Interviews
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1/9/2026
Green design
Landscape architect Franco Giorgetta discusses the evolution of green roofs between design vision and urban benefits
This interview with landscape architect Franco Giorgetta traces the historical evolution and contemporary relevance of green roofs, highlighting their transition from ancient practices to a recognised component of sustainable urban architecture. Giorgetta discusses the environmental, climatic and architectural benefits of green roofs, including improved energy efficiency, enhanced rainwater management, increased biodiversity and better overall urban well-being.
From early applications to sustainable architecture: when did green roofs become a recognised trend in urban and architectural design?
Green roofs as a form of “sustainable architecture” have ancient, perhaps even prehistoric origins. They continued to be used until the early 20th century in simple rural buildings, where roofing with plant material offered low-cost solutions with the added benefit of thermal insulation. Without considering the famous Hanging Gardens of Babylon, green terraces were already present in Roman architecture and were later adopted in several celebrated Renaissance buildings such as the Ducal Palace in Urbino, the Farnese Palace in Rome and the 18th-century garden of Palazzo Maffei in Verona. In reality, the latter was more of a feasibility challenge and was eventually abandoned because of water seepage issues. Today, thanks to effective waterproofing and other protective technical measures, such problems no longer exist. Yet even in the early 1980s, the creation of a green terrace with lawn and birch trees in Milan was considered something of a novelty, as reported by the newly launched magazine Gardenia in an article entitled “Il Prato sul Terrazzo” (“The Lawn on the Terrace”). Time has passed, but mistrust of green roofs remains. In reality, though, roof and terrace gardens today no longer pose problems, even in the case of large-size green installations such as Emilio Ambasz’s tree-covered projects in the 1970s and the “small Lombard forest” designed for the new Lombardy Regional Government headquarters in Milan, a project that was later cancelled during construction, perhaps due to scepticism.
What are the ecological, climatic and architectural benefits of green roofs, both for the urban environment and for the buildings themselves?
The benefits are evident for both the urban environment and buildings, including improved energy performance thanks to the insulation and thermal inertia of the vegetation-soil-water system. In particular, green roofs lower summer temperatures through the combined effect of reduced solar absorption and transpiration of the green covering. These energy savings also make a positive contribution to the building’s carbon footprint.
Alongside the energy benefits, another important factor is the control and management of rainwater, which is absorbed by the substrate and water-retention systems and then released gradually. Last but not least, green roofs offer opportunities for leisure activities such as gardening and horticulture and make a positive contribution to residents’ quality of life and well-being. Added to these are all the benefits of a healthy environment, increased biodiversity and mitigation of visual, aesthetic and sensory pollution.
1,700,000 species of plants have been planted on the undulating roof of the California Academy of Science in San Francisco, designed by Renzo Piano.
Are there any architects or design firms you consider pioneers or who played a particularly significant role in the use of this type of roofing?
I have already mentioned Emilio Ambasz, and perhaps Stefano Boeri’s famous Vertical Forest could also be cited, although the plants actually grow in containers rather than on a waterproofed slab. Renzo Piano’s wonderful projects are also worth recalling. One is the California Academy of Sciences in San Francisco with its undulating roof completed covered in greenery, a “living roof” consisting of 1.7 million native plants that blend perfectly into California’s natural landscape. Another is the Stavros Niarchos Foundation Cultural Centre in Athens with its gently sloping 17,000 m2 roof. Rising from ground level to a 30-m-high belvedere, it forms a large roof garden planted with 1,440 trees and 300,000 Mediterranean shrubs.
Could you tell us about a project you are particularly fond of?
Yes, the one I mentioned earlier: the small Lombard Forest planned for the roof of the new Lombardy Regional Government tower in Milan. The project began in the plaza, characterised by the presence of boulders from the Lombardy mountains and cherry tree-covered hillocks at street level yet suspended above the railway tunnel roof. Above this, the flat roofs were largely conceived as green spaces with water-retention systems and planted with mountain pine, juniper, holly, rosemary and lavender. But the most interesting feature was supposed to be placed at the very top. In agreement with the architects – Paolo Caputo’s studio and the New York design studio of Pei Cobb Freed & Partners – we had planned to leave the top five levels of the tallest tower completely open to the sky, using the mezzanine below to hold a 1.5-m layer of soil that would have served as an inert mass counteracting oscillations. That vast open-air hall was to have been filled with a small Lombard Forest. This space, with only a small, enclosed service block and lift landing, was to have become the centrepiece of the entire building. During construction, however, the project was cancelled, and the four upper floors were sadly left empty.
Studio Giorgetta
The Giorgetta studio, founded by architect Franco Giorgetta, began operating in 1965 and specialises in landscape architecture, with many important projects and achievements in Italy and internationally.
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