Roof Surface Research Articles

A comprehensive analysis of the tail-dependent structure of wind loads and its engineering applications

Wind load field characteristics on the roof surface of low-rise buildings based on field measurements have crucial engineering guidance value. In the background, tail-dependence structure from measured wind loads can assist in modeling the joint tail distribution of multivariate wind loads. In this study, the non-parameter estimation method, multi-copula function model and multivariate peak over threshold model are applied to estimate its precise value. The upper tail dependence coefficient's value is around 0.20 when the quantile for p(y) = 0.75. When p(y) = 0.95, the Gumbel copula overestimates the tail-dependence value slightly. Additionally, the lower tail-dependence values estimated by the Clayton copula are around 0.19 at 0.25 quantile. For extreme tail-dependence coefficients, little difference exists in the estimated results by the non-parameter estimation method and the peak over threshold model, in which its value varies from 0.80 to 0.90. Under roof pitch = 5°, its value exhibits some dispersion at different locations. An area weight function is applied to estimate the extreme tail-dependence value between critical regions. Then, the expectation function of tail dependence reaches the peak value in p(x) = 0.50, p(y) = 0.50 and it has different gradients for different variables and tail regions. Additionally, the lower tail dependence structure is significantly stronger than the upper tail dependence for wind loads with negative skewness. For application in wind engineering, potential applications in risk analysis for roof structures, extreme value estimation for local region block wind load, and wind load forecast for unmonitored locations are proposed.

Assessment of Solar Photovoltaic Potential of Building Rooftops Based on Multicriteria Spatial Analysis

This paper presents a methodology using Geographic Information Systems (GIS) to assess the photovoltaic potential of building rooftops by applying available data in North Macedonia. Applied to a case study, the method encompasses a high-resolution 3D model from LiDAR data to accurately represent rooftop surfaces and terrain. The approach includes generating a Digital Surface Model (DSM), analysing rooftop slopes and aspects, calculating solar radiation, and identifying suitable rooftops. It was concluded that out of 628 buildings, an area of 73 544 m², about 62% of the total rooftop area, is suitable for photovoltaic system installation. The potential electricity production from each building varies from 4 MWh to 1000 MWh annually and can be estimated at a total of 11 329 MWh from all suitable rooftops within the study area. The proposed method enables a large-scale valuation of suitable roof surfaces for photovoltaic system installation.

An Eocene conger eel (Teleostei, Anguilliformes) from the Lillebælt Clay Formation, Denmark

A conger eel (Anguilliformes, Congridae) is described from the lower Lutetian concretionary nodules of the Lillebælt Clay Formation exposed at Trelde Næs, eastern Jutland, based on two partially complete articulated cranial skeletons. One of the cranial specimens exhibits an otolith void from wich a cast was taken, used by Schwarzhans (2007) to describe the extinct Pseudoxenomystax treldeensis, which is placed herein within the new genus Smithconger gen. nov. Smithconger treldeensis (Schwarzhans, 2007) is characterized by well-developed lateral processes on the frontals, supraoccipital crest absent, sphenotic spine rather large, anteriorly pointed and exposed on the flattened surface of the skull roof, otic bullae considerably reduced, maxilla almost straight and distally pointed, maxillary and dentary teeth numerous and arranged in multiple rows, dentary with slightly convex ventral profile, opercle with smooth posterior margin and subopercle short. The otoliths of Smithconger treldeensis show high dorsal rim, broad and deep dorsal depression, no ventral furrow, sulcus straight, shallow, centrally positioned with anteriorly reduced colliculum, and ostial channel at anterior tip of colliculum short, not reaching the predorsal rim. The otolith-based species Bathycongrus waihaoensis Schwarzhans, 2019 from the Kaiatan (Bartonian/Priabonian) of New Zealand is also assigned to the genus Smithconger. Smithconger is tentatively referred to the congrid subfamily Congrinae due to the lack of hypohyals in the hyoid bar. This new Eocene genus of conger eel shows a certain degree of similarity with the extant Bassanago. The diversity and relationships of other Eocene congrids is also briefly discussed.

An Experimental Study on the Effect of Nano Zinc Oxide on Reflective Coatings and Building Roof Temperatures

Most roofs on Earth are made of dark materials. Dark roof surfaces can retain heat better than light ones; in Iraq, summer time temperatures on the roofs of dark buildings reached 70–80 degrees Celsius in July and August. The effects of this temperature rise are detrimental to cooling and energy consumption. To lessen heat transfer into the building, use reflective surfaces that can reflect infrared radiation waves. Cool roofs have both short-term and long-term advantages. They can reduce a building's annual air conditioning energy consumption by up to 15%, extend the life of the roof and its service life, improve the energy efficiency of roofs particularly those with inadequate insulation at the front of the roof improve thermal comfort in buildings without air conditioning, and lower greenhouse gas emissions and air pollution. Solar heat is one of the main factors affecting the durability of roofing membranes, according to research and real-world experience with the deterioration of these materials over time. High solar reflectance materials can reflect more sunlight and maintain their coolness in the sun. This study examines a low-cost composite cool coating that uses 60% calcium carbonate and demonstrates a 15°C drop in surface concrete temperature for roof buildings when compared to an uncoated surface. Additionally, compared to 30%wt CaCO3, the effect of 60%CaCO3 in composite coating reduces adhesion strength. According to the study, the weight of CaCO3 in the composite coating increases while adhesion strength, surface roughness, and particle homogeneity distribution decrease. Conversely, the maximum weight of CaCO360% weight percent exhibits good IR reflectance and less tribological properties. While preserving good infrared reflectance, adding 10% ZnO to the coating solution (60% CaCO3/PVac) improves tribological properties. The adhesion strength of the 60% calcium carbonate polymer composite paint increased from 10.9 MPa to 40.2 MPa when the nanomaterial was present, while this material maintained the superior optical qualities of infrared reflection. The coefficient of thermal expansion varies between concrete and coating solutions. For instance, the coating that has 10% weight added ZnO has a peel resistance coefficient of 8*10-6 1/K. The 60%CaCO3/10%ZnO/PVac coating effectively lowers the temperature by 15–12 °C when applied to a building roof.

RAINWATER HARVESTING AND LEAKAGE REDUCTION AS ALTERNATIVES TO OPTIMISE FRESHWATER MANAGEMENT

The need of water is a reality for human life. Due to climate change, rainfall patterns are being altered and there is a growing conscience of the need for water collection in society. Any additional water could help to mitigate daily needs and therefore, this study has determined the water provision that could be determined for each population based on rainwater collection "in situ". It has been estimated in several cities in Spain, which are representative of the peninsular and island climatology, according to the respective roof surface and annual precipitation. On the other hand, it is well known that water supply networks have leaks. The International Water Association (IWA) defined a series of indicative parameters, including the IFE/ILI parameter, which has been incorporated into Spanish regulations, specifically in RD 3/2023 of 10 January. Consequently, this study has also determined the aforementioned parameter for the same cities. It has also been calculated what the improvement in water savings could mean by applying corrective measures and sustained plans for repairing leaks and optimising pressures.

Aerodynamic and codification study of low-rise buildings: Part II – Partially elevated structures

This study constitutes part II of an extensive study where the aerodynamics of elevated buildings is investigated using large-scale wind tunnel testing. Part II focuses on the case of elevated buildings with partially enclosed spaces beneath the elevated floor. For this purpose, four 1:10 scaled models of elevated single-story gable-roof buildings were selected, three of which were partially elevated with enclosed regions covering areas ranging from 19% to 54% of the model footprint. The tests aimed to examine the effect of the enclosed regions below the floor on the distribution of the localized peak pressure coefficients on the walls, floor, and roof surfaces of the models. Furthermore, the study evaluates the ASCE 7–22 provisions and the proposed provisions, presented by the authors in Part I, for estimating external wind pressure coefficients acting on the floor, roof, and walls of elevated buildings. The results indicate that enclosed regions below the floor significantly alter the aerodynamics of elevated low-rise buildings and could increase the wind-induced loads on the roof and walls of such structures, with the increase in some cases exceeding 80%. Furthermore, the results align well with the proposed modifications by the authors in Part I to the ASCE 7 provisions for estimating the external pressure coefficients for the various zones of low-rise buildings, addressing the underestimation issues previously identified within the current ASCE standard.

Thermal Performance of Novel Eco-Friendly Prefabricated Walls for Thermal Comfort in Temperate Climates

The global threat of climate change has become increasingly severe, with the efficiency of buildings and the environment being significantly impacted. It is necessary to develop bioclimatic architectural systems that can effectively reduce energy consumption while bringing thermal comfort, reducing the impact of external temperatures. This study presents the results of a real-scale experimental house prototype, MHTITCA, using a unique design composed of novel eco-friendly prefabricated channel walls filled with a blend of soil, sawdust, and cement for walls and roofs. The experimental analysis performed in this study was based on dynamic climatology. A solar orientation chart of the place was constructed to identify the solar radiation intensity acting on the house. Measurements of roof surface temperatures were conducted to determine temperature damping and temperature wave lag. Monthly average temperature and direct solar radiation data of the site were considered. Compared to other alternative house prototypes, the system maximizes thermal comfort in high-oscillation temperate climates. Temperature measurements were taken inside and outside to evaluate the thermal performance. A thermal insulating layer was added outside the wall and the envelope to improve the prototype’s thermal comfort and reduce the decrement factor even more. This MHTITCA house prototype had 85% thermal comfort, 0% overheating, and 15% low heating. This eco-friendly prototype design had the best thermal performance, achieving a thermal lag of twelve hours, a reduced decrement factor of 0.109, and preventing overheating in areas with high thermal fluctuations. Comparatively, the other prototypes examined provided inferior thermal comfort. The suggested MHTITCA system can be an energy-saving and passive cooling option for thermal comfort in low-cost houses in temperate climates with high thermal oscillations in urban or rural settings.

A Calculating Method for the Height of Multi-Type Buildings Based on 3D Point Cloud

Building height is a critical variable in urban studies, and the automated acquisition of the precise building height is essential for intelligent construction, safety, and the sustainable development of cities. The building height is often approximated by the building’s highest point. However, the calculation method of the building height of the various roof types differs according to building codes, making it challenging to accurately calculate the height of buildings with complex roof structures or multiple upper appendages. Consequently, this paper utilizes point clouds to propose an automated method for calculating building heights conforming to design codes. The model considers roof types and allows for fast, automated, and highly accurate building height estimation. First, roofs are extracted from the point cloud by combining normal vector density clustering with a region-growing algorithm. Second, combined with variational Bayes, a Gaussian mixture model is employed to segment the roof surfaces. Finally, roofs are classified based on slope characteristics, achieving the automatic acquisition of building heights for various roof types over large areas. Experiments were conducted on Vaihingen and STPLS3D datasets. In the Vaihingen area, the maximum error, root-mean-square-error (RMSE), and mean absolute error (MAE) of the measured heights are 1.92 cm, 1.18 cm, and 1.13 cm, respectively. In the STPLS3D area, these values are 1.79 cm, 0.82 cm, and 0.68 cm, respectively. The results demonstrate that the proposed method is reliable and effective, which offers valuable data for the development, construction, and planning of three-dimensional (3D) cities.

Nonlinear changes in urban heat island intensity, urban breeze intensity, and urban air pollutant concentration with roof albedo

This study systematically examines how the urban heat island (UHI) and urban breeze circulation (UBC) respond to an increase in roof albedo (αr) and its influence on urban air pollutant dispersion. For this, idealized ensemble simulations are performed using the Weather Research and Forecasting (WRF) model. The increase in αr from 0.20 to 0.65 decreases the UHI intensity, UBC intensity, and urban planetary boundary layer (PBL) height in the daytime (from 1200 to 1700 LST) by 47%, 36%, and 6%, respectively. As both UBC intensity and urban PBL height decrease, the daytime urban near-surface passive tracer concentration increases by 115%. The daytime UHI intensity, UBC intensity, and urban tracer concentration nonlinearly change with αr: For 0.10 ≤ αr < 0.80, the rates of changes in the UHI intensity, UBC intensity, and urban tracer concentration with αr overall increase as αr increases. For αr ≥ 0.80, the daytime roof surface temperature is notably lower than the daytime urban near-surface air temperature, the UHI intensity, UBC intensity, and urban tracer concentration very slightly changing with αr. This study provides insights into the associations between changes in roof surface temperature and roof surface energy fluxes with αr and those in UHI intensity.

Assessing Photo-Voltaic Potential in Urban Environments: A Comparative Study between Aerial Photogrammetry and LiDAR Technologies

Abstract. Urban development and population growth have significantly increased energy demands, predominantly met by non-renewable resources, negatively impacting nature and climate. Consequently, there has been a global shift towards renewable energy sources, with solar energy being widely adopted. Photovoltaic (PV) potential measures the usable electricity from solar energy using PV technology. With conventional methods, estimating PV potential involves converting 3D point cloud data to 2.5D elevation models, which can affect the accuracy of the estimation. A research gap exists in using adequate 3D point cloud datasets for PV potential estimation considering roof surface area and the surface normal vectors. This study compares aerial photogrammetry and aerial LiDAR point clouds for PV potential estimation against the DSM-based approach. Accurate PV potential estimation must consider solar incidence, roof area, azimuth, tilt angles, and PV efficiency. Traditional 2.5D methods often overlook crucial azimuth and tilt data, limiting the accuracy of the PV estimation. Converting 3D data to 2.5D may result in information loss, while 3D analyses offer higher accuracy. To investigate the mentioned gaps, this research aims to evaluate the capabilities of photogrammetry and LiDAR for urban PV potential estimation, highlighting their feasibility and accuracy over 2.5D methods.

Study of Roof and Ceiling Surface Temperatures in Coastal Area (Case Study: Pasar Bengkulu Village)

Abstract The majority of residential roofs in Pasar Bengkulu Village are constructed using corrugated iron and galvalum metal. These coastal areas often grapple with high levels of solar heat radiation. Both corrugated zinc and galvalum roofing materials are known for their high heat conductivity and excellent heat-reflecting capabilities. To combat this, solar reflectance paint is often used to reflect solar radiation heat, thereby reducing heat absorption. This research is a qualitative research with a focus on the description and analysis of measured data which aims to compare the surface temperature of the roof and ceiling before and after being coated with reflective solar paint. This research was conducted to determine the difference in roof and ceiling surface temperatures before and after the application of solar reflective paint. The results of the roof surface temperature measurements revealed that galvalum metal roofs exhibited the most significant reduction in roof surface temperature, with a decrease of 9.1°C.

Optimization of temperature prediction algorithms and simulation of future neighborhood-scale thermal environments in Chongqing

With climate change and urbanization, predicting the outdoor thermal environment of residential areas has become increasingly crucial, particularly during extreme weather conditions. Existing studies lack a comprehensive approach to optimizing temperature prediction algorithms for Chongqing and simulating extreme thermal environments at the neighborhood scale for future decades. This study employed various algorithms, including Levenberg-Marquardt optimization, Monte Carlo simulation, ARIMA modeling, and SARIMA prediction, to simulate and forecast temperature data for the central urban area of Chongqing from 2014 to 2023. By assessing metrics such as root mean square error (RMSE), R-squared (R2), and mean absolute percentage error (MAPE), the most effective prediction algorithm was identified. Results indicate that the Levenberg-Marquardt optimization algorithm, known for its nonlinear curve fitting capabilities, demonstrated superior performance in both the test and training sets, achieving an RMSE of 0.82 °C, MAPE of 1.81 %, and R2 of 0.75. This algorithm was subsequently used to forecast the outdoor temperature trend in Chongqing from 2024 to 2050, while also simulating the outdoor wind field, temperature distribution, building surface temperatures, and wind speeds in a residential district at neighborhood scale for 2030, 2040, and 2050 at a building density of 40 %. Findings reveal that peak pedestrian-level temperatures could reach 45.62 °C, and peak roof surface temperatures could reach 93.93 °C under extreme conditions. Furthermore, the study proposes practical recommendations for building layouts and cooling strategies. These findings are expected to improve residential planning in Chongqing, enhance residents' quality of life, and provide insights for other regions facing future temperature changes.

Temperature and Light Intensity under Passively Cooled Natural Ventilated Polyhouse and Shade Net Structure During Summer Season

The high temperature &amp; light intensity inside the natural ventilated polyhouse during summer season is major challenge for cultivation and is a major hindrance in utilizing the polyhouse for round the year cultivation. This study was conducted to evaluate the reduction of temperature &amp; light intensity inside passively cooled polyhouse using various shading configuration in comparison to shade net structure. There is always increase &amp; decrease in minimum &amp; maximum temperature under the polyhouse and shade net structure respectively. The % light transmission under shade net structure is better than polyhouse. Among the various shading configuration, when shade net is used at 0.3 m above the polyhouse roof surface performs best in reducing the temperature inside the polyhouse. However the shade net structure performs better than passively cooled polyhouse using various shading configuration during summer season.

Effect of Cool Roof Paint Application on Metal Roof Surface Temperature and Indoor Air Temperature in Tropical Climates

Abstract Increasingly hot environmental temperatures and less comfortable indoor temperatures are the impacts of inappropriate choices of building roof materials. An effort to mitigate this problem is by using a cool roof. This study was conducted through a field experiment by applying cool roof paint to the metal roof of a building in Malang, Indonesia. Field measurement results show that the cool roof paint application can reduce the maximum surface temperature above the metal roof by up to 6.6ºC and under the metal roof by up to 6.3ºC, as well as the maximum indoor air temperature by up to 0.8ºC at a height of 120 cm above the floor and up to 1.2º C at a height of 50 cm below the metal roof.

Thermal Performance of Becool-Roof Coating in Reducing Heat Gain on Fisherman’s Settlement of Gorontalo City

Abstract Tanjung Kramat in Gorontalo, Indonesia is a village fostered by the department of Architecture, Universitas Negeri Gorontalo. The village is home to around two hundred families whose majority job is fishing. The people suffer from the uncomfortable condition of tropical coastal environment due to the high air temperature, humidity, and wind speed. Not to mention people in Gorontalo prefer to cover their upper structure using metal zincalume roof since they are more affordable. The highly thermal conductivity roof accounts for excessive heat gain to the house. Through a CSR program by Becool, the villagers received Cool Roof Coating to reduce heating and mitigate global warming. Before and after painting measurements of roof surface temperatures, radiant temperatures, and ground air temperatures are conducted. After the application of the coating, the analysis shows a positive result as the roof surface temperature is reduced by about 20ºC, followed by an improvement in ground air temperature by an average of 0.8ºC. The cool roof coating has succeeded in improving the neighborhood of Tanjung Kramat village.

Experimental studies on the cooling and heating performance of a highly emissive coating

In this study, the cooling effect below ambient air temperature, heat dissipation properties and heating energy efficacy of a superomniphobic self-cleaning (SSC) highly emissive (HE) coating were systematically investigated. Except at midday, the SSC-HE coating with an extremely high solar reflectance of 0.985 showed a better cooling effect than a 10-cm-thick polyurethane insulation layer. The coating substantially reduced the interior air temperature of a well-insulated system by as much as 6.9 °C. The SSC-HE coating enabled the roof surface and room temperatures of the brick bungalow to be 3.4 and 10.2 °C below the ambient air temperature, respectively. Compared with the sunshade and spray water, the SSC-HE coating exhibited better cooling effect. The SSC topcoat allowed the battery cabinet of an HE-coated distributed telecommunication base station to remain its original sub-ambient cooling effect for a long time. Regardless of the location of the HE-coated metal facility, the ultrahigh emissivity of the coating enabled it to exhibit excellent heat dissipation performance during both day and night, even under adiabatic conditions. Additionally, under identical room temperature settings, the HE-coated electric oil heater not only showed faster heating but also had heating energy efficiency of 5.9 % and 4.4 % relative to heaters coated with aluminium- and black paints, respectively. Under identical heating power consumption levels, compared to black paint-coated heater, the HE-coated heater endowed the surrounding environment with a higher equilibrium air temperature, improving the thermal comfort of the indoor environment.

Surgical pearl: Use of micropore tape for easy harvestation and transfer of suction blister epidermal graft

Epidermal graft produced by suction is useful in treating vitiligo. However, it is very difficult to handle thin, flimsy, and translucent epidermis due to its in-curling and wrinkling properties. This is due to the hemispherical blister roof surface area which is twice its circular base. The correction of the epidermal surface and its resizing is a cumbersome and time-consuming task during epidermal grafting. To combat these problems, the blister roof is patched with micropore adhesive tape as a novel technique for harvestation and transfer of the suction blister graft.

Effectiveness of Cool and Green Roofs Inside and Outside Buildings in the Brazilian Context

Several studies have assessed the thermal performance of green and cool roofs. However, few have comprehensively addressed Brazilian buildings and climates, considering indoor and outdoor environments. Considering three Brazilian cities, this study aims to assess the performance of green and cool roofs compared with traditional fibre cement roofs in a typical multifamily residential building. Energy consumption, thermal comfort, and outside surface temperature were assessed using computer simulation. The results show that the cool roofs performed better in cities with warmer climates (e.g., Cfa and Aw), reducing electricity consumption by up to 24.8% compared with traditional roofs. Green roofs are better suited for colder climates (e.g., Cfb), with up to 28.2% energy savings. Green roofs provided the highest percentage of thermal comfort hours in all climates. Cool and green roofs provided hourly reductions in outside roof surface temperature of up to 16.5 °C and 28.4 °C, respectively, compared with the traditional roof. This work reinforces that the choice between these two roof types for each city depends on the parameter used for comparison. Based on the relevant information applied to Brazilian buildings and representative climates presented, this work provided recommendations for urban planning policies and building regulations in Brazil.

An Integrated Method Using a Convolutional Autoencoder, Thresholding Techniques, and a Residual Network for Anomaly Detection on Heritage Roof Surfaces

The roofs of heritage buildings are subject to long-term degradation, resulting in poor heat insulation, heat regulation, and water leakage prevention. Researchers have predominantly employed feature-based traditional machine learning methods or individual deep learning techniques for the detection of natural deterioration and human-made damage on the surfaces of heritage building roofs for preservation. Despite their success, balancing accuracy, efficiency, timeliness, and cost remains a challenge, hindering practical application. The paper proposes an integrated method that employs a convolutional autoencoder, thresholding techniques, and a residual network to automatically detect anomalies on heritage roof surfaces. Firstly, unmanned aerial vehicles (UAVs) were employed to collect the image data of the heritage building roofs. Subsequently, an artificial intelligence (AI)-based system was developed to detect, extract, and classify anomalies on heritage roof surfaces by integrating a convolutional autoencoder, threshold techniques, and residual networks (ResNets). A heritage building project was selected as a case study. The experiments demonstrate that the proposed approach improved the detection accuracy and efficiency when compared with a single detection method. The proposed method addresses certain limitations of existing approaches, especially the reliance on extensive data labeling. It is anticipated that this approach will provide a basis for the formulation of repair schemes and timely maintenance for preventive conservation, enhancing the actual benefits of heritage building restoration.

Characterization of tornado-induced wind pressures on a multi-span light steel industrial building

This study presents the characteristics of external wind pressures of a multi-span light steel industrial building through wind pressure measurements conducted in a tornado simulator. The test model is designed as a three-span low-rise building with gable roofs according to the practical measured sizes and shapes of the light steel industrial building destroyed in the Shengze tornado, China (2021). The distance from the tornado-like vortex center to the building, building orientation, roof angle, and swirl ratio are considered as experimental parameters. The effects of the parameters on the most unfavorable peak and mean pressure coefficients of each surface are analyzed. The roof zoning specified in ASCE 7–16 was re-analyzed based on the characteristics of wind pressure coefficients, and the tornado design pressure coefficients were calculated. The results of the analysis illustrate that the wind-ward roof surface at a distance of around one vortex core radius from the center experience the most severe pressure coefficient under tornado, the most unfavorable zone of the pressure coefficients on the building roof changes with the building orientation, the model with a smaller roof angle has smoother pressure coefficient contours than that with a larger roof angle because of the cutting effect of the ridge, and the simulated tornado with the lower swirl ratio generate higher external pressure coefficients on the building model. Moreover, the roof zoning in ASCE 7–16 for the boundary layer wind is not precise for tornado, thus an updated roof zoning for the tornado design pressure coefficients is defined.