b'GREEN ROOF SYSTEMSPERFORMANCE OF GREEN ROOF INSTALLED ON HIGHLY INSULATED ROOF DECK:An experimental studyBy Fitsum Tariku, Ph.D. and Sara Hagos, B.Sc., M.A.Sc., CTRG reen roof systems have been increasingly imple-mented around the world due to reducing building energy consumption, heat island effects and urban noise, improving air quality, increasing biodiversity and the longevity of roofing systems, providing aesthetic value and reducing and delaying rain runoff. Green roofs can be categorised into extensive, intensive and semi-intensive systems. Extensive green roof is widely used due to its lightweight, thin-growing media, limited or no maintenance, low cost and high poten-tial application for use over the new or existing lightweight structures. Here, the energy and rainwater retention performances of extensive green roofs, when coupled with a highly insulated roof deck, are presented based on a field experimental study conducted at BCIT. Three test modulesconventional roof (CR) and two extensive green roofs withplants (GR) and with no plants (GM)FIG. 1. BUILDINGS WHERE THE TEST ROOF MODULES ARE INSTALLED ON (A) SOUTH TEST BUILDINGare constructed and instrumented,ROOF, (B) WITH CR AND GM TEST MODULES AND (C) GR ON THE NORTH TEST BUILDING ROOF.and their responses to real environ-mental conditions are monitored and analyzed for summer, fall, winter andTo make modular test roofs with anare installed. Then, a one-inch-diameter spring climatic conditions in Vancouver,interior dimension of 4 ft. by 4 ft.,PVC pole is glued at the centre of each Canada. The test modules were installedframes are made from two-inch-thicktest roof module to support and accu-on the roofs of twin research buildingsextruded polystyrene foam (XPS), andrately position sensors in the growing that have a roof thermal resistance valuethen the frames are wrapped by themedia and above. Then, the test of R-43 (RSI-7.6), which is 1.72 timesroot barrier to restrict lateral heat andmodules are filled with four-inch-thick higher than the national building codemoisture transfers. A slit is made atgrowing media that consist of 70-per-roof insulation requirement for thethe bottom corner of the roof modulescent pumice and 30-per-cent compost, location (R-25). The test buildings haveand connected to trough to directand the sedum acre plug plants are identical construction, orientation andexcess water to the rain gauges. The testplanted 15 cm apart. Root barrier and dimensions (250-sq.-ft. floor area andmodules are placed on the roofs topdrainage layers are installed on the 10-ft. height) (Fig. 1). and the drainage layers of the modulesremaining roof area of the conditioned SPRING/SUMMER 2023 17'