When it comes to designing an energy-efficient city, think green. Even a single, leafless tree can serve as a significant windbreak for pedestrians. But, more importantly, trees also block wind pressure on buildings which helps keep heating costs down, according to a study published in the journal Advances in Water Resources.

Why it matters: Everyone knows a windy day feels cooler than a still one – the same is true for buildings. As much as one-third of a building's heat loss and energy consumption can be caused by wind pressure. Past models and observational studies have shown how trees impact wind in cities, but this is the first time scientists have simulated the effects in a real, replicated neighborhood.

What they did: The scientists created a computer model of Vancouver that included every building and tree. They modeled airflow around the buildings in three scenarios: one with leafy summer trees, leafless winter trees, and no trees at all.

"Using our model, we found that removing all the trees around buildings drove up the building's energy consumption by as much as 10% in winter and 15% in summer," said Marco Giometto, a civil engineer at the University of British Columbia in Vancouver and an author on the study.

The bottom line: Trees make a difference in cities even in the wintertime. Even bare winter branches reduced pressure on the buildings, the research showed.