Quantification of Green Roof Benefits and the Implementation into Urban Politics

A special issue of Buildings (ISSN 2075-5309). This special issue belongs to the section "Architectural Design, Urban Science, and Real Estate".

Deadline for manuscript submissions: closed (31 December 2019) | Viewed by 43397

Special Issue Editors


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Guest Editor
University of Applied Sciences
Interests: Green roof research, living walls, indoor greening, biodiversity, rain water management, ecosystem services, green infrastructure
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
British Columbia Institute of Technology
Interests: green roof ecology, vegetation dynamics, pollinator ecology, soil plant feedbacks, microbial inoculation, stormwater/ greywater recycling, green infrastructure policy, biophilia/ -phobia, bog restoration

Special Issue Information

Dear Colleagues,

In times of climate change, it is important to find solutions to adapt or to mitigate the effects of higher temperatures and increasing stronger rain events.

The loss of vegetation structures in cities causes a loss of biodiversity in cities.

Roofs are a space resource that bring back functional vegetation into cities.

Knowledge about green roofs has increased significantly in the last 30 years. These publications show that this technology is fit for all climate zones and is possible in nearly all types of buildings.

Green roofs are one prominent key element in the list of green infrastructure solutions.

To convince decision makers in cites to integrate more green roofs in the future, it is best to give countable numbers of these ecological benefits. It is also important to learn from case studies. What is the best way to calculate the benefit of new projects? Are there new instruments to simulate or to calculate? What are the best instruments to expand the green roof numbers from currently around 9% in some cities to 50%? All expected effects are connected with the increasing size of green space. Are there well working concepts, either incentives or regulations, to push this great instrument forward—and is it finally possible to mitigate the urban heat island?

Contributions are welcome to these all these levels of information:

-Long-time real measurements and knowledge about countable effects and benefits;

-The best way to proceed from measurements to implementation. We must learn from successful urban strategy instruments.

Prof. Dr. Manfred Köhler
Guest Editor

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Keywords

  • green roofs: climate effects, biodiversity, rain water management, implementation

Published Papers (6 papers)

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Research

26 pages, 4903 KiB  
Article
Green Roofs and Greenpass
by Bernhard Scharf and Florian Kraus
Buildings 2019, 9(9), 205; https://doi.org/10.3390/buildings9090205 - 14 Sep 2019
Cited by 29 | Viewed by 7084
Abstract
The United Nations have identified climate change as the greatest threat to human life. As current research shows, urban areas are more vulnerable to climate change than rural areas. Numerous people are affected by climate change in their daily life, health and well-being. [...] Read more.
The United Nations have identified climate change as the greatest threat to human life. As current research shows, urban areas are more vulnerable to climate change than rural areas. Numerous people are affected by climate change in their daily life, health and well-being. The need to react is undisputed and has led to numerous guidelines and directives for urban climate adaptation. Plants are commonly mentioned and recommended as one key to urban climate adaptation. Due to shading of open space and building surfaces, as well as evapotranspiration, plants reduce the energy load on the urban fabric and increase thermal comfort and climate resilience amongst many other ecosystem services. Plants, therefore, are described as green infrastructure (GI), because of the beneficial effects they provide. Extensive green roofs are often discussed regarding their impact on thermal comfort for pedestrians and physical properties of buildings. By means of Stadslab2050 project Elief Playhouse in Antwerp, Belgium, a single-story building in the courtyard of a perimeter block, the effects of different extensive green roof designs (A and B) on the microclimate, human comfort at ground and roof level, as well as building physics are analyzed and compared to the actual roofing (bitumen membrane) as the Status Quo variant. For the analyses and evaluation of the different designs the innovative Green Performance Assessment System (GREENPASS®) method has been chosen. The planning tool combines spatial and volumetric analyses with complex 3D microclimate simulations to calculate key performance indicators such as thermal comfort score, thermal storage score, thermal load score, run-off and carbon sequestration. Complementary maps and graphs are compiled. Overall, the chosen method allows to understand, compare and optimize project designs and performance. The results for the Elief Playhouse show that the implementation of green roofs serves a slight contribution to the urban energy balance but a huge impact on the building and humans. Variant B with entire greening performs better in all considered indicators, than the less greened design Variant A and the actual Status Quo. Variant B will probably bring a greater cost/benefit than Variant A and is thus recommended. Full article
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16 pages, 4875 KiB  
Article
Increasing Evapotranspiration on Extensive Green Roofs by Changing Substrate Depths, Construction, and Additional Irrigation
by Daniel Kaiser, Manfred Köhler, Marco Schmidt and Fiona Wolff
Buildings 2019, 9(7), 173; https://doi.org/10.3390/buildings9070173 - 23 Jul 2019
Cited by 26 | Viewed by 5210
Abstract
Urban environments are characterized by dense development and paved ground with reduced evapotranspiration rates. These areas store sensible and latent heat, providing the base for typical urban heat island effects. Green roof installations are one possible strategy to reintroduce evaporative surfaces into cities. [...] Read more.
Urban environments are characterized by dense development and paved ground with reduced evapotranspiration rates. These areas store sensible and latent heat, providing the base for typical urban heat island effects. Green roof installations are one possible strategy to reintroduce evaporative surfaces into cities. If green roofs are irrigated, they can contribute to urban water management and evapotranspiration can be enhanced. As part of two research projects, lysimeter measurements were used to determine the real evapotranspiration rates on the research roof of the University of Applied Sciences in Neubrandenburg, Germany. In this paper, we address the results from 2017, a humid and cool summer, and 2018, a century summer with the highest temperatures and dryness over a long period of time, measured in Northeast Germany. The lysimeter measurements varied between the normal green roof layer (variation of extensive green roof constructions) and a special construction with an extra retention layer and damming. The results show that the average daily evapotranspiration rates can be enhanced from 3 to 5 L/m2/day under optimized conditions. A second test on a real green roof with irrigation was used to explain the cooling effects of the surface above a café building in Berlin. Full article
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18 pages, 5241 KiB  
Article
Evidence of the Climate Mitigation Effect of Green Roofs—A 20-Year Weather Study on an Extensive Green Roof (EGR) in Northeast Germany
by Manfred Köhler and Daniel Kaiser
Buildings 2019, 9(7), 157; https://doi.org/10.3390/buildings9070157 - 28 Jun 2019
Cited by 23 | Viewed by 8224
Abstract
Approximately 10 km2 of new green roofs are built in Germany every year. About 85% of these are Extensive Green Roofs (EGR). An EGR with several research features was installed on new buildings belonging to the University of Applied Sciences Neubrandenburg in [...] Read more.
Approximately 10 km2 of new green roofs are built in Germany every year. About 85% of these are Extensive Green Roofs (EGR). An EGR with several research features was installed on new buildings belonging to the University of Applied Sciences Neubrandenburg in 1999. The results of the almost 20-year permanent survey of the climate effects of the green roof in contrast to gravel roofs are presented here. High-quality sensors, similar to those used by official weather stations, are in use, and data is collected every 10 s and aggregated to hourly values which enable comparisons to official measurements made by the DWD in Neubrandenburg and Berlin. The results show the typical urban heat island effect (UHI) and the mitigation effect of EGR. Whilst the temperature increased over the years due to the urban heat island effect, the temperature within the growing media in the green roof remained constant. The EGR has a stabilization effect of 1.5 K. This is good news for all those seeking a UHI mitigation solution for city centers. In a best-case scenario, the green roof potential of cities in Germany is between 3 and 8%. A value of 50% can be achieved for all buildings; roofs represent about ¼ of urban surfaces, and the cooling effect of 1.5 K in 20 years is a reasonable contribution to cooling cities and achieving environmental goals by greening urban surfaces. Full article
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17 pages, 5962 KiB  
Article
Function-Based and Multi-Scale Approach to Green Roof Guidelines for Urban Sustainability Transitions: The Case of Bogota
by R. Andrés Ibáñez Gutiérrez and Mónica Ramos-Mejía
Buildings 2019, 9(6), 151; https://doi.org/10.3390/buildings9060151 - 22 Jun 2019
Cited by 6 | Viewed by 5969
Abstract
A growing number of local green roof niches across the globe are transitioning into the mainstream domain. Guidelines are key to this process, as they define technological environments and set the criteria for best practices in a given socio-technical setting. Although the German [...] Read more.
A growing number of local green roof niches across the globe are transitioning into the mainstream domain. Guidelines are key to this process, as they define technological environments and set the criteria for best practices in a given socio-technical setting. Although the German Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau (FLL) cornerstone guidelines provided solid empirical ground and established technical parameters for the successful application of green roofs across continents, investigations about alternative green roof guidelines for emerging markets remain very scarce. The paper presents the inclusive approach followed by the Bogota Green Roof Guidelines, which were the result of a multi-actor participatory process that examined how to embrace a wide range of emerging green roof technologies and local adaptations while promoting quality of application at different scales, regardless of the system used, and despite the absence of local robust empirical data on performance parameters. As a result, Bogota’s Green Roof Guidelines incorporated ad hoc elements: (1) new definitions and taxonomy, (2) function-based contents, (3) multi-scale approach, and (4) performance scoping. These aspects are discussed to provide novel insights for the advancement of green infrastructure policies in diverse institutional settings aiming to promote quality and simultaneously support markets that make room for a wide variety of green infrastructure practices. Full article
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11 pages, 1779 KiB  
Article
Water Resilience by Centipedegrass Green Roof: A Case Study
by Shuai Hu, Lijiao Liu, Junjun Cao, Nan Chen and Zhaolong Wang
Buildings 2019, 9(6), 141; https://doi.org/10.3390/buildings9060141 - 11 Jun 2019
Cited by 5 | Viewed by 3746
Abstract
Centipedegrass (Eremochloa ophiuroides) is a low-maintenance turfgrass. The first extensive green roof of centipedegrass was established in TongZhou Civil Squares in 2014. However, storm-water-runoff reduction, water-retention capacity, and plant-water requirements by a centipedegrass green roof has not yet been defined. The [...] Read more.
Centipedegrass (Eremochloa ophiuroides) is a low-maintenance turfgrass. The first extensive green roof of centipedegrass was established in TongZhou Civil Squares in 2014. However, storm-water-runoff reduction, water-retention capacity, and plant-water requirements by a centipedegrass green roof has not yet been defined. The soil moisture dynamics, rainwater-retention capacity, runoff reduction, and plant evapotranspiration were investigated by simulated centipedegrass green roof plots, which were constructed in the same manner as the green roofs in TongZhou Civil Squares in 2018. The results showed that the centipedegrass green roof retained 705.54 mm of rainwater, which consisted 47.4% of runoff reduction. The saturated soil moisture was 33.4 ± 0.6%; the excess rainfall over the saturated soil moisture resulted in runoff. The capacity of rainwater retention was negatively related to the soil moisture before rain events and was driven by plant evapotranspiration. Drought symptoms only occurred three times over the course of a year when the soil moisture dropped down to 10.97%. Our results indicate that the rainwater retained in the soil almost met the needs of plant consumption; a further increase of rainwater retention capacity might achieve an irrigation-free design in a centipedegrass green roof. Full article
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17 pages, 1864 KiB  
Article
Selection of (Green) Roof Systems: A Sustainability-Based Multi-Criteria Analysis
by Paolo Rosasco and Katia Perini
Buildings 2019, 9(5), 134; https://doi.org/10.3390/buildings9050134 - 27 May 2019
Cited by 44 | Viewed by 11744
Abstract
A wide diffusion of green envelopes in cities can be an opportunity to improve urban environment conditions and reduce negative effects of climate change. The green roof system is a widespread solution adopted all over the world due to the relative simplicity of [...] Read more.
A wide diffusion of green envelopes in cities can be an opportunity to improve urban environment conditions and reduce negative effects of climate change. The green roof system is a widespread solution adopted all over the world due to the relative simplicity of installation and the large private and social benefits provided. Despite this, some factors hinder the diffusion of the green roof system, not only economic factors (due to the higher installation costs compare to a traditional roof solution), but also technical factors connected to lack of knowledge. The present paper investigates the factors influencing designers in the choice of a building roof systems, comparing a traditional solution and a greening system. The involvement of architects, engineers, and researchers allows the selection of the most important factors. Results of the study identifies their priority, and through a sustainability-based multicriteria analysis, the role played by each one in the decision process. This approach provides interesting hints to identify effective strategies to support a wider diffusion of greening systems for urban resilience. Full article
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