The Irish people have always worshipped trees, but there is a new reason to be feeling good about our arboreal friends.
Even a single urban tree can help moderate wind speeds and keep pedestrians comfortable as they walk down the street.
How do we know this? Because boffins at the University of British Columbia studied what effect trees had on the street they grew in. Losing a single tree can increase wind pressure on nearby buildings and drive up heating costs.
The researchers used remote-sensing laser technology to create a highly detailed computer model of a neighbourhood down to every tree, plant and building. They then used computer simulation to determine how different scenarios – no trees, bare trees, and trees in full leaf – affect airflow and heat patterns around individual streets and houses.
“We found that removing all trees can increase wind speed by a factor of two, which would make a noticeable difference to someone walking down the street. For example, a 15 km/h wind speed is pleasant, whereas walking in 30 km/h wind is more challenging,” said lead author Marco Giometto, who wrote the paper as a postdoctoral fellow in civil engineering at UBC.
Trees also moderated the impact of wind pressure on buildings, particularly when it goes through small gaps in and between buildings.
“Wind pressure is responsible for as much as a third of a building’s energy consumption. Using our model, we found that removing all the trees around buildings drove up the building’s energy consumption by as much as 10 per cent in winter and 15 per cent in summer,” said Giometto.
The researchers also discovered that even bare trees in the winter months can moderate airflow and wind pressure, contributing to a more comfortable environment. Even bare branches play a role. Deciduous trees, which shed their leaves every year, reduce pressure loading on buildings throughout the year. So it’s not only evergreens that are important in the city.
Information from such models can help city planners in designing buildings, streets, and city blocks to maximise people’s comfort and limit wind speed to reduce energy loss.
So there you go, the Irish were right about trees all along.