As summer temperatures soar across the United States and Europe, cities are being forced to confront the difficult reality that they’re getting dangerously hot.

Record-breaking heat waves strain power grids, send people to cooling shelters and can make the top floors of some apartment buildings unlivable.

One way to help cool buildings is to install green roofs – living rooftops covered by plants that can transform heat-absorbing rooftops into cooling solutions.

Green roofs have long been promoted as a method to help cities stay cool. Often cities offer developers incentives to install them. But just building a green roof isn’t enough.

Our research shows that what happens after a green roof is built is as important as the decision to install a green roof in the first place. We found that many green roofs fall into neglect and don’t survive beyond a few years, likely due to the cost of maintenance. When buildings’ operational budgets are cut, landscape elements – including green roofs – are often altered or maintenance is scaled back to save money.

What is a green roof?

Unlike a traditional roof made of asphalt, metal or tiles, a green roof is made up of layers, including insulation, water proofing and drainage, that allow plants to grow atop the building.

Depending on their design, these roofs can support everything from low-growing sedums to shrubs and trees. Rockefeller Center’s rooftop terrace gardens in New York City were designed in the 1930s to hold trees, grass, shrubs and seating areas to double as........

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