Exterior motorized shades place the
sun-filtering fabrics on the exterior of a
window, providing solar protection by stop-
ping excessive glare, UV rays, and heat
before they enter a building. Movable shad-
ing devices on building exteriors are difficult
to maintain, however, and they deteriorate
rapidly unless made of a copper alloy or
stainless steel. Awnings are highly reliable,
but their aesthetic appeal is limited.
Stationary Controls
Fixed awnings and building overhangs serve
to shade direct sunlight and reduce glare
through the upper area of windows (figure
5.12). They also reduce the daylight entering
the room, decreasing the illumination close
to the window and the penetration into the
room. The maximum depth of useful light
penetration is calculated from the outer
edge of the awning or overhang instead of
the vertical plane of the window.
Although they reduce the quantity of
skylight entering the building, overhangs can
collect light from a light-colored exterior sur-
round and reflect it into the interior. This
results in a more even distribution of light.
An overhang located on the southern
side of a building is especially efficient at
controlling both light and heat from the sun
(figure 5.13). In the summer, the overhang
shields the glass from the sun’s direct rays
yet allows daylight to enter from the lower
sky and by reflection from the ground. In the
winter, the overhang allows the low-angle
sun to penetrate for warmth, but seating
must be oriented to avoid direct sun glare.
Exterior horizontal louvers may pick up
direct sun, causing excessive luminance and
discomforting or disabling glare (figure
5.14). Exterior or interior vertical louvers are
useful for low sun angles that occur in the
early morning or late afternoon, particularly
on building walls oriented toward the east or
west (figure 5.15). When it is necessary to
control both high sun and low sun, “egg-
crate” louvers are used because they com-
bine horizontal and vertical shielding.INTERIOR LIGHTING FOR DESIGNERS
Figure 5.12Awning.Figure 5.13Overhang.