ASHRAE Journal - September 2023 - 30

TECHNICAL FEATURE
FIGURE 1 VAV system control network levels.
Plant Level Components
Plant Controller Panels
Chillers, Boilers, Towers, Pumps, Etc.
System Level Components
Air Handler Controllers
Air Handlers
Zone Level Components
VAV Box Controllers
VAV Boxes
Occupant Level Components
Workspace Controllers
Server
Workspace Sensors, Comfort Devices
Lights, Plugs, Blinds, Etc.
System Network
Level
Zone Network
Level
Occupant Network
Level
Plant Network
Level
evaluation of CP for other potential individual thermal
comfort devices.20
Effective integration of devices that can adjust local
thermal comfort levels separately for each workspace
into the HVAC system can ensure each will achieve
its occupant's desired comfort level. Further, such
integration offers the opportunity to couple this
improvement in comfort with improved ventilation
that together can achieve dramatic reductions in energy
consumption and help meet ASHRAE sustainability and
decarbonization goals for new office buildings. And
it can be a highly effective energy reduction retrofit
strategy for existing office buildings, while providing
very attractive financial returns by improving the office
building's fundamental economic value-occupant
work performance.
Using Standard 55-2020 Most Effectively
Despite an improved understanding of human
physiology and the technological advances that
have occurred over the last few decades, methods of
distributing comfort conditioning to workspaces in
office buildings with VAV systems have experienced
surprisingly few improvements. Achieving the highest
Standard 55-2020 thermal environmental control
classification in VAV systems with maximum efficiency
requires a method of coordinating occupant thermal
comfort preferences with the operation of comfort
measures in each workspace as well as those in adjacent
workspaces and with the HVAC system.21
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ASHRAE JOURNAL ashrae.org S E PTEM B ER 2023
Research by the author has found substantial benefits
from combining personal workspace comfort measures
of Standard 55-2020 with two additional features: first,
adding a new network in occupant areas that connects
the thermal comfort controls and instrumentation in
each workspace with its occupant(s), other workspaces
and with the VAV system serving each workspace;
and second, replacing zone-wide distribution of
conditioning with a method of directing and controlling
the distribution of primary VAV conditioning directly to
individual workspaces, controlled together with other
thermal comfort control measure(s) at each workspace
to achieve the local desired thermal comfort level.
Figure 1 shows diagrammatically a VAV system with this
new occupant network level highlighted. The equipment
configuration down to the zone level components is
essentially unchanged from conventional VAV systems.
What is different is the occupant network level of
communication with the locally controllable thermal
comfort and ventilation resources and workspace
sensors and devices in each workspace that ensure each
occupant's comfort and air quality needs are satisfied.
The occupant network also communicates with
the workspace occupant(s) via smart devices and is
incorporated into or interfaced with the building
automation system (BAS) control network. It
incorporates an extensive database in a server that
collects and analyzes data to direct this and the other
system levels to satisfy occupant comfort expectations
with optimum overall operating efficiency. The second
key to maximize effective and efficient operation is to
use this new network level to direct and control the
delivery of the primary VAV thermal and ventilation
conditioning to each occupied workspace instead of
applying conventional zone-wide conditioning.
Controlling the delivery and mixing of the system's
primary air directly within each workspace provides
many advantages. Such a distribution configuration
will provide fresher air more directly to each occupant
and enable the use of partitions or walls for acoustical
and visual privacy without concerns of stagnant air.
Workspace-based primary air distribution can also
reduce the likelihood of airborne pathogen transmission
by confining much of the room air mixing to within each
workspace. And workspace-based VAV distribution saves
energy by focusing conditioning on the occupied spaces,
while those that are unoccupied are maintained only in
a standby condition that is dependent on the likelihood
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ASHRAE Journal - September 2023

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