Thermal Bridges Research Articles

The thermal performance of a typical prefab container house

Prefabricated container houses have been widely used in recent decades, particularly at construction sites. To improve their energy efficiency, the thermal deficiencies of a typical prefab container house were firstly analyzed using infrared thermography. Detailed measurements of the thermal behavior of its envelope were conducted, focusing on thermal bridges, air infiltration rates, and window solar heat gains. The energy consumption from various sources were then calculated based on the measured data. It showed that there were thermal bridges near the joint of the walls and the panels. The reserved space for rainwater pipes and cables, as well as the panel connecting seams, were inadequately insulated, resulting in higher surface temperatures and heat fluxes compared to the adjacent walls. The energy consumption from the windows, the thermal bridges and air infiltration accounted for around 50% of the total energy consumption. The thermal bridge insulation structures could reduce more than 60% and around 40% energy consumptions of the corners and the seams. The external louvers could reduce around 40% energy consumption of the windows. After the energy-saving retrofit, the total energy consumption of the prefab house was reduced by approximately 25.9%.

Design model for shear keys used as thermal break systems in balcony-slab joints under combined shear and bending loads

Balcony-slab joints (BSs) are common in residential buildings. Integrating thermal break systems (TBSs) can reduce the energy loss resulting from thermal bridging. However, the mechanical performance of BSs equipped with TBSs against shear and bending remains hardly explored in design and experimentation. The aim of this study is to evaluate the mechanical behavior of BS joints under combined shear and bending actions, taking into account the presence of TBSs. Seven large-scale balcony-slab specimens were fabricated and tested under vertical loading with different moment-shear ratios (M/V). The BSs are equipped with TBSs comprising steel bars and shear profiles. A simplified finite element (FE) model was then developed using the ABAQUS software. The FE model employs spring-like elements to simulate the bond and contact behavior between concrete and steel, reproducing both the resistance and stiffness of the tested specimens. On the basis of the experimental and FE results, a resistance model consistent with the Eurocode design guidelines was drawn. Finally, moment-shear (M-V) interaction curves for balcony-slab joints were generated at the ultimate (ULS) and serviceability (SLS) levels, considering the impact of horizontal loading to achieve comprehensive design insights. The tests and FE results showed that the moment-shear ratio (M/V) significantly influences the shear capacity of the BS joints. The steel profiles effectively acted as shear keys connecting the balcony and the slab. A strength reduction coefficient of 0.701 was introduced for the design.

Thermal and mechanical analysis of thermal break structure in balcony with basalt fiber reinforced polymer

Thermal break structure is an effective design to reduce building energy consumption in balcony. The traditional stainless-steel bars or other FRP components reinforced thermal break structures can't enable both mechanical performance and thermal insulation concurrently because these materials are difficult to have low thermal conductivity and high mechanical properties at the same time. This paper proposes to use basalt fiber reinforced polymer (BFRP) to construct the thermal break structure due to the high load-bearing capacity and thermal insultation of BFRP. The thermal performance of the structure is systematically verified through three-dimensional simulation. Influence of thermal break widths, loading point positions, shear reinforcement forms and reinforcement types on the mechanical properties of the structure is investigated. The results show that BFRP can significantly reduce the linear heat transfer transmittance while ensuring structural mechanical properties. A larger thermal break width leads to the low load-bearing capacity of the structure. Lower BFRP compressive reinforcements need enough diameter to provide compressive strength and shear reinforcement forms can significantly increase the mechanical properties of the thermal break. Upper tensile reinforcements can be selected depending on the stiffness and insulation requirements in practical engineering. Based on experimental results, force transfer mechanism is analyzed and the rationality of the structural design is identified. The maximum length of the cantilever slab without shear reinforcement forms is approximately 2.94 m when meets the serviceability limit state. The results suggest that newly designed BFRP thermal break structure can effectively solve thermal bridge problems in balcony.

Study on heat transfer behavior of CFS-PSB composite walls

The cold-formed thin-walled steel (CFS)-paper straw board (PSB) composite walls takes as the research object. The thermal performance of the wall was analyzed by the building heat transfer theory and the finite element analysis software ANSYS, explored the influence of relevant parameters on heat transfer coefficient of composite wall and proposed supplementary correction coefficient for applying the type of composite walls. The heat flux density field, temperature distribution field, node temperature, and heat transfer coefficient of the walls were also obtained. The specific parameters analyzed using this model mainly included the insulation material, web height, thickness of the section steel, width of the flange, length of the hole, number of hole rows, and horizontal and longitudinal spacing of the holes. The findings show that an increase in the web height reduces the heat transfer coefficient of the composite wall, which is conducive to improving the thermal insulation performance of the walls. The CFS-PSB composite wall with a web opening can significantly improve the heat transfer performance of the wall, reduce heat loss, and control the local thermal bridging phenomenon. The hole length, specific gravity of the openings, and number of openings were the main parameters affecting the thermal insulation performance of the walls.

Interpretable reduced-order optimization research for improving indoor environmental quality in buildings based on dimensional analysis and surrogate-based optimization

Implementing large-scale optimization designs and identifying optimal design variables in fields such as architectural engineering is crucial for improving indoor environmental quality. However, the high-dimensional nonlinear characteristics complicate the understanding of the optimization process and increase the difficulty of finding optimal solutions. This study proposes an interpretable reduced-order optimization (ROO) method based on dimensional analysis, which integrates numerous variables into a single reduced-order coefficient through a power form. The goal is to develop a reduced-order and approximately one-dimensional nonlinear relationship during the optimization process and to reveal the mechanisms of single-objective and multi-objective optimization, thereby enhancing the interpretability of the optimization process. The reliability of the ROO is validated through single-objective optimization of building thermal bridges and multi-objective optimization of squirrel cage fans. The study shows that the power in the reduced-order coefficient can be used to determine the sensitivity and impact of design variables on optimization targets. The nonlinear relationship between the composite structural parameters of the building thermal bridge and the total heat flux can be reduced to an approximately one-dimensional linear relationship, significantly reducing the total heat flux of the thermal bridge by 10.3 %. The ROO accurately describes the aerodynamic performance of the fan and its high-dimensional nonlinear relationship with eight design variables, eliminating optimization conflicts among multiple operating conditions and significantly enhancing the aerodynamic performance. The ROO method proposed in this study offers a new approach to making the optimization process more interpretable, playing a crucial role in optimization design and revealing optimization mechanisms in engineering applications.

Controlling Thermal Bridging as a Value-Added Technique to Enhance Energy Efficient Building Envelopes

Controlling Thermal Bridging as a Value-Added Technique to Enhance Energy Efficient Building Envelopes

Experimental Analysis of the Mechanical Behavior of Shear Connectors for Precast Sandwich Wall Panels When Subjected to the Push-Out Tests

Precast concrete sandwich panels consist of two outer layers connected by a central connector and an inner insulating layer that enhances thermal and acoustic performance. A key challenge with these panels is eliminating thermal bridges caused by metallic connectors, which reduce energy efficiency. PERFOFRP connectors, made from perforated glass fiber-reinforced polymer (GFRP) sheets, have been proposed to address this issue. These connectors feature holes that allow concrete to pass through, creating anchoring pins that enhance shear resistance and prevent the separation of the concrete layers. This research aimed to evaluate the effect of the diameter and number of holes on the mechanical strength of PERFOFRP connectors. Three diameters not previously reported in the literature were selected: 12.70 mm, 15.88 mm, and 19.05 mm. A total of 18 specimens, encompassing 6 different configurations with varying numbers of holes, underwent push-out tests. The most significant resistance increase was a 15% gain over non-perforated connectors, observed in the configuration featuring three holes of 19.05 mm. The connections exhibited rigid and nearly linear behavior until failure.

Evaluation of aerial thermography for measuring the thermal transmittance (U-value) of a building façade

In efforts to mitigate greenhouse gas emissions in the construction sector, policies promoting energy efficiency improvements in existing buildings are being implemented. Accurately assessing the impact of energy retrofit strategies requires precise determination of thermal envelope performance through energy audits. Aerial thermography, employing unmanned aerial vehicles (UAVs) equipped with infrared thermal cameras (IRT), is an underused method overcoming limitations in energy audits of large buildings or complexes. This approach offers an elevated perspective, providing an overview of the building’s thermal patterns, aiding in the identification of thermal envelope defects. By measuring temperature distribution, even in inaccessible envelope areas, the severity of identified defects can be estimated. Beyond detecting thermal bridges, air leaks, and moisture, aerial thermography is valid for estimating thermal transmittance (U-value) of enclosures. The aim of this research is to evaluate this method to calculate the U-value of the façade of an university building located in a Subtropical Mediterranean climate, during a typical full day in different seasons of the year. Concurrently with aerial thermography, the thermometric method (THM) was applied to compare results and refine the operational conditions during U-value measurement using different statistical indices and uncertainty analysis. The results demonstrated the validation of airborne thermography as a method for U-value calculation under specific meteorological and operational conditions, overcoming the common physical limitations of traditional building audit methods.

Numerical assessment of thermal bridging effects in 3D-printed foam concrete walls

Abstract Integrating smart technology and advanced materials in the construction industry has revolutionized traditional building practices, enhancing efficiency, sustainability, and overall performance. Researchers and professionals in the construction sector have shown significant interest in three-dimensional concrete printing (3DCP) for automating structural engineering tasks. Despite its potential as a sustainable solution to modern construction issues, there is a lack of research on the thermal insulation performance of three-dimensional printed concrete (3DPC) building envelopes, and the potential for integrating foam concrete (FC) to enhance energy efficiency has not yet been studied. This paper presents a numerical analysis examining how different infill geometries affect the thermal performance of 3D-printed foam concrete (3DPFC) lattice envelopes. Six lattice structures were designed with identical thickness, height, length, and comparable insulation areas. The effects of the contact (intersection) area of webs with the interior face shell, webs, and infill rows on the thermal performance of granularly insulated envelopes were studied. The effectiveness of insulation was also established. The findings indicate that the thermal transmittance of 3DPC envelopes correlates directly with the contact area of the webs and the interior surface, with U-values ranging from 0.151 W m2·K to 0.652 W/m2·K. Notably, the absence of direct connections between exterior and interior surfaces enhances insulation efficiency, with double-row structures achieving up to 94% insulation efficiency. However, when there is a direct connection between the two surfaces, the thermal performance of these envelopes is mainly affected by the contact (intersection) area of the webs with the interior face rather than the number of webs. By integrating foam concrete and double-row walls, this study demonstrates an innovative approach to reducing thermal bridging and improving energy performance in 3D-printed construction. The results offer novel insight into optimizing the thermal behavior of 3DPC systems for sustainable building practices.

REDUCING THE INFLUENCE OF THERMAL BRIDGES IN THE BASEMENT SLAB OF CAST-IN-SITU FRAME BUILDINGS IN EXTREMELY COLD REGIONS

Introduction. Heat insulation of multi-story buildings with a reinforced concrete frame on pile foundations under climatic conditions with extremely low outdoor air temperatures is complicated by high air infiltration. When such buildings are used in winter, the most characteristic are temperature regime violations on the first floor. Purpose of the study: The study aimed to evaluate various methods to reduce the influence of thermal bridges in the basement floor of a cast-in-situ frame building with pile foundations under extreme climatic conditions. Methods: Thermal performance of 3D models of enclosing structures was determined using the certified HEAT3 program. Options of internal and external heat insulation of the basement floor with thermal breaks in the structures were considered. Results: As a result of numerical analysis of standard basement floor designs, it was established that low temperature on the inner surface and significant heat losses are associated with the presence of through thermal bridges: reinforced concrete raft — basement slab — column — concrete block masonry. The most effective solution for heat insulation of cast-in-situ frame buildings is external heat insulation of the basement floor with a thermal break in the raft. Compared to the standard solution, heat losses through the corner section of the slab with the offset column are reduced by 33.6 %, and the minimum temperature on the inner surface is higher than the dew point.

Full-Scale Comparison of Two Envelope Systems for Lightweight Wooden Framing in Cold Climates

Residential homes and apartments’ cooling and heating needs account for 63% of total building energy consumption. Improvements in the properties of building envelopes are among the best ways to reduce their energy consumption. The project’s general objective was to compare the performance of externally insulated and traditional envelopes of light wooden frame buildings at full scale. Two houses were constructed and equipped with relative humidity sensors and temperature probes to assess the physical properties of the building envelope. The first house was built according to the conventional method (insulation between the studs), and the second house was built according to the method with the insulation outside the wall (also known as the perfect wall). The results showed that external insulation effectively mitigates internal condensation risks by relocating dew points to the exterior surface, thereby enhancing structural durability and thermal stability. Thermographic imaging confirmed reduced thermal bridging and improved thermal performance in the externally insulated walls. Overall, this study supports, with a full-scale experiment, the adoption of external insulation as a viable strategy for enhancing energy efficiency, thermal comfort, and durability in residential buildings.

Performance Evaluation of Low Thermal Bridging Drywall System with Separating Clips for C-Studs

Drywall systems comprising gypsum boards and steel C-studs are widely used due to their lightweight structure, rapid construction, and ease of installation. These systems must meet the required thermal insulation performance for their specific applications. However, metal C-studs penetrate the insulation layer at intervals, leading to additional heat loss, reduced thermal insulation performance, and lower indoor surface temperatures, which can result in condensation and mold growth. To address these issues, this study proposes a drywall system with low thermal bridging studs made up of two small-sized studs and four or five separating clips made of reinforced plastic. These clips separate the studs to minimize heat transfer through metal elements, maintain structural stability despite the spacing between them, and facilitate easy assembly. The results from mock-up tests showed that the proposed system’s thermal transmittance was 0.370 W/m2K, which is 28.8% lower than the 0.52 W/m2K observed with conventional C-studs. The proposed drywall system also met Korean regulations for acoustic insulation level 3 and the 2 h fire resistance criteria, similar to existing drywall systems with conventional C-studs. Moreover, the maximum and residual displacements were within an acceptable range for a horizontal load of 3000 N applied vertically to the non-load-bearing wall. Building energy analysis indicated that using the proposed drywall adjacent to unconditioned spaces could reduce the annual heating and cooling load by 2.5–3.0%, despite a 1.5–1.9% increase in the annual cooling load. The annual heating load decreased by 4.8–5.9% under infiltration rates of 0.5 to 1.5 air changes per hour for adjacent unconditioned spaces, making this drywall system’s improved insulation quality crucial for achieving heating-dominant zero-energy buildings.

Evaluate Recent Numerical Methods for Long-Term Simulation to Study the Effect of Different Shapes of Thermal Bridges in Walls

Evaluate Recent Numerical Methods for Long-Term Simulation to Study the Effect of Different Shapes of Thermal Bridges in Walls

The Effect of Fly Ash Additive on the Thermal Conductivity of Polystyrene Concrete

The use of fly ash in compositions as a substitute for a part of cement is economically favorable and ecologically feasible in connection with large accumulations of waste at the enterprises of the energy sector. In addition, the technology of cement production provides high-temperature treatment of mineral substances in kilns with significant emissions of carbon dioxide. One of the most effective directions of the utilization of fly ash is their use in concrete composites. The use of this material will provide the required temperature and humidity conditions in residential premises, solve the problem of “cold bridges” in structures, minimize heat losses of the structure, and increase the energy efficiency of buildings in general. At the same time, polystyrene concrete, due to its structural structure and the presence of thermally conductive concrete, has limited opportunities for thermal and physical–mechanical properties. To improve the operational properties of polystyrene concrete, it is proposed to use composite binders, including fly ash from the thermal power station of Astana. The main aim of this study is to develop compositions of polystyrene concrete with reduced thermal conductivity and improved physical and mechanical properties. The objectives of this study include the determination of characteristics of fly ash from Astana, formulation of polystyrene concrete mixtures with different proportions of fly ash, and evaluation of their thermal conductivity properties. These tasks are in line with the objectives of the ISO 50001 standard to improve energy efficiency and reduce environmental impact. The results showed that the addition of fly ash from Astana to polystyrene concrete leads to a marked reduction in thermal conductivity, contributing to improved energy efficiency of the building envelope. Optimal results were achieved by using 15% of Astana fly ash as an additive in polystyrene concrete, which led to a significant reduction in thermal conductivity of 51.47%. This reduction is in line with improving the energy efficiency of building materials, especially in cold climates.

Steady Heat Transfer Analysis of the Refrigerator Seal Considering Rigid and Flexible Contact

The rigid and flexible contact of the refrigerator seal has a significant impact on its heat transfer characteristics, but existing research has ignored this important factor. In this paper, the assembly physical model at the seal region is established by static structural analysis. Then a three-dimensional heat transfer numerical simulation is carried out. The assembly distance affects the contact state of the seal by changing the contact position between the seal and the door or the cabinet. The calculation results show that the calculated temperature at the seal region considering the actual assembly deformation is closer to the measured temperatures. In the case study, the heat leakage load decreases by 18.57% and 19.99% at the compressed state, while it increases by 4.45% under the stretching state. The proportion of heat transfer load in the path of rubber strip-cold air and rubber strip-outer shell of the cabinet is the largest, reaching over 30.0%. The heat transfer load of the cold bridge also accounts for over 20.0%. When optimizing the seal structure, reducing the contact interface length of rubber strip-cold air, reducing thermal conductivity, and increasing the contact thermal resistance of cold bridge should be focused on.

Thermal and energy efficiency in 3D-printed buildings: Review of geometric design, materials and printing processes

Applying 3D printing in construction is a promising, sustainable alternative to conventional methods. However, the thermal and energy performance of 3D-printed buildings remains underexplored, particularly regarding the interactions between geometric design, material selection, and printing parameters. This review addresses this gap by critically examining how the main steps of the printing process impact the thermal efficiency of 3D-printed buildings. Key findings indicate that material development needs to focus on mixes that balance thermal properties,printability,and structural integrity. The review demonstrates how optimising wall cross-sections and cavity shapes can reduce thermal conductivity and enhance energy efficiency. Innovative geometric designs, such as cellular and honeycomb structures, have shown improvements in thermal insulation. Optimising printing parameters, such as extrusion rate and nozzle travel speed, is crucial to minimising thermal bridges and reducing material anisotropy. Advanced numerical models, validated by experimental data and incorporating factors like inhomogeneous porosity, anisotropy, and surface roughness, are essential for accurately predicting the thermal behaviour of 3D-printed structures. The review underscores the need for large-scale, long-term performance studies of 3D-printed buildings under diverse climatic conditions. Additionally, developing standardised fabrication protocols and testing methods is essential for ensuring consistent quality and broader adoption. Addressing these research gaps is crucial to fully realising the potential of 3D printing in sustainable construction and accelerating the adoption of additive manufacturing in the construction sector.

Natural Lime–Cork Mortar for the Seismic and Energetic Retrofit of Infill Walls: Design, Materials, and Method

Recent seismic events have prompted research into innovative and sustainable materials for strengthening and repairing obsolete and vulnerable buildings. These earthquakes have exposed the high seismic vulnerability of existing reinforced concrete (RC) buildings, particularly in secondary structural elements like infill walls. In addition to structural issues, these buildings often face significant energy deficiencies, such as thermal bridges, due to inadequate insulation. Traditionally, structural and energy improvements for residential buildings are addressed separately with different methods and protocols. This preliminary study is part of a broader research initiative at the University of Reggio Calabria (Italy), aiming to design an innovative fiber-reinforced plaster using natural, sustainable, and locally produced materials to enhance the energy and structural performance of existing wall infills. The study investigates two plaster matrices made of natural hydraulic lime and silica sand, with 15% and 30% cork granules added. Mechanical and thermophysical tests on multiple specimens were conducted to evaluate their suitability for seismic and energy retrofitting of infill walls. Results indicate that adding cork reduces mechanical strength by approximately 42% at a 30% cork content without compromising its use in seismic retrofitting. Thermophysical tests show improved thermal performance with a higher cork content. These findings suggest that the lime–cork mixture at 30% is effective, offering excellent ductility and serving as a promising alternative to traditional cementitious plaster systems. The next experimental phase will test matrices with varying percentages of gorse fiber.

Theoretical and experimental study of heat transfer in a two-channel flat plate solar air collector

Abstract In this article, a theoretical-experimental study was conducted on a two-channel solar air collector (SAC-2C). For the experimental study, a prototype of the SAC-2C was designed, built, and instrumented with dimensions of 1.860 m in length, 0.605 m in width, and featuring 2 air channels of 5.5 mm and 5 mm thick each, respectively. The collector operates via forced convection and was positioned at an inclination angle of 18.88° at the Tecnologico Nacional de Mexico CENIDET campus (TecNM/CENIDET) located in Cuernavaca, Morelos, Mexico. For the theoretical analysis, the method of global energy balances in two dimensions (2D) and under transient conditions was applied. Temperature differences of up to 3.0°C are observed with respect to mathematical models that do not consider heat conduction terms in solid elements. These differences are accentuated in the glass cover. Furthermore, altitude's impact on air density calculations could influence theoretical temperature profiles up to 3.0°C. The theoretical results of the numerical model were validated with the information obtained from the experimental tests, which showed good similarity. It was observed that the elements of SAC-2C are sensitive to sudden changes in meteorological conditions. The system's response time is not only associated with the characteristics of the materials but also with the thermal bridges between the absorber plate and the casing. The calculation of the appropriate heat transfer coefficients allowed the evaluation of energy gains or losses in the SAC-2C collector.

Atmospheric Pressure Plasma Treatment of Glass Surface and Its Influence on the Reliability of Adhesive Bonding

Glass load-bearing structural elements are currently used more often in civil engineering. However, due to the brittle fracture of glass, it is necessary to design these structures with sufficient reliability. Adhesive joints have a number of advantages over mechanical connectors of glass commonly used in construction. Adhesives can eliminate thermal bridges and provide a more uniform stress distribution along the connection without weakening the bonded material.A variety of chemical methods have been developed for cleaning and activating glass surfaces prior to adhesive bonding. Recently, these methods have been substituted by glass surface cleaning and activation using ambient (humid) air plasma. Such an approach is considered much faster, technically simpler, and more environmentally friendly than the traditional chemical methods. For example, it eliminates the need for the so-called primer interlayer, where the primer is usually considered a heavy chemical with significant environmental impact.The presented work is focused on the surface activation of glass by atmospheric pressure plasma to improve adhesion using specially selected transparent adhesives. We studied Diffuse Coplanar Surface Barrier Discharge (DCSBD) plasma treatment of different float-glass, heat-treated and tempered glass surfaces in ambient air. The DCSBD plasma effect was evaluated by surface free energy and peel-test adhesion measurements. The morphological changes on the glass surface were investigated by scanning electron and atomic force microscopy. The glass-to-glass adhesion at elevated temperatures was tested with respect to the artificial ageing of adhesive bonding due to the environment. Acknowledgement: This research was supported by project LM2023039, funded by the Ministry of Education, Youth and Sports of the Czech Republic and supported by project No. GA23-06016S, funded by the Czech Science Foundation (GAČR).

APPLICATION OF MODULAR CSIPS TO TRADITIONAL KOREAN HANOK TIMBER STRUCTURES FOR THERMAL AND ENERGY PERFORMANCE

ABSTRACT This study examines the thermal and energy performance capabilities of composite structural insulation panels (CSIPs) for traditional Korean architecture, specifically Hanok. Hanok buildings, renowned for their cultural and architectural significance, often face thermal efficiency and energy consumption challenges. This research aims to explore the environmental potential of CSIPs to improve the thermal performance of Hanok structures while maintaining the traditional aesthetics of these buildings. Simulations were conducted to analyze the thermal behavior, heat flow, and energy use intensity (EUI) by wall cases of Hanok buildings, applying continuous-fiber-reinforced thermoplastic composites as a type of CSIP. The findings demonstrated that applying continuous-fiber-reinforced thermoplastic composites (CFRTCs) to the target Hanok building significantly enhanced the thermal performance, including the thermal bridge and envelope airtightness, as these composites can reduce the thermal conductivity and minimize heat loss, thus improving the insulation capabilities. Furthermore, adopting modular CSIPs in Hanok architecture offers environmental benefits and aligns with sustainability and constructability goals. By reducing reliance on mechanical heating and cooling systems, CSIP-enhanced Hanok buildings can contribute to lower energy consumption and greenhouse gas emissions. This simulation study highlights the significant potential of CSIPs with fiber-glass-reinforced thermoset (FRT) polymer skins to enhance the thermal and energy performance of traditional Korean Hanok buildings. CSIPs as applied to the target Hanok can potentially reduce heating energy consumption by approximately 21% to 29%, leading to overall energy savings of about 4% to 5% in site EUI and CO2 emissions levels per unit area.