A new study by The Royal Horticultural Society (RHS) and University of Reading has found that ivy is the most effective plant cover for cooling buildings and reducing humidity.
The paper looked at the impact of three plant species (Hedera helix – ivy, Parthenocissus tricuspidata – Virginia creeper, and Pileostegia viburnoides – climbing hydrangea) on temperature and humidity when grown as building cover. The experiment used model mini buildings and the study was carried out in the summer and winter.
All plant species reduced the air temperature internally and externally during the summer daytimes by at least 1oC compared to bare ‘buildings’.
The evidence showed that the best plant for summer cooling was provided by ivy. It was able to reduce the internal and external wall temperature by 7.2oC and 5.7oC respectively. Not only did ivy provide the best summer cooling for buildings, but it also demonstrated the greatest summer reduction in daily variation of relative humidity (RH).
Dr Tijana Blanuša2, RHS Principal Horticultural Scientist said: ‘Our research is an important step forward in growing our understanding of green walls.
‘The RHS has been keen to encourage new ways of gardening and the development of technically simple vertical green walls using affordable climbing plants has proved to be a welcome addition. I hope that this research will help people decide which plants they want to grow.’
In spring 2021, the RHS is opening its new Centre for Horticultural Science and Learning at its flagship RHS Garden Wisley.