Comfort Considerations in Net ZEBs: Theory and Design - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 109

- In the psychological approach, thermal comfort is “that condition of
mind which expresses satisfaction with the thermal environment” (ISO,
2005). This definition is reported in the international standard ISO
7730. A similar definition is reported in the ASHRAE Standard 55;
although the ASHRAE definition highlights the subjective character of
such a concept by adding to the previous definition the sentence “[…]
and is assessed by subjective evaluation” (ANSI/ASHRAE, 2010).
- In the heat-balance approach, thermal sensation is related to the heat
balance of the human body with its surroundings. Thermal comfort is
the condition in which heat fluxes leaving the human body balance
those incoming and the skin temperature and the sweat rate are within
specified ranges depending on metabolic activity (Höppe, 2002).
In summary, the term thermal comfort is used to provide information about
the thermal state of an individual within a given thermal environment.
However, thermal comfort is not a single quantity that can be directly
measured; its assessment is complex. Over time, a number of models and
metrics have been proposed in the literature to quantify what thermal
comfort is by predicting optimal environmental conditions or by assessing
the predictable thermal stress caused to an individual given certain
environmental conditions. Among all the proposed models, two main
families have been used to describe the human thermal response in
moderate environments: (i) the rational (or heat-balance) and (ii) the
adaptive comfort models. These models have been used to develop
standards that will be introduced in Section 3.2.2.3.
3.2.2.1 A comfort Model Based on the Heat-Balance of the Human
Body
The heat-balance comfort model was mainly developed by Fanger and was
derived by analyzing surveys carried out on Danish students exposed to
steady-state conditions in controlled climate chambers for a 3 h period
in winter at sea level, and by modeling the heat balance of the human
body using a steady-state heat transfer model (Fanger, 1970). Fanger's
experiments showedthat(i)skin wetness mainly indicates warm discomfort
and mean skin temperature is strongly related to cold discomfort, (ii) skin
wetness and mean skin temperature are both functions of activity level, and
(iii) thermal dissatisfaction may be due to discomfort of the human body
as a whole (general discomfort) or to the involuntary heating or cooling of