Front runners to inspire you to build green roofs

by Elizaveta Fakirova – 15.04.24

There’s a growing trend of implementing green rooftops across the globe. Through this, authorities strive to create new leisure spaces, improve ecological balance, and nurture wildlife. So, what steps should cities take to breathe life into their urban landscapes and offer residents a vibrant ‘fifth facade’? Elizaveta Fakirova, during her scholarship at the German Chancellor Fellowship, shared her insights with Plus-one.ru in an article in  2021 which she shares with us here again.

Cover image: London, the garden above The Crossrail Station, credits: iStock

Green roofs offer innovative solutions to urban challenges, providing additional green spaces in densely built-up areas with limited room for new parks and gardens. Plants on rooftops purify the air by capturing dust and harmful pollutants, while also serving as habitats for birds, butterflies, and other insects. Moreover, green roofs absorb rainfall, reducing pressure on stormwater drainage systems and minimizing the risk of urban flooding.

When designing these solutions, urban authorities employ various tools and pursue diverse goals. Examples from Basel, Berlin, and London showcase three distinct approaches. In Basel, the aim was to reduce energy consumption; in Berlin, to improve the ecological situation; and in London, to preserve dwindling urban bird species. Now, let’s explore how they turned these visions into reality.

BASEL

Basel, Switzerland, stands as the undisputed European leader in green roof coverage per capita, boasting an impressive 5.2 square meters per person. These findings stem from an unpublished study conducted in 2015 by experts from Humboldt University.

In the early 1990s, Basel’s authorities enacted the country’s first law to reduce energy consumption, with green roofs emerging as one of its pivotal measures. Green rooftops act as an additional layer of insulation, preventing overheating in the summer and retaining warmth during winter. This ingenious strategy has led to significant energy savings in heating and cooling buildings.

Thanks to Basel’s semi-cantonal status, innovative technologies were implemented rapidly. The city operates to a certain extent independently of the surrounding region, and such autonomy contributed to the swift implementation of innovative solutions.

The introduction of green roofs was facilitated through a combination of financial incentives, changes in building regulations, and educational campaigns. In 1996-1997 and 2005-2006, the state’s Energy Conservation Fund launched a subsidy program for private developers and residents to encourage the implementation of green roofs. 5% of all electricity payments made to the fund were allocated to programs aimed at energy conservation.

During the first campaign period, 135 subsidy applications were received, resulting in the greening of 85,000 square meters of rooftops and an annual energy saving of 4 GW. Encouraged by these outcomes, authorities allocated funds to study the impact of green infrastructure on rare plant and animal species. The city regularly held competitions for the best rooftop greening projects and launched a series of promotional campaigns to showcase the program’s results.

In 2002, an amendment to the Building Law was passed: all new and reconstructed flat roofs had to be greened. By 2006, almost a quarter of all roofs had transformed into green spaces. The amendments remain in effect to this day, with developers commonly integrating gardens or vegetable patches atop their buildings.

Even large-area rooftops, like those of the Stücki shopping center (35,000 square meters) and the Basel trade and industrial center (8,000 square meters) have been tansforemd into green rooftops. Solar panels have also been installed on the latter, and the energy generated is sold back to the city.

BERLIN

The history of green roofs in Berlin traces back to the 1980s with the emergence of the Green Party. Stemming from the environmental movements of the 1970s against nuclear energy and pollution, the quest for a cleaner city has remained a prominent theme for Berliners.

In 1983, West Berlin initiated a state program to increase greenery by greening courtyards, facades, and rooftops in densely built-up areas. 

Over 12 years, 1,643 projects were approved, greening 740,000 square meters of facades and courtyards (equivalent to the size of 105 football fields) and 65,000 square meters of rooftops.

By 1996, the city shifted from direct funding to indirect incentives. Property owners were mandated to pay a stormwater tax, with green roofs serving as “sponges” to absorb rainfall. The less water that entered the drainage system, the lower the tax.

In 1997, Berlin introduced a Biotope Area Factor (BAF), determining the portion of a building’s surface area that must be allocated to greenery. For instance, new residential buildings have a coefficient of 0.6. This coefficient is calculated based on the sum of the values ​​of all surfaces divided by the total built-up area. Impermeable surfaces like concrete have a coefficient of 0 per square meter, while green roofs range from 0.5 to 0.8 per square meter, depending on the type of greening. This system preserves developers’ freedom to choose technologies and balances construction and greening. Similar green coefficient systems have been introduced in the UK, Sweden, Finland, and other countries.

The reunification of East and West Berlin allowed the implementation of the revolutionary “blue-green” infrastructure project in the city center. The reconstructed Potsdamer Platz complex, comprising 19 buildings, stands as a symbol of the new Berlin. 

30,000 square meters of green roofs, artificial ponds, and underground reservoirs collect 80% of rainfall.

Water absorbed by green roofs undergoes purification and is directed to cover the building’s needs. During summer, the greenery and ponds cool the air temperature by 2-3 °C.

By 2019, Berlin had created 18,000 green roofs, accounting for only 4% of the total rooftop area. In the same year, the “1000 Green Roofs” program was launched, offering partial reimbursement to citizens for roof landscaping expenses.

LONDON

In London, the capital of the United Kingdom, the widespread greening of rooftops began a decade ago, during a construction and reconstruction boom in the city center. As of 2017, green roofs covered 290,000 square meters — an area equivalent to 40 football fields — translating to 1.26 square meters per Londoner.

The massive construction efforts took a toll on the population of the black redstart — a small urban songbird often nesting in abandoned areas. To prevent its disappearance, green roof professionals began replicating its familiar habitats using recycled gravel and brick fillings. The first roof covering 400 square meters was installed atop the Laban Dance Centre in 2003.

Rooftop greening became part of the city’s comprehensive development program and was also integrated into the Mayor’s Biodiversity Strategy and Climate Change Adaptation Strategy. 

London is a unique case worldwide, as the city didn’t provide subsidies or support to developers. Similar to Berlin, green roofs allow developers to meet the required greening coefficient and obtain construction permits.

A prime example is the Woodberry Down residential complex, where a landscaped area of 25.8 hectares is linked to the Woodberry Wetlands reserve. Green roofs covering 4,700 square meters serve as popular recreational spots for city dwellers and as nesting sites for swallows and other birds.

An interactive map showcasing green roofs in each London borough can be found on the livingroofs.org website, with data available up to 2017. Although the latest data were collected in 2019, they have yet to be published.

What cities can do

The European experience underscores a vital lesson: greening urban rooftops necessitates robust government support at federal, regional, and local levels. Here are some engaging tools the EU employs to embrace green roofs:

• Implementing requirements for greening coefficient, stormwater management  and urban planning. They can be used to stipulate the need to create green roofs on a mandatory basis.
• Direct financial support. State grants and subsidies.
• Indirect financial support. Reduction of taxes or crediting green roofs as compensation for trees cut down during construction.
• Underscoring the use of green infrastructure to achieve the SDGs. Green infrastructure can be used to achieve Sustainable Development Goals, primarily No. 3 – “Good Health and Well-being,” No. 11 – “Sustainable Cities and Communities,” No. 15 – “Life on land.” But this is recommendatory.
• Education. Increasing the awareness of residents through the publication of the results of scientific research, educational programs, and publications in the media.

INTERESTING FACTS:

1. 1 sq.m. of green roof can capture 137 litres of water that is equivalent to one bathtub.
2. 6th June is the World Green Roof Day. Save the date!

KEY TAKEAWAYS:

1. Roofs can be more than just green!
2. Independently on what type of green roof you would prefer to employ, it brings benefits to the city and its citizens

DO YOU WANT TO KNOW MORE:

1. Join us at the “Rooftops can be more than just green!” discussion on April 16 
2. Check out our latest WTG? Podcast episode titled “Transforming cities, one green roof at a time“, featuring Olivier Faber from Roofscapes Studio 
3. Rooftop Catalogue developed by MVRDV 
4. Multifunctional Roofs & How to Implement Them in Your City 
5. Check out the TEDxTalk: Elizaveta Fakirova: Your Roof Can Fix Climate Change