A New Method to Determine How Compaction Affects Water and Heat Transport in Green Roof Substrates

Although compaction affects water and heat transport processes in porous media, few studies have dealt with this problem. This is particularly true for substrates, which are artificial porous media used for engineering and technological solutions, such as in vegetated or green roofs. We propose a methodology to study the effect of substrate compaction on the characterization of physical, hydrodynamic and thermal properties of five green roof substrates. The methodology consists in a parametric analysis that uses the properties of a substrate with known bulk density, and then modifies the substrate properties to consider how compaction affects water and heat fluxes. Coupled heat and water transport numerical simulations were performed to assess the impact of the changes in the previous properties on the hydraulic and thermal performance of a hypothetical roof system. Our results showed that compaction reduced the amplitude of the fluctuations in the volumetric water content daily cycles, increasing the average water content and reducing the breakthrough time of the green roof substrates. Compaction changes the thermal behavior of the green roof substrates in different ways for each substrate due to the dependence of the air, water and soil fraction of each substrate.

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The GREENROOF module (v7.3) for modelling green roof hydrological and energetic performances within TEB

Geoscientific Model Development ◽

10.5194/gmd-6-1941-2013 ◽

2013 ◽

Vol 6 (6) ◽

pp. 1941-1960 ◽

Cited By ~ 16

Author(s):

C. S. de Munck ◽

A. Lemonsu ◽

R. Bouzouidja ◽

V. Masson ◽

R. Claverie

Keyword(s):

Water Content ◽

Green Roof ◽

Green Roofs ◽

Model Interaction ◽

Drainage Layer ◽

Extensive Green Roof ◽

Hydrological Characteristics ◽

Drainage Layers ◽

The Impact

Abstract. The need to prepare cities for climate change adaptation requests the urban modeller community to implement sustainable adaptation strategies within their models to be tested against specific city morphologies and scenarios. Greening city roofs is part of these strategies. In this context, the GREENROOF module for TEB (town energy balance) has been developed to model the interactions between buildings and green roof systems at the scale of the city. This module, which combines the ISBA model (Interaction between Soil Biosphere and Atmosphere) and TEB, allows for one to describe an extensive green roof composed of four functional layers (vegetation – grasses or sedums; substrate; retention/drainage layers; and artificial roof layers) and to model vegetation-atmosphere fluxes of heat, water and momentum, as well as the hydrological fluxes throughout the substrate and the drainage layers, and the thermal fluxes throughout the natural and artificial layers of the green roof. TEB-GREENROOF (SURFEX v7.3) should therefore be able to represent the impact of climate forcings on the functioning of green roof vegetation and, conversely, the influence of the green roof on the local climate. An evaluation of GREENROOF is performed for a case study located in Nancy (France) which consists of an instrumented extensive green roof with sedums and substrate and drainage layers that are typical of this kind of construction. After calibration of the drainage layer hydrological characteristics, model results show good dynamics for the substrate water content and the drainage at the green roof base, with nevertheless a tendency to underestimate the water content and overestimate the drainage. This does not impact too much the green roof temperatures, which present a good agreement with observations. Nonetheless GREENROOF tends to overestimate the soil temperatures and their amplitudes, but this effect is less important in the drainage layer. These results are encouraging with regard to modelling the impact of green roofs on thermal indoor comfort and energy consumption at the scale of cities, for which GREENROOF will be running with the building energy version of TEB – TEB-BEM. Moreover, with the green roof studied for GREENROOF evaluation being a type of extensive green roof widespread in cities, the type of hydrological characteristics highlighted for the case study will be used as the standard configuration to model extensive green roof impacts at the scale of cities.

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Seismic Performance of a Green Roof Structure

Sustainability ◽

10.3390/su13084278 ◽

2021 ◽

Vol 13 (8) ◽

pp. 4278

Author(s):

Svetlana Tam ◽

Jenna Wong

Keyword(s):

Green Roof ◽

Time History ◽

Green Roofs ◽

Moment Frame ◽

Steel Moment Frame ◽

Roof Structure ◽

Nonlinear Time History Analyses ◽

Vegetated Roofs ◽

Nonlinear Time History ◽

The Impact

Sustainability addresses the need to reduce the structure’s impact on the environment but does not reduce the environment’s impact on the structure. To explore this relationship, this study focuses on quantifying the impact of green roofs or vegetated roofs on seismic responses such as story displacements, interstory drifts, and floor level accelerations. Using an archetype three-story steel moment frame, nonlinear time history analyses are conducted in OpenSees for a shallow and deep green roof using a suite of ground motions from various distances from the fault to identify key trends and sensitivities in response.

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Heat Transfer Behavior of Green Roof Systems Under Fire Condition: A Numerical Study

Buildings ◽

10.3390/buildings9090206 ◽

2019 ◽

Vol 9 (9) ◽

pp. 206

Author(s):

Gerzhova ◽

Blanchet ◽

Dagenais ◽

Côté ◽

Ménard

Keyword(s):

Heat Transfer ◽

Failure Time ◽

Numerical Study ◽

Fire Hazard ◽

Green Roof ◽

Green Roofs ◽

Heat Transfer Process ◽

Heat Fluxes ◽

Substrate Thickness ◽

Time To Failure

Currently, green roof fire risks are not clearly defined. This is because the problem is still not well understood, which raises concerns. The possibility of plants catching fire, especially during drought periods, is one of the reasons for necessary protection measures. The potential fire hazard for roof decks covered with vegetation has not yet been fully explored. The present study analyzes the performance of green roofs in extreme heat conditions by simulating a heat transfer process through the assembly. The main objective of this study was to determine the conditions and time required for the roof deck to reach a critical temperature. The effects of growing medium layer thickness (between 3 and 10 cm), porosity (0.5 to 0.7), and heating intensity (50, 100, 150, and 200 kW/m²) were examined. It was found that a green roof can protect a wooden roof deck from igniting with only 3 cm of soil coverage when exposed to severe heat fluxes for at least 25 minutes. The dependency of failure time on substrate thickness decreases with increasing heating load. It was also found that substrate porosity has a low impact on time to failure, and only at high heating loads.

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State-of-the-Art Green Roofs: Technical Performance and Certifications for Sustainable Construction

Coatings ◽

10.3390/coatings10010069 ◽

2020 ◽

Vol 10 (1) ◽

pp. 69 ◽

Cited By ~ 2

Author(s):

Alejandra Naranjo ◽

Andrés Colonia ◽

Jaime Mesa ◽

Heriberto Maury ◽

Aníbal Maury-Ramírez

Keyword(s):

Environmental Assessment ◽

State Of The Art ◽

Green Roof ◽

Green Roofs ◽

Assessment Method ◽

Assessment System ◽

Sustainable Construction ◽

Runoff Water ◽

Technical Performance ◽

The Impact

Green roof systems, a technology which was used in major ancient buildings, are currently becoming an interesting strategy to reduce the negative impact of traditional urban development caused by ground impermeabilization. Only regarding the environmental impact, the application of these biological coatings on buildings has the potential of acting as a thermal, moisture, noise, and electromagnetic barrier. At the urban scale, they might reduce the heat island effect and sewage system load, improve runoff water and air quality, and reconstruct natural landscapes including wildlife. In spite of these significant benefits, the current design and construction methods are not completely regulated by law because there is a lack of knowledge of their technical performance. Hence, this review of the current state of the art presents a proper green roof classification based on their components and vegetation layer. Similarly, a detailed description from the key factors that control the hydraulic and thermal performance of green roofs is given. Based on these factors, an estimation of the impact of green roof systems on sustainable construction certifications is included (i.e., LEED—Leadership in Energy and Environment Design, BREEAM—Building Research Establishment Environmental Assessment Method, CASBEE—Comprehensive Assessment System for Built Environment Efficiency, BEAM—Building Environmental Assessment Method, ESGB—Evaluation Standard for Green Building). Finally, conclusions and future research challenges for the correct implementation of green roofs are addressed.

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Building and Urban Cooling Performance Indexes of Wetted and Green Roofs—A Case Study under Current and Future Climates

Energies ◽

10.3390/en13236192 ◽

2020 ◽

Vol 13 (23) ◽

pp. 6192

Author(s):

Madi Kaboré ◽

Emmanuel Bozonnet ◽

Patrick Salagnac

Keyword(s):

Thermal Comfort ◽

Emission Scenario ◽

Green Roof ◽

Heat Fluxes ◽

Temperate Climate ◽

Passive Cooling ◽

Thermal Discomfort ◽

Indoor Thermal Comfort ◽

Performance Indexes ◽

The Impact

We developed and studied key performance indexes and representations of energy simulation heat fluxes to evaluate the performance of the evaporative cooling process as a passive cooling technique for a commercial building typology. These performance indexes, related to indoor thermal comfort, energy consumption and their interactions with their surrounding environments, contribute to understanding the interactions between the urban climate and building for passive cooling integration. We compare the performance indexes for current and future climates (2080), according to the highest emission scenario A2 of the Special Report on Emission Scenario (SRES). Specific building models were adapted with both green roof and wetted roof techniques. The results show that summer thermal discomfort will increase due to climate change and could become as problematic as winter thermal discomfort in a temperate climate. Thanks to evapotranspiration phenomena, the sensible heat contribution of the building to the urban heat island (UHI) is reduced for both current and future climates with a green roof. The performance of the vegetative roof is related to the water content of the substrate. For wetted roofs, the impacts on heat transferred to the surrounding environment are higher for a Mediterranean climate (Marseille), which is warmer and drier than the Paris climate studied (current and future climates). The impact on indoor thermal comfort depends on building insulation, as demonstrated by parametric studies, with higher effects for wetted roofs.

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Is Smart Growth a smart adaptation strategy?: Examining Ontario's proposed growth under climate change

Ekistics and the new habitat - India and Jugaad: The Impact of Innovation by the Resilient Indian Mind on Habitat ◽

10.53910/26531313-e200471424-426224 ◽

2004 ◽

Vol 71 (424-426) ◽

pp. 57-62

Author(s):

Brad Bass

Keyword(s):

Climate Change ◽

Energy Consumption ◽

Urban Areas ◽

Green Roof ◽

Smart Growth ◽

Green Roofs ◽

Adaptation Strategy ◽

University Of Toronto ◽

Conducting Research ◽

The Impact

The author is a member of Environment Canada's Adaptation and Impact Research Group, located in the Centre for Environment at the University of Toronto. His primary research interests include the use of ecological technologies in adapting urban areas to atmospheric change, the impacts of climate change on the energy sector, and the characteristics of adaptable systems. His current work on ecological technologies includes green roofs, vertical gardens and living machines. Dr Bass has been involved in two major projects, in Ottawa and Toronto, to evaluate the impact of green roofs on the urban heat island, energy consumption, stormwater runoff and water quality. Currently, Dr Bass is conducting research on integrating green roof infrastructure with other vegetation strategies at a community scale, simulating the impact of a green roof on the energy consumption of individual buildings.

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On the impact of porous media microstructure on rainfall infiltration of thin homogeneous green roof growth substrates

Journal of Hydrology ◽

10.1016/j.jhydrol.2019.124286 ◽

2020 ◽

Vol 582 ◽

pp. 124286 ◽

Cited By ~ 1

Author(s):

Kaj Pettersson ◽

Dario Maggiolo ◽

Srdjan Sasic ◽

Pär Johansson ◽

Angela Sasic-Kalagasidis

Keyword(s):

Porous Media ◽

Green Roof ◽

Rainfall Infiltration ◽

Growth Substrates ◽

The Impact

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Impact of Green Roofs on Energy Demand for Cooling in Egyptian Buildings

Sustainability ◽

10.3390/su12145729 ◽

2020 ◽

Vol 12 (14) ◽

pp. 5729 ◽

Cited By ~ 1

Author(s):

Ayman Ragab ◽

Ahmed Abdelrady

Keyword(s):

Thermal Conductivity ◽

Energy Consumption ◽

Energy Demand ◽

Soil Depth ◽

Green Roof ◽

Green Roofs ◽

Climatic Regions ◽

Reduce Energy Consumption ◽

The Impact ◽

Reducing Energy

Energy consumption for cooling purposes has increased significantly in recent years, mainly due to population growth, urbanization, and climate change consequences. The situation can be mitigated by passive climate solutions to reduce energy consumption in buildings. This study investigated the effectiveness of the green roof concept in reducing energy demand for cooling in different climatic regions. The impact of several types of green roofing of varying thermal conductivity and soil depth on energy consumption for cooling school buildings in Egypt was examined. In a co-simulation approach, the efficiency of the proposed green roof types was evaluated using the Design-Builder software, and a cost analysis was performed for the best options. The results showed that the proposed green roof types saved between 31.61 and 39.74% of energy, on average. A green roof featuring a roof soil depth of 0.1 m and 0.9 W/m-K thermal conductivity exhibited higher efficiency in reducing energy than the other options tested. The decrease in air temperature due to green roofs in hot arid areas, which exceeded an average of 4 °C, was greater than that in other regions that were not as hot. In conclusion, green roofs were shown to be efficient in reducing energy consumption as compared with traditional roofs, especially in hot arid climates.

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Impact of chaotic mixing on reactive transport: experiment in porous media at high Pe and Da

10.5194/egusphere-egu21-15447 ◽

2021 ◽

Author(s):

Hugo Sanquer ◽

Joris Heyman ◽

Tanguy Le Borgne ◽

Khalil Hanna

Keyword(s):

Porous Media ◽

Reactive Transport ◽

3D Imaging ◽

Fluid Phase ◽

Reaction Rates ◽

Transport Processes ◽

Chaotic Mixing ◽

Pore Scale ◽

Chemical Gradients ◽

The Impact

Solute transport in porous media plays a key role in a range of chemical and biological processes, including contaminant degradation, precipitation, dissolution and microbiological dynamics. Increasing evidences have shown that the conventional complete mixing assumption at the pore scale can lead to a strong overestimation of reaction rates. Recent 3D imaging experiments of mixing in porous media suggest that these pore scale chemical gradients may be sustained by chaotic mixing dynamics. However, the consequences of such chaotic mixing on reactive processes are unknown.In this work, we use reactive transport experiments coupled to 3D imaging to investigate the impact of micro-scale chaotic flows on mixing-limited reactions in the fluid phase. &#160;We use optical index matching and laser-induced fluorescence to characterize the pore scale distribution of reactive product concentration for a range of Peclet and Damkh&#246;ler numbers. We use these measurements to develop a reactive lamellar theory that quantifies the impact of pore scale chemical gradients induced by chaotic mixing on effective reaction rates. These results provide new perspectives for upscaling reactive transport processes in porous media.

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Analyze the energy balance and energy-saving benefits of green roofs

10.5194/egusphere-egu21-14130 ◽

2021 ◽

Author(s):

Chuan Ching Pang

Keyword(s):

Energy Balance ◽

Energy Saving ◽

Green Roof ◽

Green Roofs ◽

Radiant Heat ◽

Building Energy ◽

Control Group ◽

Indoor Temperature ◽

The Impact ◽

Experimental Group

In the context of rapid global urbanization, problems such as urban thermal effects often occur, which may cause the increase in building energy consumption. Green roofs have the effect to regulating the indoor temperature of buildings. This study is expected to evaluate the cooling and energy-saving benefits of green roofs and build an experimental to simulation buildings situation , the control group without green roof and the experimental group with green roof, compare the indoor temperature and heat flux changes in the control group and the experimental group, and calculate the radiant heat, latent heat, sensible heat, conduction heat in the green roof layer , And build a model to simulation energy project to discuss the energy balance of the green roof and the impact on the energy of the buildings below, and analyze the cooling and energy saving effects of the green roof.

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