18 BUILDINGS 04.15
or solar film, it’s a great opportunity to
gain dual functionality.
“A window renovation may be
necessary if the existing building was
designed with only fixed windows,”
says Lisa Jackson, manager for window products and sustainability with
Kawneer Company. “Switching to high-performance operable windows can be
a cost-effective way to introduce natural
ventilation into occupied spaces and
improve overall energy efficiency.”
Keep in mind that it may not be necessary to have all windows unlock and
you can save on costs by limiting the
number of openings to upgrade. Many
properties will add operable windows
only on one side of a building, a single
floor, or even just a row, says Frank.
Before you commit to replacements,
evaluate your site for cross wind, buoyancy, and the stack effect to determine
which spots on your facade receive the
most wind, Frank recommends.
4) Do You Have Zone Heating and
Cooling Paired with Controls?
Depending on how deep your building
is, keep in mind that operable windows
will only benefit spaces close to the perimeter as fresh air can’t easily reach the
core without mechanical help, notes Brinton. Open plans are also helpful as there
are fewer barriers that could block air
flow, adds Frank, though you can always
add ceiling fans to help carry a breeze.
If you don’t want occupants guess-
ing when it’s a good day to ventilate
naturally, there are several ways to add
■ Full Automation: In addition to a
remote panel or switch, “windows can
be integrated with the HVAC system using sensors. This configuration balances
the use of air conditioning with natural
ventilation whenever it is feasible or
desirable,” Jackson says. “An integrated
HVAC system is best when approached
during the design phase.”
■ Notification System: You can install
outdoor weather stations that measure
air conditions. These sensors connect to
your BAS and will trigger your perimeter
HVAC to shut off when presets are met,
Frank explains. This ensures your air
conditioning isn’t running full blast when
the windows are open.
This ventilation sequence also includes a reset for the interior supply air
or room setpoint temperature to ensure
those units aren’t maxed out, he adds. If
your HVAC isn’t connected to your BAS,
note that this option will necessitate a
■ Interlocking Controls: Another possibility is to add interlocking controls to
the windows. These use a binary contact
that is broken when a window is opened,
which in turn sends a message to the
HVAC system to shut off.
In addition to these controls, you may
5) Will Your Occupants Be On Board?
elect to add a ventilator, notes Jackson:
“These are typically small horizontal
devices constructed within the framing
system that allows air to flow into oc-
cupied spaces. When windows are in the
open position, the ventilators provide a
steady amount of outdoor air. They are
usually equipped with screens to keep
out insects and weather.”
It goes without saying that for operable windows to be effective, they need
to be easily accessed by occupants. That
means they’re within reach, don’t require
much force to open, and aren’t blocked
by any objects, says Jackson.
If you don’t have full automation, you
have to rely on occupants to open windows, and more importantly, close them,
she adds. Without good habits, employees may neglect to shut windows at the
end of the day or over the weekend. This
can present energy, moisture, and security concerns if left unaddressed.
A little occupant training can go a
long way, so take the time to educate users about the benefits of open windows
and what they can do to be good environmental stewards. If that falls short,
you can always task your cleaning crew
to shut open windows just as they might
already be doing with lights that are left
on, advises Frank.
When hitting the sweet spot for the
trifecta of temperate weather, acceptable outdoor air quality, and smart HVAC
controls, operable windows can be a
sustainable and energy-efficient way to
supply natural ventilation to occupants.
Jennie Morton jennie.morton@buildings.
com is senior editor of BUILDINGS.
continued from page 17
Could fresh air alleviate in- door pollution levels or only
create a bigger problem?
A 2013 NREL study called
Natural Ventilation in California
Offices: Estimated Health Effects
and Economic Consequences
set out to determine if opening
windows was an answer or a
problem to poor IAQ.
For buildings with natural
ventilation, the researchers
found that while fresh air could
OUTDOOR POLLUTION VS. SICK BUILDING SYNDROME
reduce sick building symptoms, it also increased the number
of respiratory issues workers experienced. The cost to treat exposure to particulate matter was higher than the cost savings
to reduce sick building syndrome. Despite these findings, you
don’t need to abandon fresh air altogether.
“The health effects and costs from increased exposure to
ozone and particulate matter in naturally ventilated buildings
could be substantially reduced by keeping windows closed on
the days with the 10% highest levels of ozone and particulate
matter,” note the authors. “Mechanical cooling would likely be
needed to maintain comfort, and mechanical ventilation would
be needed to prevent an increase in sick building syndrome