Abstract/Summary

This study investigated the seasonal impact of indoor plants on the humidity and air temperature of three naturally-ventilated, unoccupied offices, with low air exchange rates. The introduction of 12 Ficus or 6 Epipremnum plants resulted in a small but significant increase in the office’s (28 m3) moisture content, measured every 5 minutes for 24-hour periods for up to six test days during spring and winter, compared to the days without plants. Depending on the season, plants emitted between 35 g (in winter) and 68 g (in summer) of moisture via evapo-transpiration (ET), per plant, per day. In summer, however, due to higher room air exchange rates, we did not detect significant impact of plants despite higher plants’ ET rates. Most of the moisture emitted from the plants in all seasons was removed through room air exchange and moisture sorption. Air exchange rate had a greater impact on indoor RH than plants. Additional controlled-environment chamber studies showed there is a significant difference in the humidification capacity between five different indoor plant species. Leafy Epipremnum had the highest ET rate under all tested environmental conditions and would have the greatest humidification potential for indoor environments. Succulent Sansevieria had the lowest ET rate, not significantly higher than bare substrate; this species would present a good choice for environments where a low moisture contribution is required. ET rates were highest at low ambient humidity and high temperatures; thus, the greatest water vapour contribution by plants would be made to hot, dry indoor environments and lower in cool rooms with high humidity levels.