Window Design For

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Window Design For Daylighting Sarah Joubert
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• Issues Related to the Effectiveness of Windows
• Weather Location
• Room Proportion
• Room Reflectance
• Building Massing Shape
• Ceilings

• Design Issues For Sidelighting
• Location of Openings
• Shape of Openings
• Number of Openings
• Shading Devices
• Sunlight Redirecting Devices
• Shutters, Blinds, and Screens

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Five Basic Strategies to Promote Effective Use of
Daylight Maximize solid angle of sky seen from
the task Shade to prevent glare Do not block
light Locate openings high Shape space to
minimize absorption of light
Five Basic Strategies to Promote Effective Use of
Sunlight Shade to prevent glare and excess
heat Redirect sunlight where it is needed Control
the amount of light entering in a space Use the
light efficiently Integrate forms for
sunlighting with the architecture
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Weather Data Location (note consult
publications from the National Oceanic and
Atmospheric Administration)
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Room Proportion Proportion, not size determines
light distribution
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Room Reflectance Light distribution is highly
dependant on room reflectance, primarily walls
and ceiling.
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Building Shape and Massing When using
sidelighting only, in general, a narrow form has
the greatest access to exterior openings and
will be the easiest to illuminate.
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Ceilings In general, ceilings are the most
effective light-reflecting and light-receiving
surfaces. It should be unobstructed, of
high reflectance, and seen by most horizontal
task areas.

• Increase the distance between task and
• ceiling to allow the task to see more
• ceiling.

2. Increase the distance between light source and
ceiling to distribute light more evenly across
the ceiling.
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Ceilings
3. Use low windows and ground-reflected
light, but be careful to avoid glare at eye
level.
4. Use high-reflectance Surfaces.
5. Shape ceiling for min. surface area and
use smooth surfaces.
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Openings The location of openings affects both
light distribution and the perception of
distribution.
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Openings-Upper Section The upper window sees the
brightest zenith of the overcast sky
and therefore has the best distribution of light
on overcast days. Upper windows have potential
for sun and sky glare so should be properly
baffled.
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Openings-Middle Section The middle window is not
optimal for light distribution on sunny days or
overcast days, yet it is the most commonly used
location because of the view afforded. (note
that in places such as Florida we need to design
for both sunny and overcast skies so the middle
section is a compromise between both situations.)
Again, glare is a problem that must be dealt
with.
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Openings-Lower Section The lower window provides
optimal distribution of reflected sunlight. This
is because it maximizes the distance between the
light source and the ceiling and provides the
greatest uniformity. The lower window will
typically not be a source of direct glare, but
can be a source of reflected glare when located
below eye level.
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Openings-Lower Section The value of the view out
a low window depends on its scale. The view from
the bottom third of a 24-foot wall can be very
good, but the view from the bottom third of a
9-foot or 12-foot wall with the window head only
3-4 feet above the floor is likely to
be unsatisfactory.
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Openings-Near Interior Walls Vertical
high-reflectance walls can also be utilized as a
surface to receive and redistribute sunlight.
These windows will encourage distribution while
minimizing shadows, and reducing glare and
contrast between the opening and the interior.
Walls are especially useful for controlling
low-angle (horizontal) sunlight, which is
difficult to redirect to the ceiling.
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• Shape of Openings-Displacement
• Projecting lower sills will maximize illumination
  from area sources
• such as overcast skies. It should be used in
  orientations that do not
• require shading.
• 2.The overbite confirguration is best for
  ground-reflected sunlight and
• shades direct sun and skylight.

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Multilateral Openings In general, locating
openings in more than one wall will enhance the
distribution of light. Light coming from
multiple directions helps provide a softer, more
diffuse light with less shadows and silhouetting.
(note these qualitative differences will
improve visibility without increasing the
quantity of daylight.)
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Multilateral Openings
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• Shape of Openings-Walls
• Sills which slope to the exterior will minimize
  the possibility of glare
• from the sill and will allow penetration of
  ground-reflected light.
• These sills are not good at reducing contrast on
  the interior or
• bouncing light deeply into space.

Sills which slope or curve on the interior will
create intermediate gradients of light that
effectively soften a contrast between interior
and exterior. They can also bounce light deep
into a space.
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• Shading Devices-Horizontal
• Horizontal devices provide shade based on the
  altitude angle of the
• sun. They let in low-angle sunlight and block
  high-angle
• sunlight their effectiveness varies seasonally
  with the changing
• solar altitude.

Most commonly seen in the form of overhangs, they
are particularly effective for shading north and
south elevations.
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• Shading Devices-Vertical
• Vertical devices provide shade based on the
  bearing angle of the sun.
• Their effectiveness varies diurnally, as the sun
  moves around the
• horizon.

Vertical devices have the ability to block
low-angle sun, and consequently they are often
used on openings facing east or west.
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• Shading Devices-Egg-Crate
• Egg-Crate shading devices combine the
  characteristics of vertical and
• horizontal devices to improve the shading
  coverage.

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• Sunlight-Redirecting Devices-Light Shelves
• Light shelves are horizontal shading and
  redirecting devices. They
• effectively create two apertures in a window
  wall, an upper clerestory
• window which is primarily for illumination and a
  lower window for view.

For best distribution, light shelves should be
located as low in a space as possible without
causing glare, typically above standing eye
level.
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• Sunlight-Redirecting Devices-Light Shelves
• To be effective, the minimum depth of a light
  shelf is determined by
• shading requirements. To prevent glare
  conditions, direct light from the
• upper window should not penetrate past the edge
  of the light shelf.

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Sunlight-Redirecting Devices-Light Shelves
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Sunlight-Redirecting Devices-Light Shelves The
location of the glazing affects the amount of
solar radiation admitted into a building.
Recessed glazing has shade throughout the year
glazing flush to the exterior maximizes heat
gain. For buildings with seasonal heating
requirements, the glazing should be located
midway.
Note light shelves are most effective on the
south side. To achieve effective shading, on the
east and west sides they can be augmented with
vertical devices, or additional horizontal
louvers. Light shelves are not useful for light
distribution on the north side, but they do not
substantially reduce illumination and may make
views more comfortable by blocking sky glare.
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Sunlight-Redirecting Devices-Suncatchers Suncatche
rs are vertical sunlight-redirecting devices
parallel to the building façade. They are best
for intercepting low-angle sunlight on the east
and west sides of buildings. They also catch
sunlight on the North side of buildings,
substantially increasing the illumination.
Note light which they catch tends to be
reflected downward, which can result in glare.
Therefore, they should be used to redirect light
toward walls or, in conjunction with a light
shelf, to redirect the light toward the ceiling.
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Shutters, Blinds, And Screens Shutters, blinds,
and screen do not redirect light they only
diffuse or reject it. They have the advantage of
being movable which allows them to be used when
glare needs to be controlled.