environmental variables were not covered in the algorithms [20,21].
In addition, ASHRAE proposed and used the effective temperature,
ET, from 1919 till 1967 [22]. In 1971, Gagge introduced ETn which
was more accurate than ET because it covers simultaneously
radiation, convection and evaporation. Table 1 shows the development
of indices related thermal comfort.
In parallel, Fanger [39] developed theories of human body heat
exchange. Fanger stated that the human body strives towards
thermal equilibrium. He proposed the following formula: