shelves make it possible for daylight to penetrate the space up to 2.5 times the
distance between the floor and the top of the window. Today, advanced light shelf technol-
ogy makes it possible to increase the distance up to 4 times.
Light shelves can also provide shade near the windows, due to the overhang of the
shelf, and help reduce window glare. Exterior shelves are generally more effective shad-
ing devices than interior shelves, as they block radiation before it enters the building. A
combination of exterior and interior shelves will work best in providing an even illumi-
nation gradient. For maximum benefit, perimeter lighting should be controlled by photo-
sensors, with lighting zones to the particular installation.
