Building Elevation & Fenestration
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design in relation to elevations and lighting of rooms
various arrangements to achieve acceptable daylight factors within a
building for specific visual functions. The arrangement of the windows
and other openings in the walls provides the main architectural
character of a building, generally called fenestration.
account is taken of the influence of direct sunlight, but various
methods of calculating daylight factors have been devised for overcast
sky conditions. Modifications to values can be made for glazing
materials other than clear glass, dirt on the glass and reductions
caused by the window framing.
windows or skylights are within the normal field of vision inside a
building, they are likely to be distractingly bright compared with other
things occupants may wish to study. To reduce this apparent brightness,
or glare, the openings should generally be placed away from interior
focal points. Glare can also be reduced by reducing the brightness of
the light source (tinted glass, exterior louvres or curtaining) while
increasing the brightness of the interior spaces by better light
distribution techniques, such as the use of lighter colours for
surfaces, or in extreme conditions by supplementary artificial lighting.
Although exerting a very pleasing influence, brightening interior colours and providing both psychological and physical warmth, direct sunlight in a building can cause intensive glare, overheating and fading of surface colours. For this reason, sunlight used to illuminate a building is also often diffused or reflected to reduce its intensity. Shading and reflecting devices include trees, awnings, exterior and interior louvres, blinds, shades and curtaining. Overhead shading devices (brise soleil) block or filter direct sunlight, allowing only reflected light from the sky and ground to enter a building. Louvres and blinds are capable of converting direct sunlight, into a softer indirect - reflected light.
chief drawback of day lighting is its inconsistency, especially its
total unavailability after dusk and before sunrise. Artificial lighting
can he instantly and constantly available, is easy to manipulate and can
be controlled by the occupants of a building. However, day lighting and
artificial lighting should be regarded as complementary. Artificial
lighting is used mainly for night-time illumination and as a daytime
supplement when day lighting alone is insufficient.
acceptable balance of brightness within a building can be accomplished
by an integration between the design of natural daylight sources and
artificial supplementary lighting to provide the combined level of light
appropriate to a specific visual task. During daylight hours natural
light should appear dominant wherever possible.
quite apart from artificial light sources supplementing lighting levels,
the use of artificial lighting in a building could lead to more flexible
internal planning arrangements and to the incorporation of fewer or
smaller windows. Thus daytime supplementary artificial lighting schemes
directly affect the appearance of a building and its economy of
this must be levelled the probability of greater energy usage, although
reference should be been made to the effects which artificial lighting
installations have upon the heating load for an interior, and the
possible economic advantages obtained by the recycling of heat generated
by lamps, etc.