How Light Shelves Maximize
BRING NATURAL LIGHT FURTHER INTO YOUR BUILDING
“The spaces where I see daylighting with
light shelves installed are often classrooms,
office buildings and higher education facilities,” explains Theresa Lehman, LEED Fellow
and Director of Sustainable Services for
Miron Construction Co. Inc., a building construction management firm. “They work in
low-rise and high-rise buildings.”
TIPS FOR LIGHT SHELF
As a rule of thumb, the width of a light
shelf should be the same as the height of
the vertical glass above it and will bounce
light a distance of roughly two and a half
times that height. For example, if there
are 2 feet of vertical glazing above your
light shelf when it’s installed, the light shelf
should be 2 feet wide and you can assume
it will bounce light 5 feet into the floorplate,
“When the project team discusses daylight-
ing a building and the design strategies include
the use of light shelves, the team has to look
at it from a holistic, integrated perspective. The
color of the space impacts how far the light will
reflect or be absorbed,” Lehman adds. “Darker
colors absorb light, whereas light colors reflect
sunlight deeper into the floorplate. The size of
the glazing matters; taller glazing is better for
bouncing daylight into the space. The Visual
Transmittance Value of the glass indicates how
much pure daylight the window will allow to
enter, so selecting a glass type that allows light
to come in but blocks heat gain is ideal.”
Pairing the light shelves with daylight
sensors that ramp down artificial lighting in
response to the amount of daylight can reduce
energy use in those spaces by 40-50% due
to additional HVAC savings from the lighting
system generating less heat. However, the only
way to extract maximum energy savings from
light shelves (or any energy efficiency measure,
for that matter) is by incorporating holistic
design concepts that consider every design
feature and the building's system type.
“The window-to-wall ratio and the size and
placement of windows are very important;
you want to make sure the light shelves are
placed correctly. That could be inside or outside depending on your climate and where
the building is located relative to sun angles,”
Lehman says. “Building orientation is also a
factor, and consider the locations of daylighting sensors because the window shades, soffits, and the locations of sprinkler heads, light
shelves and light fixtures can interfere with
sensing daylight. Human comfort is important,
and proper lighting and thermal comfort are
critical for satisfaction.”
Janelle Penny firstname.lastname@example.org is
Senior Editor of BUILDINGS.
Your building’s access to natural ight isn’t limited to the daylight hat comes through the windows. A simple horizontal surface called a light shelf can help natural light
penetrate further into your building, saving
you money on artificial lighting and providing
occupants with the benefits of daylighting.
Could a light shelf fit your facility?
WHAT IS A LIGHT SHELF?
The term “light shelves” usually refers to
horizontal surfaces mounted inside a building.
These interior light shelves divide windows
between the viewable portion and the part
that lets in additional natural light, bouncing it
upward and reflecting it off the ceiling to let
daylight penetrate deeper into the floorplate.
However, there are two other variants.
Exterior sun shades also direct daylight toward
the building's interior ceiling, hence their classification as a type of light shelf, but their
primary purpose is usually providing exterior
shade for windows, which reduces glare,
improves uniformity and reduces solar heat
gain. Baffles are vertically oriented interior
light shelves and are most common in atriums
or spaces with large skylights or roof monitors.
These are usually made from fabric and help
to evenly distribute daylight and reduce glare.
Interior light shelves also assist with shading
and glare control, particularly for people who
are sitting directly adjacent to a window, but
they’re mainly intended to maximize daylight.
QUALITY GLAZING is a crucial ingredient for
LEED's daylighting credit. Pair light shelves
with tall glazing for peak performance.
EXTERIOR SUN SHELVES assist with window
shading and also help direct daylight toward
the ceiling inside.