The Green Roof Innovation Testing Laboratory, or GRIT Lab, is located at the University of Toronto, John H. Daniels Faculty of Architecture, Landscape, and Design. A platform for multidisciplinary collaboration, GRIT Lab links the fields of Landscape Architecture, Biology, Hydrology and Building science, with the goal of investigating the environmental performance associated with ‘green’ & ‘clean’ technologies such as green roofs, green walls, and photovoltaic arrays.
GRIT Lab offers students a unique hands-on opportunity to work directly with the latest material and digital technologies, as well as with both industry experts and academics from a wide range of disciplines.
This wide range of partnerships with industry, academic institutions and government agencies have far reaching implications for education and knowledge transfer, innovation and commercialization, as well as policy and guidelines. The cross-pollination between these disciplines is designed to promote new innovations, while the links to industry enable their implementation.
This state-of-the-art facility, established in 2010, includes 33 green roof test beds, 3 green walls, 2 photovoltaic modules, a weather station, and over 300 sensors connected to over 5,000 linear feet of wiring. Data is collected on soil moisture, flow rates, temperature, rainfall, humidity, solar, and wind every five minutes. This robust installation will permit a comprehensive and dynamic understanding of the water-energy-biology nexus in context of climate specific priorities.
GREEN ROOF RESEARCH
GRIT Lab is evaluating the City of Toronto’s Green Roof Construction Standard with respect to four performance criteria:
1) Stormwater Retention
2) Evaporative Cooling
4) Life Cycle Cost
Thirty-three test beds compare and manipulate the four parameters:
1) Growing Media Type (FLL/organic)
2) Depth (4″/6″)
3) Vegetation (sedum/biodiverse)
4) Irrigation (none/timer/moisture sensor)
Each bed is instrumented with thermal and moisture sensors, a rain gauge and an infrared radiometer; where the data is analyzed against base-climate data, acquired via the onsite weather station. Constructed to simulate green roofs, each 4′ x 6′ module includes a roof membrane, foam insulation, parapet and flashing, drainage board, geotextile, filter cloth, growing media and vegetation.
To accurately quantify stormwater management and evaporative cooling, several data points are required. Base climate data is gathered through a weather station installed on site. This data includes: wind speed and direction, barometric pressure, solar radiation, rainfall, relative humidity and ambient temperature. In order to calculate stormwater runoff and quantify water retention capacity, each bed is equipped with a tipping bucket rain gauge (measuring volume/time) and a soil moisture sensor (measuring volumetric water content, temperature and electrical conductivity in the soil).
In order to quantify the thermodynamic magnitude of each bed and calculate evaporative cooling, five temperature sensors and an infrared radiometer are installed on a vertical gradient: one temperature sensor is installed at the top of the growing media and a second at the bottom. This allows the heat flux through the media to be determined. A third temperature sensor is positioned at the bottom of each bed to a high degree of accuracy with respect to heat flux. Two temperature sensors are positioned at heights of 6in and 2ft above the media. These are used to determine the distance at which the evaporative cooling effect takes place. An infrared radiometer is mounted 4ft about the bed surface to record the average surface temperature (3ft circle).
The biological component of the green roof is being studied through field observations. The primary purpose of this analysis is two-fold:
1) To accurately document and quantify plant diversity and composition, and
2) To determine the affect of various treatments (growing media type, depth and irrigation regime) on specific species.
Included in this process is the documentation of germination density during the establishment period, the recovery rate after the dormant winter months and the annual changes over the study period.
GREEN WALL RESEARCH
GRIT Lab investigates the growth potential of green facades (i.e. three-dimensional metal screens and tensile cables) in context of the Toronto climate and in elevated heights. The study focuses on the leaf coverage of two vine species over time and their influence on the thermal regulation of a building envelope.
In order to quantify the thermodynamic influence of each vine species on the building envelope, three temperature sensors are installed behind each green façade panel, as well as a number of blank (control) panels. Leaf area index, or leaf coverage is being studied through field observations. Included in this process is the documentation of leaf density during the growing season, the recovery rate after the dormant winter months and the annual changes over the study period.
PHOTOVOLTAIC ARRAY RESEARCH
Integrating photovoltaic and green roofs reduces environmental impacts by simultaneously providing renewable energy, evaporative cooling, and stormwater retention on building rooftops. In Phase II, two different photovoltaic module heights (2, 4ft) will be tested above two roofing surfaces (white & green) for optimal photovoltaic performance, exposure to wind, practicality of installation and maintenance, and effect of shading of plants.
GRIT Lab is testing the hypothesis that green roofs reduce local air temperature through evapotranspiration and solar reflectance, in order to optimize the performance of the photovoltaic arrays and extend their lifetime.