Trying to balance natural light and dis- tracting influences like glare and solar
heat gain is a major challenge for buildings
with many windows. In recent years, electrochromic windows have emerged in the
marketplace, affording facilities managers the
ability to electronically modulate the amount
of light admitted into a building.
As technology has progressed, so too
have the best practices for implementation.
The General Services Administration (GSA)
reported on two case studies of buildings
implementing electrochromic windows
through its Green Proving Ground (GPG).
Learn how to best leverage electrochromic
windows in your workplace.
ELECTROCHROMIC IN PRACTICE
The HVAC benefits of electrochromic
windows have been well-documented. This
study, conducted by Lawrence Berkeley
National Laboratory, looked at occupant
satisfaction in two different locations: the
911 Federal Building in Portland, OR, and the
Moss Federal Building in Sacramento, CA.
Both buildings have curtain wall designs
with high window-to-wall ratios.
Before retrofits, the 911 Federal Building
had dark-tinted, dual-pane, low-e windows
with fitted venetian blinds. Electrochromic
windows were installed adjacent to the
south facade on the sixth and seventh floors
and later on the third, fourth and fifth floors
after receiving positive feedback from building occupants.
In Sacramento, the Moss Federal Building
received electrochromic windows in the
south facade of the sixth floor, which
replaced 84 double-pane low-e units.
In both facilities, most building occupants
were satisfied with the change. In Portland,
85% of occupants in private offices and 92%
in open offices preferred electrochromic windows over the previous ones. In Sacramento,
63% of occupants preferred electrochromic
windows to the previous options.
Reception to the new windows wasn’t
without some reservations. Some occupants
complained that the windows took too long
to tint. For some manufacturers, this prob-
lem is exaggerated by the fact that users
cannot cancel a transition with an override
function without finishing the current tint
GETTING THE MOST OUT OF
In addition to finding out how many occupants liked the change to electrochromic,
GSA made some key conclusions about the
best practices for installation and operation,
■ Select clear windows to facilitate a broad
switching range. Because they tried to
match the legacy windows aesthetically,
the Portland facility added a blue-tinted
layer of glass to the electrochromic windows. As a result, the windows were limited in being able to
let light into the building. Electrochromic
windows with a clear
inboard glass layer are
■ Configure electrochromic window installations into zones. The
two buildings installed
windows in the south-facing facade, but it
can get too dark if
all the windows are
set for the darkest tint.
Installing them in zones
or equipping them with
individual controls can help mitigate this
■ Test before you install to avoid any
■ Educate occupants and manage expectations. Let occupants know how electrochromic windows operate, whether they
have override controls and how to use
them. If occupants understand how the
new windows work, they will more likely
be satisfied with them.
WHAT’S THE BEST FIT FOR
Based on the findings from the reports,
GSA determined these were among the best
applications of electrochromic windows.
■ Facilities where outside views are criti-
IDENTIFY BEST PRACTICES FOR OPERATION
ELECTROCHROMIC WINDOWS TYPICALLY HAVE
AUTOMATIC SETTINGS to transition from clearer to
more heavily tinted settings as sunlight becomes more
intense. Some systems have a user override function.
If building occupants know how to operate it, they are
typically more accepting of the new windows.
HOW ELECTROCHROMIC WINDOWS WORK
cal. A previous GSA study at the Land
Port of Entry (LPOE) in Donna, TX, found
that electrochromic windows worked well
in locations where glare compromises
mission critical outdoor visibility. The electrochromic windows at the Donna LPOE
had a 100% user preference over previous
■ Facilities with seasonal thermal comfort
challenges. For buildings that experience seasonal discomfort, electrochromic
windows help to provide dark tinted glass
in the summer and clearer glass in the
■ Facilities with atriums and skylights. The
heat gain that atriums and skylights can
bring to a building can neutralize the positive effects they might otherwise have
on building occupants. Although it hasn’t
been evaluated yet, the evaluation team
believes electrochromic windows would
work well with atriums and skylights.
■ Facilities needing to reduce peak cooling
load. Electrochromic windows can help
reduce peak cooling load. Like in Portland,
this ability to reduce HVAC energy
requires occupants to accept darker tint
■ Facilities with radiant cooling. Buildings
with radiant cooling and other low-energy
cooling systems benefit from the control
that electrochromic windows provide,
since HVAC systems take time to respond
to atmospheric conditions.
For more information on the electrochromic installations in Portland and Sacramento,
as well as other key findings and lessons
learned, visit www.gsa.gov/gpg.