In southern Europe, the present stock of social housing is ventilated naturally, with practice
varying in the di erent seasons of the year. In winter, windows are kept closed most of the day
with the exception of short periods for ventilation, whereas the rest of the year the windows are
almost permanently open. In cold weather, air changes depend primarily on the air infiltrating
across the envelope and when the temperature is warm, on the air flowing in through open windows.
CO2, PM2.5, and TVOC concentration patterns were gathered over a year’s time in three social
housing developments in southern Europe with di erent airtightness conditions and analyzed to
determine possible relationships between environmental parameters and occupants’ use profiles.
Correlations were found between TVOC and CO2 concentrations, for human activity was identified
as the primary source of indoor contaminants: peak TVOC concentrations were related to specific
household activities such as cooking or leisure. Indoor and outdoor PM2.5 concentrations were
likewise observed to be correlated, although not linearly due to the presence of indoor sources.
Ventilation as presently practiced in winter appears to be insufficient to dilute indoor contaminants in
all three buildings, nor does summertime behavior guarantee air quality
