APPENDIX C (continued)
The Bioclimatic Chart. The bioclimatic chart, (see Figure 4), can
be used to determine whether comfort will be achieved at a given time when the
interior air velocity, air temperature, and humidity levels are known.
The procedure for determining comfort using the bioclimatic chart is the same
as that described in Appendix A, para. 1.4, except that expected interior
conditions rather than the exterior climatic conditions are plotted. The
effects of the building envelope and the internal gains due to people, lights,
equipment, and solar gain are factored into the expected interior temperature
and humidity levels based on the daily average, monthly average, specific hour
of the day, or other long-term climate data (see Appendix C, para. 2.2). If
the plotted point falls at or below the expected interior air velocity, then
comfort can be expected for that space under the specified conditions.
The J.B. Pierce Human Thermoregulatory System Model. The J.B.
Pierce two-node mathematical model of the human thermoregulatory system is the
most appropriate computer model for predicting human comfort under natural
ventilation conditions. The model is a "rational" index, derived in a logical
manner from established principles of heat transfer physics. It describes
through empirical equations the effects of the body's thermoregulatory
controls. (Refer also Appendix A, Section 1.)
The model has been tested against human experiments and found to be
effective at conditions near the comfort zone with subjects under low to
moderate activity. It may underestimate convective (air movement) heat loss
at higher wind velocities because it does not differentiate between clothed
and exposed skin areas of the body.
The model is of the body only, requiring manual input of climatic
conditions. To use it to predict percentages of time that a building will be
comfortable, the designer must modify it to read hourly weather data files or
the hourly output of a thermal loads program.