ASHRAE Journal - September 2023 - 28

TECHNICAL FEATURE
Research has found just small variations from an
office worker's thermal comfort preference significantly
reduce work performance,2,3 which is generally found
in more recent studies to be in the range of about a 2%
to 4% reduction in work productivity for each 1°C (1.8°F)
from that desired thermal condition.4 And surveys
consistently find only about half or less of office building
occupants register as satisfied with their workspace
thermal environment.5,6 In addition, though evidence
is still considered inconsistent, some studies now show
that providing a fresher workspace environment with
reduced CO2 levels may significantly improve cognitive
capacity, which leads to work performance gains
that could be even larger than those from improving
comfort.7-9
Every bit as important in terms of the effect on
office work performance is the way modern offices
are configured. Open plan office spaces are at times
favored because they facilitate the long-standing
method of mixing conditioning air with room air and
reduce the likelihood of stagnant air areas. But these
more open office configurations allow an easy path
for pathogen transmission.10 Also, research has found
work performance reductions of more than 20% in open
offices compared to partitioned private workspaces for
work that requires concentration.11 The " awfulness " of
open offices is being ever widely expressed-with studies
sometimes cited to back up the claim.12
While additional research is needed to better quantify
some of these work performance factors and the
interaction among them, it can be estimated with some
confidence based on published averages for office
building occupant density, profit margins and costs
along with the performance research cited above that
improving thermal comfort satisfaction alone could
increase a typical office building's net financial bottom
line with improved work performance by more than
$10/ft2 ($108/m2) each year.13-16
By including conservative estimates for the effects
that better overall conditioning combined with
improved workspace layouts could have on all work
performance, absenteeism and turnover, the total
financial opportunity is easily several times this value
for typical offices-a huge financial opportunity for
firms that occupy these buildings. While this work
performance value metric, along with a focus on
occupant satisfaction, has historically been considered
only indirectly-if it is considered at all, it may become
28
ASHRAE JOURNAL ashrae.org S E PTEM B ER 2023
increasingly important as building owners and tenants
look to encourage the return of workers to the office.
Comfort Standard Developments
ASHRAE Standard 55 defines relationships that
determine the level of thermal comfort in buildings.
Four are environmental thermal comfort components or
factors, space temperature, mean radiant temperature,
air movement and humidity; and two are personal
factors, clothing and activity levels. However, there
is a developing recognition that other environmental
thermal comfort factors beyond those considered in
Standard 55 and differences among individuals yield
variances in thermal comfort preferences17 that can only
be accommodated by some degree of individualized
thermal control for each workspace.
It has become increasingly clear that the industry's
long-standing practice of configuring large multiworkspace
zones with limited local control cannot
ensure the thermal preferences of many occupants will
be satisfied. As a result, Section 6 of Standard 55-2020
requires designers to designate the classification of
thermal environmental control that is to be provided
in each occupied space type. The classification ranges
from 5: no occupant control, to 1: control of at least two
separate comfort factors or measures for each occupant
with minimum thermal comfort corrective power (CP)
requirements specified in the standard.
This, for the first time, encourages designers
to consider how individual occupants at their
workspaces are to be thermally satisfied instead of
presuming a conventional zone-wide diffused mixed
air-conditioning arrangement will achieve suitable
thermal comfort conditions for occupants throughout
each zone. And this new feature of Standard 55-2020
encourages systems that control more than just space
temperature for thermal comfort in office spaces.
To assist designers and manufacturers, work is
being done to estimate the CP of personal devices
that can manipulate comfort factors beyond air
temperature. Of these, the use of localized low
velocity air movement is best understood and is
already incorporated into the Center for the Built
Environment's online Thermal Comfort Tool,18 which
is a web-based tool for thermal comfort calculations
according to ASHRAE Standard 55-2020. Information
is now available to calculate air movement and CP
for small ceiling fans,19 or desk fans, along with an
http://www.ashrae.org
ASHRAE Journal - September 2023

Table of Contents for the Digital Edition of ASHRAE Journal - September 2023
