Search Results (115)

A major challenge in the optimization of thermal performance of opaque envelope components is that the calculation workload of energy consumption simulations of full factorial combinations leads to a prohibitive increase as the factors and levels multiply. Nevertheless, a reliable method for designing calculation schemes to reduce the calculation workload without sacrificing the accuracy of the results is still lacking. Accordingly, a building energy consumption simulation scheme (BECSS) based on a uniform design method (UDM) was proposed, and its feasibility was verified. A multiobjective optimization model (MOM) with the life cycle cost (LCC) and life cycle carbon emission (LCCE) as optimization objectives was established, and it was solved using the non-dominated sorting genetic algorithm-II (NSGA-II). Furthermore, an entropy-based TOPSIS method was introduced to calculate the optimal insulation thickness (OIT) of opaque building envelopes in severe cold and cold zones. The proposed framework was demonstrated through a case study of a typical residential building in Xuzhou. Extruded polystyrene panels (XPS) were used as insulation materials, and coal-fired boiler (CFB), gas-fired boiler (GFB), and air source heat pump (ASHP) were used as heat sources. Compared with the results specified by the current energy conservation standards, the MOM could achieve a balance between energy savings and environmental benefits. The LCCs change by −3.16–11.34%; nevertheless, the thermal performance of the external wall improves by 42.32–49.31%, while that of the roof improves by 6.46–21.59%; the building energy consumption (BEC) levels and the LCCEs are reduced by 25.24–30.16% and 19.25–24.74%, respectively. The indicator weights determined via the entropy weight method underscore the necessity of incorporating environmental performance indicators in the optimization of thermal performance of opaque building envelope components. Full article

Under extreme steady-state temperature gradients, external thermal insulation composite systems (ETICSs) are prone to thermal deformation, which can cause mortar cracking, hollowing, and even delamination and detachment of insulation boards, thus degrading building envelope performance and threatening structural and personal safety. In this study, a combined method of numerical simulation using ANSYS software and experimental testing was adopted to investigate the thermal deformation characteristics of three commonly used insulation materials: Expanded Polystyrene (EPS), Extruded Polystyrene (XPS), and Polyurethane (PU). The effects of temperature difference from 10 °C to 30 °C, insulation board thickness from 30 mm to 100 mm, and surface mortar thickness from 5 mm to 10 mm on strain distribution and deformation mechanism were systematically analyzed. Experimental validation showed good agreement with the simulation results, quantified by an estimated relative error of less than 15% across the investigated insulation thicknesses and steady-state temperature conditions. The results indicate that the strains of EPS, XPS, and PU boards all increase significantly as the temperature difference across the board rises. Under outdoor temperatures of 30 °C, 40 °C and 50 °C with a constant indoor temperature of 20 °C, the thickness-direction strain at the EPS–mortar interface increases by approximately 35% when the temperature difference increases from 10 °C to 30 °C. Increasing both insulation board thickness and mortar protective layer thickness effectively reduces thermal deformation. Specifically, when the EPS board thickness increases from 30 mm to 100 mm, the thickness-direction strain decreases by approximately 73%; and when the mortar thickness increases from 5 mm to 10 mm, the interfacial strain decreases by approximately 32%. Due to differences in linear expansion coefficients, the three insulation materials exhibit distinctly different thermal deformation behaviors, with the thickness-direction strain following the order EPS > XPS > PU. These findings provide a theoretical basis and data support for material selection, structural optimization, and safety design of external wall insulation systems. Full article

Aging populations have intensified the demand for thermally comfortable and energy-efficient housing, particularly for elderly residents whose diminished thermoregulatory capacity renders them disproportionately vulnerable to indoor temperature fluctuations. Existing senior apartments in cold-climate regions frequently fail to meet age-specific thermal comfort standards, yet systematic retrofit optimization frameworks explicitly tailored to elderly occupants remain scarce. This study presents a data-driven multi-objective optimization framework for building envelope retrofitting, which is validated using on-site temperature measurements from a representative 1980s brick–concrete senior apartment building in Beijing. The framework integrates Latin Hypercube Sampling (LHS) for design space exploration, a Long Short-Term Memory (LSTM) surrogate model for simultaneous prediction of three performance objectives, and Non-dominated Sorting Genetic Algorithm II (NSGA-II) for Pareto-optimal solution generation, with final selection performed via a weighted Mahalanobis distance-based Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS). Optimization targets—annual energy consumption, indoor thermal discomfort hours, and retrofit cost—are parameterized using the age-sensitive comfort thresholds specified in GB 50340-2016. The LSTM surrogate achieved R² values of 0.91–0.93 across all objectives with training–testing differences below 0.02. The optimal retrofit package—Polyvinyl Chloride (PVC) Low Emissivity (Low-E) double-glazed windows (5 + 6A + 5), glass fiber roof insulation (65.25 mm), and Extruded Polystyrene (XPS) external wall insulation (65.39 mm)—reduces annual energy consumption by 47.1% (from 40,867 to 21,626 kWh) and annual thermal discomfort hours by 62.4% (from 2454 °C·h to 923 °C·h). SHapley Additive exPlanations (SHAP)-based sensitivity analysis further identifies wall U-value and roof thickness as the dominant performance drivers. A reproducible and computationally efficient pathway is provided by the proposed framework for evidence-based envelope retrofit decision-making in existing senior residential buildings. Full article

Maintenance is crucial for the durability of the existing building stock and should be perceived as an opportunity to improve the built environment. The implementation of thermal retrofitting measures to the building’s envelope enhances global energy performance, which is economically and environmentally beneficial. Building-related energy consumption during the operation phase is key to tackling carbon neutrality and climate change. Introducing thermal retrofitting within the context of maintenance planning can be cost-optimizing, as it reveals the technical–economic synergy between building pathology and energy efficiency. Maintenance activities and energy demand throughout the building’s service life influence life-cycle costs (LCCs). Decision-making based on LCC awareness is an advantage for owners. This study discusses the impact of implementing an optimal retrofitting solution (ORS), according to different maintenance strategies, on the LCC of an existing single-family home. The ORS comprises the following measures: adding an external thermal insulation composite system (ETICS) to external walls, extruded polystyrene (XPS) panels to the roof, and replacing the existing windows with others with improved thermal performance. The three maintenance strategies involve different complexity levels, concerning the type, number and timing of activities. Moving beyond isolated assessments, this study develops an integrated framework that bridges based on two existing background methodologies, involving optimal thermal retrofitting and condition-based maintenance planning, which, combined with new research, enable the assessment of maintenance, energy and global LCC for a time horizon of 100 years. The evaluation of energy-related LCC is based on simulations. The results indicate that these costs represent the majority of the global LCC. The ORS has a considerable positive impact on energy and global LCC. Adopting a maintenance strategy characterized by fewer planned activities and an earlier schedule of replacement interventions, which determines the implementation of the retrofitting measures, is better in terms of LCC savings. Full article

Residential buildings in Erbil City are increasingly facing challenges due to climatic extremes, rapid urbanization, and inadequate insulation practices. This study investigates the effects of insulation material type and placement on the thermal performance of external walls in both newly constructed and refurbished houses under the hot semiarid climate (BSh). Using integrated environmental solutions virtual environment (IES-VE) simulations, various wall systems—concrete, brick, and lightweight block—were assessed with different insulation types (expanded polystyrene (EPS), extruded polystyrene (XPS), rock wool (RW), and mineral wool (MW)) applied either internally or externally. Field surveys combined with numerical simulations demonstrated that external insulation significantly enhances thermal mass without diminishing insulation effectiveness, leading to greater energy savings and improved indoor comfort. Among all configurations, externally applied XPS on concrete and lightweight block walls achieved the highest resistance values (R-values) and the greatest reductions in heating and cooling loads. The results indicate that prioritizing the placement of external insulation can support the development of more energy-efficient and climate-responsive housing policies in Erbil. This research offers evidence-based recommendations for optimizing building envelope design in similar climatic contexts. Full article

Rapid urbanization has significantly increased energy demand in buildings, which now represent nearly 30% of global energy use. In India, buildings are built across highly varied climatic conditions, from hot-dry and warm-humid to cold, high-altitude areas, making climate-responsive envelope design essential to enhance thermal performance. Among envelope components, roofs are the most exposed to solar and outdoor thermal loads, playing a key role in managing indoor heat transfer. This study offers a parametric analysis of climate-responsive roof design strategies for India’s five main climatic zones, using transient simulations and statistical evaluation. The effectiveness of insulation placement, insulation material and thickness, and external surface absorptivity was systematically assessed based on roof heat gain and heat loss. Results indicate that over-slab insulation can lower roof heat gain by approximately 15–35% compared to under-slab insulation in warm-humid, hot-dry, composite, and temperate zones. In comparison, under-slab insulation decreases heat loss by about 10% in colder areas. Among insulation materials, 50 mm polyurethane foam (U = 0.433 W/m²·K) consistently outperformed extruded polystyrene and expanded polystyrene, achieving 82–83% reductions in maximum heat gain in cooling-dominated climates and 89% reductions in heat loss in cold regions relative to uninsulated roofs. When combined with a white reflective surface finish (α = 0.26), the total heat transfer reduction increased further to 89–92%. Surface treatments alone cut heat gain by 37–51% in non-cold climates, highlighting their potential as cost-effective retrofit options. Statistical analysis confirmed that dry-bulb temperature is the primary climatic factor influencing roof heat transfer (R² = 0.86–0.98, p < 0.0001), while solar radiation had a weaker effect, especially in optimized roof systems. The findings emphasize the importance of climate-specific roof design and demonstrate that insulation U-value has a greater impact on thermal performance than surface absorptivity, although both are significant. This research offers practical, climate-adjusted guidance for architects, engineers, and policymakers to enhance the thermal performance of roofs in Indian buildings. It supports the development of more resilient, energy-efficient building envelopes. Full article

A novel type of ultra-high-performance concrete–normal concrete (UHPC-NC) superimposed sandwich slab is introduced, which eliminates the need for conventional longitudinal reinforcement. This sandwich slab consists of a prefabricated thin UHPC layer at the bottom, a cast-in-place NC layer at the top, and an extruded polystyrene foam core that provides both acoustic and thermal insulation. The resulting lightweight composite sandwich structure is integrated with web walls reinforced by a three-dimensional truss reinforcement system. The flexural performance is examined through four-point bending tests and compared with that of a fully UHPC sandwich slab of identical structural configuration and casting progress. Relative to the fully UHPC slab, the UHPC-NC slab demonstrates superior flexural structural integrity, significantly reduces costs and improves construction efficiency. The ductility coefficient of the UHPC-NC slab reaches 3.23, which is superior to the UHPC slab. This indicates that it has a stronger collaborative working ability with the rebars and the compressed concrete. Comprehensive analytical, numerical, and experimental investigations into the flexural behavior of the proposed UHPC-NC sandwich slab yield accurate evaluation of cracking and ultimate load capacities, thereby offering valuable guidance for the engineering application of this innovative superimposed sandwich slab system. Full article

As a prevalent integrated structure-insulation system, sandwich insulation wall panels have emerged as a critical structural configuration for zero- and nearly zero-energy green buildings, owing to their high construction efficiency and superior thermal insulation performance which directly aligns with the core goals of sustainability and sustainable energy utilization in the built environment. However, connectors penetrate the insulation layer and form systematic thermal bridges, which cause substantial heat loss and become a key bottleneck limiting further improvement in the overall thermal performance of wall systems. This study established three-dimensional numerical models of sandwich insulation wall panels with four typical connectors (fiber-reinforced polymers (FRPs), clamp-type stainless steel, plate-type stainless steel, and truss-type stainless steel) using Ansys Fluent 2021R1. The model reliability was verified by calibrated hot-box experiments, with relative errors between simulation and experimental results ranging from 2.1% to 16.1%. Systematic numerical simulations were then performed to investigate the effects of connector type, insulation material, climate zone, inner–outer temperature difference, connector quantity, and wall dimensions on the thermal bridge effect. The results indicated that FRP connectors caused the minimal heat flux increment (only 0.27%), followed by clamp-type stainless steel connectors (9.59%), while plate-type and truss-type stainless steel connectors led to significant increments (27.17% and 27.62%, respectively). The lower the heat transfer coefficient (K-value) of the wall was, the more prominent the connector-induced thermal bridge effect was. Within the typical temperature difference range, the heat flux increment of each connector remained stable, and polyurethane (PU) insulation exhibited a more significant inhibitory effect on thermal bridges than extruded polystyrene (XPS) under the same K-value. Linear fitting formulas for the relationship between wall K-value/temperature difference and the heat flux correction coefficient were derived, with high goodness-of-fit. The maximum impact of connectors on wall thermal performance did not exceed 30%. This study provides theoretical support and design references for the selection of connectors, material optimization, and thermal performance calculation of sandwich insulation wall panels, contributing to the promotion of energy-saving building envelope technologies. Full article

Improving the thermal performance of building envelopes is an effective approach for reducing energy consumption and carbon emissions in cold and heating-dominated regions. This study presents an experimentally calibrated thermal–economic optimization of external wall insulation systems for residential buildings in Northwest China, using Xi’an as a representative cold–dry continental climate. A guarded hot-box apparatus was employed to measure the steady-state thermal transmittance (U-value) of multilayer wall assemblies incorporating expanded polystyrene (EPS), extruded polystyrene (XPS), and rock wool at different insulation thicknesses. The measured U-values were integrated into a dynamic building energy simulation model (DeST-h), and the simulated energy demand was subsequently evaluated through life-cycle cost (LCC) analysis to identify cost-optimal insulation configurations. The results indicate a nonlinear reduction in heating energy demand with increasing insulation thickness, with diminishing marginal returns beyond approximately 50 mm. Among the investigated materials, XPS exhibits the most favorable thermal–economic performance. For the climatic and economic conditions of Xi’an, a 50 mm XPS insulation layer minimizes total life-cycle cost while reducing annual building energy consumption by approximately 23–24% compared with the uninsulated reference case. This experimentally calibrated framework provides practical and policy-relevant guidance for insulation design and retrofit strategies in cold and dry regions. Full article

The sandwich-insulated concrete block is one of the innovative building units developed to enhance thermal insulation in buildings. However, there are still some drawbacks that hinder the optimum utilization of these types of insulating blocks. Therefore, this study aims to conduct a systematic and comparative assessment of the performance of the sandwich-insulated concrete block available in the local market. To accurately assess the efficiency of the insulated concrete blocks, several samples from various sources available in the local market were collected and examined. Visual inspection, dimensional tolerance, compressive strength, physical properties, thermal performance, and environmental resistance tests have been conducted in accordance with local and international standards. The obtained experimental results revealed that the mixture proportion of the concrete shell plays a crucial role in the properties and performance of the whole insulated concrete block. Blocks with volcanic aggregates exhibited lower compressive strength, ranging between 3.19 and 5.26 MPa, but better thermal conductivity with an average of 0.25 W/m·K. In comparison, normal aggregate blocks showed higher compressive strength up to 8.12 MPa but slightly reduced thermal insulation around 0.44 W/m·K. Water absorption varied widely from 5% to 16%, and chloride contents in volcanic aggregates exceeded the permissible 1% limit. Broken edges and cracks were mainly observed in low-strength blocks, emphasizing the importance of proper curing and material selection. Durability assessments revealed that accelerated weathering experiments demonstrated the susceptibility of expanded and extruded polystyrene to UV-induced degradation. Nevertheless, all tested polystyrene samples showed high resistance to fungal attack, with varying antibacterial activity. Full article

This study investigates how external insulation materials used for energy efficiency affect indoor radon accumulation, using a scale model room built with ignimbrite, a highly radon-emitting volcanic rock. Two insulation materials—mineral wool (open-cell, 98% porosity) and extruded polystyrene (XPS, closed-cell, >95%)—were applied to the outer walls of the model room. Their effects were tested in combination with three internal radon barriers (silane-terminated membrane, silicone sealant, bitumen membrane) and under varying ventilation rates (0.11 h⁻¹ and 0.44 h⁻¹). Radon concentrations were measured using calibrated detectors over five experimental phases. Without ventilation, XPS increased indoor radon by up to +351%, while mineral wool showed a milder effect (+26%). The silicone sealant reduced radon by up to 90%, outperforming other barriers. Ventilation significantly lowered radon levels, simulating the “flushing” effect of wind. The combination of impermeable insulation and lack of air exchange led to the highest radon accumulation. High-performance insulation can compromise indoor air quality by trapping radon, especially in buildings with high geogenic radon potential. Effective mitigation requires pairing insulation with high-performing radon barriers and adequate ventilation. These findings highlight the need to balance energy efficiency with indoor environmental safety. Full article

Extruded polystyrene (XPS) has recently been used for construction such as in walls, and floors. When it is used for walls, axial load is inevitably applied along the length direction, raising concerns of collapse owing to buckling deformation. To address this, the buckling behavior of XPS should be appropriately characterized. However, such characterization has often been ignored because XPS has not conventionally been used as a structural material but solely as a thermal insulation material. In addition, the classical methods typically applied to analyze buckling behaviors are well-established; therefore, many researchers might not consider buckling analysis to be novel. However, as the use of XPS in construction increases, its buckling behaviors cannot be ignored, and few studies have investigated them to date. In this study, buckling tests of XPS were conducted using columns with various slenderness ratios, and the buckling stress–slenderness ratio was analyzed using the following three methods: the authors’ proposed method, Southwell’s method, and the modified Euler method. Independently of the buckling tests, short column compression and three-point bending tests were performed, and the buckling stress–slenderness ratio relationship was predicted using the properties obtained from these tests. Buckling stress could be effectively determined by these three methods across a wide range of slenderness ratios, whether elastic or inelastic buckling has occurred. Our proposed method was superior to the other two methods owing to its simplicity. In contrast, it was difficult to predict the buckling stress–slenderness ratio using the properties obtained from either the compression tests alone or three-point bending tests alone. However, the relationship could be appropriately determined using the properties obtained from both tests together. Full article

Plastics are inexpensive and widely used but persist in the environment due to improper disposal. Insect-mediated biodegradation has gained attention, notably involving Tenebrio molitor larvae. Despite morphological similarities and larger size, Zophobas atratus larvae remain less studied. This work evaluated the impact of larval stage on the biodegradation of pristine and post-consumer extruded polystyrene (XPS) and the physiological effects of an XPS-based diet. Smaller (L1) and larger (L2) larvae were tested. L2 showed higher XPS consumption, weight gain, and survival, while XPS-fed larvae overall exhibited reduced lipid content and increased moisture, flavonoids, and phenolics compared to wheat bran-fed controls. Scanning electron microscopy revealed surface fragmentation in frass, more pronounced in L1, suggesting greater mechanical or enzymatic action. High-performance size exclusion chromatography indicated molecular weight reduction, with L1 more effective on pristine XPS and L2 on post-consumer XPS, likely due to nutritional residues. FTIR analysis showed oxidative changes in both groups, more prominent in L1. Thermogravimetric analysis revealed earlier degradation onset in L1 frass, supporting the presence of oxidized oligomers. Overall, Z. atratus larvae can biodegrade XPS, with degradation influenced by developmental stage and substrate type. These findings inform biotechnological strategies for sustainable plastic waste management. Full article

This manuscript is aimed at analyzing how operating factors may affect the durability of thermal insulation in building partitions located underground. It examines the durability of inverted insulation systems where thermal insulation is installed above the waterproofing layer and used in residential foundation slabs. The article demonstrates that, despite their popularity due to cost efficiency, the long-term success of these systems depends on thorough investigations of thermal isolation, especially considering different climate conditions. The analysis was based on an extensive literature review (2016–2024), supplemented with laboratory test results on extruded (XPS) and expanded (EPS) polystyrene boards. Additional tests examined the water penetration mechanism into insulation layers that are in direct contact with groundwater, revealing that cyclic freezing and thawing significantly increase moisture levels. The findings highlight the need for updated region-specific guidelines for the underground insulation in Central and Eastern Europe. Full article

Three-dimensional concrete printing (3DCP) is advancing rapidly, yet its sustainable adoption requires alignment with circular-economy principles. This study evaluates the substitution of natural aggregates with recycled constituents, 3DCP waste, brick debris, glass cullet, mixed rubble, fly ash, and slag, and the use of lightweight fillers (expanded perlite, lightweight expanded clay aggregate (LECA), and expanded polystyrene (EPS)) to reduce density and improve insulation. Key properties, such as particle-size distribution, printability, mechanical performance, thermal conductivity, and water absorption, were determined. Results indicate that grading strongly affected mixture behavior. Narrow distributions (fly ash, milled 3DCP waste) enhanced extrudability, while broader gradings (glass, rubble, slag) increased water demand and extrusion risks. Despite these differences, all systems remained within the printable window: flow spread decreased with most recycled additions (lowest for brick) and increased with glass. Mechanical responses were composition-dependent. Flexural strength typically decreased. Compressive strength benefited from broader gradings, with replacement levels up to ~6% enhancing strength due to improved packing. Loading anisotropy typical of 3DCP was observed, with perpendicular compressive strength reaching up to 13% higher values than parallel loading. Lightweight fillers significantly reduced thermal conductivity. LECA provided the best compromise between strength and insulation, perlite showed intermediate behavior, and EPS achieved the lowest thermal conductivity but induced significant strength penalties due to weak matrix-EPS interfaces. Water absorption decreased in recycled-aggregate mixes, whereas lightweight systems, particularly with perlite, retained higher uptake. The results demonstrate that non-reactive recycled aggregates and lightweight insulating fillers can be successfully integrated into extrusion-based 3DCP without compromising printability. Full article