Simulation Case-study on Outdoor Air Quality Demand Controlled Ventilation

Ventilation systems assume that the outdoor air quality is better than the indoor air quality at al times as they use outdoor air to dilute pollutants emitted by humans, activities, the building itself and other objects. However, the outdoor air quality is not always as clean as assumed. Traffic, industry and agriculture can pollute the outdoor air making the outdoor air also a source of certain unhealthy pollutants indoors. This challenges the before stated assumption as in this case less ventilation would lower this source of pollution to the indoor environment.
A reference apartment for Belgium is simulated considering 4 categories of outdoor pollutants (NO2, Ozone, PM2.5 and PM10 for a street in the city-center of Antwerp, Belgium provided by aircheckr) and two indoor pollutants generated by the 4 occupants and their activities (CO2 and H20). In this apartment, 3 variations of a control algorithm both taking into account the outdoor- and indoor air quality are simulated and compared to a control algorithm only taking into account the indoor air quality. Results are evaluated for three aspects: health, comfort and energy use. The system that does not consider outdoor pollution can safeguard the comfort of the occupants the best but also leads to the highest energy consumption and highest exposure to unhealthy outdoor pollutants. For each other case, a trade-off is made between the three aspects. Allowing higher peak exposures to CO2 and H20 during times of unhealthy outdoor air quality leads to less energy use and less exposure to unhealthy outdoor air.
A clear potential for the consideration of outdoor air quality in demand controlled ventilation systems can be concluded as not only health is improved but also energy is saved. In practice however, it will be necesarry to quantify the state of both the indoor air quality and the outdoor quality and compare these in a more holistic manner than presented in these results.