Performance monitoring of three ecoroofs in Portland, Oregon

Abstract

Ecoroofs, also known as green roofs, are becoming widely installed with relatively little data collected on their in situ performance. For this study, three large ecoroof portions (280-500 m 2 ) located on two different buildings in Portland, OR, USA were instrumented and monitored continuously for more almost 3 years. For the Broadway Building, a student dormitory on the campus of Portland State University, measurement of ecoroof energy conservation and rainwater discharge abatement helped qualify the building for its Leadership in Energy and Environmental Design silver award. Using an electromagnetic flowmeter, stormwater discharge was monitored and compared to rainfall. Over a 3-year period, rainwater discharge was reduced by about 25%. Rooftop heat flux was simultaneously measured using an array of temperature sensors. When compared to a rock ballast roof exposed to the same weather conditions, the ecoroof heat flux was reduced by 13% in winter and 72% in summer. Retrofit ecoroof installations on the Multnomah County Building, an office building, were also monitored for almost 3 years for two separate ecoroof sections with different plantings, using similar electromagnetic flow meters and a rain gauge. Overall reductions of rainwater discharge were 12% and 17% for those two ecoroofs. For all three ecoroofs, discharge reductions varied widely by month due to seasonal differences in the amount of rainfall. Based on the measurements taken in this study, ecoroofs in Portland, OR, USA appear to offer some performance advantages.

The Influence of Hydrologic Parameters on the Hydraulic Efficiency of an Extensive Green Roof in Mediterranean Area

“…Few literature studies have developed models which accurately predict the hydraulic efficiency of green roofs [2,13,26]. In this study the conceptual model developed by for the green roof described in the previous section was used [2].…”

“…From an energy prospective, green roofs also promote evaporative cooling, thereby offsetting the energy requirements associated with air conditioning systems and reducing urban heat island effects [6,7]. From a hydraulic perspective, several studies have shown that green roofs have significant effects on retaining rainfall volumes [8][9][10][11], delaying the peak flow rate [12,13] and reducing the runoff volume discharged into the combined sewer systems (CSSs) [14][15][16]. Many literature studies have, indeed, investigated the hydraulic efficiency of green roofs, but only few have focused on the performance of such systems under Mediterranean climate condition.…”

Seasonal and Diurnal Thermal Performance of a Subtropical Extensive Green Roof: The Impacts of Background Weather Parameters

“…The literature has generated extensive studies on green-roof thermal effects in various climatic contexts. These studies roughly fall into three categories in terms of study approaches and objectives, including: (1) on-site monitoring to investigate green-roof impacts on summer temperature parameters and building heat flux patterns [9][10][11][12][13][14][15][16][17][18][19][20][21][22]; (2) dynamic energy modeling to analyze the heat and moisture processes within the green-roof layers and identify key influential factors [23][24][25][26][27][28]; and (3) building energy simulation or meso-scale climatic modeling to predict the cooling and energy effects of individual or multiple green-roof installations [29][30][31][32][33][34]. The studies have reported that green roofs can reduce summer daily peak surface temperature by 15 °C-45 °C and peak air temperature by up to 5 °C.…”

Wpływ Wysokości Opadów Na Wielkość I Szybkość Odpływu Wód Z Dachów Zielonych

“…Dzięki zastosowaniu do ich budowy wielu warstw o różnych funkcjach posiadają szereg zalet, do których należy zaliczyć: retencję wód opadowych [17][18][19][20][21], opóźnienie spływu wód opadowych [7,22,23], zmniejszenie szczytowej fali odpływu [24,25], racjonalizację zużycia energii w budynku [26,27], redukcję hałasu [28], ograniczenie efektu "wyspy ciepła" [29,30] oraz obniżenie poziomu zanieczyszczeń w powietrzu [31,32]. Dodatkowymi korzyściami wynikającymi z zastosowania dachów zielonych jest zwiększenie bioróżnorodności i poprawa mikroklimatu w terenach zurbanizowanych.…”