Roof Slope Research Articles

Full-scale experimental study on the smoke descent and stratification in a two-storey building with varying ventilation conditions

This paper presents a full-scale experimental research on the smoke descent and stratification in a two-storey residential building under the coupling influences of vertical connection channels and ventilation conditions. The two floors were connected by one atrium and one stair, and the fire source was located on the second floor. Wood crib and gasoline were selected as representative fuels to reflect typical residential fire scenarios, with heat release rates of 82kW and 140kW, respectively. The states of the building openings were varied to simulate different ventilation conditions. Results showed that the smoke tended to spread in the ridge direction due to the structural limitations of slope roofs. The temperature distribution in both the ridge and slope directions was obtained. A special “three-zone” smoke stratification structure including upper smoke layer, intermediate air layer and lower smoke layer is observed, which is significantly different from the well-known “two-zone” model. The “three-zone” stratification resulted in a nonmonotonic vertical temperature distribution in the atrium. The lower smoke layer thickness Zl,g was found to be greatly affected by ventilation conditions. Based on the boundary layer theories and the law of energy conservation, a series of expressions were established to calculate Zl,g and intermediate air layer thickness δw, which are the key parameters of the “three-zone” stratification. The theoretical calculations matched the experimental data well and explained the sharp trends of δw and Zl,g under different ventilation conditions. This study can provide theoretical guidance about fire detection, smoke exhaust and people evacuation in residential buildings.

Simulation and Analysis of Factors Influencing Climate Adaptability and Strategic Application in Traditional Courtyard Residences in Hot-Summer and Cold-Winter Regions: A Case Study of Xuzhou, China

Residential buildings consume significant amounts of energy worldwide. Traditional courtyard houses have substantial energy-saving potential due to their low energy consumption and high climate adaptability, which has heightened interest in their climate-responsive design. In recent years, extensive research on traditional houses has been conducted in China, indicating significant variations in energy performances among traditional courtyards within hot-summer and cold-winter climate zones. Therefore, this study, based on research conducted on traditional courtyard houses in the Xuzhou area and utilizing Ecotect and Phoenics ecotechnology software for simulation analysis, comparatively examines the factors influencing energy consumption to assess the energy-saving potential of these houses in hot-summer and cold-winter climate zones. Research has indicated that when traditional Xuzhou courtyard houses meet certain criteria—including an orientation of 20° east of south for the main building, width-to-depth ratio of 2:1, roof slope of 35°, courtyard width-to-depth ratio of 1.7:1, use of branch pick windows, building height of 4.5 m, and a specific window-to-wall ratio—they achieve optimal climate adaptability. This study proposes dimensions for traditional residential buildings suited to the Xuzhou climate and explores their practical application, providing targeted optimization and retrofitting suggestions to support sustainable architectural and ecological development.

Investigation of the cooling effect of wind on rooftop PV power plants

This study investigates the cooling of PV panels installed on the roof of a 5.9 MW power plant in Bursa, Turkey, under varying wind conditions. Meteorological measurements were conducted during the summer period to analyse the cooling effects. When wind speed differences were below 0.5 m/s, the cooling effect on the PV panels ranged between 2-3°C. However, when the wind speed differences approached 1 m/s, the cooling effect increased up to 7°C. At lower wind speeds, winds blowing from behind the panels provided better cooling, whereas side winds offered improved performance as wind speed increased. Due to the roof slope and the minimal gap between the panels and the roof, winds from behind were less effective, as they could not penetrate the back of the PV panels. Side winds, on the other hand, faced no difficulty in flowing over the panel surfaces but lost their cooling effect as they passed along the long rows of panels. These findings suggest that during the design phase of PV power plants, high wind speed locations should be prioritized, and optimal configurations should be implemented to ensure uniform wind access to all PV arrays.

Design of a Novel Hybrid Concentrated Photovoltaic–Thermal System Equipped with Energy Storages, Optimized for Use in Residential Contexts

Concentrated photovoltaic (CPV) technology is based on the principle of concentrating direct sunlight onto small but very efficient photovoltaic (PV) cells. This approach allows the realization of PV modules with conversion efficiencies exceeding 30%, which is significantly higher than that of the flat panels. However, to achieve optimal performance, these modules must always be perpendicular to solar radiation; hence, they are mounted on high-precision solar trackers. This requirement has led to the predominant use of CPV technology in the construction of solar power plants in open and large fields for utility scale applications. In this paper, the authors present a novel approach allowing the use of this technology for residential installations, mounting the system both on flat and sloped roofs. Therefore, the main components of cell and primary lens have been chosen to contain the dimensions and, in particular, the thickness of the module. This paper describes the main design steps: thermal analysis allowed the housing construction material to be defined to contain cell working temperature, while with deep optical studies, experimentally validated main geometrical and functional characteristics of the CPV have been identified. The design of a whole CPV system includes thermal storage for domestic hot water and a 1 kWh electrical battery. The main design results indicate an estimated electrical conversion efficiency of 30%, based on a cell efficiency of approximately 42% under operational conditions and a measured optical efficiency of 74%. The CPV system has a nominal electric output of 550 Wp and can simultaneously generate 630 W of thermal power, resulting in an overall system efficiency of 65.5%. The system also boasts high optical acceptance angles (±0.6°) and broad assembly tolerances (±1 mm). Cost analysis reveals higher unit costs compared to conventional PV and CPV systems, but these become competitive when considering the benefit of excess thermal energy recovery and use by the end user.

Review of Wind Field Characteristics of Downbursts and Wind Effects on Structures under Their Action

Downbursts belong to sudden, local, and strong convection weather, which present significant destruction for structures. At any given time, there are approximately 2000 thunderstorms occurring on the Earth. Many studies have investigated the effects of downbursts on different structures. However, the extensive range of varying wind field parameters and the diverse representations of wind speeds render the study of structural wind effects complex and challenging under downbursts. This study firstly reviews the research of wind field properties of downbursts according to four common approaches, and the major findings, advantages, and disadvantages of which are concluded. Then, failure analysis of transmission line systems under stationary and moving downbursts is explored. The article also reviews the wind pressure on the roof of different kinds of low-rise buildings, and some dominant parameters, namely roof slope, distance of building from downburst center, wind direction angle, and so on, are discussed. Moreover, the wind effects caused by downbursts on high-rise buildings and some specialized structures are also considered because more and more wind hazards are related to downbursts. Finally, the limitations of the current study are pointed out, and recommendations for further research are given for the accurate assessment of the effects of wind on buildings, with a view to providing safer and more economical wind-resistant design solutions for structures.

How vertical drainage positions of extensive green roofs affect the runoff control performance

The capacity of extensive green roofs (EGRs) in runoff reduction and pollutants control significantly decreased with increasing rainfall intensity. This is attributed to most of EGRs are the lower-drainage method and use a thinner substrate layer because of the structural load-bearing limits of buildings. Existing solutions depend on increasing the rainwater storage by thickening the substrate layer of EGRs, or replacing the substrate materials. We propose to enhance the water retention capacity of EGRs by adjusting vertical drainage positions and moving the lower-drainage at the bottom to upper-drainage over the substrate layer. To test the runoff control performance of EGRs with the upper-drainage method, we designed three EGR models with two different (upper- and lower-) drainage methods based on the common EGR’s structure in practice and carried out total 48 experiments under different rainfall intensities with an artificial rainfall simulator. The experimental design also included adjusting structural factors of the EGR to further explore the influences of roof slope, status of vegetation growth (height and canopy cover ratio), and model size. The average runoff retention rate for the upper-drainage EGR was 61.82 %, which was much higher than the 23.94 % for the lower-drainage EGR. The concentrations of TN and TP in runoff with the upper-drainage were 2.83 and 0.18 mg/L, which were much lower than the 8.47 and 2.10 mg/L for the lower-drainage EGR. EGRs with upper-drainage overall performed better in runoff control than EGRs with lower-drainage. Vegetation height and model size did not significantly affect the rainwater control performance for different drainage methods, while the change of slope affected the rainwater interception of the EGRs with upper-drainage method.

Research on probabilistic analysis of trapezoidal triangle truss

As a region affected by the Mongolian Siberian high-pressure system, the Northeast area of China faces extreme low temperatures and snowy weather in winter, which poses a high demand for local energy. As a relatively mature sustainable energy source, laying solar photovoltaic panels on the roofs of residential buildings relied on sufficient local sunlight resources has become a feasible measure. From the perspective of engineering safety, this paper studies the stability of a single span double slope roof steel truss with added solar photovoltaic panels under snow loads. First, the types of loads on the truss are analyzed, assuming the distribution of the load and capacity of any member in the truss structure. Then, Monte Carlo algorithm is used to simulate the failure probability, and finally the failure probability of the member as well as the overall structure is obtained. As a conclusion, this paper finds that the stability of this structure is basically not affected by the above factors, and this provides certain reference significance for balancing safety and economic benefits in practical engineering design.

State-of-the-Art Review: Effects of Using Cool Building Cladding Materials on Roofs

Cool roofs are roofing systems designed to reflect significant solar radiation, reducing heat absorption and subsequent cooling energy demands in buildings. This paper provides a comprehensive review of cool roof technologies, covering performance standards, material options, energy-saving potential, and hygrothermal considerations. The review examines provisions in current codes and standards, which specify minimum requirements for solar reflectance, thermal emittance, and solar reflectance index (SRI) values. These criteria often vary based on factors like roof slope, climate zone, and building type. Different cool roof materials are explored, including reflective paints and coatings that can be applied to existing roofs as cost-effective solutions. Several studies have demonstrated the energy performance benefits of cool roofs, showing significant reductions in cooling loads, indoor air temperatures, peak cooling demand, and overall cooling energy consumption compared to traditional roofs. However, hygrothermal performance must be evaluated, especially in cold climates, to optimize insulation levels and avoid moisture accumulation risks, as reduced heat absorption can alter moisture migration patterns within the building envelope. While cool roofs provide substantial energy savings in hot climates, further research is needed to validate modeling approaches against real-world studies, investigate the impact of seasonality and green spaces on cool roof efficacy and urban heat island mitigation, and explore energy-saving potential, moisture control, and condensation risks in cold and humid environments.

Passive Design Strategy in Vernacular House of Samin, Indonesia

Vernacular architecture embodies passive design principles and strategies to create comfortable dwellings. This study investigates the impact of passive design strategies on temperature comfort in Samin vernacular houses. Visual observation is employed to assess the suitability of house elements based on passive design criteria. At the same time, field measurements are conducted to evaluate comfortable temperature conditions using data loggers over one month. The research focuses on the Original Samin house and the New Samin house situated in Klopoduwur Village, Blora Regency, Central Java, Indonesia. The visual observation reveals that the roof volume, slope, and thin walls with low conductivity in both Samin houses align with passive design principles. The New Samin house also incorporates other passive design strategies, including an east-west building orientation with the long side perpendicular to the wind direction, an open-plan room layout, and varying floor heights. The temperature comfort performance in both houses falls within the neutral temperature range during 16 hours. The New Samin house exhibits the largest daytime air temperature decrease at 5.5°C, while the Original Samin house experiences the largest nighttime decrease at 0.7°C. The evolution of passive designs in Samin vernacular houses encompasses considerations such as building proportion and width, terrace width, positioning and size of window openings, vegetation, and shading elements.

Design and demonstration of a sensing network for full-scale wind pressure measurements on buildings

There is a need for full-scale wind pressure measurements to evaluate the accuracy of peak wind load estimates from wind tunnel measurements, numerical simulations, or building codes. The objective of this study was to design a sensing network for obtaining long-term records of fluctuating wind pressures, and to demonstrate the network’s potential through deployment. A custom data-logger using the BMP388 absolute pressure sensor, which can measure pressure coefficients within ±0.1 at a wind speed of 10 m/s, was designed. The accuracy of the measured statistics was established through comparison with a standard differential sensor in a wind tunnel experiment. A network of 10 motes was deployed on the sloped roof of the 184 m tall Space Needle, obtaining over 1000 h of fluctuating pressure data. The measurements reveal a windward separation region with strong dependency of the approach wind turbulence on the pressure statistics, but positive skewness limits the peak values. The skewness becomes negative near the edge of a second, leeward separation region, resulting in peak factors up to 2.6 times larger than the code-prescribed value of 3.4. The results demonstrate that long-term full-scale measurements provide valuable insight into peak wind pressures and their dependence on approach wind characteristics.

Analysis of rainwater utilization technology and current situation in the roof garden

The urban water environment has been deteriorating over the last decade due to land development and climate change, increasing the pressure on urban stormwater drainage systems. With economic development, the value of buildings has also been challenged at a higher level. Roof garden, as a new form of roof treatment, can effectively increase the urban greening area and compensate for the ecological and water environments that have been damaged by building development and utilization. This paper analyzes the advancement of roof garden by comparing it with the traditional sloped roof. The analysis finds that roof gardens can store water and control drainage, and have significant advantages in reducing rainwater discharge, reducing building water demand, and improving the urban water cycle. Roof gardens not only have the ability to utilize rainwater efficiently, but also come with a series of economic, ecological, and social benefits, such as improving the urban heat island effect, saving the amount of water demanded by buildings, and energy consumption. By analyzing domestic and international cases of roof gardens, it is verified that roof gardens are designed as a combination of utility and aesthetics.

Predicting Wildfire Ember Hot-Spots on Gable Roofs via Deep Learning

Ember accumulation on and around homes can lead to spot fires and home ignition. Post wildland fire assessments suggest that this mechanism is one of the leading causes of home destruction in wildland urban interface (WUI) fires. However, the process of ember deposition and accumulation on and around houses remains poorly understood. Herein, we develop a deep learning (DL) model to analyze data from a series of ember-related wind tunnel experiments for a range of wind conditions and roof slopes. The developed model is designed to identify building roof regions where embers will remain in contact with the rooftop. Our results show that the DL model is capable of accurately predicting the position and fraction of the roof on which embers remain in place as a function of the wind speed, wind direction, roof slope, and location on the windward and leeward faces of the rooftop. The DL model was augmented with explainable AI (XAI) measures to examine the extent of the influence of these parameters on the rooftop ember coverage and potential ignition.

The Extraction of Roof Feature Lines of Traditional Chinese Village Buildings Based on UAV Dense Matching Point Clouds

Traditional Chinese buildings serve as a carrier for the inheritance of traditional culture and national characteristics. In the context of rural revitalization, achieving the 3D reconstruction of traditional village buildings is a crucial technical approach to promoting rural planning, improving living environments, and establishing digital villages. However, traditional algorithms primarily target urban buildings, exhibiting limited adaptability and less ideal feature extraction performance for traditional residential buildings. As a result, guaranteeing the accuracy and reliability of 3D models for different types of traditional buildings remains challenging. In this paper, taking Jingping Village in Western Hunan as an example, we propose a method that combines multiple algorithms based on the slope segmentation of the roof to extract feature lines. Firstly, the VDVI and CSF algorithms are used to extract the building and roof point clouds based on the MVS point cloud. Secondly, according to roof features, village buildings are classified, and a 3D roof point cloud is projected into 2D regular grid data. Finally, the roof slope is segmented via slope direction, and internal and external feature lines are obtained after refinement through Canny edge detection and Hough straight line detection. The results indicate that the CSF algorithm can effectively extract the roofs of I-shaped, L-shaped, and U-shaped traditional buildings. The accuracy of roof surface segmentation based on slope exceeds 99.6%, which is significantly better than the RANSAC algorithm and the region segmentation algorithm. This method is capable of efficiently extracting the characteristic lines of roofs in low-rise buildings within traditional villages. It provides a reference method for achieving the high-precision modeling of traditional village architecture at a low cost and with high efficiency.

Wind Pressure of Low-rise Buildings Based on Wind-tunnel Numerical-simulation Test

Based on the numerical-simulation test data from the wind tunnel, the wind-pressure characteristics of low-rise buildings with gable roofs are examined and compared to standard values under different roof slopes, eave heights and terrains. To further investigate the underlying mechanisms of variation, a numerical-simulation study was conducted for selected conditions. The results indicate that when the roof slope is less than 3:12, the negative value of the shape coefficient for the windward roof of the building can reach up to -0.89, far exceeding the code value of -0.5. It is suggested that when the slope is not larger than 3:12, the shape coefficient for the windward roof should be -0.9 and the coefficient for the leeward roof should be determined through linear interpolation within the range from -0.4 to -0.75 based on the roof's slope size. With the increase of eave height and the decrease of ground roughness, the vortex intensity of the roof and the leeward surface increases and the area proportion of high negative pressure area in the vortex influence range increases. Thus, the negative value of the shape coefficient for the roof and the leeward surface becomes larger, which is higher than the code value. It is proposed that under an eave height of 12 m, the shape coefficient for the windward roof should be -0.95. Meanwhile, those of the leeward roof, leeward surface and sidewall 2 should be -0.6 under open terrain. Keywords: Low-rise buildings, Wind-tunnel test, Wind load, Shape coefficient, Numerical simulation

ОЦЕНКА УСТОЙЧИВОСТИ ОБШИВКИ БОКОВЫХ СТЕН И КРЫШИ КУЗОВА ПАССАЖИРСКОГО ВАГОНА ПРИ ВЫПОЛНЕНИИ РЕМОНТНЫХ РАБОТ

The lining stability of the side walls and roof of the passenger car body is assessed during repair work related to its asymmetric lifting with a jack at one end of the body. Using mathematical modeling, the lifting height is determined which is necessary to ensure the possibility to dismantle the springs of the spring set of the central suspension. The stability of the reinforced lining of the car body was assessed using the developed problem-oriented elastic-dissipative finite element model of the supporting structure of the passenger car body. The calculations are performed in a static non-linear formulation, taking into account the geometric nonlinearity and non-conservativeness of the operating loads. The stability of the reinforced load-bearing lining of the car was assessed both for the initial structure and for a structure with geometric imperfections such as technological loss. The analysis of the research results allows to conclude that during the technological operation associated with lifting the passenger car body with a jack under one support, it can lead to a loss of stability of the sill belt lining of the side wall and the smooth sheathing of the roof slope. The results obtained agree with the results of the inspection of full-scale cars in operation.

Reconstruction of Single-Bay Buddhist Architecture Based on Stylistic Comparisons in Northeast Fujian, the Core Hinterland of the Changxi River Basin—Using Gonghoulong Temple as an Example

In the Changxi River Basin in eastern Fujian, a few stone elements remain and Buddhist buildings with one bay in width and three bays in depth have been preserved dating from the timespan of the Tang to the Song dynasty. These features are characterized by a regional form of early Buddhist architecture seldom seen in Chinese history. The article focuses on the reconstruction of a Song dynasty Buddhist building at the Gonghoulou Temple site in Huotong Town, Jiaocheng District, Ningde City, and aims to analyze the potential characteristics and rules of single-bay Buddhist architecture. From the styles of the remaining stone columns, the direction of the lotus carving at the column base, and the mortises of the plinth stone, a spatial arrangement is indicated that includes an open front corridor and a closed rear section. A “reconstruction” of the ruler used in the original building reveals the possibility that a local Fujian ruler was used, shorter than the standard measurement device employed elsewhere. The analysis of the frame construction indicates that this hip-gable roof-covered Buddhist hall utilizes the horizontally layered logic of multi-storied palatial-style halls. Key elements include its gentle roof slope, restraint from the practice of shortening the roof ridge, use of the traditional chuji method, and the interior columns use of internal longitudinal architraves secured to beam supporting brackets. This research brings to light a unique architectural type that has disappeared in the course of history and was previously unknown to the academic community. It holds significant importance and value for deepening the understanding of the history of timber frame architecture technology in Fujian.

Створення тривимірної моделі культової споруди за даними комбінованих геодезичних знімань

The purpose of the research is to test algorithms for creating a three-dimensional model of an object based on point clouds obtained from combined geodetic surveys (UAV survey and ground laser scanning). The methodology is based on the collection of a cloud of points by ground laser scanning and the acquisition of a cloud of points on the same object by the photogrammetric method based on data taken from a UAV. The formation of the resulting three-dimensional model is performed according to the most reliable data from the point of view of geometric accuracy. The results. Each of the point cloud acquisition methods (UAV or laser scanning) has its advantages for certain parts of the building. Thus, the modeling of the upper part of the building, sloping and complex roofs is best performed based on the data taken from the UAV, vertical walls and the elements placed in them (windows, decoration elements, etc.) – based on point clouds obtained from laser scanning. Scientific novelty and practical significance. The method of processing point clouds obtained from various sources on the basis of free software was tested. The approach discussed in the article has significant potential for use in many branches of the national economy. The performer can combine measurement data from various sources on the basis of free software and prepare them for further export to the necessary software for creating a model.

City-scale analysis of PV potential and visibility in heritage environment using GIS and LiDAR

Increasing the share of renewables, especially utilizing solar power in our energy mix is a highly prioritized aim of the EU. Budapest, the largest city and the capital of Hungary, contains almost 1 million flats in more than 190 thousand buildings, organized in various characteristic urban fabric types. Although on-site renewable energy production is severely limited in dense urban environments, the roofs offer a considerable potential to generate energy on-site.The present paper introduces a method to estimate the PV potential of rooftops on a large scale applying a GIS approach. Using LiDAR data, a Digital Surface Model (DSM) was created. The DSM was utilized to evaluate roof slope, orientation, and global irradiation. Solar potentials, available roof area, photovoltaic (PV) system capacities and estimated annual electricity production were derived from the GIS model. The method was used to develop an open access website called the Budapest Solar Map, which provides decision-makers with solar PV data. However, the nominal PV potential is limited by layers of heritage protection regulations that safeguard the sight of our case study area, Budapest, which is a World Heritage Site. Visibility is also surveyed with GIS and geometrical modeling from designated high points and from the street level, respectively.

Assessment of purlins with paired torsion bracing in sloped roof systems: Direct strength method approach

A Direct Strength Method based methodology has been developed by the authors for the prediction of local buckling and distortional buckling strength of purlins with paired torsion bracing. In a previous study, the methodology was presented and discussed for zero slope roof systems in by the authors. In this paper, the authors reformulated the developed methodology to include the effect of slope in the structural behavior of the roof systems. Equations have been developed for the strength prediction of sloped roof systems for simple span and multi-span interior conditions (fixed support conditions at both ends). As downslope forces are introduced to the sloped roof systems, the lateral displacement of the diaphragm is affected, and the stress distributions are impacted along the purlin cross sections. Typically, with the increase in the roof slope, the lateral diaphragm deflection decreases during which the stress distributions approach the constrained bending distribution increasing the strength. When the roof slope is increased further and the lateral deflection of the purlins moves downslope, there is a considerable decrease in the predicted strength. Therefore, for steep roof slopes, a considerable inelastic reserve capacity is observed which when accounted for will improve the predicted strength. The component stiffness method is utilized in the process, considering displacement compatibility for the calculation of the anchorage forces within the purlin system. Partial restraint of the diaphragm that is provided by the sheathing is considered in the procedure. The developed methodology herein this paper incorporates the effects of first-order and approximate second-order torsion for the prediction of the actual stress distributions along purlin cross sections. This stress distribution may significantly differ from the conventionally assumed constrained bending distributions which may result in substantial differences in the predicted local buckling and distortional buckling strengths for purlin systems.

Green Energy Harvesting and Management Systems in Intelligent Buildings for Cost-Effective Operation

Nowadays, the rise of Internet of Things (IoT) devices is driving technological upgrades and transformations in the construction industry, the integration of IoT devices in buildings is crucial for both the buildings themselves and the intelligent cities. However, large-scale IoT devices increase energy consumption and bring higher operating costs to buildings. Therefore, harvesting the ambient cost-effective and clean energy sources is essential for the future development of intelligent buildings. In this work, we investigate the feasibility of integrating a typical triboelectric droplet energy harvester (DEH) into buildings. We demonstrate the energy harvesting capabilities of DEH on different sloped roof surfaces and complex curved building surfaces by simulating rainy weather with various rainfall intensities. The results indicate energy harvesting efficiency increases with larger tilt angles, which guides future smart architectural designs. This work is significant for the future integration of diversified, all-weather green energy collection and management systems, including raindrop energy, wind power generation, and solar energy, which will contribute to energy conservation and cost control in the next generation of smart buildings.