Assessment of green roof performance for sustainable buildings under winter weather conditions

A green roof is a specialized roof system that supports vegetation growth on rooftops.This technology is rapidly gaining popularity as a sustainable design option for buildings.In order to contribute to an understanding of green roof in regions with cold winters and snow,an on-site experimental investigation was present with a focus on the assessment of green roof performance during the winter.This field experiment took place on a six small buildings during the winter of 2010-2011.The work monitored three buildings with green roofs,two buildings with reference roofs and one building with a bare soil coverage for the roof.These six buildings were identically constructed and instrumented with sensor networks to provide heat flux data through the roofs.The 15 min averaged data were statistically analyzed for a week under the two separate periods,first without a snow cover and second with a snow cover.The results show that the roof type is a significant factor in affecting the thermal performance of these buildings.Most importantly,green roofs reduce heat flow through the roof and thus reduce the heating energy demand during the winter.However,the energy savings for buildings with the green roofs are reduced under snow conditions because the snow diminishes thermal resistance of the roof and increases the heat transfer process through the roofs.

Ecological Function of Urban Green Roof and Analysis of Its Influencing Factors

Based on the analysis of the multiple ecological functions of green roofs, the main factors affecting the ecological functions of green roofs are expounded and the numerical simulation methods for quantitative calculation of ecological functions of green roofs are summarized in order to provide theoretical and method support for the construction of urban green roofs.

PV-green Roofs植被层高度对系统性能影响

绿化屋顶(GR)和光伏发电系统(PV)在调节室内热湿环境与降低建筑能耗中发挥着重要作用,利用两系统互效性耦合而成的光伏-绿化屋顶(PV-green Roofs)是推进建筑节能的创新型举措。结合PV-green Roofs数学模型,分析植物高度对系统性能的影响,通过实验测定,以落地生根和佛甲草为绿化屋顶植被层材料,实测不同工况下PV-green Roofs系统的电量输出值,同时结合EnergyPlus数值模拟结果分析采用不同植株高度的PV-green Roofs系统对建筑消耗净能量的影响。结果表明:植物高度通过改变绿化屋顶种植层蒸发阻力和植被层冠状层风速影响系统性能;在夏热冬冷的气候条件下,植物生命中期对应的高度对光伏系统工作环境的冷却效果最为明显,引起输出电量的增值最大,且环境湿度对系统性能存在影响。

Green roofs for storm water management:a review

The rapid urbanization and industrialization involve an unsustainable use of natural systems,leading to various problems in cities.The urban hydrological system experiences fluctuating amount of surface runoff water when it rains heavily.It has been suggested that green roofs significantly mitigate storm water runoff generation even in tropical climate.Green roofs have become popular due to its proven benefits by mitigating urban heat island effects and protecting biodiversity.The annual rainfall and runoff relationship for green roofs is determined by the depth of the substrate.Water retention capacity mostly depends on substrate's physical conditions such as dry or wetness.Generally 6 mm to 12 mm rainfall is required for dry substrate to initiate runoff whereas response of wet conditions is mostly straight.Besides,there are some other factors affecting runoff dynamics such as type of a green roof and its slope,age of green roof,type of vegetation,soil moisture characteristics,weather.The review indicates that there is not much research in green roofs performance over storm water runoff;hence there is a need for further research.This paper reviews and addresses the role of green roofs in urban storm water management.

Application of Green Roof in Relieving Urban Waterlogging: A Review

Green roof plays a critical role in regulating roof runoff by reducing runoff, delaying runoff generation, reducing runoff peak flow and improving runoff water quality effectively. On the basis of introducing significance and role of green roof, this paper reviewed domestic and international researches on the green roof's control over roof runoff, and analyzed the factors that influence the control of green roof over the runoff, so as to provide a theoretical support and method for the construction of green roofs in urban districts.

Green Roof Performance for Stormwater Management in Equatorial Urban Areas Using Storm Water Management Model (SWMM)

Many Low Impact Developments (LIDs) have recently been developed as a sustainable integrated strategy for managing the quantity and quality of stormwater and surrounding amenities. Previous research showed that green roof is one of the most promising LIDs for slowing down rainwater, controlling rainwater volume, and enhancing rainwater quality by filtering and leaching contaminants from the substrate. However, there is no guideline for green roof design in Malaysia. Hence, Investigating the viability of using green roofs to manage stormwater and address flash flood hazards is urgently necessary. This study used the Storm Water Management Model (SWMM) to evaluate the effectiveness of green roof in managing stormwater and improving rainwater quality. The selected study area is the multistory car park (MSCP) rooftop at Swinburne University of Technology Sarawak Campus. Nine green roof models with different configurations were created. Results revealed that the optimum design of a green roof is 100 mm of berm height, 150 mm of soil thickness, and 50 mm of drainage mat thickness. With the ability to reduce runoff generation by 26.73%, reduce TSS by 89.75%, TP by 93.07%, TN by 93.16%, and improved BOD by 81.33%. However, pH values dropped as low as 5.933 and became more acidic due to the substrates in green roof. These findings demonstrated that green roofs improve water quality, able to temporarily store excess rainfall and it is very promising and sustainable tool in managing stormwater.

Thermal Behaviour in Buildings with Green Covers Combined with Natural Ventilation, Green Facades and Green Roofs

The main aim of this paper was to study the influence of ventilation during a typical experimental day, in the internal air temperature as well as in internal surface temperatures under the conditions of the outer environment, using an experimental method which allows a comparison of the thermal performance between four cell tests： a prototype called control （no vegetation） and three with different combinations of vegetation （roofs and facades） installed in a region of tropical climate. The experiments were developed in four test cells with dimensions 2.0 m × 2.50 m × 2.7 m. Measurements of internal surface temperatures and internal air temperatures were collected with the use of specific equipment, a data logger （CR1000, Campbell Scientific Inc.）, connected with two multiplexers 32 channels （416AM Campbell Scientific Inc.）. Data were recorded over a year and a typical heat day was selected, which was September 24, 2015. The results show that ventilation affects the internal temperature of the air, so that this gets even surpass the external temperature. Regarding surface temperatures, increased temperature, except those which are provided with vegetation, namely, the surfaces which have green walls and green roofs file the lower temperatures. Therefore, we can confirm the ability of vegetation to maintain more pleasant internal conditions compared to the test cells built with conventional materials, thus it can reduce cooling load efficiency.

Thermal Response to Heat in Buildings with Green Covers for Tropical Climate： Green Facades and Green Roofs

The main aims of this paper were to study and demonstrate the benefits the plant systems can provide indoors in a critical heat day. This study proposed an experimental method to try to understand the thermal response to heat of four different systems： a prototype called control （no vegetation） and three with different combinations of vegetation （green roofs and green facades） installed in a tropical climate region. The experiments were developed in four test cells with dimensions 2.0 m × 2.50 m× 2.71 m. Measurements of internal surface temperatures and internal air temperatures were collected with the use of specific equipment, a data logger （CR1000, Campbell Scientific Inc.）, connected with two multiplexers 32 channels （416AM Campbell Scientific Inc.）. Data were recorded over a year and a critical day heat was selected, which was September 24, 2015.The results show that the use of plant systems in buildings establishes a passive technique in reducing energy consumption because of the high incidence of summer solar radiation which is reduced and simultaneously, it maintains thermal internal conditions more pleasant than external ones, because of the best thermal behaviour, which was observed in the test cell with vegetation on both roofs and facades. The biggest difference between maximum internal air temperatures registered was 2 ℃.

Understanding the Challenges of Implementing Green Roofs in Multi-Family Apartment Buildings:A Case Study in Khulna

Green roofs are widely recognized for their multifaceted benefits to the environment,economy,and society,constituting the fundamental pillars of sustainability.These roofs contribute to the enhancement of bio-physical diversity,provision of food resources,regulation of temperature and rainfall-runoff patterns,creation of wildlife habitats,and augmentation of aesthetic and recreational value.While Bangladesh,with its favourable climatic conditions and rapid urbanization,possesses immense potential for harnessing the advantages of green roofs,their adoption remains limited in both research and practical applications within the country.Addressing this research gap,the present study aims to investigate the barriers impeding the implementation of green roofs in existing or new multi-family apartment buildings,focusing specifically on the city of Khulna.Through a combination of case studies and a comprehensive questionnaire survey administered to diverse stakeholders including apartment dwellers/owners,architects,developers,and government officials with varying levels of expertise,this research sheds light on the obstacles hindering Green Roof Implementation(GRI).The identified barriers encompass a lack of governmental policies,inadequate technological advancements,inaccurate estimation of economic benefits,and individual resistance.In light of the perspectives of various GRI stakeholders,strategic proposals encompassing policy,technical,economic,and social dimensions are presented to surmount these barriers.The outcomes of this study contribute to the dissemination of knowledge pertaining to the impediments to GRI implementation,thereby inspiring further research endeavours and enabling decision-makers to formulate robust policies facilitating the widespread adoption of green roofs.

Landscape Design of Green Roofs Against the Background of Sponge City Construction: A Case Study of the California Academy of Sciences

In this paper, the green roof of the California Academy of Sciences was selected for example to illustrate the role of green roofs in sustainable urban planning from three aspects: landscape connection, building energy conservation and urban environment and elaborate the innovative design elements of the California Academy of Sciences, and the enlightenment of green roofs on the construction of sponge cities in China and the guiding role for future urban design were analyzed combined with the current urban problems in China and the research status of green roofs at home and abroad.

Analysis on thermal measuring of green roof

Comparison of thermal performance between a green roof room and a bare roof room was presented during the cooling period in Shanghai. The results show that the electricity can be saved about 0.08 kW·h/(d·m2),and the heat flux can be reduced by about 70%; the inner surface temperature variation is about 1.0 ℃ comparing with the indoor temperature when using the green roof,and the extra equivalent heat resistance is 1.0 m2·K/W.

Landscape Design of Urban Extensive Green Roofs

This study analyzed the structure and ecological characteristics of extensive green roofs in cities, proposed the concept of combining landscape and ecological environment elements, and expounded the guiding role of green roofs in China's future urban design, in order to provide new ideas for the effective development of the ecological and aesthetic functions of the extensive green roofs in the future urban landscape design.

Employing Green Roofs to Support Endangered Plant Species: The Eastern Suburbs Banksia Scrub in Australia

The purpose and context for the study relates to urban growth. Australian cities are experiencing particularly rapid urbanization, taking the form of land clearing to accommodate outward expansion as well as developing to higher densities in existing urban areas. Both forms of development degrade native biodiversity, resulting in loss of vegetation with the possibility that the remnant indigenous plants will become locally extinct. One endangered ecological community in Sydney, the Eastern Suburbs Banksia Scrub (ESBS), still survives along some sections of Sydney’s heavily urbanized coastline. At the time of European settlement, the ESBS covered approximately 5300 ha, but it is now a highly fragmented 146 ha across 24 sites with some sites under imminent threat of development. Conservation legislation enacted by the state of New South Wales (NSW), Australia has declared the ESBS as critically endangered. Despite recovery plans, in 2016 the NSW Threatened Species Scientific Committee indicated that the community faces an extremely high risk of extinction in Australia in the immediate future. A practical option in the face of declining open space in our cities is to examine the potential of urban rooftops for conserving and propagating threatened or endangered flora. While there is a limited amount of international research on using green roofs for endangered plant protection, there is no information from Australia about how green roofs perform in this geographic region. The approach taken in this research has been firstly, to review the current academic and “grey” literature from a global perspective to identify options for conserving endangered flora on green roofs. We derive an evidence-based research protocol to be used to test the green roof environment in Sydney for propagating the endangered ESBS. We establish the general applicability of green roofs for protecting vanishing flora through the literature review and conclude that our research design will be a suitable framework for the task for monitoring growth and germination performance over the ESBS community’s development cycle, with the longer-term objective of establishing a viable rooftop seed orchard.

Performance Evaluation of Hybrid Green Roof System in a Subtropical Climate Using Fluent

Energy disaster is one of the major obstacles in the progress of human society. There are some on-going researches to overcome this for a sustainable environment. Green roof system is one of them which assist to reduce energy consumption of the buildings. The green roof system for a building involves a green roof that is partially or completely covered with vegetation and plant over a waterproofing membrane. Green roofs provide shade and remove heat from the air through evapotranspiration, reducing temperatures of the roof surface and the surrounding air. This paper reports the thermal performance of hybrid green roof system for a hot and humid subtropical climatic zone in Queensland, Australia. A thermal model is developed for the green roof system using ANSYS Fluent. Data were collected from two modelled rooms, one connected with green roof system and other non-green roof system. The rooms were built from two shipping containers and?installed at Central Queensland University, Rockhampton, Australia. Impact of air temperature on room cooling performance is assessed in this study. A temperature reduction of 0.95°C was observed in the room with green roof which will save energy cost in buildings. Only 1.7% variation in temperature was found in numerical result in comparison with experimental result.

Evaluating the technical and economic aspects of thermal performance of extensive green roofs:A GIS-based case study in the urban setting of Na dor,Morocco

The increasing demand for green spaces in cities underscores the urgent need for sustainable solutions to reduce the ecological impact of urban areas.This research focuses on converting unused rooftops into extensive green roofs in Nador,Morocco,offering an innovative approach to enhancing outdoor thermal comfort in this region.Several advanced techniques were used,including photogrammetric restitution(for creating land use maps),integration of light detection and ranging data(for three-dimensional urban modeling),and meteorological data collection(for modeling urban climate conditions).The urban-multiscale-environmental-predictor solar and longwave environmental irradiance geometry(UMEP-SOLWEIG)model was crucial for precisely evaluating the thermal performance of green roofs and their influence on urban microclimates.This model considers considered various parameters,such as the sky view factor,wall height and aspect,and shading conditions,for accurate,comprehensive analysis.Additionally,for accurate,comprehensive analysis,a comparative evaluation was performed between the UMEP-SOLWEIG and ENVI-met models to assess the UMEP SOLWEIG results.The findings were notable,demonstrating a substantial reduction(averaging over 3℃)in the mean radiant temperature on 60%of rooftops,covering 55%of the total surface area.This highlighted the effectiveness of green roofs in improving outdoor thermal comfort.Furthermore,green roofs were closely associated with reductions in air-conditioning energy consumption,with considerable reductions ranging from 17.53%to 43.82%.These savings translated to estimated financial benefits ranging from USD 1.63-4.07 million.These figures clearly verified the notable economic impact of green roofs despite their initially high costs(approximately USD 84.44 million).These potential long-term savings indicated that these investments are financially viable in the long run.The collected data were used to create thermal maps of the area using geographic-information-system tools.A thermal cadaster specific to green roofs was also developed,accessible online through Web mapping.Overall,this approach facilitates decision-making in urban planning by providing visual information on thermal variations,thereby aiding in the precise planning of measures against urban heat and promoting the use of green roofs to reduce environmental impact.

EFFECT OF GREEN ROOF AGE ON RUNOFF WATER QUALITY IN PORTLAND,OREGON

Green roofs have become a common method to increase water retention on-site in urban areas.However,the long-term water quality of runoff from green roofs is poorly understood.This study evaluated the water quality of stormwater runoff from a regular(non-vegetated)roof,a green roof installed 6 months previously,and a green roof installed 6 years ago in Portland,Oregon.Samples of runoff were taken during every rain event for 10 months,and analyzed for total phosphorus(TP),phosphate(PO_(4)^(3-)),total nitrogen(TN),nitrate(NO_(3)^(-)),ammonia(NH_(3)),copper(Cu),and zinc(Zn).Runoff from the green roofs had higher concentrations of TP and PO_(4)^(3-)and lower concentrations of Zn compared to the regular roof.Average TP concentrations from the 6-year old roof and 6-month old roof were 6.3 and 14.6 times higher,respectively,than concentrations from the regular roof,and average PO_(4)^(3-)concentrations from the 6-year old roof and 6-month old roof were 13.5 and 26.6 times higher,respectively,compared to the regular roof.Runoff from the 6-month old green roof had higher concentrations of TP and PO_(4)^(3-)than the 6-year old green roof during the wet season,but lower concentrations during the dry season.The 6-month old green roof installations where receiving waters are sensitive or impaired may need additional treatment methods to reduce phosphorus levels.As green roofs age,water retention decreases and phosphorus leaching increases during the dry season.

GREEN ROOFING IN INDIANA: CASE STUDIES AND DESIGN NOTES

Green roof technology and implementation are taking root in North America at an accelerating pace.Growing recogni-tion of the benefits of green roofs and increasing interest in green infrastructure are leading to expansion of green roof tech-nologies that have been in use for decades in Europe and elsewhere.While some regions have adopted the use of green roofs on a large scale,other areas are warming up to the concept more slowly.Large-scale implementation of green roofs has not yet occurred in Indiana,but a number of exemplary projects have been constructed,and there are signs that interest in the technology is increasing in the state.The purpose of this article is to provide an overview of green roof technology,analyze selected green roofs in Indiana,explore trends in the state,and address issues for future development of green roof technol-ogy in the region.A variety of green roofs were investigated throughout the state.Discussions were held with individuals involved in each project to obtain technical and logistical details of green roof design,installation,and performance.

MEDIA COMPOSITION INFLUENCES GREEN ROOF PLANT VIABILITY IN THE OZARK HIGHLANDS

Plant selection and establishment are critical components for green roof health and success. Plant palettes (sets of plant species selected for specific conditions) for green roofs vary in their ability to confer benefits depending on the species make-up and their adaptation to particular environments and climates. The response of various species to climatic factors on rooftops is unknown for the Ozark Highlands region. The objective of this study was to compare plant survival and spread in three growing medium treatments (course and fine texture with compost and fine texture with no compost) installed as part of a green roof system. The study was performed on a green roof system at the University of Arkansas in Fayetteville over 3 years. Data were collected on 13 species installed in September of 2006 and surveyed on three dates thereafter: April 30, 2007;May 19, 2009;September 10, 2009. The treatments with added compost had statistically greater vegetated cover (from 73 to 87%) compared to the fine medium without compost (36 to 43%). In most cases the spread of individual plants was not significantly different between treatments. Results indicated that rooting medium containing compost increased survival and overall vegetated roof coverage, and identified various potential green roof plant species for the Ozark Highland environment. Two species, Sedum middendorffianum var. diffusum and Sedum spurium ‘Roseum’, did particularly well in all treatments. One species, Sedum kamtschaticum, did well only in the treatments with compost.

Vegetation composition of old extensive green roofs(from 1980s Germany)

Introduction:Since their development in the late 1970s in Germany,extensive green roofs(EGR)have become increasingly popular as mitigation tools for urban environmental issues around the world.EGRs are planted with select species,which ensure consistent cover and performance over time.This research presented herein is part of a systematic re-evaluation of EGR technology since the German industry began.Methods:Given the opportunity to access a small sample of old EGRs installed over 20 years ago in south-west Germany,this research surveyed the vegetation and substrate with an interest in describing these parameters with time-through-space substitution.Results:Similar to previous studies,this preliminary work found correlations between roof age with vegetation(cover abundance and species diversity)and substrate properties(e.g.,depth,organic content,pH,and nutrients).Roof age had positive relationship with soil organic content(Corg),and negative relationships with substrate depth and soil pH.These soil variables are inter-related,as shallow acidic substrates create unfavourable conditions for decomposition and thereby the accumulation of duff.Substrate variables correlated with EGR vegetation,suggesting a trend of simplified species composition over time.Indeed,Corg had a negative relationship with cover and species diversity of most life forms;only Sedum species had positive associations with Corg.Conclusions:Considering the dynamics associated with shallow mineral substrates,and the greater floristic diversity of younger roofs,simple Sedum-based vegetation may represent a steady state for conventional EGRs.