Appendix C 405
- concentrations of pollutants and odors in indoor air and amount
of pollutants on surfaces; - lighting intensity and quality;
This document provides more detailed information on indoor air
pollution than on thermal comfort and lighting because the users of the
IPMVP are less likely to be knowledgeable about indoor air pollution.
4.2 INDOOR THERMAL CONDITIONS
The influence of the indoor thermal environment on thermal com-
fort is widely recognized. Thermal comfort has been studied for decades
resulting in thermal comfort standards and models for predicting the
level of satisfaction with the thermal environment as a function of the
occupants clothing and activity level
(ASHRAE 1997). Despite the significant attention placed on thermal
comfort by building professionals, dissatisfaction with indoor thermal
conditions is the most common source of occupant complaints in office
buildings (Federspiel 1998). In a large field study (Schiller et al. 1988), less
than 25% of the subjects were moderately satisfied or very satisfied with
air temperature. Also, 22% of the measured thermal conditions in the win-
ter, and almost 50% of measured thermal conditions in the summer, were
outside of the boundaries of the 1988 version of the ASHRAE thermal
comfort zone. These findings indicate that greater effort should be placed
on maintaining thermal conditions within the prescribed comfort zones.
Even in laboratory settings with uniform clothing and activity levels, it is
not possible to satisfy more than 95% of occupants by providing a single
uniform thermal environment (Fanger 1970) because thermal preferences
vary among people. Task conditioning systems that provide occupants
limited control of the air temperature and velocity in their workstation
are being explored as a means to maximize thermal comfort (e.g., Arens
et al. 1991, Bauman et al. 1993).
Extremes in humidity will adversely influence thermal comfort
(ASHRAE 1997, Chapter 8). ASHRAE s thermal comfort zones for sum-
mer and winter have a lower absolute humidity boundary of 0.045 g
H 2 O per kg dry air corresponding approximately to a 30% RH at 20.5°C
and a 20% RH at 27°C. Relative humidities below approximately 25%
have been associated with complaints of dry skin, nose, throat, and
eyes. At high humidities, discomfort will increase due substantially to