Tagged: green roofs

Has green gone mainstream?

Here’s some food for thought…….The following commentary blog was posted on the World Design Summit’s ‘Designing the Future’ website –  world design summit taking place over 10 days in Montreal in October, 2017. The event is described as, ‘an international gathering of diverse disciplines with a common focus: how design can shape the future.’ 

“Green has gone mainstream. But as green walls, rooftop farms, and tree covered skyscrapers become the norm in cities around the world, critics ask if these developments are simply the latest face of ‘greenwashing’. Environmental advocates such as Naomi Klein have long warned of corporations that attempt to mask questionable records by emphasizing green elements. Klein has challenged industrialists who partake in flashy, eco-conscious campaigns but do little to alleviate the impact of their businesses on the climate. Many companies spend more money convincing consumers that they are green than they do on actual green initiatives; some corporate green initiatives actually harm the environment.

Urbanists worry that greenwashing has spread to urban design and architecture by literally covering up buildings with plants. The vertical farms, plant-covered towers, and eco-villages that once seemed far-fetched are now not only possible but all the rage. Bringing greenery into the city may reduce emissions and improve air quality, but it does little to address the deeper causes of urban and environmental stress. Greening initiatives increase the economic value of places, risking displacement of economically vulnerable residents. Does a greenroof on top of a superstore help uninsured workers? What difference does a green tech-campus make if it requires hundreds of parking spaces?

One architect who questions greenwashing is Alejandro Aravena, director of the firm ELEMENTAL in Chile. At last year’s Venice Architecture Biennale, Aravena exposed the wasteful side of design by exhibiting 90 tons of detritus from the previous year’s event. He also tackles underlying challenges, by collaborating with communities to empower them to design affordable and sustainable housing for themselves. In this age of tree-covered skyscrapers, Aravena’s commitment to modest and even monotonous design stands out.

Questioning greenwashing demands that designers ask whether the green city must be a luxury for the privileged and whether sustainability initiatives accelerate inequality. Designers in all disciplines must look beyond rhetoric and aesthetics to evaluate the impact of environmental design. How can we, as designers, reconcile our role, which is closely linked with the market economy and over-consumption, with environmental and social awareness? Designers invested in truly sustainable practice are encouraged to submit a proposal for the topic “Questioning Greenwashing” at the Congress for the World Design Summit.”

The article is not attributed to any particular author but it would be interesting to hear your thoughts?  What’s your opinion in relation to #greenwashing? The article is illustrated by Stefano Boeri‘s proposals to build “forest cities” in Shijiazhuang, China plus an image of Bosco Verticale, Milan although the latter is not credited – (neither  design is referred to by name in the article). Both designs incorporate vegetation on the outer construction with the twin towers of Bosco Verticale – constructed with a $2.5 billion public-private investment as part of the redevelopment of Milan’s Porta Nuova district – housing 800 trees between 9 and 30 feet tall, over 4,000 shrubs, and 15,000 ground cover plants including vines and perennials.

The summit focuses on 6 key themes including ‘Design for Earth’ and 108 topics including ‘Questioning greenwashing’,

“Designers are sensitive to environmental issues and announce their willingness to conform their practices. However, beyond appearances and words, critical scrutiny is essential. How can we, as designers, reconcile our role, which is closely linked with the market economy and over-consumption, with environmental and social awareness?”

To read Naomi Klein’s, ‘The hypocrisy behind the big business climate change battle’ . Source: The Guardian, Sept, 2014.

naomi klein

Call for empirical evidence for climate resilient urban planning.

Regulating urban surface runoff through nature-based solutions – An assessment at the micro-scale.  Zölch,T, Henze, L, Keilholz, P & Pauleit, S.  Environmental Research, Volume 157, August 2017, Pages 135–14.

Key findings

  • Runoff after heavy rain events accounts for approx. 95% of total precipitation in highly sealed urban areas.
  • By enhancing water storage capacities green infrastructure reduces runoff by max. 14.8% compared to the baseline.
  • Green roofs and trees both show to be effective but due to different functions.
  • The reduction of runoff is larger with higher shares of green cover in the case area.

Abstract

Urban development leads to changes of surface cover that disrupt the hydrological cycle in cities. In particular, impermeable surfaces and the removal of vegetation reduce the ability to intercept, store and infiltrate rainwater. Consequently, the volume of stormwater runoff and the risk of local flooding rises. This is further amplified by the anticipated effects of climate change leading to an increased frequency and intensity of heavy rain events. Hence, urban adaptation strategies are required to mitigate those impacts.

A nature-based solution, more and more promoted in politics and academia, is urban green infrastructure as it contributes to the resilience of urban ecosystems by providing services to maintain or restore hydrological functions. However, this poses a challenge to urban planners in deciding upon effective adaptation measures as they often lack information on the performance of green infrastructure to moderate surface runoff. It remains unclear what type of green infrastructure (e.g. trees, green roofs), offers the highest potential to reduce discharge volumes and to what extent.

Against this background, this study provides an approach to gather quantitative evidence on green infrastructure’s regulation potential. We use a micro-scale scenario modelling approach of different variations of green cover under current and future climatic conditions. The scenarios are modelled with MIKE SHE, an integrated hydrological modelling system for building and simulating surface water and groundwater flow, and applied to a high density residential area of perimeter blocks in Munich, Germany. The results reveal that both trees and green roofs increase water storage capacities and hence reduce surface runoff, although the main contribution of trees lies in increasing interception and evapotranspiration, whereas green roofs allow for more retention through water storage in their substrate. With increasing precipitation intensities as projected under climate change their regulating potential decreases due to limited water storage capacities. The performance of both types stays limited to a maximum reduction of 2.4% compared to the baseline scenario, unless the coverage of vegetation and permeable surfaces is significantly increased as a 14.8% reduction is achieved by greening all roof surfaces.

The authors conclude that the study provides empirical support for the effectiveness of urban green infrastructure as nature-based solution to stormwater regulation and assists planners and operators of sewage systems in selecting the most effective measures for implementation and estimation of their effects.

Conclusions

Urban green infrastructure as nature-based solution to regulate surface runoff becomes increasingly important, as climate change and urbanisation alter the urban water balance. The present study assessed the performance of two urban green infrastructure (UGI) types, trees and green roofs, on relevant hydrological processes, especially surface runoff. The two measures were applied in scenarios of different greening quantity and for heavy rain events of different intensities as projected for the future. This scenario approach revealed that both trees and green roofs contribute positively by interception, evapotranspiration and infiltration. Differences in their performance showed to be dependent on the greening quantity, share of permeable surfaces leaf area index (LAI) and finally, intensity of the rainfall event. Generally, their effectiveness remains low under heavy rain events, unless a significant proportion of the case area is greened to provide sufficient water storage capacities (Artmann, 2014).

For urban planning the presented results have practical implications for the selection of UGI types to reduce surface runoff volumes and in consequence reduce discharge loads, the sewage system has to handle. An effective nature-based solution increases the storage capacities within the area of interest as much as possible, while using open spaces that have not been used previously and/or while providing benefits to other areas of urban planning. Trees increase the storage capacity mainly by intercepting and evapotranspiring rainwater, their infiltration capacity is limited to the tree pits. But trees can normally not be implemented in large quantity in dense urban areas due to their requirements of open space. Green roofs on the other hand, provide storage capacity mainly by retaining rainwater in their substrates and can be implemented at larger scale on previously unused roof surfaces.

Furthermore, both types are multifunctional and can provide co-benefits for urban planning. The approach represents a first step in allowing planners as well as operators of sewage systems to estimate reductions in runoff volume when locally implementing UGI measures. These estimations could be further improved by integrating additional stormwater management practices and the drainage system in more detail into the modelling setup. Thus, conducting a larger systematic study of UGI scenarios would allow for including e.g. more UGI types, different species and LAI values as well as planting conditions. Such a study could enhance the provision of empirical evidence for climate resilient urban planning.

Gi_LI

In March 2013 the Landscape Institute published an updated Mission Statement, ‘Green Infrastructure: An integrated approach to land management’. The document was described as,

“An opportunity to showcase a range of successful strategic GI work and completed
projects. The aim is to give public and private sector bodies, clients and natural and built environment professionals fresh insights into the benefits GI can bring by creating multifunctional landscapes and show how people can collaborate to deliver it.”

London’s Green Roofs: Mapping and case studies.

Living roofs play an important role in helping to achieve London’s target to increase green cover in central London by 5% by 2030. They can improve the city’s resilience to the impacts of climate change by reducing the amount and speed of storm water run-off and helping to keep buildings, and the surrounding areas, cooler during increasingly frequent hot spells. They also provide much needed outdoor living space, improving life for both residents and adding to the beauty of the local neighbourhood.

The illustrated publication, City of London green roof case studies provided to the City of London Corporation includes a number of green roof applications in The City describing their context, format, drivers, barriers, benefits and notes on biodiversity.

green roof2

It is estimate that there are around 700 green roofs in central London alone, shown on the map below. New green roofs need to be built to meet the greening targets, installed through both new development proposals and through the retrofit of existing buildings, to deliver as many of the following objectives as possible:

  • Reduction of Urban Heat Island – Research in Tyndale Centre for climate change suggests we need a 10% increase in green space in our cities to combat climate change. This is particularly relevant to the reduction in the Urban Heat Island [UHIE]. Green roofs are recognized to have a positive effect on reducing the UHIE
  • Biodiversity – Green roofs can provide important refuges for wildlife in urban areas. Research in Switzerland and the UK has demonstrated that green roofs can provide important refuges for rare invertebrate populations.
  • Water – Green roofs can significantly reduce the surface run off volumes and rates of rainfall leaving roofs. As a source control mechanism in the Sustainable Urban Drainage System green roofs can help reduce flash floods as a consequence of intense rainfall events. This will become increasingly important as a consequence of climate change.  Green roofs also improve the quality of water and although the amount of water is reduced it is possible to rainfall harvest from roofs that have been greened.
  • Thermal Performance – Green roofs cannot be given a U-value at present. However they have been shown to significantly reduce the need for air conditioning in summer and can provide a degree of insulation in winter.
  • Sound Insulation – The combination of soil, plants and trapped layers of air within green roof systems can act as a sound insulation barrier. Sound waves are absorbed, reflected or deflected. The growing medium tends to block lower sound frequencies whilst the plants block higher frequencies.
  • Protection of Waterproofing – The original green roofs in Germany stem from covering wet bitumen with 6cm of sand, which became vegetated. This covering was to protect the wet bitumen from fire. Green roofs have now been shown to double if not triple the life of waterproofing membranes beneath the green roof.
  • Air Quality – airborne particles and pollutants are filtered from the atmosphere by the substrates and vegetation on a green roof.
  • Amenity Space – in dense urban environments there is often a lack of green space for residents. Roof Gardens and roof top parks provide important green spaces to improve the quality of life for urban residents.
  • Urban Agriculture – in the form of Urban Rooftop Food Growing – roofs, where strong enough provide a space for urban food growing. Although many large flat roofs may not have the loading capabilities to hold food growing some roofs will and the many balconies in are urban areas are ideal.

green roof3

Transport for London have installed green roofs at St James’s tube station and West Ham bus garage and a green wall at Edgware Road tube station.

This green roof map of London below shows there are around 700 green roofs in central London alone, covering an area of over 175,000m2. That’s 17.5 hectares or around 25 football pitches. The green roof map was produced by the GLA and the Green Roof Consultancy by studying aerial images of London taken in 2013 (by The Geoinformation Group).

green roof

The map currently contains 678 known green roofs, but there are many which are missing, including those that have been installed since the summer of 2013.  If you would like us to add a green roof to the map please email, GIMap@london.gov.uk. Or, if you would like to add more information about a green roof currently on the map – such as a photo, or links to a website with further details of the roof – then please click on the green roof on the map and the ‘email us’ link, which will open a new email window

Image sources: City of London Corporation