b'GREEN ROOF SYSTEMSDRAINAGE LAYER IMPACTON THE THERMAL AND MOISTURE PERFORMANCE OF EXTENSIVE GREEN ROOF SYSTEMS:An experimental studyBy Fitsum Tariku, PhD and Sara Hagos, B.Sc., M.A.Sc., CTR, GRPG responses to outdoor environmental conditions are monitored reen roof systems are becoming a popular nature-based solution worldwide due to their potentialand analyzed, Figure 1(a) and Figure 1(b). to reduce building energy consumption, heatTo make modular test roofs with an interior dimension of island effects and urban noise, improve air quality,four ft. by four ft., frames are made from two-inch-thick increase biodiversity and the longevity of roofingextruded polystyrene foam (XPS) and then the frames are systems, provide aesthetic value and reduce and delay rain runoff. Green roofs can be categorized into exten- wrapped by the root barrier. The use of these materials (XPS sive, intensive and semi-intensive systems. Extensive greenand root barrier) is intended to restrict lateral heat and mois-roofs are widely used due to their lightweight, thin growingture transfers. A slit is made at the corner of the root barrier media, limited or no maintenance, low cost and high poten- and the frames to drain and measure the rain runoff from the tial application for use over the new or existing lightweightmodules. The slit is connected to a trough that directs the structures. Here, the dynamic thermal and moisture responseswater to the rain gauges mounted on the test building. The of the extensive green roofs, varying in terms of drainagetest modules are placed on the roofs top and the drainage layers, are presented based on a field experimental studylayers of the modules are installed. Then a one-inch diam-conducted at the BCIT Building Science Centre of Excellenceeter PVC pole is glued at the centre of each test roof module using the Whole Building Performance Research Laboratoryto position sensors in the growing media and above. After (WBPRL). A green roof with non-reservoir polypropylenesecuring the sensors in place, the test modules are filled with drainage (GR), a green roof with a reservoir polypropylenefour-inch-thick growing media that consist of 70-per-cent drainage (RES) and a green roof with non-reservoir expandedpumice and 30-per-cent compost, and the sedum acre plug polystyrene (EPS) drainage layers are constructed, installedplants are planted 15 cm apart. Fertilizer is applied every week on a roof deck of the test building, instrumented, and theirand irrigation is provided every other day for two months until the plants are fully grown. A root barrier and a drainage mat are installed in the space between the roof modules and filled with a growing media to create uniformity and provide lateral support to the modules. Plants Growing Mediaers and locations of sensors in the three test roofs (GR, The layFilter Fabric Drainage Layer RES and EPS) are the same except for the drainage layers, Root Barrier Waterproofing Membrane Figure 1(c). The thicknesses of the drainage layers of GR, Plywood Sheathing 1.5 Air Gap between Purlins 2x12 Wood Joist RES and EPS are 0.45 in., 1.5 in. (0.4 in reservoir core) and R-48 Batt Insulation Vapour Barrier Gypsum Bo3 in., Figure 1(d) to Figure 1(f), respectively. Type T thermo-ard (A) (B)couples and GS1 Moisture content sensors are installed at the PlantsSensors Symbolstop, middle and bottom layers of the growing media, which Growing Media Filter Fabricare at x, y and z from the bottom surface. Pyranometer Drainage LayerType T ThermocouplesRoot Barrier Waterproofing MembraneMoisture Content Sensor Plywood SheathingRelative Humidity Transducer type CMP3-L and tipping bucket rain gauges type E-802-1.5 Air Gap between PurlinsHeat Flux TransducerKIPP004 are installed to measure the solar radiation received 2x12 Wood Joist R-48 Batt Insulation Vapour BarrierPyranometer and reflected, and the rain runoff from the green roofs, Gypsum Board respectively. Heat flux transducers are installed at the bottom of the roof insulation and the growing media to measure the Sensors Symbols Type T Thermocouples heat loss/gain through the green roofs. Two additional ther-Moisture Content Sensormocouples are installed in each roof module to measure the Relative Humidity Transducer (E) (F) roof sheathing and ceiling temperatures. All measurements (D)Heat Flux TransducerFIGURE 1. (A) TEST BUILDING, (B) MODULAR GREEN ROOFS ON TEST BUILDING, (C)in the green roof modules are taken in five-minute intervals, Pyranometer GR SENSORS LAYOUT, (D) GR DRAINAGE LAYER WITH LAMINATED FILTER FABRIC,except for the weather and runoff measurements, which are (E) RES DRAINAGE LAYER, (F) EPS DRAINAGE LAYER. recorded in one-minute intervals. FALL/WINTER 2024 17'