Green Roofs Perks and Policies - Making our cities green one roof at a time!
Updated: Sep 1, 2020
It is a secret to none, our summers are getting hotter! If you live in Brussels as I do, it might not be obvious at first glance from the greyish sky and the meagre periods of sun we get once a week. Worry not, soon we will be praying for the rain to come back!
The reasons are multiple but to put it simply, we have less green areas to retain humidity. In turn, this means we do not have any way to keep temperatures down. Due to increased pollution levels, the sunshine has a harder time escaping the atmosphere. I feel the more scientific minds among our readers may not be content with this explanation, but worry not! The topic of this article is not city temperatures but Green Roofs!
The benefits of green roofs have been widely demonstrated, studies show cooling the effect at street level ranges between 0.03–3C°. Pollution, small particle removal, air cleaning and changes in energy consumption have yet to be properly measured. Studies claim changes in annual consumption range between an increase of 7% to a 90% decrease (Francis, L. Fjendbo Møller, & Jensen, M. Bergen, 2017). As discussed in the introduction a higher density of green roofs could potentially have a very high impact on our quality of life!
Green roofs provide stormwater management by storing rainwater (Versini et al., 2015), urban heat island mitigation by producing evapotranspiration (Santamouris, 2014) and biodiversity protection by providing habitats (Madre et al., 2014). Thus not only can we cool our local environment down, but we can also benefit from green roofs in a myriad of other ways. It is also important to note that while studies on green roofs are not recent, hight densities of green roofs are very scarce and we might not have uncovered all the potential benefits from developing such infrastructure.
While benefits cannot be contested, the green roof culture is rather scarce around Europe. New trends are starting to emerge as recent policies are facilitating access to such design. Although it is interesting to note that the policies are recent and implemented in cities with already higher percentages of green roofs, thus outlining a pre-existent green culture and not completely justifying the higher density of green roofs.
In certain countries not disposed to include green architecture to the city plans, green roofs policies can appear avant-garde and avert architects (Versini, Gires, Tchiguirinskaia & Schertzer, 2020). What is often disregarded, are the costs of maintenance of green roofs. Subsidies for installations often do not take into account the toll for keeping the roofs alive and the conservation of building infrastructures.
Thus the poor increase of green roofs number cannot only be taken into account by lack of will from decision-makers at the city level. A wide variety of factors must be taken into account. City expansion and traditional architectural design can greatly affect green roofs development as installation of green roofs on existing buildings does not account for the same technical issues as creation on a new building (greater load on building structure, shape and slope of roofs, property rights of the building’s roof). As said previously, some countries do not have a green culture and thus this does not only affect choices for current architects but also will influence professional knowledge of the technical system and specialisation in the city’s architectural plan (Rosasco & Perini, 2019).
Green roofing projects are therefore no easy tasks! On top of seizing the rare occasions to actually implement them in the urban architectural design, city halls must also consider a large number of factors for proper implementation. For instance, I mentioned in the introduction that green roofs provide stormwater management by storing rainwater. Thus, green roofs must be heavily monitored to avoid the concentration of “water-resistant” areas responsible for local flooding.
Besides, green roofs biodiversity protection feature does not come on its own. Indeed, one green roof alone will not do much for pollinators or bird conservation. City halls need to innovatively design green corridors allowing for “biodiversity tunnels” from one green area to another. Essentially working as biodiversity service areas between green clusters (Versini, Gires, Tchiguirinskaia & Schertzer, 2020)
What's the situation in Europe?
The European Federation for Green Roofs and Walls is composed of the founding members, Austria, Germany and Switzerland and additional members; Netherlands, Belgium, France, Scandinavia, Hungary, Italy, Poland, Czech Republic, Portugal, England, Spain and Serbia. While some very obvious countries are missing from this list, most notably Luxembourg and the Balkan states.
Their mission statement is to “actively promote the use of green roofs and green facades throughout Europe”. By organizing conferences, their goal is to spread awareness and knowledge of the benefits of such infrastructures. The European plan to impose urban greening for cities of more than 20,000 people will thus hopefully include green roofs in the mix as their role is complementary to that of parks and green areas.
Obviously, green roofs are not the only type of urban green initiatives out there! We will soon cover more alternatives to make cities greener! Ideas are thriving ranging from installation of beehives in cities, developing parks, growing urban forests…. All with their perks and inconveniences! If you wish to know more about the topic of green roofs, do not hesitate to ask a question in the comments or to look at the website of the green roofs association!
On this note, stay safe, live long, live green!
References and insightful reads:
Bush, J. (2020). The role of local government greening policies in the transition towards nature-based cities. Environmental Innovation and Societal Transitions, 35, 35–44. doi:10.1016/j.eist.2020.01.015
Francis, L. Fjendbo Møller, & Jensen, M. Bergen. (2017). Benefits of green roofs: A systematic review of the evidence for three ecosystem services. Urban forestry & urban greening, 28, 167-176. doi: 10.1016/j.ufug.2017.10.015
Mocca, E., Friesenecker, M., & Kazepov, Y. (2020). Greening Vienna. The Multi-Level Interplay of Urban Environmental Policy–Making. Sustainability, 12(4), 1577. doi:10.3390/su12041577
Rosasco, P & Perini, K. (2019). Selection of (Green) Roof Systems: A Sustainability-Based Multi-Criteria Analysis. Architecture and Design Department, University of Genoa, 16123 Genoa, Italy.
Schaefer, A., Williams, S., & Blundel, R. (2018). Individual Values and SME Environmental Engagement. Business & Society, 000765031775013. doi:10.1177/0007650317750134
Terkenli, T. S., Bell, S., Tošković, O., Dubljević-Tomićević, J., Panagopoulos, T., Straupe, I., … Živojinović, I. (2020). Tourist perceptions and uses of urban green infrastructure: An exploratory cross-cultural investigation. Urban Forestry & Urban Greening, 49, 126624. doi:10.1016/j.ufug.2020.126624
Versini, P.-A., Gires, A., Tchiguirinskaia, I., & Schertzer, D. (2020). Fractal analysis of green roof spatial implementation in European cities. Urban Forestry & Urban Greening, 126629. doi:10.1016/j.ufug.2020.126629
Vierikko, K., Gonçalves, P., Haase, D., Elands, B., Ioja, C., Jaatsi, M., … Yli-Pelkonen, V. (2019). Biocultural diversity (BCD) in European cities – interactions between motivations, experiences and environment in public parks. Urban Forestry & Urban Greening, 126501. doi:10.1016/j.ufug.2019.126501
Zepp, H., Groß, L., & Inostroza, L. (2020). And the winner is? Comparing urban green space provision and accessibility in eight European metropolitan areas using a spatially explicit approach. Urban Forestry & Urban Greening, 126603. doi:10.1016/j.ufug.2020.126603