Conference Presentations by Liat Margolis
Extensive green roofs have some capacity to retain precipitation and slow down peak flow during r... more Extensive green roofs have some capacity to retain precipitation and slow down peak flow during rainstorm events. These characteristics mean that green roofs are finding their way into the Low-Impact Development toolkit for urban watershed management. Green roofs are also widely touted as having thermal properties; from the R value of the porous media, shading by the vegetation and evaporative cooling. In the Southern Ontario climate it is this potential summertime cooling effect which is of greatest interest.
Maximizing evaporative cooling requires that the green roof contain moisture and so regular irrigation would be indicated. But, our hottest months are often those with the most extreme rainfall events and water already within the planting media can hinder the storm water performance of the green roof.
Methodology:
The GRIT Laboratory at the University of Toronto is a pioneering multidisciplinary research facility; equipped with an onsite meteorological station and thirty-three individual extensive green roof modules. Each module is equipped to capture rainwater runoff and measure vertical thermal profiles, providing the opportunity to explore the relationship between water balance and microclimate. In addition to irrigation programming, further variables explored include: the planting substrate type and depth, and the selection of vegetation.
Preliminary Results:
The sensors came online, monitoring and recording thermal and hydrological data at the start of the 2013 growing season. Through a summer of remarkable storms and fluctuating temperatures, irrigation was determined as the primary indicator for predicting decreased storm water retention. Over the six months, May-October, daily irrigation reduced storm water retention by up to 75%. However, the supplementary irrigation had a huge impact on the localized ambient temperature. In some instances through July, the observed difference was up to 20 ºC between irrigated and non-irrigated modules at 15cm from the surface (defined as top of growing media).
Lessons:
Many green roofs already have irrigation systems installed; although their usage varies widely. As such this early research is a foundation step in developing recommendations for best maintenance practices to optimize the infrastructural benefits of new and existing extensive green roofs.
Papers by Liat Margolis
International Low Impact Development Conference 2015, 2015
The second phase of the University of Toronto's Daniels Faculty of Architecture, Landscape and De... more The second phase of the University of Toronto's Daniels Faculty of Architecture, Landscape and Design Green Roof Innovation Testing Laborarty (GRITlab) officially opened in 2014. The GRITlab project is an interdisciplinary research facility which brings together engineering, architecture and biology researcher. Phase II of GRITlab involved the retrofitting of the Daniels 106-year old roof to allow for the construction of two full-scale integrated green and photovoltaic systems. The completed GRITlab will serve as a research, educational and demonstration facility for green infrastructure. This paper will present the planning, design and construction of GRITlab Phase II and discuss the challenges of retrofitting rooftops to support green infrastructure.
Journal of Environmental Management, 2013
ecoweekconference.org
Contemporary water and sanitation infrastructure in the Jordan River Watershed is often massive i... more Contemporary water and sanitation infrastructure in the Jordan River Watershed is often massive in scale and its environmental impacts are visually and logistically detached from its context. This infrastructure limits water management to the jurisdiction of ...
Low impact development (LID) is an innovative and alternative land-development approach to tradit... more Low impact development (LID) is an innovative and alternative land-development approach to traditional stormwater drainage. Extensive green roof (GR) is an LID technology that can be implemented to reduce the runoff generated by rainfall on building rooftops. When a GR is integrated with a photovoltaic system (PV), it may lower localized ambient temperature through evapotranspirarion (ET). Lowering the operating temperature of PV cells increases the conversion efficiency and useful lifetime of PV panels. PV panel shading may block solar radiation on GR partially, which may affect ET rates. Understanding the ET process in shaded and unshaded areas of combined system (GR-PV) is the goal of this study. Two Smart Field Lysimeters were modified to measure the ET of two GR modules, one in a shaded area (under the PV panels) and one in an unshaded area. The measured ET for PV shaded GR under PV shadow was 81% and 38% lower than measured ET for unshaded GR in summer-irrigated and fall-non-i...
Out of Water - Design Solutions for Arid Regions, 2015
Ecological Engineering, 2018
Abstract The thermoregulation of buildings and cities by green roofs is a primary driver of their... more Abstract The thermoregulation of buildings and cities by green roofs is a primary driver of their integration into urban environments. In warm seasons, green roofs cool buildings (thereby reduce interior air conditioning costs), and cities (impervious surfaces contribute to urban heat islands and vegetation mitigates contributions by conventional roof surfaces). In cool seasons, green roofs insulate buildings by reducing heat flux through the roof surface. Here we investigate thermoregulation services provided by extensive green roofs in warm and cool seasons from temperature data points recorded at 5-minute intervals over a four-year period, and from modules containing either Sedum or perennial grasses and herbaceous flowers, mineral- or organic-based substrate, 10 cm or 15 cm substrate depth, and supplemental irrigation or none. We demonstrate that Sedum outperformed a mixture of perennial grasses and herbaceous flowers over the total inter-annual survey period. The meadow mixture was more dependent on supplemental irrigation than Sedum, but more susceptible to inter-annual climate variability. Our findings point to the durability of Sedum as a plant for extensive green roof cooling, as well as the importance of plant selection and identifying traits that match not just microclimatic conditions in summer, but also in winter.
Journal of Hydrology, 2018
Abstract The hydrology and stormwater management benefits of green roofs (GRs) when integrated wi... more Abstract The hydrology and stormwater management benefits of green roofs (GRs) when integrated with photovoltaic (PV) arrays are currently not well understood. This study is the first quantitative study of an integrated full-scale GR-PV system in Canada. In this project, two GR-PV systems, with low (0.6 m) and high (1.2 m) differential height (LDH and HDH) between the GR surface and PV panels have been compared with a GR test module for storm water retention and biomass. Over 51 rainfall events in summer and fall 2016 and spring 2017, rainwater retention, peak flow reduction, NRCS curve number, and biomass of GR-PV and GR systems were examined. Rainwater retention and peak flow reduction were not significantly different between the LDH and HDH systems. Vegetation growth was 47% greater in the HDH system compared to the LDH system. This was attributed to greater solar radiation and rain exposure of vegetation in the HDH system due to the greater vertical distance between the PV panels and the GR modules.
Journal of Hydrologic Engineering, 2017
This study assesses the relative influence of four independent variables on green roof hydrologic... more This study assesses the relative influence of four independent variables on green roof hydrological performance under rainstorm conditions. Twenty-four extensive green roofs representing all combinations of the following four design factors were used: native meadow species versus Sedum; mineral-based versus biologically derived planting medium; 10-cm versus 15-cm depth; and irrigation provided daily, sensor controlled, or not at all. From events covering the period May-October in 2013 and 2014, mean values were determined for the seasonal volumetric runoff coefficient (C vol ¼ 0.4), peak runoff coefficient (C peak ¼ 0.12), and U.S. Natural Resources Conservation Service (NRCS) curve number (CN ¼ 94). Irrigation had the largest overall impact: daily irrigation increased C vol to 0.5 compared to 0.3 for systems with sensor-controlled or no irrigation. The biologically derived planting medium, composed of a high proportion of aged wood compost, made a significant improvement, maintaining C vol of 0.3 compared to 0.4 for the mineral-based product in the modules without irrigation. A similar pattern was found in the NRCS curve numbers.
Ecological Engineering, 2016
Vegetated roofs are a widely accepted form of green infrastructure deployed around the world to c... more Vegetated roofs are a widely accepted form of green infrastructure deployed around the world to contribute to building efficiency and climate change mitigation and adaptation through improved thermoregulation and water capture. No two roofs are the same, and the evaporative cooling functions of green roofs have been linked to a number of attributes including plant species combinations and cover, substrate type, and the use of supplemental irrigation. Using a replicated extensive green roof modular array, temperature change at five thermal sensor stations along a vertical gradient was determined to examine the effects of irrigation and attributes of the vegetation and substrate. Over two seasons, a significant 2 • C difference at the surface of the substrate and 1.5 • C difference 15 cm above the substrate layer was found between the treatment combination with the highest temperature (grasses and wildflower 'meadow' mix, inorganic substrate, no irrigation) and the lowest temperature (Sedum plant community, organic substrate, supplemental irrigation). Vegetation type and cover were important for roof cooling, and overall, Sedum cooled the roof significantly more than meadow vegetation. Irrigated meadow vegetation in organic substrate performed as well as unirrigated Sedum. Supplemental irrigation and organic substrate were important variables for roof cooling, although these lead to additional inputs that could reduce sustainability in the overall design. Sedum should be promoted to improve green roof cooling due to constant, near 100% vegetative cover. However, additional study is needed to interpret additional benefits that might come from combining Sedum and other suitable wildflowers and grasses, as well as the role of plant and substrate diversity in improving multiple green roof functions.
Out of Water - Design Solutions for Arid Regions, 2015
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Conference Presentations by Liat Margolis
Maximizing evaporative cooling requires that the green roof contain moisture and so regular irrigation would be indicated. But, our hottest months are often those with the most extreme rainfall events and water already within the planting media can hinder the storm water performance of the green roof.
Methodology:
The GRIT Laboratory at the University of Toronto is a pioneering multidisciplinary research facility; equipped with an onsite meteorological station and thirty-three individual extensive green roof modules. Each module is equipped to capture rainwater runoff and measure vertical thermal profiles, providing the opportunity to explore the relationship between water balance and microclimate. In addition to irrigation programming, further variables explored include: the planting substrate type and depth, and the selection of vegetation.
Preliminary Results:
The sensors came online, monitoring and recording thermal and hydrological data at the start of the 2013 growing season. Through a summer of remarkable storms and fluctuating temperatures, irrigation was determined as the primary indicator for predicting decreased storm water retention. Over the six months, May-October, daily irrigation reduced storm water retention by up to 75%. However, the supplementary irrigation had a huge impact on the localized ambient temperature. In some instances through July, the observed difference was up to 20 ºC between irrigated and non-irrigated modules at 15cm from the surface (defined as top of growing media).
Lessons:
Many green roofs already have irrigation systems installed; although their usage varies widely. As such this early research is a foundation step in developing recommendations for best maintenance practices to optimize the infrastructural benefits of new and existing extensive green roofs.
Papers by Liat Margolis
Maximizing evaporative cooling requires that the green roof contain moisture and so regular irrigation would be indicated. But, our hottest months are often those with the most extreme rainfall events and water already within the planting media can hinder the storm water performance of the green roof.
Methodology:
The GRIT Laboratory at the University of Toronto is a pioneering multidisciplinary research facility; equipped with an onsite meteorological station and thirty-three individual extensive green roof modules. Each module is equipped to capture rainwater runoff and measure vertical thermal profiles, providing the opportunity to explore the relationship between water balance and microclimate. In addition to irrigation programming, further variables explored include: the planting substrate type and depth, and the selection of vegetation.
Preliminary Results:
The sensors came online, monitoring and recording thermal and hydrological data at the start of the 2013 growing season. Through a summer of remarkable storms and fluctuating temperatures, irrigation was determined as the primary indicator for predicting decreased storm water retention. Over the six months, May-October, daily irrigation reduced storm water retention by up to 75%. However, the supplementary irrigation had a huge impact on the localized ambient temperature. In some instances through July, the observed difference was up to 20 ºC between irrigated and non-irrigated modules at 15cm from the surface (defined as top of growing media).
Lessons:
Many green roofs already have irrigation systems installed; although their usage varies widely. As such this early research is a foundation step in developing recommendations for best maintenance practices to optimize the infrastructural benefits of new and existing extensive green roofs.
Projects and materials are cross-referenced according to performance criteria, processes, and properties. Each of the 36 international projects and 23 material technologies is presented with drawing details and construction photographs. Descriptions of key processes and adaptive qualities provide an analysis of the various complex systems featured, such as vertical growth structures, flood prevention, stormwater infiltration and erosion control.
Projects featured include works by West8, GROSS.MAX, Weiss-Manfredi Architects, Field Operations, Kathryn Gustafson, and Vogt Landschaftarchitekten.