Appendix C 437
for equipment performance are often required. The ASHRAE handbooks
(e.g., ASHRAE 1992, 1995, 1997) are one source for many of the engineer-
ing calculations. Simple steady state and transient mass balance calcula-
tions for estimating pollutant concentrations in a single well-mixed zone
can be implemented by the user. Several computer programs, as reviewed
by National Laboratories (1997), are available for predicting air infiltra-
tion rates, airflows between zones, and indoor pollutant concentrations.
Proper use of these models generally requires considerable expertise in
IEQ and experience with the model. The difficulties in obtaining model
inputs are a major obstacle to IEQ modeling in multizone buildings.
7.3 SIGNIFICANCE OF PREDICTED CHANGES IN IEA
Once an expected change in IEQ is identified and, to the degree
possible, quantified, the resulting influence on occupants health, com-
fort, or productivity should be considered. The main approach for
evaluating the significance of predicted (or measured) changes in IEQ
parameters is to compare the initial and final values of these parameters
to the values listed as acceptable in the applicable standards or guide-
lines (see Table 1). hen assessing significance, the following points W
should be kept in mind: 1) Small changes in indoor temperature, on the
order of IT, may significantly influence thermal comfort, the prevalence
of acute non-specific building-related health symptoms experienced by
workers, and perceptions of air quality. 2) Occupants satisfaction with
thermal conditions may be estimated using thermal comfort models
(e.g., ASHRAE 1992b, Fountain and Huizenga 1996, ISO 1994); however,
recent research suggests that these models are imperfect because they
do not account for peoples behavioral, physiological, or psychosocial
adaptations to their thermal environments. 3) Changes in lighting are
much more likely to influence work performance if the work is unusu-
ally visually demanding.
For many pollutants, there are no published maximum concentra-
tion limits for non-industrial workplaces. The pollutant concentration
limits published for industrial workplaces, such as the Threshold Limit
Values (TLVs) of the American Conference of Governmental Industrial
Hygienists (ACGIH 1998), should not be directly applied to non-indus-
trial settings and workers.
In assessments of the significance of changes in IEQ, the sensitiv-
ity of occupants to IEQ is a consideration. Older workers tend to have
more stringent thermal comfort requirements and the vision of older