Roofing Materials Research Articles

Numerical modelling approach for estimation of a yield zone in the face of a deep longwall panel

In the Longwall mining method, the coal face is being supported with two-legged or four-legged shield supports which improve better roof control between the face and canopy tip. The development of load on the face increases with the face retreating rate or the increase of the overhung length behind the shield support and as a result, the coal face tends to yield/fail. The yield/failure zone in the face extends depending on intensity of developed load due to the depth of mining, panel size, height of excavation and geometry of the overhung. The broken coal from the yielded face may fall on the shearer, armoured flexible conveyor (AFC), shield supports or may hit the deployed manpower in the face and causes the face stoppage which in turn results in to the loss of the project. It is therefore, a study is conducted to understand the face yield/failure behaviour considering various geo-mining conditions based on input parameters such as main roof thickness, overhung length, and material type and setting load. This paper develops a unique statistical model to predict the yield/failure zone in the longwall face. For this purpose, a total of fifty-four (54) three-dimensional finite element models in ANSYS software are developed and analyzed considering Drucker-Prager failure criterion.

French Metallic Train Sheds of 1850 to 1930: Structural Specificities and the Evolution of the Restoration Practices

ABSTRACT Surviving historic train sheds constitute a broad and representative sample of metal construction of the period 1850 to 1930 in France. This article gives a historical overview of the life of iron or steel train shed structures and questions what makes them authentic, discussing the validity of some of the restoration choices made since the 20th century regarding heritage preservation. First, the specificities of this architectural heritage are highlighted and compared with other countries and other types of construction. Then, based on extensive archive material held by the French national railway company SNCF, the modifications the metallic structures underwent as restoration projects were carried out are analysed. It appears that the restoration practices significantly evolved between the 1970s-1980s and the beginning of the 21st century, becoming more sensitive to heritage preservation. However, choices regarding roofing materials have an impact on the loading of the structure, while structural interventions change the appearance and the load distribution. This enhances the need to include considerations regarding the preservation of the structure in the early stages of restoration projects.

Cool roof strategies for urban thermal resilience to extreme heatwaves in tropical cities

Extreme heatwaves in tropical cities represent a significant short-term weather challenge, directly impacting urban heat, exacerbating human discomfort, and increasing energy demands. To alleviate this, meteorological adjustments utilizing reflective roofing technologies, such as cool roofs, can effectively mitigate heatwave-induced excess heat and enhance thermal comfort. This study assessed the effectiveness of cool roofs in cooling urban areas following heatwaves in Kolkata, India, using comprehensive city-scale simulations. The study presumed that the existing roofing materials, with a reflectivity of 0.15 and emissivity of 0.85, indicated the unmitigated condition. These materials were replaced with third-generation cool roof materials featuring a reflectivity of 0.80 and emissivity of 0.85, leading to a substantial improvement in urban meteorology and thermal comfort compared to the unmitigated state. Notably, during heatwave episodes, the most significant computed reductions in energy flux were 181.3 Wm−2, 16.6 Wm−2, 56.3 Wm−2, and 251.9 Wm−2 for sensible heat, latent heat, ground storage, and net inflow radiation, respectively. Consequently, this led to decreases of 2.3 °C, 6.1 °C, 21.8 °C, and 1.9 °C in urban thermal parameters during peak hours (14:00 LT) for ambient temperature, surface temperature, roof surface temperature, and urban canopy temperature, respectively. The maximum drops in the planetary boundary layer (PBL) were 130.6 m, 1978.5 m, and 1010.3 m for 6:00 LT, 14:00 LT, and 18:00 LT, with an average of 870.3 m. Cool roofs demonstrated their potential to minimize thermal stress during heatwave periods, showcasing a maximum drop in the heat stress index (HSI) of up to 1.5 °C in the morning. Furthermore, outdoor thermal comfort could be significantly enhanced by lowering the universal thermal comfort index (UTCI) at the near surface, resulting in reductions of up to 1.8 °C during peak hours. On average, there was a reduction in UTCI between day and night of approximately 1.2 °C and 0.7 °C in densely populated urban areas. Additionally, the study evaluated 32 case studies that focused on cool roof strategies, revealing remarkably consistent findings that suggest a plausible justification. These findings provide a valuable framework for urban planners and policymakers considering the integration of cool roofs-based heat reduction technology at the city scale.

Disaster Vulnerability Assessment of Low-Cost Houses in Java Island

Among all of the Indonesian islands, Java poses the highest risk for all types of disasters, making it a significant threat to low-cost houses due to its high population vulnerability. The objective is to enhance comprehension of it by conducting a building typology analysis concerning various natural hazards/ risks. The methodology consists of 10 sample houses field observation, AutoCAD drawing, literature analysis, and built environment expert interviews. The results developed four categories of houses emphasising brick or timber walls with a combination of clay tile or zinc roofs. Related to disaster vulnerability, an improper building structure is the main problem. Smooth roof material is significant in a volcano eruption, a complete interconnection of structure is a must for the tornado, light materials are preferable in an earthquake zone, natural material is not recommended for high risk of forest fire, and elevating floor is mandatory in flooding. Focus on designing the four categories’ houses and quality control of the construction process are two strategies recommended. Also, a minimum of two types of disasters in the area should be considered in the design. Resilient low-cost houses will have an impact on reducing casualties, environmental damage, and economic losses. Covering more samples and areas in Java in future studies will provide a comprehensive understanding of low-cost houses.

Matrix-Material Fabrication Technique and Thermogravimetric Analysis of Banana Fiber Reinforced Polypropylene Composites

From the environmental consideration, it would be very interesting to use natural fibers such as banana, jute or coir as reinforcement materials instead of artificial fibers or any kind of synthetic materials. Natural fibers have many advantages over synthetic ones. Polypropylene banana fiber composites (PPBC) are prepared using untreated and alkalitreated banana fibers at 10-25% by weight of the fiber loading. The thermal properties of polypropylene natural fiber composites are very important for technological uses. Thermogravimetric measurements show that the incorporation of banana fiber into PP enhances the thermal stability of composites containing treated fibers, in comparison with untreated fibers. A composite of biodegradable polypropylene (PP) reinforced with short banana natural fibers was prepared by melt blending followed by a hot press molding system. The thermal properties of matrix materials were studied using thermogravimetric analyzers TGA units. It is observed that the introduction of short banana fibers slightly improved the thermo oxidative stability of PP-banana composites. Physical and chemical changes occurred through dehydration, phase transition, molecular orientation, crystallinity disruption, oxidation and decomposition, and incorporation of several functional groups. Systematic investigations of the thermal behavior of polymers in gas, vacuum or inert atmosphere give the knowledge of how change takes place in polymers. To understand such changes thermogravimetric analysis (TGA) and thermal analysis (TG) were performed. It is observed reinforcement of short banana fiber leads to little improvement in the thermooxidative stability of PPBC. Due to the enhancement of thermo-mechanical properties, such composites may be used as building materials namely roof materials, selling materials and many other engineering applications.

Experimental energy performance assessment of a bifacial photovoltaic system and effect of cool roof coating

In the quest for high albedo materials that boost the energy production of bifacial photovoltaic systems, a range of material already exists for reducing building roof surface temperatures, called cool roof materials. However, there is a noticeable absence of scientific literature addressing the combination of cool roofs and bifacial photovoltaic systems. This study investigates the photovoltaic performance of a bifacial photovoltaic system with cool roof coating on the underside and its impact on floor temperature. For this purpose, four ∼1kWp prototypes were installed on the terrace of the GAIA building of the UPC near Barcelona, Spain: (1) bifacial panels above a cool roof, (2) bifacial panels above normal floor, (3) bifacial panels above a normal floor with n-type solar cells encapsulated in TPO, and (4) monofacial panels. The results reveal 8.6 % higher PV yield for bifacial with cool roof compared to monofacial, and 4–4.5 % higher for bifacial (normal floor) compared to monofacial. Additionally, the cool roof coating contributes to reducing the floor temperatures, particularly in the unshaded (exposed) areas during summer (−3.8 °C). The presence of photovoltaic panels has also demonstrated a positive impact on floor temperatures during both winter and summer. Thus, the cool roof coating offers two benefits: increased photovoltaic yield and reduced building cooling requirements, both of which are associated with economic advantages. The cool roof coating can be integrated into existing or new bifacial roof systems.

The Impact of Roof Material Profile and Pigmentation on the Performance of Photovoltaic Modules

This study combines simulations and experiments to study the heat interactions between various types of roofs and the photovoltaic (PV) modules installed on them. Specifically, the performance of PV modules on a clay roof was compared with their performance on two types of metal roofs, a Box-profile metal roof and an Orientile metal roof, which differ in shape and geometry. Additionally, this study examined the cooling potential of three common metal roof pigments, iron (iii) oxide (Fe2O3), titanium dioxide (TiO2) and basalt, on roof-installed PV modules. An unpigmented roof was also studied for comparison purposes. Model development and simulation were implemented in COMSOL Multiphysics, and the simulation results were validated and compared with field experiments. The maximum open-circuit voltages of the PV installations were found to be 21.096 V for the clay roof, 20.945 V for the Box-profile metal roof and 20.718 V for the Orientile metal roof. This study revealed that the unpigmented roof had higher solar cell temperatures compared to the pigmented models, with temperature gains ranging from 2.2 °C to 2.71 °C. Moreover, the unpigmented model displayed significantly higher surface radiosity than the pigmented models. The performance output of the modules also varied depending on the metal roof sheet shape and geometry, with the Box-profile metal roof yielding better results than the Orientile metal roof sheet. These results indicate that a specific roof pigmentation may have a small impact on a single PV module, but it can become significant in a large array of modules, especially if cooling through natural convection is hindered.

Logistics-based design of collection system for asbeston-containing roof structures

Asbestos-containing roofing materials are an increasing hazard, which justifies their replacement by environmentally friendly roofing materials. Replacements can be carried out on an individual initiative basis, but a coordinated, systemic replacement will have a more significant impact. In order for such systemic asbestos removal to be successful from economics and logistics point of view, it is necessary to plan the associated logistics processes, as asbestos removal generates a significant transportation demand due to the large amount of waste generated. In the framework of this paper, the author presents an algorithm to plan the logistic process of centralized asbestos removal. A simple calculation method is presented to determine the cost of collection.

Mapping Roof Materials in Cities for Food, Water, and Energy Production: A Mediterranean Metropolitan Area Case Study

ABSTRACT In recent years, rooftops have been used as productive spaces for local resource (e.g. food, water, or energy) production. The main objective of this study is to demonstrate the potential of hyperspectral data to identify roof materials in cities. The case study area is located in a Mediterranean region north of Barcelona (Spain); diverse building typologies, building uses (residential, industrial, office, services and retail) and population densities constitute this study area. Two hyperspectral remote sensors (HRSs) were used to obtain hyperspectral images. Seven roof classes were identified using the k-means clustering algorithm. Most roofs were identified as metals (33 percent), followed by ceramic tiles (22 percent). The findings showed that 51 percent of roofs could be suitable for food, water, or energy production. Nevertheless, for a more reliable assessment of this potential, more criteria are needed.

Factors and determinants of housing choices in Kaduna Metropolis, Nigeria

The study examined the factors and determinants of housing choices in Kaduna metropolis. Respondents were selected using purposive and simple random sampling techniques. The data collected were analyzed using descriptive techniques. Also, data for the research adopt the use of Key Informant Interview (KII), questionnaire and field observation. The result shows the various types of houses that includes 3 Bedrooms Detached (66.7%), 2 Bedroom Detached (11.4%), 3 Bedrooms Semi Detached (9.8%) as types of housing residence. Also, the findings revealed that aluminum roofing was the major roofing material used for the houses (48%). In addition, the major sources of water supply in the study area were borehole (72.4%). Also, the distance from house to school shows that half of the respondents covered almost less than 10km. The studies revealed that MPH estate was the major housing private partnership provider with 33.3% and preferred choice followed by Tripple A, while the Tapiddac was the least private partnership provider. Despite the preferences of private partnership providers, the respondent preferred affordability of houses (43.1%) rather than housing quality (29.3%), security (15.4) and housing accessibility (12.2%) was the lowest reason for the choice of houses. The result also revealed that too much bureaucratic process as one of the major challenges during acquiring of a house unit followed by a long waiting period. Also, the findings revealed that beneficiary must be an active civil servant with monthly salary or a registered business to serve as one of the criteria to be fulfilled before he/she can own a house.

Examining the Structural and Technical Characteristics of the Water Buffalo Farms in Sivas Province from the Perspective of Animal Welfare

In Turkey, water buffalo husbandry is conducted generally by using the traditional methods in shelters designed for cattle. The present study reports the data of the items of a questionnaire, which was conducted with 122 water buffalo breeders which are located in Central, Şarkışla, and Suşehri districts of Sivas province, regarding the structural and technical aspects of shelters such as shelter location, shelter type, building material, ventilation, and lighting. It was determined that, among the water buffalo breeders in Sivas province, the shelters were generally (73.5%) located nearby the house, that the building materials used in construction of the shelters were stone in 55.4%, concrete in 21.5% and briquette in 16.5% (p<0.0001), and that the floor materials used were concrete in 99.2% (p<0.05), whereas the roofing material was sheet metal/eternit in 80% (p<0.0001). It was found that water buffalos and cattle were held together in closed tethered systems (95.8%) and the space needs of animals were met by using chains having 40-60cm in length (63.1%). In conclusion, considering the animal welfare and behaviors, it was concluded that the infrastructural improvements to ensure the standardization in water buffalo shelters should be prioritized, that the old shelters should be re-organized, and that the watering systems in shelters should be analyzed.

Energy performance of school roofing materials in hot and humid climates

Effective roof insulation plays a pivotal role in reducing the energy used for air-conditioning, particularly in Taiwan’s extreme summer climate. In the present study, 1108 cases of rooftop insulation renovations in Taiwanese schools between 2018 and 2022 were investigated, and the thermal insulation performance and air-conditioning-related electricity savings associated with these renovations were analyzed through a cost–benefit assessment of the investment in insulation. The EnergyPlus software was used to model typical classroom roofs in seven climate zones in Taiwan. All the adopted thermal insulation methods considerably reduce air-conditioning-related electricity use; however, diminishing returns occur faster for thicker thermal insulation. The four main roof insulation materials used in the analyzed cases are galvanized corrugated steel, foam concrete, polystyrene sheets, and insulating bricks, which are associated with average maximum electricity-saving ratios of 17%, 15.3%, 10.2%, and 9.7%, respectively, and payback periods of 6.1, 6.4, 4.5, and 9.3 years, respectively. Electricity savings are greater and the payback period is shorter for the hotter southern zones of Taiwan than for the cooler northern zones. Galvanized corrugated steel has average energy efficiency of 21% and 13% in the southern and northern zones, respectively. The selection of roof construction materials strongly influences the consumption of energy for air-conditioning. Moreover, different construction costs result in distinct payback periods. The results of this study serve as a reference for school administrators and governments in the selection of insulation methods and design of building energy conservation and management, respectively.

Lifecycle Analysis of Green Roofs in the Mediterranean Climate

Buildings account for a significant amount of energy consumption and greenhouse gas emissions worldwide. Electricity and fossil fuels are currently the primary sources of energy used for cooling and heating buildings, depending on the climate and location. Both energy sources are responsible for significant greenhouse gas emissions. In contrast, plants and vegetation absorb carbon dioxide and, thus, improve the quality of air. This effect indirectly influences climate change to lower energy demands and produce additional emissions due to rising energy consumption trends. Plants also reduce the ambient temperature by providing shade on roof surfaces. Hence, the large-scale deployment of green roofs reduces energy consumption, emissions, and costs. However, green roofs also impact the overall weight of a building and require additional construction costs. Therefore, the contribution of green roofs to the various structural and thermal performances of buildings varies for extensive intensive or semi-intensive systems. These interactions warranted a lifecycle analysis to optimize the extent of green roof applications. This approach highlighted sustainability performance measures, including energy, emissions, water, and waste. The presented study addressed a lifecycle analysis of green roof deployment during a hot summer in a Mediterranean climate zone. This climate applies to many areas that benefit from warming temperatures without extreme needs for cooling or heating. The emphasis on comparing two towns within the same climate zone facilitated a more detail-oriented approach to the lifecycle analysis. The results illustrated the energy consumption and associated release of greenhouse gas emissions related to structural and roofing materials and thermal operations throughout the service life of a building. The conclusions assessed the challenges and opportunities of green roof applications on new and existing buildings.

The challenge of rehabilitating relocated listed heritage Buildings: Requirements and opportunities

This study evaluates three listed farmhouses in Ørland Municipality which are going to be relocated and rehabilitated according to current Norwegian standards and requirements. Accordingly, the study assesses possible challenges and solutions regarding energy upgrading and restoration while preserving their historic features and cultural heritage. The study suggests solutions for the energy rehabilitation of the three farmhouses based on a literature review, hygrothermal simulations and energy simulations. These solutions include thermal post-insulation of external walls and above the framework of joists against the cold attics with mineral wool, vacuum insulation panels (VIP), and aerogel blankets. Additionally, fenestration renovation options and the potential for implementation of building integrated photovoltaics (BIPV) are reviewed. Lastly, simulations of multiple energy-saving measures for each of the farmhouses have been conducted.A new foundation due to the relocation, together with post-insulation of the cold attic are found to be feasible measures considering the preservation of architectural appearance and authenticity. Regarding the external walls, post-insulating externally is preferable for the farmhouses considering moisture issues and interior space savings. However, it is important to consider any possible loss of cultural heritage value. Alternatively, internal thermal insulation with aerogel blankets may be a feasible solution due to its high thermal resistance applying small thicknesses. The results show that in some cases, enhancing old original windows with a secondary glazing is an equally good solution compared to a total replacement of the windows, and is recommended for cultural preservation. Implementation of BIPV contributed to meet the net energy demand requirement. Nevertheless, it is recommended that the chosen BIPV systems resemble an accepted roofing material from the regulatory requirements, e.g., slates, to accommodate the building’s architectural aesthetics and authenticity.This study provides insight and recommendations for the rehabilitation of three listed traditional farmhouses in Trøndelag County, addressing energy efficiency while preserving their cultural significance. The findings show that it is possible to achieve today’s energy requirements when rehabilitating listed heritage buildings. Results from energy simulations show that a reduction in net energy demand between 55 % and 75% is possible, while it is essential to note that each building is unique, and a case-by-case approach is needed. Nevertheless, the findings can be applicable for a general energy upgrading of heritage buildings.

Mechanochemical preparation of low cost kaolinite-based BiVO4 hybrid pigments with high near infrared reflectance

For accelerate construction of the energy and resource-saving and environmental-friendly society, cleaner preparation of low-cost and high-performance colorful near-infrared reflective inorganic pigments with the decorative function is indispensable to reduce the hazards of urban heat island and simultaneously beautify the appearance of the buildings. Due to the non-toxicity, good chemical stability and narrow band gap, BiVO4 has been becoming a promising environment-friendly yellow inorganic pigments among the conventional heavy metals-containing inorganic pigments. In this study, the low-cost and brilliant kaolinite-based BiVO4 hybrid pigments were fabricated by cleaner mechanochemical method based on cheap and abundant kaolinite using crystal water of the hydrated metal salts as trace solvent, which could effectively promote the interaction of the involved components at the molecular level during grinding and then decreased the mass transfer resistance for the formation of monoclinic scheelite BiVO4 in the following calcination. The obtained hybrid pigments at the optimal preparation conditions exhibited brilliant color properties (D65-10°, L * = 83.45 ± 0.08, a * = 4.17 ± 0.08, b * = 88.59 ± 0.17), high near-infrared reflectance of 86.22%, infrared solar reflectance of 88.14% and high emissivity of 0.9369 in the waveband of 8–13 μm. Furthermore, the hybrid pigments could be used for coloring epoxy resin with high emissivity of 0.8782 in 8–13 μm. Therefore, the brilliant and low-cost kaolinite-based bismuth yellow hybrid pigments have the enormous potential to be served as colorful functional nanofillers for cooling roofing materials.

Bayesian belief network modelling approach for predicting and ranking risk factors for malaria infections among children under 5 years in refugee settlements in Uganda

BackgroundMalaria risk factors at household level are known to be complex, uncertain, stochastic, nonlinear, and multidimensional. The interplay among these factors, makes targeted interventions, and resource allocation for malaria control challenging. However, few studies have demonstrated malaria’s transmission complexity, control, and integrated modelling, with no available evidence on Uganda’s refugee settlements. Using the 2018–2019 Uganda’s Malaria Indicator Survey (UMIS) data, an alternative Bayesian belief network (BBN) modelling approach was used to analyse, predict, rank and illustrate the conceptual reasoning, and complex causal relationships among the risk factors for malaria infections among children under-five in refugee settlements of Uganda.MethodsIn the UMIS, household level information was obtained using standardized questionnaires, and a total of 675 children under 5 years were tested for malaria. From the dataset, a casefile containing malaria test results, demographic, social-economic and environmental information was created. The casefile was divided into a training (80%, n = 540) and testing (20%, n = 135) datasets. The training dataset was used to develop the BBN model following well established guidelines. The testing dataset was used to evaluate model performance.ResultsModel accuracy was 91.11% with an area under the receiver-operating characteristic curve of 0.95. The model’s spherical payoff was 0.91, with the logarithmic, and quadratic losses of 0.36, and 0.16 respectively, indicating a strong predictive, and classification ability of the model. The probability of refugee children testing positive, and negative for malaria was 48.1% and 51.9% respectively. The top ranked malaria risk factors based on the sensitivity analysis included: (1) age of child; (2) roof materials (i.e., thatch roofs); (3) wall materials (i.e., poles with mud and thatch walls); (4) whether children sleep under insecticide-treated nets; 5) type of toilet facility used (i.e., no toilet facility, and pit latrines with slabs); (6) walk time distance to water sources (between 0 and 10 min); (7) drinking water sources (i.e., open water sources, and piped water on premises).ConclusionRanking, rather than the statistical significance of the malaria risk factors, is crucial as an approach to applied research, as it helps stakeholders determine how to allocate resources for targeted malaria interventions within the constraints of limited funding in the refugee settlements.

Use of Rubber Crumb Obtained from Waste Car Tires for the Production of Road Bitumen and Roofing Materials from Residues of Ukrainian Oil Processing

The process of modifying road bitumen obtained from the residues of Ukrainian oils processing with rubber crumb has been studied. The dependence of the softening temperature, ductility, penetration, and elasticity of the three-component bituminous composition “bitumen : linseed oil : rubber crumb” on its formulation has been examined. Based on the mentioned composition a new type of cold-applied bitumen roofing has been developed. A process flow diagram for the production of modified bitumen and special-purpose bituminous composition has been developed.

Evaluation of renovation strategies for existing residential districts in Shanghai based on coupling calculation of microclimate and energy consumption

This study aims to analyze the impact of renovation strategies on the air-conditioning load in existing residential districts in Shanghai by using the Grasshopper platform coupled with ENVI-met and EnergyPlus. These strategies include increasing the greening rate (G), improving pavement reflectivity and permeability (P), increasing the reflectivity of external wall coatings (C), increasing roof material reflectivity or applying green roofs (R), and improving the thermal performance of windows (W). The results show that microclimate and weather station data cause a 13.9% maximum deviation in energy consumption simulations. W and R4 significantly reduce the air-conditioning load throughout the year. W contributes to a decrease of 34.8 kWh in the cooling load and 110.4 kWh in the heating load. When the application level of P is low, and that of other strategies is high, the cooling load of the target building reaches its minimum. The minimum cooling load scenario is 302 kWh (25.1%) lower than the maximum. When the application level of G and C is low, other strategies have a high application level, and green roofs are used, the heating load of the target building is minimal. The minimum heating scenario is 386 kWh (29.3%) lower than the maximum.

Thermal properties of green, white and other building roof materials and solar insolation: A case study in New York City

This report presents results from a case study of surface temperatures of an urban green roof, a white roof, and other roof surfaces, at Hunter College, of the City University of New York. The analysis includes manual as well as automated observations between 2012 and 2016. The cooling effect, defined as the surface temperature differences between the green and white surfaces compared to a black surface, are often greater than 20 °C, and sometimes greater than 30 °C for both green and white roofs. Solar insolation is found to be the best predictor of the cooling effect, explaining over 72% and 77% of the variance for green and white roofs (respectively), with a 2-3 °C enhanced cooling effect for every 100 W/m2 increase in solar insolation. The response times of both green and white roofs to solar insolation is estimated to be 20 min (±10 min). Green roofs are found to have a slight cooling advantage (∼1.7 °C) over white roofs at higher solar insolation (∼1000 W/m2) and higher surface temperatures (∼45 °C). Key components of the surface energy balance are considered to help explain the observed thermal behavior of the green and white roofs. Manual observations, instrument maintenance, as well as data transcription and quality control, were performed largely by undergraduate students, demonstrating that green infrastructure can provide valuable learning experiences that may be difficult to otherwise provide in urban environments.

Phenomenon of courtyards being roofed and its significance for building energy efficiency

Courtyard building is an important type of vernacular architecture, widely distributed in different climate zones around the world. Traditionally, courtyards are characterized by opening to the sky, providing buffer spaces for ventilation and light for the surrounding buildings. However, in Hebei, China, local buildings are showing an evolution trend characterized by the courtyards being roofed (CBR). This spontaneous evolution presents the diversity of CBR technologies (CBRTs), including light-transmitting CBRTs (T-CBRTs) and non-light-transmitting CBRTs (NT-CBRTs). Based on field measurements and simulation technology, the improvement effect of CBR on building energy efficiency (EE) is analyzed, and the EE of different CBRTs is compared. The results show that, T-CBRT and NT-CBRT can reduce the annual total energy consumption of open courtyards by 19.97% and 15.41% respectively without upgrading the original envelope structure. The analysis of the impact mechanism shows that CBRT increases the temperature of the courtyard and the room by improving the solar energy collection efficiency and expanding the heat storage space, which effectively reduces the heat leakage caused by the envelope and ventilation, and shortens the heating time. The light transmittance of the roof material is the most critical parameter affecting the EE of T-CBRT, and the roof height largely determines the performance of NT-CBRT. Multi-layer glass or concrete panels are not the best choice for CBRT roofing materials, and plastic films or polycarbonate sheets with high light transmittance and anti-aging are recommended. CBR is considered as a promising development direction because it can reduce the economic burden of energy consumption for local farmers by improving the EE of buildings.