While Outdoor Green Walls help bring beautiful examples of nature back to often concrete-driven environments, they can negatively affect Indoor Air Quality. Learn more, below.
Outdoor green walls in heatwave-prone, polluted environments could be increasing pollution in office buildings and affecting worker health, new research from the University of York has found.
Concentrations of ultra–fine particles – which are a health concern as they can carry potentially toxic species into the lungs – were simulated for offices in Athens, Helsinki and Milan during heatwave conditions and for typical summer conditions.
The researchers found indoor concentrations of UFPs were highest in the Milan and Athens offices, reflecting high outdoor air pollution levels in these cities (the pollutants can make their way indoors through doors, windows and ventilation systems, as well as through gaps in the building fabric).
Indoor UFP levels were predicted to be higher in heatwave conditions, however they were well above those expected through penetration of outdoor particles alone. Further investigation found that reactive volatile organic compounds emitted by plants and trees were to blame.
Once in the atmosphere, VOCs from plants rapidly oxidise to form a range of secondary gas and particle-phase products, the researchers said, which exist in a dynamic equilibrium. During heatwaves, emissions of VOCs increase.
When outdoor air is drawn into an office air inlet, it is often filtered to partially remove outdoor particles. However, removing these particles disturbs the equilibrium of the secondary products and in order to re-establish a balance, new particles quickly form once the air reaches the office environment.