The concept of “green roofs” is not new, dating back to ancient Rome and Mesopotamia. Now, researchers are looking for ways to make this ancient concept more sustainable and cost-effective. Europe is now focusing on research and product development as the foundation for the green roof industry.

A 2023 study by the University of Technology Sydney found that green roofs, when combined with solar panels, not only increased biodiversity and solar power output by 107%, but also reduced temperatures by 8oC.

Green roofs have gained traction since recent research showed that adding volcanic ash to roofs can stabilize temperatures, suppress weeds, withstand extreme weather, drain water efficiently, and require little maintenance. Germany, Switzerland, and Scandinavia have done much of the pioneering research.

According to the German Green Building Association (BuGG), Germany will have accumulated around 3.1 million ^square kilometers of green roofs by the 2020s. In 2015, France became the first country to pass a nationwide law requiring the roofs of new commercial buildings to have plants or solar panels.

According to the latest market research, the green roof sector in North America has grown by more than 45%, with about 1,215 green roof projects. Chicago, which has more green roofs than any other city in the US, installed about 56,000 ^{square meters} of green roofs last year and plans to implement 600 projects to bring the total number of green roofs to about 650,000 ^{square meters} .

North American green roof research started later than in Europe. Environmental consultancy American Rivers estimates that a $10 billion investment in green roofs could create 190,000 jobs and cover 4.5 billion ^square meters of rooftop space.

Despite growing awareness of carbon neutrality and environmental concerns, green roofs still face barriers in terms of investment, cost, and trust, said Dr. Chris Lawson, senior designer at CK Architectural. Some areas offer incentives for building owners and developers to install green roofs. For example, the City of Philadelphia offers a tax credit that covers 50 percent of the cost of a green roof up to $100,000.

Large eco-resorts are also seeing the benefits of green roofs. At the NH Collection Copenhagen hotel in Denmark, 3,000 ^square meters of sedum cover most of the roof. The plants are aesthetically appealing, changing from green to yellow and pale pink, while absorbing 50% to 70% of rainfall.

Guests at the H2hotel in Healdsburg have been asking for a living roof with flowers, birds and bees, says Circe Sher, co-founder of Piazza Hospitality. The roof is 75 percent green, mimicking the surrounding hills.

David Goldberg, director of Stensgar Pavilion Design at Coeur d'Alene Casino Resort Hotel, Idaho, USA, said the board wanted to showcase the environmental benefits of living roofs, such as reducing heating and cooling loads, creating a living environment and managing stormwater.

As green roofs continue to grow, their potential to transform urban landscapes is becoming increasingly clear. With proven benefits such as increased biodiversity, energy efficiency and stormwater management, the future of green roofs is expected to be even more beneficial.

LAM DIEN