Performance Of Roofs Research Articles

Above-roof air temperature effects on HVAC and cool roof performance: Experiments and development of a predictive model

In building performance simulations it is typically assumed that outdoor HVAC equipment is exposed to air at the outdoor ‘ambient’ temperature, obtained from a weather file. However, in reality, significant spatial variations in the outdoor air temperature can exist close to buildings. This simplification may lead to significant errors, especially when comparing simulations of buildings with and without cool roofs, since the colder surface of the cool roof would reduce above-roof air temperatures, thereby influencing the energy consumption of rooftop HVAC equipment.Above-roof temperature variations were measured in detail at three shopping centre buildings, and the experimental data was used to develop a model that can estimate air temperatures above hot or cold roof surfaces. The model requires only four input variables, all of which are available in typical building simulation tools.Implementation of the model in a set of case-study simulations revealed that above-roof air temperatures can have a large effect on the predicted performance of cool roofs. In cases where cooling equipment and ventilation inlet ducts were both located on the roof, the electricity savings and gas ‘penalties’ attributable to cool roofs would have been underestimated by 44–85% (61% on average) if above-roof air temperature variations had not been modelled accurately.

Measurements of the water balance components of a large green roof in the greater Paris area

Abstract. The Blue Green Wave of Champs-sur-Marne (France) represents the largest green roof (1 ha) of the greater Paris area. The Hydrology, Meteorology and Complexity lab of École des Ponts ParisTech has chosen to convert this architectural building into a full-scale monitoring site devoted to studying the performance of green infrastructures in storm-water management. For this purpose, the relevant components of the water balance during a rainfall event have been monitored: rainfall, water content in the substrate, and the discharge flowing out of the infrastructure. Data provided by adapted measurement sensors were collected during 78 d between February and May 2018. The related raw data and a Python program transforming them into hydrological quantities and providing some preliminary elements of analysis have been made available. These measurements are useful to better understand the hydrological processes (infiltration and retention) conducting green roof performance and their spatial variability due to substrate heterogeneity. The data set is available here: https://doi.org/10.5281/zenodo.3687775 (Versini et al., 2019b).

Thermal and hydrological performance of extensive green roofs in Amazon climate, Brazil

Improper urban planning has been proven to produce excessive environmental impacts in urban areas, such as urban flooding and urban heat islands. A new approach to protecting the urban environment brought forward the idea of low-impact urban development, which uses rainwater-control devices such as cisterns, permeable pavements and green roofs. This study aimed to evaluate the potential of green roofs in two important environmental dimensions: thermal and hydrological. An experimental study was conducted at the Federal University of Pará Guamá Campus, Belém, Brazil. Hydrological and thermal data from a green roof and a fibre-cement roof were collected and compared to analyse the performance of the roofs. The results showed extensive green roofs to be an effective tool for reducing rainfall run-off at the roof scale, particularly for small-storm events, as well as an efficient thermal roof insulation.

Green roof performance under malaysia tropical climates: a review

<span>Green roof system is one of sustainable approach for energy consumption reduction and improving the aesthetic value of the built environment. The system has been adopted by most of developed countries; and in Malaysia, research on green roof studies are quite evolving however the implementation of the system is slow due to some perceptions and obstacles. Green roof has potential on providing benefits such as reduction on the urban heat island effect, reduces temperatures, pollution and improves the attenuation of stormwater. This paper will highlights on a preliminary review of the implementation green roof system in Malaysia and explores the performances of Malaysian green roof in order to highlight the performance of green roof under tropical climatic conditions using local configurations.</span>

Thermal Insulation Performance of Radiant Barrier Roofs for Rural Buildings in the Qinba Mountains

Strengthening the roof insulation is the main method for improving the indoor thermal environment of rural buildings during summer. This study proposed a radiant barrier roof with a roof insulation structure based on climatic conditions in the Qinba Mountains and the characteristics of rural buildings, in which radiant barriers were installed on the underside of the roof in the attic space to enhance roof insulation. To study the thermal insulation performance of radiant barrier roofs, aluminum foil bubble composites were installed on the underside of the roof in the attic space in the Qinba Mountains, and comparative experiments were carried out. Based on the results, the average temperature of the second-floor bedrooms dropped by 1.1°C, thus proving the effectiveness of thermal insulation with radiant barrier roofs. The thermal insulation performance of radiant barrier roofs made of aluminum foil bubble composite was studied through numerical simulation analysis. Based on the findings of this study, radiant heat transfer contributed 65% to the thermal insulation effect when aluminum foil bubble composites were applied. Based on the analysis of thermal performance and cost, it is recommended to use radiant barrier materials with an emissivity of less than 0.3 and a thermal resistance of no more than 2 m2K/W. Furthermore, the application of radiant barrier roofs made of aluminum foil bubble composites can have a positive effect on thermal insulation during winter. This facilitates the widespread use of radiant barrier roofs for rural buildings throughout hot-summer/cold-winter zones.

A numerical and experimental investigation of the effectiveness of green roofs in tropical environments: The case study of Mauritius in mid and late winter

The present work is a preliminary assessment of the performance of green roof at Reduit in Mauritius, located at latitude 20.23∘S and longitude 57.49∘E (Indian Ocean), which is influenced by a tropical humid climate. The efficiency of the green roof is gauged by evaluating its effect on indoor temperature fluctuations, conductive heat fluxes and the daily peak indoor temperature. On site measurements of weather data and indoor temperature are collected round the clock from July 11, 2017 to October 08, 2017. It is found that green roof increases the thermal mass of the experimental cells thereby reducing the fluctuations in indoor temperature. The conductive heat flux variation is significantly low in the case of the green roof. The green roof reduces the daily peak indoor temperature, which is attenuated significantly as compared to a conventional roof. A one dimensional mathematical model is also proposed in order to simulate the evolution of the heat and moisture transfer in a porous multilayer material. The model is validated using the measured data.

Experimental and numerical study on the thermal performance of ventilated roof composed with multiple phase change material (VR-MPCM)

In the hot summer, roof is the prime location absorbed the most solar radiation for both residential and commercial buildings. Hence, enhancing the thermal performance of roofs is essential for reducing the heat gain thus building load. In this study, a novel ventilated roof composed with multiple phase change material (VR-MPCM) was proposed and its thermal performance was investigated experimentally and numerically. A contrast experiment was conducted in two full-scale chambers. The research results indicated that VR-MPCM can reduce the indoor peak temperature by 16.9–18.8%, and push back the peak temperature occurrence time by 30–50 min compared with the conventional ventilated roof (CVR). In addition, the cumulative heat flux during 4320 min demonstrated that the energy conservation rate of VR-MPCM can go up to 97.1% compared with the CVR. A verified three-dimensional transient heat transfer model was introduced for further research. Through the simulation research, intermittent opening of vents was found to be the best operating strategy for reducing heat gain. Regional comparison indicated that VR-MPCM in severe cold and cold climate zones had obvious energy saving potential. In conclusion, VR-MPCM has a potential of energy saving by reducing the diurnal heat gain and utilizing the nightly free cooling.

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

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.

The Value of Alpha SPF Roofing: An Alpha Case Study at William Lipscomb Elementary School

An Alpha roof is a type of Spray Polyurethane Foam (SPF) roofing system that has been documented to be one of the highest performing roofs in the industry. Despite the high level of performance of the Alpha SPF roofs, owners still try to protect themselves by purchasing warranties. When the Dallas Independent School District (DISD) did not receive enough funding to purchase the Alpha roofs for their school buildings, general contractors started shopping the Alpha contractors. The demand for Alpha roofs during DISD bond programs exceeded the supply of Alpha vendors. DISD lowered the requirements and the contractors and manufacturers delivered lower quality roofs. DISD still required the performance of the Alpha roofing system, even though they bought lower performing systems without the quality control requirements of the higher performing Alpha roofs. DISD was not happy with the lower performance on some of the inexpensive roofs. This paper describes a case study that proposes that high roof performance is a result of expert contractors proving their past performance, detailed preplanning, manufacturers doing quality control, contractors tracking their time and cost deviations and independent third party inspections. The expert Alpha contractor completed the project with the best dimensional stability metrics (dimensional stability is a metric of long lasting roofs). The roof installation was completed in 20 days and saved DISD over 20% of the cost of the roof, despite an increase in the scope of work. It was the first DISD project that had no punch-list items after the final walkthrough. DISD was extremely satisfied with the roof and the Alpha program demonstrated its effectiveness in the installation of roofs.

Experimental Evaluation and Numerical Simulation of the Thermal Performance of a Green Roof

In the building sector, both passive and active systems are essential for achieving a high-energy performance. Considering passive solutions, green roofs represent a sustainable answer, allowing buildings to reach energy savings, and also reducing the collateral effect of the Urban Heat Island (UHI) phenomenon. In this study, a roof-lawn system was investigated by means of an extended measurement campaign, monitoring the heat transfer across the roof. Heat-flow meters and air- and surface-temperature probes were applied in a real building, in order to compare the performance of the roof-lawn system with a conventional roof. This experimental approach was followed to quantify the different thermal behaviors of the building components. Moreover, an equivalent thermal model of the roof-lawn system was studied, in order to obtain the equivalent thermal properties of the roof, useful for setting building models for yearly energy simulations. The roof-lawn system revealed its advantages, showing a higher thermal inertia with no overheating in summertime and a lower thermal transmittance with energy savings in wintertime, and, consequently, better indoor conditions for the occupants of the building.

State-of-the-Art Green Roofs: Technical Performance and Certifications for Sustainable Construction

Green roof systems, a technology which was used in major ancient buildings, are currently becoming an interesting strategy to reduce the negative impact of traditional urban development caused by ground impermeabilization. Only regarding the environmental impact, the application of these biological coatings on buildings has the potential of acting as a thermal, moisture, noise, and electromagnetic barrier. At the urban scale, they might reduce the heat island effect and sewage system load, improve runoff water and air quality, and reconstruct natural landscapes including wildlife. In spite of these significant benefits, the current design and construction methods are not completely regulated by law because there is a lack of knowledge of their technical performance. Hence, this review of the current state of the art presents a proper green roof classification based on their components and vegetation layer. Similarly, a detailed description from the key factors that control the hydraulic and thermal performance of green roofs is given. Based on these factors, an estimation of the impact of green roof systems on sustainable construction certifications is included (i.e., LEED—Leadership in Energy and Environment Design, BREEAM—Building Research Establishment Environmental Assessment Method, CASBEE—Comprehensive Assessment System for Built Environment Efficiency, BEAM—Building Environmental Assessment Method, ESGB—Evaluation Standard for Green Building). Finally, conclusions and future research challenges for the correct implementation of green roofs are addressed.

The Role of the Extensive Green Roofs on Decreasing Building Energy Consumption in the Mediterranean Climate

Buildings portion in global energy consumption is 40%, and in the building envelope, the roof is a crucial point for improving indoor temperature, especially in the last and second last floors. Studies show that green roofs can be applied to moderate roof temperature and affect the indoor temperature in summer and winter. However, the performance of green roofs depends on several parameters such as climate, irrigation, layer materials, and thickness. In this context, the present research deals with a comprehensive experimental analysis of different thermal impacts of green roofs in summer and winter in a Mediterranean climate. Measurements carried out in one year in three different types of green roofs with different thicknesses, layers, and with and without the insulation layer. The analysis determined the possible period that indoor cooling or heating might be required with and without green roofs and demonstrated the positive impact of green roofs in moderating the roof temperature and temperature fluctuations, which in summer was remarkable. In conclusion, since in the Mediterranean climate, the thermal differences between green roofs and conventional roofs in summer are much higher than winter, it seems that the green roof without an insulation layer would show better performance.

绿色屋顶降温效应的多维时空变化特征

PDF HTML阅读 XML下载 导出引用 引用提醒 绿色屋顶降温效应的多维时空变化特征 DOI: 10.5846/stxb201812032630 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2017YFE0196000）；国家自然科学基金项目（51878328，31670470） Measuring the performance of green roof cooling effects from a multi-dimensional perspective Author: Affiliation: Fund Project: The National Natural Science Foundation of China (General Program) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:准确量化和挖掘绿色屋顶降温效应的时空特征是科学评价其热环境调控服务效益与潜力的重要前提。以南京市金陵小学轻型佛甲草绿色屋顶为例，基于夏季典型气象条件下的定点观测数据，率定ENVI-met模型中的相关参数，验证模拟结果的有效性；从传统"点"和"面"角度测度了绿色屋顶降温效应的二维变化特征，并采用三维"冷岛"逐时降温累积值和降温质心的时空变化来定量刻画绿色屋顶降温效应的四维变化特征（即三维"冷岛"随时间变化的特征），进而阐明其主要影响因素。研究结果表明：（1）轻型佛甲草绿色屋顶在日间（6：00-18：00）降温效应很弱，但在夜间（19：00-次日5：00）降温效应比较明显；（2）基于三维空间刻画的日夜间降温效应差异较传统二维方法测度的结果更为明显，绿色屋顶点、面与三维降温效应日夜间比值分别为3.1、5.0和8.1；（3）降温质心与降温强度在空间上呈现明显的集聚分布特征，夜间的降温强度与集聚程度明显高于白天，夜间的降温质心在绿色屋顶几何中心上方集聚，而白天质心分布较为分散且向靠近裸露屋顶一侧偏移；（4）绿色屋顶降温效应时空变化特征主要受下垫面属性、植被生理特征和局地微气象因子的多重影响。与传统的二维降温效应分析相比，从"四维时空变化"角度实现了对绿色屋顶降温效应更加客观的定量表征，可为其成本收益分析与建设效益评价提供重要的量化手段与决策依据。 Abstract:Effectively measuring cooling performance is important for evaluation of the thermal environmental regulation services of green roofs. Using the case study of the extensive green roof on the buildings of Jinling primary school, Nanjing, China, this study modeled the effects of green roof on local microclimate by using simulation-based ENVI-met software, and the simulation results were further validated based on the typical summer meteorological weather observations. Using meteorological data and ENVI-met simulation results, the cooling performance of the green roof was first analyzed from "point" and "surface" perspectives, similar to that by most previous studies, and then a novel analysis method was developed and applied to more comprehensively analyze the cooling performance from a 4D perspective. Accordingly, the hourly cooling effect and the spatio-temporal variations in the "cooling island" mass center were quantified, and simultaneously, the related factors potentially affecting the cooling performance of the roof were explained. The results showed that (1) the cooling effect of extensive green roof with Sedum lineare Thunb. was weaker during the daytime (6:00-18:00) than during nighttime (19:00-5:00 the following day). (2) The diurnal cooling effect was much more obvious when measured from a three-dimensional perspective than a two-dimensional one (ratio 3.1, 5.0, and 8.1 for the hourly cooling effects during daytime to that of nighttime from a point, surface, and three-dimensional perspective, respectively). (3) The mass center and intensity of the cooling island showed a pronounced spatial aggregation within the modeled area. The intensity of the cooling island was stronger during nighttime than during daytime. The mass centers gathered above the geometric center of the green roof during nighttime, whereas at nighttime, they scattered and shifted to the side of the bare roof. (4) The overall green roof-cooling performance indicated that the cooling effect was mainly affected by the properties of the underlying surface, the physiological characteristics of the vegetation, and the local micro-meteorological factors. Compared with that of the traditional method, the measurement from the four-dimensional perspective, achieved a more objective assessment of the green roof-cooling effect. The proposed novel method will be extremely helpful in the cost-benefit analysis and of green roof-construction projects. 参考文献 相似文献 引证文献

Investigating the hydrological performance of green roofs using storm water management model

The green roof, also known as vegetated roof covers, or eco-roofs or natural roofs, is one of the recently developed low impact development (LID) techniques, which significantly increases water retention and thus helps to mitigate the urban flooding. In the present study, the installation of green roofs is assumed as a hypothetic retrofitting scenario according to a sustainable storm water mitigation strategy for a selected urban catchment and performance has been evaluated using Storm Water Management Model (SWMM). The model has been calibrated for the measured flow data of eight events using Nash-Sutcliffe Efficiency (NSE) Coefficient. The lowest and highest value of NSE was found 0.67 and 0.93 respectively. The hydrologic performance of the green roof was conducted under event-based as well as continuous simulation. Based on simulation results, peak flow has been reduced from 7.13 ltr/sec to 6.36 ltr/sec for Green Roof – 1 (GR-1) and 1.45 ltr/sec to 1.30 ltr/sec for Green Roof – 2 (GR-2). The simulation results point out that the integration of green roof LID contributes to the reduction of the quantity of storm water runoff by increasing the retention period. However, the hydrological behavior of a green roof is site-specific, and therefore the site-specific conditions and parameters like characteristics of the vegetation, physical properties of its layers, etc. have to be considered in the evaluation of its performance. Further, the research at the micro-level is necessary to evaluate the role of the green roof slope, the effect of vegetation cover, and the antecedent period on the performance of the green roofs for more reliable results.

Detention-based green roofs for stormwater management under extreme precipitation due to climate change

Abstract Rooftops cover a large percentage of land area in urban areas, which can potentially be used for stormwater purposes. Seeking adaptation strategies, there is an increasing interest in utilising green roofs for stormwater management. However, the impact of extreme rainfall on the hydrological performance of green roofs and their design implications remain challenging to quantify. In this study, a method was developed to assess the detention performance of a detention-based green roof (underlaid with 100 mm of expanded clay) for current and future climate conditions under extreme precipitation using an artificial rainfall generator. The green roof runoff was found to be more sensitive to the initial water content than the hyetograph shape. The green roof outperformed the black roof for performance indicators (time of concentration, centroid delay, T50 or peak attenuation). While the time of concentration for the reference black roof was within 5 minutes independently of rainfall intensity, for the green roof was extrapolated between 30 and 90 minutes with intensity from 0.8 to 2.5 mm/min. Adding a layer of expanded clay under the green roof substrate provided a significant improvement to the detention performance under extreme precipitation in current and future climate conditions.

Techno-economic inquiry into implementation barriers in Green Roof adoption as an energy retrofit measure in temperate climates: UK Study.

Green roof technology has been established through research and in-situ monitoring to provide good potential for stormwater retention, mitigation of urban heat island (UHI) effect, reduction of local air pollution, increase local biodiversity and most importantly, passive energy savings both for new buildings and as a retrofit option for older buildings. However, even with this existing wide range of benefits, green roof technology research and markets in terms of implementation and widescale commercial adoption is relatively non-existent in temperate climates of the world such as the UK, compared to other regions with different prevailing climatic characteristics. This research investigates the causative factors and barriers for this relatively slow rate of adoption both from technological and economic perspectives with the United Kingdom as a case study. A number of experimental papers on energy savings benefits from green roofs were compiled; and from the analysis of collated data, it was found that green roofs tend to perform better from an energy savings perspective in hotter climates of the world or during the summer season in colder climates when temperatures are higher such as seasonal heatwaves. Further research into the energy savings behaviour during winter in temperate regions is required to assert the all-season suitability of green roofs for implementation in new builds within the United Kingdom. Government legislation and incentives could potentially increase wide-scale adoption. The performance of green roofs is however found to be largely climate dependent, meaning the performance varies across different regions of the world, therefore increased local research and quantification into metrics will lead to better understanding and potential adoption of green roofs and how to best optimise their design according to the region in which they are to be installed.

Thermal performance analysis of a roof with a PCM-layer under Mexican weather conditions

The thermal performance of a concrete roof with a phase change material (PCM) layer on its interior surface under a Mexican warm weather (Merida) is presented. We analyzed a roof with three types of PCM: Paraffin wax - MG29 (R-PCM1), N-Eicosane (R-PCM2), and Salt Hydrates (R-PCM3). We also considered different thickness of the PCM layer. A conventional concrete roof (R–C) was considered as a reference to compare the results. The numerical simulations were conducted during the warmest and the coldest days of the year. A numerical in-house code was developed, and it was verified by solving reference solutions, obtaining good agreement. The results indicate that the case R-PCM1 with 2 cm of PCM layer had the lowest values of thermal load during the coldest (204.5 W h m−2) and the warmest day (610.7 W h m−2); such values are up to 57% lower than the thermal load corresponding to the R–C. The use of R-PCM1 with 2 cm of PCM-layer in Merida city will have a payback period of 12.18 years, Taking into account that buildings in Mexico have a 30-year ordinary service life, the use of these materials is cost-effective. Therefore, it is recommended the R-PCM1 to improve the thermal behavior of buildings located in Merida.

A continuous simulation approach to quantify the climate condition effect on the hydrologic performance of green roofs

ABSTRACT In order to effectively estimate the hydrologic performance of green roofs, continuous simulation approaches are recently used thus allowing to include the precipitation regime features as well as the varying soil moisture conditions. Continuous simulations are implemented in the EPA Storm Water Management Model (SWMM) using as input data the climate data series recorded at three Italian sites (Bergamo, Genoa and Castelbuono) while a simple methodological approach is adopted to estimate the actual evapotranspiration. Results are examined at the event scale by means of the volume and the peak reduction rates. Results confirm the positive impact of green roof retrofitting scenario for all the investigated climate regimes. On the other hand, the specific rainfall characteristics at the event scale (mainly rainfall depth and antecedent dry weather period) affect both the retention and detention performance of green roofs.

Performance of Green Roof Integrated Solar Photovoltaic System

Green roofs and solar photovoltaics are green technologies that developed to meet the sustainable and low carbon emission targets by the ways of effective stormwater management and renewable energy generation. Previous studies have proved that the cooling effects from the evapotranspiration process in green roofs can keep the photovoltaics (PV) near the best operational temperature, while PV panel can provide the shading benefit to the green roof’s vegetation. The paper aims to synthesize the influential factors, including solar PV and green roof designs on solar power output efficiency. This review identifies the research gaps in the previous studies of green roof integrated solar PV system and highlights the desirable characteristic for each component. This review also suggests a guideline to construct practical green roofs integrated solar PV system.

In-situ monitoring of energetic and hydrological performance of a semi-intensive green roof and a white roof during a heatwave event in the UK

Due to the increasing magnitude and high frequency of urban heatwaves, recently, there has been a surge of interest in the reflective roofs and the vegetative green roofs. Along with the rising temperature, there are also more frequent droughts and rainfall which have led to wider changes in weather conditions subsequently affecting the performance of green roofs and white roofs. However, there is still a lack of research in comparing dynamic energetic and hydrological performance of green roof and white roofs during heatwave events. This paper introduces a newly constructed outdoor test rig (installed with a semi-intensive green roof and an aluminium white roof) and a few initial monitoring results. The hydrological performance monitoring results showed that, although a noticeable peak runoff reduction of the white roof was observed, more significant water retention of green roofs had been established. The energetic performance monitoring results indicated that the green roof performed better than the white roof during the heatwave event reducing solar heat gains by 76% during day time, improving U-value by 28% and reducing indoor air temperature by 2.5°C. The peak indoor air temperature reduction in the green roof space occurred during late afternoons (around 7 pm).