France Leads the Way With Green Roof Revolution
France has become the first country to mandate green roofs on new commercial buildings nationwide in an effort to combat the urban heat island effect. As of January 2022, a groundbreaking law requires that all new structures built in commercial zones have either solar panels or vegetation covering at least 30% of their roof.
The bold policy demonstrates France’s commitment to leveraging natural climate solutions and decreasing the environmental footprint of its built environment. But what exactly are green roofs, and how can they benefit cities facing hotter temperatures?
What is a Green Roof?
A green roof, also known as a living roof, is a layer of vegetation installed on top of a conventional flat or sloped roof. The “green” roofing system consists of waterproofing material, drainage components, lightweight soil, and hardy plant cover.
Green roofs can be as simple as a 2-inch layer of hardy succulent plants like sedum. More complex systems have diverse mixes of grasses, herbaceous plants, and even shrubs growing in several inches of lightweight soil. Accessible green roofs function as elevated parks or gardens.
Green Roof Benefits
Requiring green roofs on commercial buildings provides France numerous interlinked benefits:
- Urban cooling – Plants and soil reduce summer air temperatures through shading and evapotranspiration. Green roofs can decrease surface temperatures by up to 80F.
- Stormwater management – Soils absorb and retain rainfall, reducing runoff. Paris saw a 5% drop in runoff from increased green roofs.
- Improved air quality – Vegetation filters pollutants and dust while increasing oxygenation.
- Biodiversity – Green roofs support bees, birds and other urban wildlife by providing habitat.
- Energy savings – Evaporative cooling and added insulation reduces HVAC costs. Chicago’s City Hall saw $5,000 annual energy savings after adding a green roof.
- Mitigating heat island – Less heat radiates to the surrounding area, reducing the “heat island” effect.
Paris Leads Europe in Green Roofs
France’s new national green roof legislation follows pioneering efforts by Paris over the last decade. Since 2008, Paris has required green roofs on all new buildings or renovations over 5000 m2. There are now over 200 green roofs covering over 180,000 m2 across the city. This includes iconic sites like the Musée du Quai Branly and Opéra Garnier.
“Paris has emerged as a laboratory for green roofs” according to city environment official Paul Youru. The city has an ambitious goal of adding 100 hectares of vegetation across walls and roofs by 2020 to combat rising temperatures. France is now looking to take Paris’ successful green roof model countrywide.
Growing Movement Worldwide
While pioneering, France’s legislation reflects a broader movement to naturalize cities. Toronto mandates green roofs on industrial and residential buildings. Singapore aims to cover 80% of its buildings in greenery by 2030.
With cities facing hotter summers and intensifying storms, forward-thinking urban planners view green roofs as critical infrastructure investments. Nature-based solutions allow cities to build resilience while improving liveability.
Despite the benefits, barriers to mainstream green roof adoption remain. Key challenges include:
- Costs – Green roofs have higher upfront installation costs compared to conventional materials. Lifecycle cost savings from energy and stormwater benefits are important to consider.
- Structural requirements – Buildings may require reinforcement to support the weight of soil, plants and retained water.
- Maintenance – Although low compared to gardens, green roofs need occasional maintenance like weeding and irrigation.
- Lack of incentives – More cities need to follow France’s model in creating codes and incentives for green roofs.
However, as green roof industry matures, the costs continue to fall. With proper policy support, the scale of France’s new requirements will drive rapid cost decreases in coming years.
An Inspiring Policy for Sustainable Cities
France’s ambitious law signals the massive potential for green roofs to make cities environmentally sustainable and climate-resilient. As an innovator in using nature-based solutions to combat urban heat islands, France also hopes its legislation will inspire other countries.
The 2022 law could prove a historic policy accelerating green roof adoption worldwide. If even a fraction of the world’s billions of square feet of rooftops turn green, cities may realize transformative environmental benefits from above. France’s legislative journey will be watched closely by urban sustainability advocates across the globe.