Moving
through the sky, the sun is one of architecture’s few constants. Precisely
predictable throughout the year, its presence and ferocity has shaped the
nature of architecture throughout human history. Regional typologies around the
world have developed to either welcome its warmth or shade from its heat. In
India, the numerous geographical differences in the country have created a vast
variety of mechanisms to control the sun and none is more remarkable than the
humble courtyard. To the untrained eye, an empty void nestled in the midst of a
dense built environment would seem like a waste of space. However, it is an
architectural device of astounding value and simplicity. The light diffuses
into the surrounding spaces and the courtyard itself can be used for a myraid
of activities throughout the day and night.
As
an architectural typology it has endured for millenia, yet it is completely
absent from modern cities. The pressure on the land, soaring densities and
archaic building bye-laws have all, but eradicated the courtyard from the urban
townhouse – It simply isnt feasible to provide so much open space within each
individual home. The agglomeration patterns do not permit all spaces to be
naturally lit from exterior windows. So how is one to sufficiently illuminate
all interior spaces? One of the more successful solutions is one that imbibes
the best qualities of the courtyard and marries them to the best fenestration
technologies prevalent today – Operable Skylights.
Skylights
have been around long enough, but have always had a plethora of problems. They
are essentially holes in the roof, so water penetration is always an
issue. The glasshouse effect, where the
effect of the heat gets compounded because it cannot escape – is a boon for
colder countries, but very uncomfortable for an already hot climate. It is also
important to diffuse the light coming from a skylight for the same reason, the
glare in the summer rendering the area useless for anything other than
sunbathing.Also, a critical function of the courtyard was to draw out hot air
from the centre of the house, forcing in fresh air from the periphery, thereby
generating some much needed air movement.
Operable
skylights address all of these concerns and more. Modern sealing systems use a
multitude of neoprene gaskets and draining systems that allow for minimal water
penetration. The little bit of water that does enter is drained through
perforations in the profiles. Powder coated aluminum ensures a robust finish to
the framework that holds the glass panels in place. The operable panels
themselves can be electronically controlled, based on internal temperature and
humidity levels. A high-performance glazing system will generally admit more
light and less heat than a typical window, allowing for daylighting without
negatively impacting the building cooling load in the summer. This is typically
achieved through spectrally-selective films. These glazings are typically
configured as adouble pane insulated glazing unit, with two 0.25 in. (6 mm)
thick panes of glass that are separated by a 0.50 in. (12 mm) air gap. This
construction gives the insulated glazing unit a relatively high insulation
rating, or R-value, as compared to single pane glass. A low-emissivity coating
is also often part of these high-performance glazing units, which further
improves the R-value of the unit.
Many
daylighting designs will employ skylights for toplighting, or admitting
daylight from above. While skylights can be either passive or active, the
majority of skylights are passive because they have a clear or diffusing medium
that simply allows daylight to penetrate an opening in the roof. They are often
comprised of a double layer of material, for increased insulation. Active
skylights, by contrast, have a mirror system within the skylight that tracks
the sun and are designed to increase the performance of the skylight by
channeling the sunlight down into the skylight well. Some of these systems also
attempt to reduce the daylight ingress in the summer months, balancing
daylighting with cooling loads.
Daylight
redirection devices take incoming direct beam sunlight and redirect it,
generally onto the ceiling of a space. These devices serve two functions: glare
control, where direct sun is redirected away from the eyes of occupants, and
daylight penetration, where sunlight is distributed deeper into a space that
would not be allowed otherwise. Daylight redirection devices generally take one
of two forms: a large horizontal element, or louvered systems. Horizontal
daylight redirection devices are often called lightshelves.Tubular daylight
devices are another type of toplighting device. These devices employ a highly
reflective film on the interior of a tube to channel light from a lens at the
roof, to a lens at the ceiling plane. Tubular daylight devices tend to be much
smaller than a typical skylight, yet still deliver sufficient daylight for the
purpose of dimming the electric lighting.
As
mentioned previously, the windows must be carefully designed to control the
solar gains and potential glare stemming from a daylighting design. To this
end, solar shading devices are often employed to minimize the amount of direct
sun that enters the space. These can take the form of louvred slats, which
soften the lighting by bouncing it off the dark wooden surfaces.
This article originally appeared in Fensterbau, a monthly tabloid of the Indo-German Chamber of Commerce
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