Researchers develop AI-powered tool to map sustainable roofs globally
As cities around the world continue to urbanize, there is a greater need to expand and optimize existing spaces. Cities have accelerated research into how underutilized rooftop spaces can contribute to climate action, food production and other purposes. Sustainable roofs, such as green roofs and photovoltaic panels, can contribute to the roadmap for reducing cities’ carbon footprints, but while studies have been done to measure their potential, few are tracking the actual performance of cities.
To address this, Dr. Filip Biljecki, Presidential Young Professor of the Department of Architecture at the National University of Singapore (NUS) School of Design and Environment, and NUS Master of Architecture, Mr. Abraham Noah Wu, have developed an automated tool that uses satellite imagery to track how rooftops around the world are adopting solar panels and/or vegetation. Known as Roofpedia, it uses a fully convolutional neural network (deep learning) that allows researchers and policymakers to study how cities around the world are greening their roofs and using them for photovoltaic installations.
This is a research project under the NUS Urban Analytics Lab, a multidisciplinary research group at the NUS School of Design and Environment. Their research has been published in the international journal Landscape and urban planning.
Tracking the adoption of solar and green roofs in 17 cities
With Roofpedia, the researchers created an open roof registry with data from 1 million roofs in 17 morphological and geographical cities, spread across Europe, North America, Australia and Asia. These cities are: Berlin, Copenhagen, Las Vegas, Los Angeles, Luxembourg, Melbourne, New York, Paris, Phoenix, Portland, San Diego, San Francisco, San Jose, Seattle, Singapore, Vancouver and Zurich.
Using this data, the researchers developed the Roofpedia Index, to benchmark the cities based on the degree of sustainable roof landscape in terms of solar energy penetration and green roofs. This is derived by considering both the surface coverage and the number of buildings with solar and green roofs in a city as a percentage value of the entire area.
Zurich received an index score of 100 due to its high scores for both area coverage and number of green roof buildings. The high green roof coverage is the result of efforts by the Zurich city government to make green roofs mandatory for all new buildings since 1991. Las Vegas topped the index with a score of 86. This may be due to the high solar potential of the geographical area.
By collecting such data, Roofpedia makes it possible to measure how cities can further use their roofs to reduce CO2 emissions and how much untapped potential their roof landscape has. For example, users can supplement Roofpedia with other data sources to measure the effectiveness of government subsidies. In addition, by collecting current data from satellite imagery, users can more accurately determine the current carbon offsetting capacity of cities,” said Dr. Biljecki.
Roofpedia ranks Singapore third in solar roof coverage
Based on the Roofpedia Index, Singapore ranks third out of 17 cities, with a score of 75, for the application of solar energy on roofs, behind Las Vegas (score of 86) and Zurich (score of 81). The scores in the Index have normalized, and while Singapore ranks high in total area, it lags behind some other cities in having relatively fewer buildings equipped with solar panels.