Energy utilization and its structural layout are not only key factors and indicators of human development but also represent important aspects of human civilization and scientific and technological progress. They are crucial parameters determining the progress of human activities and key elements of economic and social development in various countries [
1,
2,
3]. Energy consumption has gradually become one of the increasingly focused global issues. Global energy and resource consumption are rapidly increasing at an average annual rate of 2.2%. With the rapid growth of the global economy, the pressure on energy resources is increasing [
4,
5,
6,
7]. Energy consumption from buildings accounts for approximately 40% of the total global energy consumption. As the global economy continues to grow rapidly, the total energy consumption of buildings will continue to rise. Therefore, research on improving the energy efficiency of buildings has gradually become a hot topic of study [
8,
9]. In addition, the emissions of greenhouse gases from buildings account for one-third of global energy-related greenhouse gas emissions, making it one of the main causes of climate change [
10,
11]. From another perspective, climate change has further intensified the increase in energy demand for building insulation and other related purposes. Existing scholars believe that the energy demand of buildings and the associated greenhouse gas emissions are significantly influenced by the characteristics of buildings and local climatic conditions. In the future, the annual energy demand of all types of buildings shows a net increase, with the highest increase in heating energy demand [
12,
13]. Energy consumption and greenhouse gas emissions have a significant impact on the global environment. Therefore, improving the energy utilization efficiency of buildings can help in the efficient use of energy, reduce greenhouse gas emissions, and alleviate the pressure on energy and the environment. In this context, this paper focuses on the GCIM, innovatively proposing a novel research approach and method. In the past, modeling of thermal conductivity (TC) for insulation materials has mostly revolved around common materials or traditional methods. However, the GCIM has unique structural characteristics, with complex interactions among its internal components. The key challenge currently faced is how to accurately construct a theoretical calculation model for its TC based on these characteristics.
In recent years, research in the construction industry has mainly focused on developing sustainable, environmentally friendly, and energy-efficient building materials, advocating for energy-efficient, environmentally friendly, health-appropriate, and highly practical building materials. Numerous scholars have also devoted a great deal of effort to developing energy-efficient and environmentally friendly green building materials. The research and development of building insulation materials with good TC and green environmental protection is very necessary. On the one hand, this can greatly improve the thermal insulation performance of buildings, significantly increase the energy efficiency of buildings, and reduce building energy consumption. On the other hand, the application of green and environmentally friendly insulation materials can greatly reduce the emission of harmful gases and greenhouse gases, helping to alleviate the trend of global temperature rise. Insulation materials are mainly divided into organic insulation materials and inorganic insulation materials [
14]. Both domestic and international research has focused on the thermal conduction theory, experimental studies, and formulation processes of insulation materials, yielding many research achievements. Shrestha et al. [
15] established a model to calculate the solid and gas TC coefficients of porous materials. They validated the model by combining literature data and experiments, discussing the contributions of solids and gases. Wang et al. [
16] explored the temperature and humidity variations of 8 common insulation materials through experimental methods and provided principles for selecting insulation materials, laying the groundwork for accurately determining the TC coefficients of insulation materials. Tariku et al. [
17] discussed the effects of temperature, moisture, and aging on the performance of commonly used insulation materials. They presented theoretical calculations for the TC coefficient variations with temperature and moisture content, investigating the patterns of these variations. Pan et al. [
18] conducted in-depth research on the mechanical and thermal properties of low-density foam concrete and explored its manufacturing process. Tan et al. [
19] prepared a new type of organic-inorganic composite insulation material (EPS-AEA) and found that adding Al
2O
3 to EPS can reduce the TC of the composite material and enhance its mechanical properties. Ajabli et al. [
20] studied eco-friendly insulation solutions and compared the TC performance with traditional insulation materials, laying the groundwork for the research and development of new eco-friendly insulation materials. Özçelikci et al. [
21] utilized construction waste to prepare ultra-lightweight recycled building insulation materials, further investigating the factors influencing their thermal and mechanical properties. Cosentino et al. [
22] explored the various properties of natural insulation materials, emphasizing the importance of thermal capacity, lifespan, and environmental impact of insulation materials, providing directions for insulation material research. Zhou et al. [
23] prepared bio-based insulation materials using rice straw and natural binders, investigating the influence of fiber dimensions and binder properties on their hygrothermal performance. Majumder et al. [
24] utilized jute, wool fibers, and loofah fibers as raw materials to manufacture building insulation materials, conducting comparative analyses on their insulation, soundproofing, and insulating properties. Hasanzadeh et al. [
25] carried out a comparative analysis of common insulation materials using decision-making methods, establishing a theoretical predictive model for overall TC and validating it through experimental results. Liu et al. [
26] provided a reference for predicting the TC of polymer composites for directional fillers by training a convolutional neural network model, contributing to the prediction of the TC properties of composite materials. Zha et al. [
27] reviewed the thermal conduction theory of composite materials and conducted an in-depth analysis of the impact of interfacial thermal resistance on heat transfer. Lou et al. [
28] discussed the heat transfer mechanisms and TC testing methods of nanoporous insulation materials, summarizing and prospecting their theoretical research and applications. Wang et al. [
29] developed a novel bio-based insulation material primarily using corn cob as the main raw material, proposing a preparation method for bio-based insulation materials, offering new methods and ideas for the development of multifunctional insulation materials. Dong et al. [
30] studied the advantages and disadvantages of various external wall insulation technologies, providing recommendations for different forms of external wall insulation. Numerous studies indicate that insulation materials play a crucial role in improving building energy efficiency. However, there is still significant research space in the efficiency and methods of calculating the TC of insulation materials. Improving predictive methods for TC significantly enhances the efficiency of calculating insulation materials’ TC. This is of great importance for the optimization design, improvement, and development of new products in insulation materials.
Previous studies have mainly focused on the theoretical and experimental research of thermal insulation materials, formulation processes, exploration of different material properties, as well as discussions on the advantages and disadvantages of specific insulation techniques. However, there are still shortcomings in the efficiency and methods of calculating the thermal conductivity of insulation materials. The lack of an efficient and accurate method for calculating the thermal conductivity of insulation materials restricts the further optimization, improvement, and efficient development of new products in insulation material design. Based on this, in order to improve the efficiency of calculating the TC of insulation materials and to make up for the shortcomings of existing research, this paper takes the graphite composite insulation material (GCIM) as the research object and establishes a theoretical calculation model of the TC of composite materials based on its structural characteristics. By utilizing theoretical calculations to quickly predict the TC of the GCIM, the efficiency of TC calculations is enhanced. Furthermore, a numerical model of the GCIM is established. Through the calculation analysis of the theoretical model and numerical model, the influence of changes in material composition on the TC of the GCIM is further explored. Compared to the majority of previous studies that focused on a single perspective or conducted shallow analyses of material performance, a more systematic and in-depth approach can provide a more comprehensive and valuable reference basis for the development of new insulation materials.
This study aims to focus on graphite composite insulation materials as the core research object, addressing key issues in the thermal conductivity research of insulation materials. By utilizing a numerical model of graphite composite insulation boards and combining it with the aforementioned theoretical calculation models, this research intends to provide a comprehensive and highly valuable reference basis for the development of new insulation materials. This, in turn, will drive further advancements in the field of insulation materials in terms of thermal conductivity calculations and material development applications, contributing to alleviating building energy consumption pressures, addressing climate change, and tackling other real-world challenges. The research results have important theoretical significance for improving the efficiency of calculating the TC of composite materials and the development of new insulation materials.