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.

Enhanced Thermal Performance of Roofing Materials by Integrating Phase Change Materials to Reduce Energy Consumption in Buildings

This work focused on characterizing and improving the thermal behavior of metal sheet roofing.To decrease the heat transfer from the roof into a building,we investigated the efficiency of four types of phase change materials,with different melting points:PCMІ,PCM II,PCM III and PCM IV,when used in conjunction with a sheet metal roof.The exterior metal roofing surface temperature was held constant at 50℃,60℃,70℃and 80℃,using a thermal source(halogen lights)for 360 min to investigate and compare the thermal performance of the metal sheet roofing with and without phase change materials for each condition.The thermal behaviors of the phase change materials were analyzed by differential scanning calorimeter(DSC).The results showed the melting points of PCMІ,PCM II,PCM III and PCM IV were around 45℃,50℃,55℃and 59℃,respectively.The integration of PCM IV into the metal roofing sheet increased the thermal performance by reducing the room temperature up to 2.8%,1.4%,1.0%and 0.7%when compared with the normal metal roof sheet,at the controlled temperatures of 50℃,60℃,70℃and 80℃,respectively.The thermal absorption of the phase change materials also caused a time delay in the model room reaching a steady temperature.The integration of phase change materials with metal roofing sheets resulted in better thermal performance and conservation of electrical energy by reducing the demand for cooling.

Experimental Study of the Thermal Behavior of a Bioclimatic Building Prototype in a Sahelian Zone

Buildings constructed with modern materials (cement blocks, sheet metal, reinforced concrete, etc.) in the Sahelian zone often generate excessive electricity consumption and consequently very high electricity bills. This study is a contribution to the development of new building types based on the principle of bioclimatic construction. The aim is to find materials suited to the Sahelian climate and improve thermal comfort. To this end, an experimental study of the hygrothermal behavior of a bioclimatic building prototype with a domed roof is being carried out. Site meteorological data, air temperature and relative humidity of the building’s internal environment were measured for three climatic seasons in Burkina Faso. The data acquisition system consists of thermocouples, solarimeters and humidity meters, and the data are processed using Excel and Origin Pro software. The results show that, despite the high temperature values (between 36˚C and 39˚C) of the internal environment measured in the hot season, good thermal performance is achieved, in particular an average phase shift of 7.17 h and an average damping of 10.81˚C. The dome-roofed building could therefore contribute to limiting heat transmission to the building interior, improving thermal comfort all year round. Analysis of humidity profiles shows that indoor humidity varies between 66% and 80% for the September period, and between 44% and 69% for the January period. The high values of internal ambient humidity could be reduced by very good ventilation of the building. This study shows that the proposed bioclimatic building prototype with domed roof could be integrated into the Sahelian habitat.

Effects of Street-Bottom and Building-Roof Heating on Flow in Three-Dimensional Street Canyons

Using a computational fluid dynamics （CFD） model, the effects of street-bottom and building-roof heating on flow in three-dimensional street canyons are investigated. The building and street-canyon aspect ratios are one. In the presence of street-bottom heating, as the street-bottom heating intensity increases, the mean kinetic energy increases in the spanwise street canyon formed by the upwind and downwind buildings but decreases in the lower region of the streamwise street canyon. The increase in momentum due to buoyancy force intensifies mechanically induced flow in the spanwise street canyon. The vorticity in the spanwise street canyon strengthens. The temperature increase is not large because relatively cold above-roof-level air comes into the spanwise street canyon. In the presence of both street-bottom and building-roof heating, the mean kinetic energy rather decreases in the spanwise street canyon. This is caused by the decrease in horizontal flow speed at the roof level, which results in the weakening of the mean flow circulation in the spanwise street canyon. It is found that the vorticity in the spanwise street canyon weakens. The temperature increase is relatively large compared with that in the street-bottom heating case, because relatively warm above-roof-level air comes into the spanwise street canyon.

Shell Roof of Tall Buildings in Earthquake Zones

This paper studies and analyzes tall buildings with shell and flat roof responses designed for gravity and earthquake loads in different zones having different soil profiles. These tall buildings having two different heights and different configurations are simulated with different load combinations. The responses of the simulated structural models with flat and shell roofs are studied and analyzed. These responses draw recommendations and guidelines for preliminary design of structurally efficient and reliable tall buildings with shell roof in earthquake zones. Five different earthquake zone factors (Z1 - Z5) along with the five different soil profiles (S1 - S5) are selected in this study. The non-linear dynamic response of buildings was obtained using three simulated models of buildings;square/rectangular, circular, and tube-shaped building. Total of 12 building models, four under each category, are analyzed using the finite element software (STAAD pro) subjected to the gravity as well as earthquake loading defined by UBC and IBC codes. Each building model is analyzed with two different story heights;which are 120 meters for 30 stories and 72 meters for 18 stories respectively. Horizontal and vertical displacement comparison is made among the flat roof and shell roof building for 32 and 18 stories building satisfying the ACI code of design requirement and drift index of 1/500 (0.002). The results showed that the drift index value for all the studied buildings is close to 0.002. All the maximum horizontal and vertical deflections occur under the earthquake zone-5 (0.40 gravitational acceleration) with soil profile-5 (Soft soil). The shell roof slab with less thickness than the flat roof slab did satisfy the horizontal and vertical deflection limits, therefore, it is more economical than the flat roof slab.

Landscape Design of Roof Gardens of Urban Public Buildings

This article explores the constraints in the landscape design of roof gardens of public buildings. Based on this,the constituent elements of the roof landscape of public buildings and the cultural ties connecting the elements are studied in detail. Exploring diverse landscape design of roof gardens of public buildings can not only make full use of the building space but also bring more economic,social and ecological benefits.

THE ADOPTION OF AN INNOVATION:BARRIERS TO USE OF GREEN ROOFS EXPERIENCED BY MIDWEST ARCHITECTS AND BUILDING OWNERS

While green roof technologies are increasingly employed in Northern European countries,adoption is progressing at amuch slower rate in the US.This manuscript discusses results of a survey that quantified knowledge,barriers,and perceivedcosts and benefits to use of green roof technology among a sample of architects and building owners in the Midwest.The survey also examined conditions that may encourage use of this technology among the respondents.Resultsshow that many respondents do not fully recognize the economic or performance advantages offered by green roof technologies.The payback period for economic advantage is longer than owners are willing to consider.Both owners andarchitects possess a wide range of misconceptions about the performance advantages of green roofs.While green roof technologyoffers clear environmental advantages such as reduced stormwater runoff,increased habitat,and cooler temperaturesthat mitigate heat island effects,many building owner respondents either do not know about or value these advantages.This research quantified potential adopters’perceptions of an innovative technology and the survey results areinterpreted and discussed within the conceptual framework of innovation diffusion literature.Strategies to hasten theadoption of green roof technology are suggested.

COMPARING BUILDING SURFACES’ORIENTATIONS TO OPTIMIZE SOLAR ENERGY COLLECTION

Net-zero and other high performance green buildings normally do or should include optimized solar energy systems.While detailed computer-based energy simulations of buildings’energy systems are becoming near-commonplace for many projects,simple,easy-to-use data tables are beneficial earlier in the design process to help guide preliminary decisions in all projects.Practical lookup tables,and then comparison of the data they contain,are also very useful for teaching new concepts,in this case for learning about solar orientations in sunny locations.Engineers,architects,design-build contractors,students,and other designers of green buildings can benefit through knowing,in advance,how exterior surfaces’orientations increase or decrease the total annual solar energy arriving upon those surfaces.For example,maximizing the incoming energy on a particular roof is advantageous for gathering solar energy for heat or for conversion of that sunlight to electricity,but various requirements often limit designers’choices for surfaces’orientations.This paper presents simple tables that form a tool for making initial decisions on surfaces’directions and slopes;the user can then study various effects further,such as local factors including cloudiness and shading,with detailed software.The classical solar geometry equations utilized are documented here for repeatability of the research,but are not necessary for use of this paper’s tables.Practical examples are given too to help readers use the tables.

OKANAGAN COLLEGE CENTRE OF EXCELLENCE IN SUSTAINABLE BUILDING TECHNOLOGIES AND RENEWABLE ENERGY CONSERVATION

The Centre of Excellence at Okanagan College in Penticton,British Columbia is being designed as one of the most innovative and sustainable post-secondary facilities in the world.On schedule for design and construction to be complete by April 2011,the two-storey multi-purpose facility has a mandate to provide trades and technology training and professional development to students from the province of British Columbia and beyond.It is aimed at attaining the highest standard of sustainable building design,the Living Building Challenge.The building will support a syllabus with a focus on the design,installation,and support of sustainable building technologies and processes,and the development and application of alternative and renewable energy.The building itself will become an essential element of the educational programs that will reside there,a teaching tool for education on building trades and engineering technologies.In addition,the Okanagan Research Innovation Centre will be incorporated into the building,providing opportunities for start-up companies to develop and prototype new green technologies in a supportive and synergistic environment.This article will demonstrate that a project with this level of sustainable objectives is achievable at a cost comparable to conventional building design.It will address how this can be attained through an integrated design process,along with the numerous innovative features that have been incorporated into the building design to help it function with a small environmental impact,and a large educational one.

Brief Discussion about the Design of Intelligent Domestic Roof Garden

Based on the existing roof gardens,this study aims to elaborate the functions of intelligent domestic roof gardens and the problems that should be noticed in the design of intelligent domestic roof gardens.

Simulation of roof snow loads based on a multi-layer snowmelt model:Impact of building heat transfer

To investigate the impact of building heat transfer on roof snow loads,roof snow loads and snow load thermal coefficients from 61 Chinese sites over a period of 50 years are simulated based on basic meteorological data such as temperature,humidity,wind speed,and precipitation,and a multi-layer snowmelt model considering the building heat transfer.Firstly,the accuracy of the multi-layer snowmelt model is validated using the data of observed ground snow load and roof snow melting tests.The relationship between meteorological conditions,snow cover characteristics,and thermal coefficients of snow loads in three representative sites is then studied.Furthermore,the characteristics of thermal coefficients in each zone are analyzed by combining them with the statistical results of meteorological data from 1960 to 2010,and the equations of thermal coefficients in different zones on indoor temperatures and roof heat transfer coefficients are fitted separately.Finally,the equations in this paper are compared with the thermal coefficients in the main snow load codes.The results indicate that the snowmelt model using basic meteorological data can effectively provide samples of roof snow loads.In the cold zone where the snow cover lasts for a long time and does not melt easily,the thermal coefficients of the snow loads on the heating buildings are lower than those in the warm zone due to the long-term influence of the heat from inside the buildings.Thermal coefficients are negatively correlated with indoor temperatures and roof heat transfer coefficients.When the indoor temperature is too low or the roof insulation is good,the roof snow load may exceed the ground snow load.The thermal coefficients for heated buildings in the main snow load codes are more conservative than those calculated in this paper,and the thermal coefficients for buildings with lower indoor temperatures tend to be smaller.

某地仿古高层建筑的结构设计

以位于7度抗震设防区内的某仿古高层建筑为工程背景,介绍了拥有大型坡屋面的仿古高层建筑项目的特点以及在设计中遇到的重、难点问题。该建筑因建筑造型要求导致结构具有大开洞、跃层柱、体型收进、刚度不连续等抗震不利的特点,该项目采用了YJK结构设计软件进行设计分析,采用合并标准层的设计方法来避免软件出现不合理的薄弱层判定;采用弹性时程分析来补充计算结构顶层因抽柱形成空旷房间的情况。计算结果表明,该项目结构设计合理,经济安全。文中列举了计算结果,分析阐述了针对设计中遇到的重、难点问题的处理方法,如何在设计中调整各设计参数以避免结构被判定为超限建筑,从而实现缩短设计周期并满足现行结构设计技术规范的要求,并对同类型项目提出了设计建议。

Performance Comparison and Analysis of Heating and Ventilation of Two Kinds of Roof Solar Collectors

Two roof solar collectors (RSCs), conventional single pass RSC and new double pass RSC, were compared. The new roof solar collector, which is formed by integrating a double pass solar air collector with the roof of the building, can be operated more efficiently for space heating in winter, and for natural ventilation in other seasons. To evaluate the performances of the two RSCs for both space heating and natural ventilation, a single traditional Chinese style house, on which the two RSCs will be mounted, was developed. The efficiency of solar energy conversion for the new RSC is higher than that of the single pass one by 10% on average, and the ventilation rate contributed by natural ventilation for the new RSC can be improved to a great extent for most cases, indicating that the new RSC is superior to the single pass one from the viewpoint of both space heating and natural ventilation. The new RSC is more potential for improving indoor thermal environment and energy saving of buildings.

Application of Stone as a Roofing in the Reconstruction and Construction

In architecture, in the past, different materials were used for covering of the buildings. The selection of the type of roofing depended on the purpose and size of the building; thus all the churches, administrative buildings and important medieval buildings were originally covered with stone or lead slabs as the final roofing material. The tendency of return of stone as an authentic roofing in the reconstruction of medieval buildings and churches, as well as the introduction of stone as a roofing on the new buildings in protected historic cores, is possible only if fulfilled modem principles and requirements of the physics of construction. The application of modem principles of double ventilated roofs and the use of stone as a roofing enables the restoration and preservation of the original appearance of medieval buildings, as well as the preservation and conservation of existing frescoes that have been present for centuries in these facilities. It also enables a successful reconstruction of a large number of medieval buildings. In this way it has been given a contribution to the preservation of old medieval buildings as the improvement of world cultural heritage.

上海虹桥国际机场T1航站楼改造结构设计

上海虹桥国际机场T1航站楼历经多次改造和扩建,介绍了2018年实施完成改造设计的难点和特点。针对不同年代建造的结构单体共存问题,通过全面比较选择拆除或保留原结构,合理确定不同单体的后续工作年限。A楼出发大厅屋盖拆除新建,为减小改造对原结构的影响,采用钢屋盖-立面-雨篷一体化的结构方案;介绍了一体化结构的概念方案、分析结果和优化设计过程。1988年设计的B楼原结构抗震构造薄弱、抗震性能差,采用减少变形缝、改变结构体系、增设屈曲约束支撑等手段提升其抗震性能,满足大震不倒的设防要求。

气候变化下窑居建筑屋顶适宜性改造研究

调研发现陕北地区自2010年以来降水量开始呈现明显增加的趋势,而传统窑洞屋顶缺少良好的防水设计,易导致窑洞在经受暴雨时漏水甚至坍塌。村民采取在原屋顶上加建彩钢板的改造方式防雨,然而这种窑洞屋顶构造的自更新不仅未能充分解决屋顶防水问题,还在一定程度上破坏了窑洞村落的传统风貌。以陕北地区传统民居的典型代表窑洞为研究对象,通过调研测试与软件模拟分析窑洞屋顶加盖彩钢板构造对室内热环境的影响,发现加盖彩钢板能够提升屋顶的耐久度和防雨性能,但是不能改善室内热环境,并且不能充分融入到传统的乡村环境中。在此基础上提出了新型窑洞屋顶构造,以期进一步改善屋顶防水性能并延续传统民居建筑风貌,为后期窑居建筑更新改造提供参考。

基于深度学习的机载点云屋顶平面提取算法

为了准确提取不同类型建筑物屋顶点云的各个平面,采用度量学习的方式,将每个平面视为单独的实例,为每个平面上的点学习单独的高维深度特征。利用所提取的高维深度特征对平面点进行初步的聚类,通过简单的欧氏距离和特征空间距离进行综合度量将未聚类的点分配至各个平面;所提出的方法分别在合成数据集和公开的机载点云建筑物屋顶数据集RoofN3D上进行了训练和测试。结果表明,在合成数据集上,所提取的建筑物平面的准确率、召回率和F_(1)分数分别为0.990、0.998和0.994;在机载点云数据集RoofN3D上,所提取的建筑物平面的准确率、召回率和F_(1)分数分别为0.945、0.971和0.957。该方法不仅可以准确有效地提取出不同建筑物屋顶平面,且平面边缘非常准确,还可以准确区分建筑物屋顶平面内容和非平面内容,为建筑物3维建模提供重要帮助。

建筑屋面风雨场及突出建筑立面风驱雨的实测研究

文章对某多层建筑屋面区域风驱雨(wind-driven rain,WDR)开展实测,结合3类典型降雨事件的分析,揭示大气湍流特征以及风速、风向对雨滴的影响特性,并针对突出屋面建筑,实测分析立面WDR分布特性,量化国际标准化组织(International Organization for Standardization,ISO)半经验模型对突出屋面建筑WDR预测的偏差。结果表明,在3类降雨事件中,湍流度、阵风因子和湍流积分尺度的实测值与基于地面实测建立的公式理论值之间存在较大差异;实测的雨滴数量与标准M-P谱计算的雨滴数量差值最大为125个。在风速和雨强差异较小时,建筑立面WDR分布受来流与立面夹角的影响显著。由于ISO半经验模型是基于地面实测建立的,其对突出屋面建筑WDR的预测存在偏差,在模型适用的降雨条件下实测值约为ISO预测值的2倍。