I/O ratio

In recent years, population exposure to air pollution has been a major concern. Indoor air quality (IAQ) is mainly monitored with CO2-concentration-based indicators. High levels of CO2-concentration are avoided in buildings when airing by the windows is done and/or when air exchange rate of the existing ventilation is regulated, based on a CO2-level-information. However, as contributing to maintain low CO2-concentration-levels indoors, the increase of outdoor air intake is associated with a more or less important introduction of outdoor air pollutants in the building.

Naturally ventilated (NV) buildings, when well designed and operated, can provide adequate indoor environmental quality (IEQ) while reducing the building energy demand. However, in dusty outdoor air, this ventilation technique may increase the penetration of outdoor particulate matter (PM) indoors, leading to adverse health effects. Given the increasing frequency of outdoor dust episodes in Mediterranean climates, an important research question is whether NV buildings can provide adequate indoor air quality (IAQ) during increased outdoor air dust episodes.

According to past researches, most people spend 80%-90% of their time indoors. The ventilation is very important to people’s health and the comfortable surroundings around us. From the viewpoint of energy saving, mechanical ventilation will consume a large amount of additional energy. So variety of ways measuring natural ventilation is worth considering. In fact, in real life, many people tend to have their windows shut rather than open, and the reasons are complex.