scholarly journals Impact of Vegetation, Substrate, and Irrigation on the Energy Performance of Green Roofs in a Mediterranean Climate

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2016 ◽  
Author(s):  
Gomes ◽  
Silva ◽  
Valadas ◽  
Silva
Keyword(s):  
Mediterranean Climate ◽  
Energy Use ◽  
Soil Depth ◽  
Green Roof ◽  
Green Roofs ◽  
Energy Performance ◽  
Area Index ◽  
Vegetation Height ◽  
Energy Needs ◽  
Irrigation Levels

Green roof energy performance is still a challenging topic, namely in a Mediterranean climate since it depends on building characteristics, roof type, and also on climatic conditions. This paper evaluates green roof buildings’ energy needs and use in a Mediterranean climate. An experimentally calibrated numerical model was used to perform a parametric analysis and identify the influence of key parameters in heating and cooling energy needs, as well as annual energy use. The vegetation height, the soil depth, and LAI (leaf area index) were identified as the key parameters. The irrigation levels were also crucial for the energy performance of green roofs, particularly during the summer period and in a Mediterranean climate. Heating energy needs were mainly associated with soil depth due to higher thermal resistance, whereas cooling energy needs depended mostly on LAI, which influenced evapotranspiration and shading effects. A reduction of soil depth from 1.0 m to 0.1 m increased winter energy needs by up to 140%, while low values of LAI increased cooling energy needs up to 365%. Annual energy use in a Mediterranean climate showed a higher dependence on soil depth, with oscillations of up to 115%, followed by LAI and vegetation height. Finally, irrigation levels impacted the annual energy use more significantly for lower watering flow rates. Reductions of about 500% were obtained when changing watering flowrates from 0 mm/day to 6 mm/day in intensive green roofs. Since green roofs with native species expect low values of watering, this may increase their cooling energy needs.

scholarly journals Effects of Extensive Green Roofs on Energy Performance of School Buildings in Four North American Climates

Water ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 6 ◽  
Author(s):  
Milad Mahmoodzadeh ◽  
Phalguni Mukhopadhyaya ◽  
Caterina Valeo
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Plant Height ◽  
Green Roof ◽  
Green Roofs ◽  
Energy Performance ◽  
Design Parameters ◽  
Soil Thickness ◽  
Area Index ◽  
Roof Design

A comprehensive parametric analysis was conducted to evaluate the influence of the green roof design parameters on the thermal or energy performance of a secondary school building in four distinctively different climate zones in North America (i.e., Toronto, ON, Canada; Vancouver, BC, Canada; Las Vegas, NV, USA and Miami, FL, USA). Soil moisture content, soil thermal properties, leaf area index, plant height, leaf albedo, thermal insulation thickness and soil thickness were used as design variables. Optimal parameters of green roofs were found to be functionally related to meteorological conditions in each city. In terms of energy savings, the results showed that the light-weight substrate had better thermal performance for the uninsulated green roof. Additionally, the recommended soil thickness and leaf area index for all four cities were 15 cm and 5 respectively. The optimal plant height for the cooling dominated climates is 30 cm and for the heating dominated cities is 10 cm. The plant albedo had the least impact on the energy consumption while it was effective in mitigating the heat island effect. Finally, unlike the cooling load, which was largely influenced by the substrate and vegetation, the heating load was considerably affected by the thermal insulation instead of green roof design parameters.

scholarly journals A Comparison of Energy and Thermal Performance of Rooftop Greenhouses and Green Roofs in Mediterranean Climate: A Hygrothermal Assessment in WUFI

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 2030
Author(s):  
Mansoureh Gholami ◽  
Alberto Barbaresi ◽  
Patrizia Tassinari ◽  
Marco Bovo ◽  
Daniele Torreggiani
Keyword(s):  
Thermal Performance ◽  
Mediterranean Climate ◽  
Green Roof ◽  
Green Roofs ◽  
Energy Performance ◽  
Building Envelope ◽  
Considerable Proportion ◽  
Urban Context ◽  
Cooling Period ◽  
The Impact

In urban areas, a considerable proportion of energy demand is allocated to buildings. Since rooftops constitute one-fourth of all urban surfaces, an increasing amount of attention is paid to achieving the most efficient shapes and component designs compatible with every climate and urban context, for rooftops of varying sizes. In this study, three types of rooftop technologies, namely insulated, green roof, and rooftop greenhouse, are evaluated for energy and thermal performance using computer simulations. Water surface exposure, absorption, and intrusion are the three important factors in the calculation of hygrothermal models that impact energy consumption and building envelope performance; however, a few studies are specifically focused on providing realistic results in multi-dimensional hygrothermal models and the assessment of the impact of moisture in roofing solutions. This paper aims at evaluating the performance of three different roofing technologies through a two-dimensional hygrothermal simulation in software WUFI. To accomplish this, a precise localized microclimate model of a complex urban context on the scale of a neighborhood was employed to evaluate the cooling and heating loads of the buildings, the impact of the water content in the green roof on the thermal behavior of the roof surface, and the feasibility of designing a building with nearly zero cooling needs. A two-story building in the city center of Bologna, Italy is modelled. Simulation results have shown that during the cooling period, the performance of the designed rooftop greenhouse is the most effective by 50% reduction in cooling loads. Besides, the impact of moisture in green roofs has been detected as a negative factor for thermal and energy performance of the building in the Mediterranean climate. The results ultimately highlighted the capability of passively-designed rooftop greenhouses to create a building with nearly zero cooling needs.

scholarly journals Green roofs in building retrofits: outdoor microclimate benefits and energy savings

2021 ◽  
Author(s):  
Melissa Ann Furukawa
Keyword(s):  
Energy Consumption ◽  
Energy Demand ◽  
Energy Savings ◽  
Soil Depth ◽  
Green Roof ◽  
Green Roofs ◽  
Area Index ◽  
Heating And Cooling ◽  
Building Energy Analysis ◽  
The Impact

The impact of green roof retrofits on the local microclimate and energy consumption of a building is investigated. This research is based on a case study of Kerr Hall located on the Ryerson University campus in Toronto. The software ENVI-met is used to simulate the microclimate while EnergyPlus is used for the building energy analysis. Results indicate that increasing the leaf area index (LAI) of the green roof leads to increased cooling effect up to 0.4 degrees C during the day at pedestrian-level; however, more significant cooling is attained at the rooftop-level. The addition of the green roof reduced both the heating and cooling demands and improved indoor comfort levels. Energy demand reductions up to 3% were obtained with the green roof retrofits with the biggest contribution form from reduction in heating on the top floor. Increasing the soil depth had a larger impact on the energy consumption compared to increasing the LAI.

scholarly journals Green roofs in building retrofits: outdoor microclimate benefits and energy savings

2021 ◽  
Author(s):  
Melissa Ann Furukawa
Keyword(s):  
Energy Consumption ◽  
Energy Demand ◽  
Energy Savings ◽  
Soil Depth ◽  
Green Roof ◽  
Green Roofs ◽  
Area Index ◽  
Heating And Cooling ◽  
Building Energy Analysis ◽  
The Impact

The impact of green roof retrofits on the local microclimate and energy consumption of a building is investigated. This research is based on a case study of Kerr Hall located on the Ryerson University campus in Toronto. The software ENVI-met is used to simulate the microclimate while EnergyPlus is used for the building energy analysis. Results indicate that increasing the leaf area index (LAI) of the green roof leads to increased cooling effect up to 0.4 degrees C during the day at pedestrian-level; however, more significant cooling is attained at the rooftop-level. The addition of the green roof reduced both the heating and cooling demands and improved indoor comfort levels. Energy demand reductions up to 3% were obtained with the green roof retrofits with the biggest contribution form from reduction in heating on the top floor. Increasing the soil depth had a larger impact on the energy consumption compared to increasing the LAI.

Energy Performance of Sustainable Roofing Systems

2013 ◽  
Author(s):  
David J. Sailor ◽  
Prem Vuppuluri
Keyword(s):  
Energy Use ◽  
Green Roof ◽  
Green Roofs ◽  
Energy Performance ◽  
Office Building ◽  
Solar Photovoltaic ◽  
Conduction Model ◽  
Exterior Surface ◽  
Photovoltaic Array ◽  
Heating And Cooling

This study presents efforts to analyze how sustainable roofing technologies can contribute to the energy budget of buildings, and the resulting implications for heating and cooling energy use. The data analyzed in this study were obtained from a field experiment performed on a four story warehouse/office building in Portland, Oregon USA. The building’s roof includes a 216 panel, 45.6 kW solar photovoltaic array in combination with 576 m2 of vegetated green roofing. While most of the surface consists of green roof shaded by photovoltaic panels, the roof also has test patches of dark membrane, white membrane and un-shaded green-roofing. Interior and exterior surface temperatures were monitored over a period of two years and heat flux into the building is estimated using a finite difference conduction model. On average, the black roof membrane was the only roof that caused a net heat gain into the building in the summer. In the winter, all four roofing technologies resulted in net heat losses out of the building. Both the PV-shaded and un-shaded green-roofs indicated a net heat loss out of the interior of the building during both the summer and winter. This latter effect is largely a result of green-roof evaporative cooling — which can benefit air conditioning demand in summer but may be undesirable during heating-dominated seasons.

scholarly journals AI-Based Campus Energy Use Prediction for Assessing the Effects of Climate Change

2020 ◽  
Vol 12 (8) ◽  
pp. 3223 ◽  
Author(s):  
Soheil Fathi ◽  
Ravi S. Srinivasan ◽  
Charles J. Kibert ◽  
Ruth L. Steiner ◽  
Emre Demirezen
Keyword(s):  
Climate Change ◽  
Energy Use ◽  
Regional Climate ◽  
Regional Climate Change ◽  
Developed Countries ◽  
Energy Performance ◽  
Energy Needs ◽  
Energy Use Prediction ◽  
Campus Energy ◽  
The Impact

In developed countries, buildings are involved in almost 50% of total energy use and 30% of global annual greenhouse gas emissions. The operational energy needs of buildings are highly dependent on various building physical, operational, and functional characteristics, as well as meteorological and temporal properties. Besides physics-based energy modeling of buildings, Artificial Intelligence (AI) has the capability to provide faster and higher accuracy estimates, given buildings’ historic energy consumption data. Looking beyond individual building levels, forecasting building energy performance can help city and community managers have a better understanding of their future energy needs, and to plan for satisfying them more efficiently. Focusing at an urban scale, this research develops a campus energy use prediction tool for predicting the effects of long-term climate change on the energy performance of buildings using AI techniques. The tool comprises four steps: Data Collection, AI Development, Model Validation, and Model Implementation, and can predict the energy use of campus buildings with 90% accuracy. We have relied on energy use data of buildings situated in the University of Florida, Gainesville, Florida (FL). To study the impact of climate change, we have used climate properties of three future weather files of Gainesville, FL, developed by the North American Regional Climate Change Assessment Program (NARCCAP), represented based on their impact: median (year 2063), hottest (2057), and coldest (2041).

scholarly journals Technical considerations in green roof retrofit for stormwater attenuation in the Central Business District

2015 ◽  
Vol 33 (1) ◽  
pp. 36-51 ◽  
Author(s):  
Sara Wilkinson ◽  
Jessica Lamond ◽  
David G Proverbs ◽  
Lucy Sharman ◽  
Allison Heller ◽  
...  
Keyword(s):  
Built Environment ◽  
Focus Groups ◽  
Energy Use ◽  
Relevant Literature ◽  
Green Roof ◽  
Green Roofs ◽  
Environmental Benefits ◽  
Design Stage ◽  
Due Diligence ◽  
Content Type

Purpose – The key aspects that built environment professionals need to consider when evaluating roofs for the purpose of green roof retrofit and also when assessing green roofs for technical due diligence purposes are outlined. Although green or sod roofs have been built over many centuries, contemporary roofs adopt new approaches and technologies. The paper aims to discuss these issues. Design/methodology/approach – A mixed methods design based on a systematic review of relevant literature from parallel disciplines was used to identify and quantify the social, economic and environmental benefits of retrofitted green roofs in commercial districts. The technical issues of concern were drawn from a desk-top survey of literature and from stakeholder focus groups undertaken in Sydney in 2012. Findings – There are perceptions amongst built environmental practitioners that may act as artificial barriers to uptake. There is little direct experience within built environment professionals and practitioners, along with a fear of the unknown and a risk averse attitude towards perceived innovation which predicates against green roof retrofit. Furthermore projects with green roofs at inception and early design stage are often “value engineered” out of the design as time progresses. There is a need for best practice guidance notes for practitioners to follow when appraising roofs for retrofit and also for technical due diligence purposes. Research limitations/implications – The focus groups are limited to Sydney-based practitioners. Although many of these practitioners have international experience, few had experience of green roofs. A limited number of roof typologies were considered in this research and some regions and countries may adopt different construction practices. Practical implications – In central business districts the installation of green roof technology is seen as one of the main contributors to water sensitive urban design (WSUD). It is likely that more green roofs will be constructed over time and practitioners need knowledge of the technology as well as the ability to provide best advice to clients. Originality/value – The benefits of green roofs as part of WSUD are increasingly being recognised in terms of reduced flood risk, reduced cost of drainage, improved water quality and lower energy use, as well as other less tangible aspects such as aesthetics and amenity. This research highlights the lack of understanding of the short- and long-term benefits, a poor appreciation and awareness of these benefits; a lack of technical knowledge and issues to be considered with regard to green roofs on behalf of practitioners. The study has highlighted the need for specific training and up-skilling in these areas to provide surveyors with the technical expertise needed. There is also a need to consider how the emerging retrofit and adaptation themes are best designed into the curriculum at both undergraduate and postgraduate levels. Clearly, if the potential benefits of green roofs are to be realised in the future, building professionals need to be fully conversant with the technology and be able to provide reliable and accurate advice.

scholarly journals Decreasing Water Footprint of Electricity and Heat by Extensive Green Roofs: Case of Southern Italy

2020 ◽  
Vol 12 (23) ◽  
pp. 10178 ◽  
Author(s):  
Behrouz Pirouz ◽  
Stefania Anna Palermo ◽  
Mario Maiolo ◽  
Natale Arcuri ◽  
Patrizia Piro
Keyword(s):  
Energy Consumption ◽  
Water Consumption ◽  
Experimental Analysis ◽  
Energy Production ◽  
Mediterranean Climate ◽  
Water Footprint ◽  
Green Roof ◽  
Green Roofs ◽  
Air Conditioner ◽  
Roof Temperature

Electrical and energy production have a noticeable water footprint, and buildings′ share of global energy consumption is about 40%. This study presents a comprehensive experimental analysis of different thermal impacts and water consumption of green roofs in a Mediterranean climate. The study aims to investigate the use of water directly for green roofs and reduce the water footprint of energy in summer and winter due to its thermal impacts. The measurements were carried out for an extensive green roof with an area of 55 m2 and a thickness of 22 cm, and direct water consumption by a green roof and direct and indirect water consumption by cooling and heating systems were analyzed. According to the analysis, in summer, the maximum roof temperature on a conventional roof was 72 °C, while under the green roof it was 30.3 °C. In winter, the minimum roof temperature on a conventional roof was −8.6 °C, while under the green roof it was 7.4 °C. These results show that green roofs affect energy consumption in summer and winter, and the corresponding thermal requirements for the building have a water footprint regarding energy production. In summer, the thermal reduction in the water footprint by a green roof was 48 m3 if an evaporative air conditioner is used and 8.9 m3 for a compression air conditioner, whereas the water consumed in the green roof was 8.2 m3. Therefore, using water directly in the green roof would reduce the energy consumption in buildings, and thus less water has to be used in power plants to provide the same thermal impact. In winter, green roofs′ water consumption was higher than the thermal water footprint; however, there is no need to irrigate the green roof as the water consumed comes from precipitation. This experimental analysis determines that in the Mediterranean climate, green roofs allow the achievement of the same thermal conditions for buildings in both summer and winter, with a reduction in water consumption.

scholarly journals Impact of Green Roofs on Energy Demand for Cooling in Egyptian Buildings

2020 ◽  
Vol 12 (14) ◽  
pp. 5729 ◽  
Author(s):  
Ayman Ragab ◽  
Ahmed Abdelrady
Keyword(s):  
Thermal Conductivity ◽  
Energy Consumption ◽  
Energy Demand ◽  
Soil Depth ◽  
Green Roof ◽  
Green Roofs ◽  
Climatic Regions ◽  
Reduce Energy Consumption ◽  
The Impact ◽  
Reducing Energy

Energy consumption for cooling purposes has increased significantly in recent years, mainly due to population growth, urbanization, and climate change consequences. The situation can be mitigated by passive climate solutions to reduce energy consumption in buildings. This study investigated the effectiveness of the green roof concept in reducing energy demand for cooling in different climatic regions. The impact of several types of green roofing of varying thermal conductivity and soil depth on energy consumption for cooling school buildings in Egypt was examined. In a co-simulation approach, the efficiency of the proposed green roof types was evaluated using the Design-Builder software, and a cost analysis was performed for the best options. The results showed that the proposed green roof types saved between 31.61 and 39.74% of energy, on average. A green roof featuring a roof soil depth of 0.1 m and 0.9 W/m-K thermal conductivity exhibited higher efficiency in reducing energy than the other options tested. The decrease in air temperature due to green roofs in hot arid areas, which exceeded an average of 4 °C, was greater than that in other regions that were not as hot. In conclusion, green roofs were shown to be efficient in reducing energy consumption as compared with traditional roofs, especially in hot arid climates.

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