*2.1.1 Ventilation and thermal comfort*

Ventilation systems are designed and incorporated in buildings to provide comfortable microclimates in the ventilated spaces [16]. The microclimate in this circumstance includes a thermal environment and air quality [21]. Therefore, in the design of natural ventilation systems these two factors (providing acceptable air quality and thermal comfort environment) are considered.

The human body's thermal balance are considered to be affected by four environmental factors (air temperature, mean radiant temperature, air velocity and


**Table 1.**

*Ventilation rates required to limit CO2 concentrations [18].*

water vapour pressure in the air) [22] and three human factors (metabolism, activity and thermal insulation of clothing) [23].
