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Cleantech Daylighting Using Smart Glass: A Survey of LEED? Accredited Professionals
Published: 2015-6-23 0:06:04
Cleantech Daylighting Using Smart Glass: A Survey of LEED? Accredited Professionals

G. M. Sottile
Research Frontiers Inc., Woodbury, NY, USA


ABSTRACT
Buildings are an important target of the clean
technology movement. According to the U.S. Green
Building Council, buildings now account for nearly forty
percent of all energy consumed in the United States. Smart
glass is an emerging category of high-performing glazings
that can regulate the amount of light, glare and heat passing
through products such as windows, doors and skylights.
When used in architectural projects, these glazings offer the
potential for two key daylighting benefits – reduced cooling
loads and lower electricity consumption for interior
illumination. This paper reports the results of a nationwide
market research survey on the clean technology potential of
daylighting using smart glass. Survey participants are
LEED? Accredited Professionals whose practice area is
architecture. In addition to general awareness, interest and
specification activity of smart glass, the study also explores
the importance of various attributes of smart glass and
expectations for its future use.
Keywords: clean technology, daylighting, market research,
smart glass, sustainability
1 INTRODUCTION
The world is experiencing a heightened call to address
sustainability across many industries. From hybrid
automobiles to solar energy systems in buildings, bold
advances that support energy efficiency, societal well-being
and environmental stewardship are being embraced in
exciting ways by governments, companies and individuals.
The development and commercialization of clean
technology are critical components of the drive toward
sustainability. Spurred by strong end-user demand, an
expansive array of high-performing clean technology
innovations are now commercially available. Many of these
innovations will play important roles for decades to come
as society’s needs for sustainability continue to accelerate
and industry’s ability to profitably meet those needs grows.
2 CLEAN TECHNOLOGY
Clean technology, commonly called cleantech,
encompasses a unique blend of altruistic ideals and
pragmatic capitalism. Such an orientation is evident in The
Cleantech Network’s definition of clean technology as
“new technology and related business models offering

competitive returns for investors and customers while
providing solutions to global challenges” [1]. According to
a survey by Ernst & Young, the two primary drivers of the
clean technology industry over the next five years will be
increasing energy costs and initiatives to raise energy
efficiency [2]. These drivers have global influence. Rising
energy costs can adversely affect inflation, balances of
trade, and the performance of economies. Likewise, efforts
to raise energy efficiency, whether government-sponsored
or of a grass roots nature, offer direct and indirect benefits
when costs are lowered and the environment is protected.
Investments in clean technology have grown
substantially. Dow Jones VentureSource reports that in
2007, venture capitalists invested $3 billion in clean
technology deals globally, an increase of 43% from 2006.
In 2007, the United States’ share of total clean technology
investments reached 83% and accounted for 8% of the
country’s venture capital investment [3]. Further, according
to Lux Research, R&D spending on clean technology
totaled $48 billion in 2006, up 9% from the prior year [4].
3 DAYLIGHTING
Clean technology supports the goals of sustainability.
The concept of sustainable development was synthesized by
the United Nations World Commission on Environment and
Development which claimed “Development is sustainable
when it meets the needs of the present without
compromising the ability of future generations to meet
theirs” [5]. Sustainable architectural design involves efforts
to increase the energy efficiency of buildings, improve the
well-being of building occupants, and lower the
environmental impact of buildings. Pursuit of such design is
warranted. The U.S. Green Building Council, for example,
observes that U.S. buildings account for 71% of the
nation’s consumption of electricity, 39% of total energy
use, and 38% of its carbon dioxide emissions [6].
Since the earliest civilizations, humankind has relied on
the sun’s energy. Over time, strategies have developed to
capture the benefits of natural light, or daylight, while
mitigating its adverse effects. For these reasons,
architecture professionals have historically employed
designs that introduce natural light into a building’s interior
while using simple systems to control the light. The use of
conventional window systems and traditional window
treatments are examples of such designs. The strategic



application of daylighting, however, involves efforts to
protect occupants from unwanted glare, provide shade from
the sun, and redirect natural light as needed [7]. Effective
daylighting can provide substantial benefit in terms of
energy efficiency, most notably by harvesting natural light
in a way that lowers the electricity consumption used to
satisfy interior lighting needs. Daylighting also has been
found to increase occupant well-being and productivity in
educational, workplace and retail settings [8].
4 SMART GLASS
Smart glass is a category of glazing materials that
changes its light-control properties in reaction to an
external stimulus. [9]. Known also as switchable glazings,
dynamic glazings and chromogenics, smart glass is a
relatively new category of high-performing glazings with
significant clean technology characteristics. Smart glass can
be used in a wide range of everyday products such as
windows, doors, skylights, partitions, sunroofs, sun visors
and more. Expectations for growth in smart glass demand
are very high. The Freedonia Group projects the value of
smart glass demand in the United States to reach $1.34
billion by 2015, an increase of 250% from 2005 [10].
Smart glass is composed of two major segments.
Passive smart glass does not involve an electrical stimulus.
Rather, it reacts to the presence of other stimuli such as
light or heat. Photochromic lenses used in self-dimming
eyewear, for example, change their light-control properties
in response to the presence of ultraviolet light. Active smart
glass does involve an electrical stimulus and it is this
segment where the prospect for widespread adoption among
large-format applications is greatest. Active smart glass is
now being offered as an innovative design solution for
products ranging from aerospace windows to architectural
skylights and automotive sunroofs.
There are three primary types of active smart glass, each
with its own unique chemistry, production requirements
and performance characteristics. Liquid crystal (LC) smart
glass is primarily used for interior partitions in architectural
applications. Possessing two light transmission states –
translucent and transparent – and adjustable in
milliseconds, LC smart glass diffuses incoming light and
thus offers a privacy benefit in its translucent state but very
little in the way of shading. Suspended particle device
(SPD) smart glass is a shading system with light
transmission levels that can be controlled to any point
between dark and clear. In its dark state, SPD smart glass
can block at least 99.4% of incoming light, a level that is 20
to 40 times darker than standard tints for windows. When
SPD smart glass is in its clear state, light transmission is
similar to that of a conventional non-tinted window. All
adjustments to light transmission levels take place within
seconds regardless of the size of the glazing.
Electrochromic (EC) smart glass is similar in one respect to

SPD smart glass in that it also offers light transmission
levels from dark to clear. Primarily used in self-dimming
automotive mirrors, switching speeds for EC smart glass
are disproportionately slower as panel size increases, with
larger glazings for architectural applications often taking
many minutes to change their light-control properties.
Because of this, EC smart glass for architectural projects is
generally offered with just two states – dark and clear.
Active smart glass will play an increasingly important
role in the world’s drive toward sustainability. Requiring
very low amounts of power to operate, architects and
designers can integrate smart glass into their projects in
ways that offer unprecedented control over incoming light,
glare and heat. In doing so, electrical energy consumption
can be lowered, cooling loads reduced, environmental
impact mitigated and occupant well-being increased. These
outcomes can be achieved by the integration of smart glass
into various daylighting strategies. Most fundamentally,
smart glass transforms conventional windows into smart
windows with expanded daylighting utility and value. For
example, curtains, blinds and other treatments have
traditionally been used to provide shading and glare
reduction through incoming windows. These solutions
typically block one’s view to the outside, an undesired
outcome for many building occupants. Windows with smart
glass allow users to control incoming light, glare and heat
without the loss of view to the outside, an option generally
not available with standard treatments but one that
improves occupants’ levels of comfort and connection with
the outside world.
Systems that use both smart glass and conventional
glazings can effectively achieve daylighting objectives. For
example, two tiers of glazings can be used in a typical
commercial office setting. A small, upper glazing of the
non-smart type can be integrated with a light shelf to reflect
natural light deep into the room. A larger smart glass
window below this glazing could be used to adjust light,
glare and heat transmission in the work area closest to the
building’s fa?ade while providing occupants with privacy
or view preservation as desired. Lastly, active smart glass
can be integrated with intelligent building systems to yield
optimally performing daylighting systems. One of the great
limitations of daylighting strategies that use non-smart
glazings is that, in the absence of purposeful shading using
view-blocking products, these glazings continue to
introduce natural light and its attendant heat into a building
even when lighting is not needed (e.g. when a room is
unoccupied). This has the effect of raising solar heat gain
levels and thus adding to the building’s cooling costs. With
the use of photosensors, timing devices or other advanced
building control systems, smart glass can block unwanted
natural light to any desired level when a room is
unoccupied, thus providing user benefits when desired
while also minimizing heat gain and cooling demands.




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