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Comparison on energy saving: Green roof and green wall
Abstract
Green building conveys undeniably numerous benefits to the environment, social and economic aspects. The most substantial benefit of green building is energy conservation. Green roofs and green walls are amongst the green components that are synonymous with green building. These green components are similar in nature as both are based on the concept of vegetation coverage on buildings. Vegetation is a well-known natural medium that performs the photosynthesis process where it releases molecular oxygen and removes carbon dioxide from the atmosphere. Many studies have proved that these two green components are efficient in reducing energy consumption of a building. Therefore, this study aims to examine and compare the annual energy savings conveyed by green roofs and green walls on residential buildings in Malaysia. The findings indicated that green walls provide greater annual energy savings than green roofs. The result shows that green walls are able to provide higher annual electricity savings for residential buildings at RM166 compared to green roofs, which provide savings of only RM139.
... Retrofitting the green roofs in existing buildings is feasible in construction and has long-term benefits (Castleton et al., 2010). Azis et al. established the potential of an integrated green wall along with green roofs with respect to the annual electricity savings (Azis et al., 2019). ...
The concept of green cities has been getting sustained focus for some time, intending to transform dispersed cities into environmentally, ecologically, and socially healthier spaces to live. The concept interlinks different domains of urban development, such as spatial planning, transport, water and sanitation services, urban greenery, renewable energy, sustainable building construction, and socioeconomic growth through green solutions. Energy planning and management play a vital role in transforming urban areas into environmentally sustainable cities. Integrating energy management as a key aspect of green city strategies from the pre-planning to post-implementation stages can expedite the process. This paper attempts to comprehend the intertwined role of energy management in green city planning through a comprehensive literature review. Relevant articles that discuss energy and management in interdisciplinary domains under the green city concept were identified and reviewed for the period—2000–2021. Diverse energy-efficient management measures and techniques are reviewed under seven domains of green city planning: green spatial planning, transportation, public infrastructure, urban agriculture, buildings, energy, and growth. The summarized literature emphasizes the relevance and significance of efficient energy management in the transition toward a green city. The study also discusses the need for a gradual transition and the challenges in successfully implementing and managing sustainable strategies. The successful implementation of climatic and environmental solutions through policy-level strategic interventions demands continuous effort and monitoring to achieve the long-term goal of sustainability. Energy-efficient urban development practices, with the foundation of a policy framework, can act as sustainable solutions to maintain the synergy between energy independence and urban development. Expediting the transformation of green cities with the adoption of energy-efficient strategies and renewables to decarbonize the energy supply is an accomplishable vision for every city.
... Pumice, lava, expanded slate, expanded split clay and recycled material from porous clay bricks and pumice are well suited for this purpose. Another determining factor when choosing the appropriate vegetation is the climatic conditions of the area, and according to the analyses carried out, the vegetation should withstand high temperatures, long periods of sun exposure and long periods of drought [17], [18]. ...
La urbanización reduce las áreas verdes en entornos construidos que producen el au-mento de la escorrentía, promoviendo las inundaciones en eventos de precipitación. En este trabajo se desarrolló un diseño de techos verdes y jardines verticales en las edifica-ciones de la Universidad Francisco de Paula Santander, Cúcuta, Colombia, como alter-nativa útil del sistema urbano de drenaje sostenible. En este sentido, se realizó el análisis estructural de las edificaciones con el software Etabs ®, en donde se comparó el diseño original con las cargas que generan las distintas categorías de techos. También, se revi-saron las condiciones climáticas y ambientales para establecer las características ade-cuadas de los componentes de las cubiertas verdes. Se obtuvo mediante los análisis que los edificios "Bienestar" y "Civil" se encuentran capacitadas para resistir las cargas aña-didas por un sistema de techo verde extensivo, siendo factible su implementación. En el diseño se generaron imágenes de los techos verdes y jardines verticales. La implemen-tación de los sistemas de cubierta verde en las edificaciones representa una herramien-ta para mitigar los impactos de la urbanización y mejorar las condiciones paisajística.
... Vegetation prevents the environment from freezing in winter, which increases the roof's insulation. It provides energy storage in winter [33,36,50,78,79,85]. ...
Sustainability has been one of architecture’s most significant trends over the last twenty years. The environmental consciousness of professionals has put sustainability at the heart of the architectural profession and has contributed to adopting and implementing sustainable designs on the scale of urban landscapes. A green roof or living roof, which is a sustainable solution in architecture, is a roof on the surface of which plants are grown. The roof is covered by plants, covering the waterproof layer beneath the vegetation. However, various types of plants can be used in this scheme. Understanding the influencing factors in choosing the right plant species and the impact that utilizing green roofs has on the overall energy consumption of the building can tremendously help scientists and clarify the possible future research topics in this field. Hence, this article investigates energy optimization in the construction process of a green roof in sustainable architecture and its advantages and challenges. The results of this study show that budget limitations, managerial and organizational policies, legal issues, technical and scientific infrastructure, and cultural and geographical aspects are all affecting the widespread use of green roofs currently and need to be considered in future studies.
... The active house is a deliberate idea for developing and upgrading houses that contribute to human health, security, and fitness in terms of the indoor and outdoor environment, as well as energy efficiency. The active house design is based on the triple energy method of sustainable design, and the main focus of its idea is on the notion that the most sustainable energy source is energy savings [48]. As a result, the active house design is more descriptive and thorough than other existing systems. ...
In modern times, the majority of the world's energy consumption is attributable to the heating and cooling of residential buildings. Because of this, the development of sustainable energy sources has increased dramatically, particularly in residential buildings, with the goal of reducing the amount of energy that is consumed within buildings. An extensive green roof system is one of the most effective ways to save energy. Not only does this lessen the impact that humans have on their surroundings, but it also has positive effects on people's health and the way their homes look. The purpose of this study was to investigate the thermal characteristics of green roofs installed on residential buildings in Qatar's hot and dry climate in order to assess their viability and determine how best to minimize energy usage. In the course of this investigation, five distinct heights ranging from 10 to 50 cm were taken into consideration to assess the energy efficiency of the roof. Of these heights, the height of 10 cm was found to be the most suitable height for planting in this environment. In addition, in order to evaluate the performance of roof energy, five plant leaf area indices with values ranging from one to five have been taken into consideration. Of these, the results indicate that the plant leaf area index is the plant planting index that works best in this environment. The larger the plant's leaves, the more protection they will provide from the sun and the higher the yield will be. In addition, to evaluate the effectiveness of the roof energy system, four height dimensions of 8, 13, 18, and 23 cm were considered for the cultivation layer. According to the findings, the height of the plant substrate layer is 23 cm, and the height of the cultivation layer is 18 cm. The cultivation layer that yields the best results for green roofs in this environment.
... ctor, a slight increase of RM30.6 billion from the previous year. The building sector is the sector that is responsible for the use of energy for high operational purposes. From 2005 to 2010, the trend for energy consumption in buildings in Malaysia increased by 34%. Public hospital buildings are among the buildings that utilise high energy levels (Ab. Azis et al., 2019). Hospitals and healthcare facilities are among the most energy-intensive buildings in Malaysia and are currently facing a more significant challenge due to the Covid-19 pandemic. Operating non-stop 24 hours a day, hospitals and healthcare facilities consume extensive energy sources from medical equipment, lighting, heating, ventilation ...
Hospitals and healthcare facilities are known to be among the most energyintensive buildings. This concern has resulted in a resurgence of sustainability awareness in the built environment. Nowadays, many have adopted environmental strategies such as natural ventilation. It offers a low-cost alternative to remove stale air and replace fresh air efficiently through cross ventilation. Studies have shown that natural ventilation is one of the most energyefficient solutions to improve thermal comfort and hospitals and healthcare facilities will greatly benefit from this initiative. Passive Design has been valued as a key strategy in controlling airborne infection, especially in hospital wards with limited resources. Comparatively, the installation of ceiling-mounted mechanical fans will create a negative ventilation pressure difference. This paper explores the potential of the passive design method based on the experience of inpatient ward users. The study utilised questionnaires based on the end user's experience in a naturally ventilated inpatient ward area. The survey administration method ensures the 51 respondents’ anonymity is preserved especially in a healthcare setting. This investigation shows that natural ventilation provides a higher ventilation rate and is more energy-efficient than mechanical ventilation. Therefore, natural ventilation is a suitable solution in public buildings such as hospitals' inpatient wards. The outcome of this study will be paramount for designers to meet passive design objectives. Consequently, these will be the guidelines and outline information for hospital design in the future.
... Pumice, lava, expanded slate, expanded split clay and recycled material from porous clay bricks and pumice are well suited for this purpose. Another determining factor in the choice of suitable vegetation is the climatic conditions of the area, and according to the analyses carried out, the vegetation should withstand high temperatures, long periods of sun exposure and long periods of drought [19], [20]. ...
La urbanización reduce las áreas verdes en entornos construidos que producen el aumento de la escorrentía, promoviendo las inundaciones en eventos de precipitación. En este trabajo se desarrolló un diseño de techos verdes y jardines verticales en las edificaciones de la Universidad Francisco de Paula Santander, Cúcuta, Colombia, como alternativa útil del sistema urbano de drenaje sostenible. En este sentido, se realizó el análisis estructural de las edificaciones con el software Etabs ®, en donde se comparó el diseño original con las cargas que generan las distintas categorías de techos. También, se revisaron las condiciones climáticas y ambientales para establecer las características adecuadas de los componentes de las cubiertas verdes. Se obtuvo mediante los análisis que los edificios “Bienestar” y “Civil” se encuentran capacitadas para resistir las cargas añadidas por un sistema de techo verde extensivo, siendo factible su implementación. En el diseño se generaron imágenes de los techos verdes y jardines verticales. La implementación de los sistemas de cubierta verde en las edificaciones representa una herramienta para mitigar los impactos de la urbanización y mejorar las condiciones paisajística.
This study is aimed to assess the performance of green roof-PV system; and determine the optimum installation height of green roof. In this study, two units PV panels of 1 kW each were setup at building rooftop level. Modular green roofs were established at three different heights of 0.3 m, 0.6 m and 0.9 m from rooftop floor level, respectively. The effects of each green roof height on the PV module temperature, ambient temperature and daily power yield were monitored for 6 months’ period. The results showed that green roof-PV system exhibited lower ambient and PV module temperatures of 3.36% and 17% compared to bare roof-PV system. Other than that, green roof enhanced the power generation efficiency averagely by 1.6%. It is found that green roof installed at 0.3 m has increased the power generation performance by 3% and 11% compared to that of 0.6 m and 0.9 m, respectively.
A very large component of the maintenance cost of any real estate property is the electricity consumption cost. The electricity consumption cost of a 700-acre university campus in Malaysia would reach an overall yearly operating expenditure of nearly RM 1 billion. Knowing this fact, the University of Malaya’s (UM) top management has conducted many projects at various scales to address energy efficiency (EE), including the replacement of old and inefficient mechanical and electrical (M&E) equipment and the installation of new EE technologies around the campus. In enhancing the overall EE effort, an energy management system is required to ensure that a calculated EE plan can be implemented and audited after it is completed to improve the overall sustainability of UM. Therefore, this study presents the formulation of an Energy Management System (EMS) for UM based on the ASEAN Energy Management Scheme (AEMAS) methodology. Results show that with the full support of the top management of the university, the EMS can be implemented with at least a 5% electricity consumption reduction per year. The formalization of the EMS is the most important step in ensuring any marked reduction in electricity consumption campus-wide.
a b s t r a c t Current systems for greening the buildings envelope are not just surfaces covered with vegetation. Greening systems, as green roofs and green walls, are frequently used as an aesthetical feature in buildings. However, the current technology involved in these systems can maximize the functional benefits of plants to buildings performance and make part of a sustainable strategy of urban rehabilitation and buildings retrofitting. During the last decades several researches were conducted proving that green walls can contribute to enhance and restore the urban environment and improve buildings performance. The aim of this paper is to review all types of green wall systems in order to identify and systematize their main characteristics and technologies involved. So, it is important to understand the main differences between systems in terms of composition and construction methods. Most recent developments in green walls are mainly focused in systems design in order to achieve more efficient technical solutions and a better performance in all building phases. Yet, green wall systems must evolve to become more sustainable solutions. In fact, continuing to evaluate the contribution of recent green wall systems to improve buildings performance and comparing the environmental impact of these systems with other construction solutions can lead to an increase of their application in buildings and therefore result in a reduction on these systems cost. The decision of which green wall system is more appropriate to a certain project must depend not only on the construction and climatic restrictions but also on the environmental impact of its components and associated costs during its entire lifecycle.
Rapid urbanization and the concern for climate change have led to a growing trend to bring nature into the cities. Due to artificial urbanization, urban heat islands have become a serious problem. Greenery is expected to be an effective countermeasure, and much research is available regarding green roofs, green walls, street trees and parks. The intent of this paper is to present a synthesis of the literature review on the design and technology for cooling of building and surroundings by using vertical greenery system. Effect of design parameters on building microclimate and the applicable cooling technologies are discussed.
Green roofs have multiple environmental benefits and are widely used around the world. In keeping with this mainstream movement, the use of green roofs has been increasing in Taiwan in recent years. This paper reviews policies promoting green roof development in Taiwan, and compares the environmental and economic performance of green roofs in Taiwan to those in East Asian countries and worldwide. National and regional government policies have stimulated the development of green roofs by establishing goals for reducing carbon emissions of cities, promoting green construction, mitigating heat island effects, and increasing urban flood control. Local studies of green roof performance are few, other than thermal investigations. These studies have shown that green roofs significantly contribute to thermal reduction and moderate temperature variations around buildings. One study sampled stormwater runoff from green roof sites and found that sediment and nutrient concentration on these roofs are up to ten times higher than on conventional bare roofs; however, acid rain can be neutralized by green roofs. Hydrographs have shown that reductions in runoff from green roofs are not as great as expected because retention and detention are affected by high rainfall intensity, which is the typical precipitation pattern in Taiwanese cities. Without additional maintenance, green roofs can contribute to nonpoint source pollution in urban cities in wet and hot weather zones, because of high runoff and associated mass loading. Moreover, the environmental benefits of green roofs in Taiwan may not be as significant as those in other countries in which utility costs are higher, where decreasing energy consumption and CO2 emissions would be of greater benefit.
Abstract The hot and arid climate in the United Arab Emirates (UAE) yields indoor temperatures much higher than the comfort zone, which poses unique challenges in improving energy performance through building construction systems. The study examines the introduction of green façades to reduce heat gain in indoor spaces as a strategy to lower cooling demand. A vegetative living wall was installed on a school building façades and experimentally studied. The experimental results showed that during day time in the peak summer month of July, the green facade can maintain on average a temperature that is 5 °C lower than a bare wall, consequently impacting building cooling load and improving energy performance.
The rapid growth in population and economy activities in the tropical countries has led to an increase in energy consumption which hastens the depletion of available energy resources. The building sector is one of the major end users of energy. On the other hand, the air conditioning system is viewed as an important tool to sustain and improve thermal comfort of occupants, but this system is often the biggest energy consumer in buildings. This has raised concerns on efficient use of the air conditioning system for reduction in energy cost. In order to identify the thermal comfort perception of occupants as well as energy conservation potentials in tropical buildings, various thermal comfort assessments were conducted which included field surveys and chamber studies. This paper provides a comprehensive review of the energy efficiency improvement potentials in air-conditioned tropical buildings by considering thermal comfort of occupants. Some of the studies conducted in the institutes of learning, offices and residential were reviewed and focus was placed on the thermal comfort studies that emphasis on balance between energy efficiency and thermal comfort. It was estimated that a reduction of 2150 GWh of energy demand annually in Malaysia can be achieved if the thermostat set-point is set higher by 2 °C, together with a reduction of 3 × 109 lbs (1.36 × 109 kg) of greenhouse gases. Besides, the use of computational simulation tools for prediction of thermal comfort and adaptive behaviour of people in the tropics towards their immediate thermal environment are also highlighted.
Statistics have confirmed that a lawn placed on a roof top can reduce the cooling load. In this study, the VISUAL DOE 4.0 energy simulation program was used to determine the effects of roof lawn gardens (RLG) on the annual energy required for cooling, and annual electrical usage in an experimental model. The overall heat transfer coefficient (U-Value) of the RLG was estimated by using data from site measurements and the effect of the RLG on the building’s energy consumption was calculated by the simulation program. The effect of different thicknesses of soil was also investigated. From the field measurements, it was confirmed that the RLG could reduce building heat gain. Thus, an experiment was set up to find the energy benefits of the RLG. With evaporative cooling by the RLG, it was found that the consumption of energy in a building with a RLG with 0.20 m of soil was 37.11% less than in a building with a bare roof surface (without evaporative cooling). Moreover, a building with 0.10 m of soil in the RLG consumed 31.07% less energy than a building with a bare roof surface. The results show that an increase in the thickness of the soil layer reduces the building energy consumption.
DOE-2 energy simulation program was used to determine the effects of rooftop garden on the annual energy consumption, cooling load and roof thermal transfer value (RTTV) of a five-story hypothetical commercial building in Singapore. The thermal resistances (R-values) of turfing, shrubs and trees were estimated using data from site measurements, and the effects on the building energy consumption of a rooftop garden with these three types of plants were simulated. Two soil types with different soil thickness on the building roof were also simulated. The results showed that the installation of rooftop garden on the five-story commercial building can result in a saving of 0.6–14.5% in the annual energy consumption, and shrubs was found to be most effective in reducing building energy consumption. The results also revealed that the increase of soil thickness would further reduce the building energy consumption and the moisture content of soil can affect the outcome quite substantially.
The objective of this research is to simulate the effects of vertical greenery systems on the temperature and energy consumption of buildings. Firstly, it involves performing TAS simulations to determine their effects on thermal comfort and energy consumption. It is found that 100% greenery coverage from vertical greenery systems is effective in lowering the mean radiant temperature of a glass facade building. Furthermore, to lower the energy cooling load significantly, the shading coefficient of plant species has to be low. Secondly, a thermal calculation of the envelope thermal transfer value (ETTV) to obtain their effects on the thermal performance of building envelope is performed. Results show a linear correlation between shading coefficient and leaf area index where a lower shading coefficient leads to a greater thermal insulation. 50% greenery coverage from vertical greenery systems and a shading coefficient of 0.041 reduce the ETTV of a glass facade building by 40.68%. Lastly, vertical greenery systems in mitigating the UHI effect within an estate is simulated using STEVE model. The increase of greenery coverage from vertical greenery systems is most significantly felt with a drop in the minimum estate air temperature throughout a large region of the estate.
The aim of the present work is to analyse thoroughly the influence of the orientation and proportion (covering percentage) of plant-covered wall sections on the thermal behaviour of typical buildings in the Greek region during the summer period. As to the effect of construction parameters, the layer position of masonry/insulation has been also considered. The investigation has been carried out using a thermal-network model that adequately simulates the building zone under assumption; its validation was based on experimental results from a recently reported study. The model makes provision for several heat-flow paths in order to take into account the leaf cover on the external wall surface, heat transfer through the surfaces that constitute the building envelope, and natural ventilation. The influence of orientation and covering percentage of plant foliage for walls with different configurations was studied using representative outdoor environmental data for the zone location at a specific time period.
After decades of fast growth, the scarcity of land in cities causes many buildings to be constructed very close to expressways, exposing occupants to serious noise pollution. In recent years, sustainable cities have found that greenery is a key element in addressing this noise pollution, giving rise to the popularity of vertical greenery systems (VGS). This research has two objectives. The first involves the study of eight different vertical greenery systems installed in HortPark, Singapore to evaluate their acoustics impacts on the insertion loss of building walls. Experiment shows a stronger attenuation at low to middle frequencies due to the absorbing effect of substrate while a smaller attenuation is observed at high frequencies due to scattering from greenery. Generally, VGS 2, 7 and 8 exhibit relatively better insertion loss. The second objective aims to determine the sound absorption coefficient of the vertical greenery system constructed in the reverberation chamber which is found to have one of the highest values compared with other building materials and furnishings. Furthermore, as frequencies increases, the sound absorption coefficient increases. In addition, it is observed that the sound absorption coefficient increases with greater greenery coverage.
Greenery in cities has long been recognized as an ecological measure to mitigate some environmental issues. The chapter discusses three major types of urban greenery: public green areas, rooftop gardens and vertical landscaping from both a systematic and thermal benefit point of view. Much related research carried out worldwide is reviewed. In order to achieve strategic landscaping in cities, some general guidelines are given.
Sustainability has been enshrined as a goal of society to ensure that the satisfaction of present needs does not compromise the ability of future generations to meet their own needs. It is thus a social objective, achievable only where all areas of society co-operate in fulfilling the associated demands. Ecological sustainability is, in turn, a basic prerequisite for sustainable economic and social development. The first step in formulating an effective response to this challenge, focused solely on the environmental issues, entails a quantification of the contribution required from the various areas of human activity for the achievement of sustainable development. Without binding sub-targets for the different sectors, it will be all but impossible to move systematically towards a sustainable society. These benchmarks for sustainable construction therefore set out to define the requirements to be met by buildings and structures in contributing to the achievement of a sustainable society. The permissible impact of buildings, in terms of energy demand and pollutant loads, during construction, maintenance and operation is determined. The analysis focuses on identifying the permissible levels of loads based on the specific energy consumption per m2 and year for heating, hot water, electricity and construction. A conscious attempt is made to combine existing methods with the general political consensus by taking account of:-the ecological scarcity method [G. Brand, A. Scheidegger, O. Schwank, A. Braunschweig, Bewertung in Ökobilanzen mit der Methode der ökologischen Knappheit (Life cycle analysis using ecological scarcity method), Environmental Publication no. 297, Swiss Agency for the Environment, Forests and Landscape (SAEFL), 1997] used to define critical pollutant loads;-the limitation of greenhouse gas emissions specified by the intergovernmental panel on climate change (IPCC) [Intergovernmental Panel on Climate Change, Climate Change 2001, IPCC Third Assessment Report, www.grida.no/climate/ipcc_tar/];-the demands of the 2000 W society [Leichter leben – Ein Verständnis für unsere Ressourcen als Schlüssel zu einer nachhaltigen Entwicklung – die 2000-Watt-Gesellschaft (Easier living – understanding our resources as the key to sustainable development – the 2000 Watt society), novatlanis, sia, energieschweiz, January 2005] for the conservation of energy resources.The study shows that buildings designed to the Passive House standard just about comply with the requirements for sustainable construction, provided electricity generation is based largely on renewable or low-CO2 resources (Swiss power supply mix). The targets are substantially harder to meet where mainly fossil-fuel-generated electricity (European supply mix UCTE) is used.
The advantages of the planned roofs are undoubtedly numerous from both the ecological and the social point of view. They act positively upon the climate of the city and its region, as well as upon the interior climate of the buildings beneath them. They give protection from the solar radiation, which is the main factor in passive cooling. By reducing thermal fluctuation on the outer surface of the roof and by increasing their thermal capacity, they contribute, to the cooling of the spaces below the roof during the summer and to the increase of their heat during the winter. Due to the decrease of the thermal losses, the green roofs save the energy consumption.This paper refers to the analysis of the thermal properties and energy performance study of the green roof. The investigation were implemented in two phases: during the first phase, extended surface and air temperature measurements were taken at the indoor and outdoor environment of the buildings where the green roof had installed and during the second phase of the study, the thermal properties of the green roof, as well as, the energy saving were examined, through a mathematical approach.
This paper deals with the experimental investigation and analysis of the energy and environmental performance of a green roof system installed in a nursery school building in Athens. The investigation was implemented in two phases. During the first phase, an experimental investigation of the green roof system efficiency was presented and analysed, while in the second one the energy savings was examined through a mathematical approach by calculating both the cooling and heating load for the summer and winter period for the whole building as well as for its top floor. The energy performance evaluation showed a significant reduction of the building's cooling load during summer. This reduction varied for the whole building in the range of 6–49% and for its last floor in the range of 12–87%. Moreover, the influence of the green roof system in the building's heating load was found insignificant, and this can be regarded a great advantage of the system as any interference in the building shell for the reduction of cooling load leads usually to the increase of its heating load.
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The passive cooling effect of green roof in high rise residential building in Malaysia
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