Air diffusers are built into columns and other
perimeter structures in your building. They release
cool air near the ground that rises as it’s warmed
by office equipment and people’s bodies. The warm
air that rises to the top is then exhausted out of the
building, carrying particulates, germs and excess
carbon dioxide with it to improve the indoor air
quality in your space.
“It provides for better thermal comfort because
Making a historic building work for a mod- ern workplace is a challenge under the best circumstances, but one tenant in Chicago’s
we’re delivering air right to the occupied thermal
zone,” Zakrzewski explains. “We’re providing for
increased outside air because the ventilation effec-
tiveness is higher, so we’re able to provide 30 per-
cent more outside air to keep our CO2 levels down.
It’s great for acoustics because we don’t have that
structure-borne noise from ductwork, and we also
don’t have diffuser noise because of the ‘low and
slow’ design of displacement ventilation.”
Don’t confuse displacement ventilation with
underfloor air distribution, notes Chris McHugh,
partner with AKF Group, a consulting engineer-
ing firm. The two are similar in that they supply
historic Commercial National Bank Building created a
state-of-the-art space inside the 1907-era structure.
HKS, an architecture firm moving its Chicago offic-
es into the building’s 11th floor, fitted the VAV-ready
space with an innovative HVAC technology: displace-
In a way, the modern technology was a fitting
choice for the once-innovative building at 125 S.
Clark St. Designed by famed Chicago architect Daniel
Burnham, it was one of the first Burnham buildings to
combine a tripartite commercial high-rise with traditional temple-like bank design.
What is Displacement Ventilation?
Displacement ventilation relies on air’s natural
buoyancy to deliver fresh air efficiently, but at a lower
velocity and higher temperature than a traditional
VAV system, explains Tommy Zakrzewski, director of
integrative energy engineering for HKS.
How displacement ventilation delivered better performance
in a 100-year-old tower
in a Historic Office Building