(JBED) - Summer 2006 - The Whole Building Design Guide

obstruction and/or daylight reflection
from the urban surroundings.
The automated shading and dimmable
lighting not only provide energy savings
but a demand response potential as well.
Studies are underway to determine how
to use the smart controls to bring the
building to a “low power” mode of operation
that would allow essential building
functions to continue while substantially
reducing overall electric power use on a
hot summer day if the stability of the grid
was threatened. The automated shades
and dimmable lighting are a key element
in the demand response strategy. The final
step in this project will be to commission
the installed systems and verify that performance
meets the design specifications.
Major construction will be completed in
2006 with occupancy in 2007.
2. THE ARCHITECTS’ HOLY GRAIL:
SMART GLAZING SYSTEMS
If the dynamic control of transmittance
was incorporated directly into glazing layers,
some of the limitations of motorized
shades and blinds might be avoided. Researchers
have been pursuing the quest
for switchable “smart glazings” for over
20 years and the laboratory accomplishments
are now becoming available for initial
purchase and use in buildings. As with
shades and blinds, the actual energy and
comfort performance in a building will depend
on the interplay of the intrinsic
properties of the materials and the operating
strategy of the building. These operating
strategies must be developed not
only for energy and load control but to
meet occupant needs in terms of comfort
and productivity. As with the shade and
blind studies above, field studies in test
rooms and mockups are an important adjunct
to the extensive computer modeling
studies that have already been completed
to quantify performance benefits and potential
energy savings.
FIELD TESTS OF ELECTROCHROMIC “SMART
WINDOWS”
In 1999, the window systems in the
two test rooms in Oakland were retrofitted
with a first generation electrochromic
window. The optical system changed from
a clear state with a transmittance of 51
per cent to a dark state transmission of 11
per cent. The system performed well
16 Journal of Building Enclosure Design
although full switching could take in excess
of 15 minutes and the coatings had a
noticeable blue tint in the switched mode.
Detailed technical results are available on
our website.
In 2002 we constructed a new test facility
at LBNL with three side-by-side test
rooms with unobstructed south views.
The entire glazed façade (3.5 m x 4 m) for
each room can be replaced. The lighting
power and the heating and cooling in each
room is individually monitored and the
rooms have a full array of illuminance and
luminance sensors for monitoring. Two of
the rooms were fitted with electrochromic
samples over the complete
façade as shown in Figure 5. Since the
prototypes were of limited size the current
façade requires 15 glazing panels.
Extensive engineering tests in the facility
were conducted over a two-year period
to explore the energy savings achieved
with different control strategies. We operated
the electrochomics over their full dynamic
range, testing different control
strategies designed to optimize lighting
savings, cooling savings and visual comfort.
We compared lighting and cooling loads
with automated electrochromics to results
from the room with fixed glazing and
shading, with and without daylighting controls.
The electrochromic systems were
able to consistently beat the energy use of
the conventional façade design but the detailed
results were highly dependent on
operating assumptions and specific control
strategies. The testing focused on the
challenge of the control optimization between
glare control and daylighting energy
savings, with associated studies of cooling
impacts and peak demand impacts.
We also conducted human factor studies
in this facility (Figure 6) to determine
desired operating and control parameters
of the glazing and lighting systems and to
better understand the issues associated
with smart glazing control strategies. Early
results suggest that the lowest transmittance
level of the current glazing prototypes,
three to four per cent, is usually adequate
for most glare situations although
additional glare control was desired by
some occupants. However, switching the
entire façade to very low transmittance
levels to control glare often requires that
electric lights be turned to full power levels.
New architectural design approaches
such as separate vision and daylighting
glazings, as well as improved switching
control strategies were then studied to
address this issue. Initial results show that
it is desirable to divide the façade into two
elements that would be designed and controlled
differently. A lower “vision” window
might have a lower transmittance
and would be designed to manage glare at
a perimeter workspace. This will tend to
have low transmittance values when sun
and sky glare are present so that LCD
screen visibility is not compromised. The
upper “daylighting” window would have a
higher visible transmittance and be managed
dynamically to control solar gain but
admit adequate daylight so that the primary
room electric lighting is off or
Figure 5
Exterior view of LBNL Façade Test Facility. Two rooms
at left have electrochromic prototypes installed, the room at
right is a control room with spectrally selective glass and
blinds.
Figure 6
Interior photo of façade test room configured for occupant
response testing.