Building Thermal Insulation Materials Research Articles

Moisture absorption and desorption characteristics and prediction model analysis of building thermal insulation materials

Understanding the isothermal moisture absorption and desorption characteristics of building thermal insulation materials and how they affect thermal conductivity, is curial for accurate building thermal design and energy-saving calculation. In this paper, five types of building thermal insulation materials are selected for investigation. First, the variation trend of the equilibrium mass moisture content of materials in different moisture absorption and desorption stages is studied employing the saturated salt solution method and the constant temperature and humidity box method, and the effect of temperature on the moisture absorption and desorption processes is evaluated. Additionally, the applicable model of the material in the moisture absorption and desorption process is obtained through a fitting analysis of the experimental data. Finally, the influence of the material’s moisture absorption and desorption characteristics on the thermal conductivity is analyzed using the transient thermal conductivity test method. The results highlight that there is a need to consider the moisture absorption and desorption processes to accurately determine the wet material thermal conductivity, and the hysteresis effect of the material in the moisture absorption and desorption processes is directly related to its microstructure and the relative humidity at the initial moisture desorption. At a temperature of 25 oC, the autoclaved aerated concrete exhibits its highest hysteresis rate of thermal conductivity during the moisture desorption process of third stage, reaching 13.2%.

Pore structure characterization and effective thermal conductivity modeling of fibrous building thermal insulation materials based on X-ray tomography

The existing structural characterization methods of building materials as well as thermal conductivity calculation models can not be directly applied when considering fibrous building thermal insulation materials with intricate skeletons. In this study, rock wool is considered the research object, and the X-ray tomography method is used to characterize the pore structure and extract structural parameters. Based on the actual pore morphology of the material, the pores in the representative elementary volume (REV) are reasonably assumed to be cubic. Additionally, considering the contact thermal resistance of fibers and the randomness of pore distribution, the curved pattern of heat conduction pathway with the ever-changing diameter is reasonably simplified into a series-parallel form of the curved heat chain with the same diameter. On this basis, the fractal models of effective thermal conductivity are established in horizontal and vertical directions. Finally, a modified formula for the effective thermal conductivity calculation of fiber thermal insulation materials is proposed, taking into account the influence of fiber orientation on the material thermal conductivity. It was shown that the relative deviation between the calculated correction value and the experimental value of the effective thermal conductivity is all less than 16.13%.

Multifunctional and recyclable aerogel/fiber building insulation composites with sandwich structure

Fire, electromagnetic (EM) pollution, and sustainability require building insulation with fire resistance, EM interference shielding, and recyclability. However, fewer building insulation materials can fulfill these multifunctional requirements. Here, we report a multifunctional building thermal insulation material with a sandwich structure that uses SiO2 aerogel powder as the insulating filler phase, α-Al2O3 fiber as the refractory reinforcing phase, and carbon fiber mat (CFF) as the electromagnetic interference shielding layer prepared by the mixing-pressing-drying method. The effects of different SiO2 aerogel power contents on fire resistance, thermal insulation, and hydrophobicity, the effects of different carbon fiber contents on EMI performance, and the effects of CFF as an interlayer on compressive strength and recyclability were investigated. The results demonstrated exceptional fire resistance properties and low thermal conductivity (0.0529 W/m·K) with a SiO2 aerogel powder content of 11.2 wt%. Specifically, the structure of the aerogel/fiber composite remains intact and the temperature of the non-heated surface is lower than 75.8 ℃ after 4 min of continuous flame combustion. It can achieve a commercial shielding standard of 20 dB at a carbon fiber content of 5 wt%. In addition, CFF as interlayers can effectively improve the compression strength of the material and solve the problem of difficult recycling of carbon fiber. In conclusion, this sandwich structure of multifunctional aerogel/fiber composites provides new ideas for the manufacture of fire resistance, energy-saving, EM-protection, and recyclable building insulation materials.

Impact of thermal conductivity of aerogel-enhanced insulation materials on building energy efficiency in environments with different temperatures and humidity levels

New building thermal insulation materials, such as aerogel-enhanced insulation materials, are constantly emerging. To study how cement-based aerogel-enhanced thermal insulation materials perform under temperature and humidity changes, various aerogel-enhanced hollow glass microsphere insulation boards (HGBs) have been developed as building thermal insulation materials. The thermal conductivity of aerogel-enhanced HGBs, expanded polystyrene (EPS), and foamed cement (FC) was measured at various relative humidity levels and temperatures, and the summer cooling load of buildings with aerogel-enhanced HGBs, EPS, or FC as the insulation layer was simulated for different building heights and thermal zones. The results show that (1) the new aerogel-enhanced HGB materials are more suitable for building insulation in humid and hot areas than FC; (2) the cooling load of small buildings with fewer floors is more sensitive to the variation in the thermal conductivity with temperature and humidity; (3) for buildings in areas with hot summers and warm winters, the impact of the outdoor relative humidity should be fully considered when calculating summer cooling loads.

Retracted: Preparation and Sound Insulation Performance of Polystyrene Building Flame Retardant and Thermal Insulation Building Materials

Retracted: Preparation and Sound Insulation Performance of Polystyrene Building Flame Retardant and Thermal Insulation Building Materials

Research on fire resistance and economy of basalt fiber insulation mortar

The construction sector has become the most critical source of carbon emissions, but the existing thermal insulation materials such as thermal insulation mortar have obvious limitations, so it is urgent to develop building thermal insulation materials with superior performance and low cost. Aiming at the problem of poor bond strength of foam thermal insulation mortar, this research team selected basalt fiber as admixture to verify the influence of basalt fiber content on its performance and the economic feasibility of thermal insulation mortar. The main finding is that basalt fiber as an additive can obviously improve the crack resistance of thermal insulation mortar. When the content of basalt fiber increases from 0 to 2.5%, the compressive strength of mortar increases at first and then decreases, and the bond strength increases nonlinearly, but the thermal conductivity and dry density also increase. Therefore, the optimal content of basalt fiber is 1.5%. The improvement effect of fire resistance of thermal insulation mortar with 1.5% basalt fiber content is better. After curing for 28 days, the mass loss rate of the sample is reduced by about 11.1% after high temperature, and the relative compressive strength is increased by about 9.71% after high temperature. The raw material cost of the new fireproof thermal insulation mortar improved by basalt fiber is lower, and the cost of the finished product is reduced by 16.98%, 28.18%, 33.05% and 38.96%, respectively, compared with the four types of thermal insulation mortar already used in the market. More importantly, the economic recovery period of the new fireproof and thermal insulation mortar is undoubtedly shorter than that of alternative thermal insulation or energy storage materials, which not only achieves low emission and environmental protection, but also satisfies the economic feasibility.

Investigation of novel expandable polystyrene/alumina aerogel composite thermal insulation material

Expandable polystyrene (EPS) foam is one of the most commonly used building thermal insulation materials due to its low thermal conductivity, apparent density as well and low cost. However, its high flammability and the release of a large number of toxic gases during combustion hinder its application. In this paper, using EPS foam and alumina aerogel (Al2O3) as insulation components, epoxy resin (EP) as a binder, and expandable graphite (EG) and ammonium polyphosphate (APP) as composite flame-retardant, a novel organic-inorganic composite thermal insulation material (EPS-AEA) was designed and fabricated. Experiment results showed that adding Al2O3 to EPS could further reduce the thermal conductivity of the obtained composite, and improve its mechanical properties. The addition of EG and APP composite flame-retardant could markedly enhance flame-retardant performance. With the addition of 4.17% Al2O3, and 50% EG/APP (1/1 mass ratio), the obtained EPS-AEA-1/1 composite showed superior fire resistance (reaching UL-94 V-0 rating and limiting oxygen index (LOI of 40.6%), high thermal insulation (thermal conductivity of 0.0487 W/(m·K)and applicable mechanical properties. In addition, EPS-AEA had excellent anti-hygroscopic properties (moisture ab-desorption rate within 0.5%) and fairly low toxic gas emissions during combustion, indicating its potential in practical application.

Composition Gradient Cellulose–Aerogel Nanocomposites Regulating Thermal Insulation

Over the last few decades, functional gradient structures have evolved through natural biological systems, while gradient structures lead to tailored mechanical and physical performance due to the gradual structural change. Herein, composition gradient cellulose and aerogel nanocomposites that regulate their thermal insulation and mechanical performance are reported. The as‐prepared gradient composite shows a thermal conductivity of 32.2 mW m−1 K−1 and flexural modulus of 660 MPa while exhibiting superhydrophobicity and superior reusability. The unique orientation‐dependent thermal insulation and mechanical strength arise from the composition gradients formed by the silica aerogel distribution during the cellulose‐fiber‐percolated network formation, which opens a pathway toward green building thermal insulation materials.

Retracted: Application of Lightweight Thermal Insulation Building Materials for Green Building Design

Retracted: Application of Lightweight Thermal Insulation Building Materials for Green Building Design

Developing thermal insulation cement-based mortars using recycled carbon black derived from scrapped off-the-road tires

This study appraised the feasibility of recycled carbon black (RCB) derived from scrapped off-the-road (OTR) tires, denoted as RCB-OTR, as aggregates to develop thermal insulation mortars. Sand in Ordinary Portland cement (OPC)-based mortars was replaced by RCB-OTR in volumetric proportions of 0, 30, 60, and 100%. The results revealed that the developed thermal insulation mortars had oven-dry densities between 1058 ± 1 and 2045 ± 5 kg/m3 and 28-day UCS between 8.6 ± 0.74 and 37.3 ± 0.76 MPa. Mortars at RCB-OTR replacement ratios below 30% can be employed as load-bearing units. Replacing all sand with RCB-OTR resulted in a considerable decrease in thermal conductivity from 1.800 ± 0.071 to 0.272 ± 0.021 W/mK, the volumetric heat capacity from 1.438 ± 0.063 to 1.044 ± 0.079 MJ/m3K, and thermal diffusivity from 1.255 ± 0.089 to 0.263 ± 0.034 mm2/s. Overall, mortars mixed with RCB-OTR exhibited good thermal insulation performance and satisfactory mechanical properties, demonstrating that RCB-OTR is a promising lightweight aggregate for thermal insulation building materials. This is the first study to incorporate RCB-OTR into the cement-based materials and evaluate the thermal properties. It contributes to the development of eco-friendly thermal insulation building materials using RCB-OTR and delivers an innovative solution for mining industry to dispose of waste OTR tires.

Evaluation of porosity, mechanical and thermal properties of self-ignition coal gangue-based foams via fast microwave foaming

Recently, the large-scale stock and pollution of solid waste has become a serious environmental and economic problem. Upcycling the solid waste to produce porous materials is a value-added waste management method. Self-ignition coal gangue-based alkali-activated foams were successfully produced via a fast microwave foaming method within a few minutes. The effect of alkali concentration on pore structure, porosity, mechanical and thermal properties of alkali-activated foams was explored. Alkali-activated foams with low bulk density (0.41–0.81 g/cm3), high total porosity (65.6–83.5 vol%), acceptable compressive strength (0.92–4.42 MPa), and low thermal conductivity (0.11–0.14 W/mK) were obtained by a fast microwave foaming method. The foams showed excellent high temperature performance. The compressive strength showed an increasing trend after heat treatment from 500 to 1100 °C. Simultaneously, a low high-temperature volume shrinkage (4.0–4.1%) was achieved. The obtained foams can be used as high-performance proppant materials, thermal insulation building materials, and in fire-resistant applications.

Effect of Particle Size and Concentration of Nanocellulose on Thermal Properties of Nanocellulose Aerogel

Traditional building thermal insulation materials are mostly from petrochemical materials or high energy consumption processing process, which seriously restricts the sustainable development of the economy. Therefore, it is urgent to develop high-performance green insulation materials with high efficiency, energy saving, light weight and environmental protection. In this paper, nanocellulose aerogels made from cellulose nanocrystal (CNC) and cellulose nanofibril (CNF) with different concentrations were prepared by freeze-drying process. The effect of the concentration of nanocellulose on the thermal properties of aerogel was fully studied by infrared thermal imager, thermogravimetric analyser, and thermal conductivity meter. The study found that the overall thermal insulation performance of CNF aerogel was better than that of CNC aerogel. The concentration had a significant effect on the thermal insulation performance and thermal conductivity of the two aerogels. Among all the prepared nanocellulose aerogels, CNF aerogel with a concentration of 1% showed the best thermal insulation performance, which had a temperature difference of 24.1°C and a thermal conductivity of 0.030 W/mK.

Predicting the effective thermal conductivity of porous building materials using improved Menger sponge fractal structure

Accurately obtaining the effective thermal conductivity of porous building materials can correctly understand its thermal insulation performance and ensure the selection of effective building thermal insulation materials, which can bring certain help to building energy conservation. A novel method based on fractal theory combined with the principle of thermoelectric analogy is proposed to predict the effective thermal conductivity of solid-fluid two-phase porous building materials whose solid phase is particles. By improving the fractal structure of the self-similar Menger sponge and considering the incomplete contact form between solid particles inside the characteristic unit, a physical model of heat conduction suitable for porous building materials is obtained. Then, the thermal resistance in the cubic characteristic unit of the improved Menger sponge is calculated using the principle of thermoelectric analogy. Finally, this study obtains a thermal conductivity prediction model that can predict the thermal conductivity of solid-fluid two-phase porous building materials in the full porosity range. The prediction effect of the prediction model is verified when the porosity is 0.55, 0.41, 0.3, and 0.17. The results show that the model is accurate and effective, and the prediction effect is much better than the theoretical prediction models such as series and parallel. And the model has good practicability, which can bring a feasible method for obtaining the effective thermal conductivity of porous building materials.

Hydrophobic Cellulose Acetate Aerogels for Thermal Insulation

As naturally derived material, cellulose aerogels have excellent thermal insulation properties due to their unique high porosity and three-dimensional mesoporous structure. However, its hydrophilic properties limit its application in the field of building insulation. Here, we propose a method to prepare high hydrophobicity by adopting the sol-gel method and chemical vapor reaction strategy using cellulose acetate type II as raw material and 2,4-toluene diisocyanate as the cross-linking agent. Thermal properties of cellulose acetate aerogels (CAAs) were measured, where pyridine was the catalyst, acetone was the solvent, and perfluorodecyltriethoxysilane (PFDS), hexamethyldisilazane (HMDS), and methyltriethoxysilane (MTES) were used as hydrophobic agents (by process hydrophobic test). Compared with MTES-modified cellulose acetate aerogels (M-CAAs) and HMDS (H-CAAs)-modified cellulose acetate aerogels, PFDS-modified (P-CAAs) cellulose acetate aerogels are the most hydrophobic. By implementing hydrophobic modification of PFDS both inside and outside the structure of cellulose acetate aerogels, the water contact angle can reach up to 136°, strongly demonstrating the potential of PFDS as a hydrophobic agent. The results show that the thermal conductivity and compressive strength of cellulose acetate aerogel with the best hydrophobic properties are 0.035 W m−1 K−1 at normal pressure and 0.39 MPa at 3% strain, respectively. This work shows that the highly hydrophobic cellulose acetate aerogel has potential as a waterproof material in the field of building thermal-insulation materials.

Application of Lightweight Thermal Insulation Building Materials for Green Building Design

In order to focus on the application of green environmental protection lightweight thermal insulation materials, an in-depth study is carried out on the basis of joint architectural design. The application of green environmental protection materials in the construction industry was successfully analyzed through methods such as layout design method, optimization design method, and scientific optimization of material selection. In the process of urbanization development in our country, the number of urban population has increased sharply, and the demand for buildings has also increased. Therefore, it is necessary to rapidly promote green building design while the construction industry is developing rapidly and complete the upgrading and transformation of the building in terms of form design. We pay attention to the needs of buildings in terms of shading and lighting, and improve the conditions of building shading and lighting through green building technology. As a result, on the basis of maintaining the residual heat of the building, the diffuse radiation of the ultraviolet rays of the sun is realized, which effectively improves the utilization efficiency of natural energy and reduces the consumption of internal energy. Architectural design under the concept of green building design not only can it meet the current functional requirements of people for architecture but also imperceptibly promote the stable development of our country’s construction industry. After the research on the application of green environmental protection materials, the integration and application of green building design concepts in architectural design is of great significance not only to meet people's health and ecological needs of buildings but also to promote social stability and sustainable development.

Influencing factors of mechanical and thermal conductivity of foamed phosphogypsum-based composite cementitious materials

In this study, the phosphogypsum-based cementitious materials were modified by adding raw lime, fly ash and cement into hemihydrate phosphogypsum. Then the modified phosphogypsum-based cementitious materials were foamed by different foaming methods. Finally, the synergistic strengthening effect of mechanical and thermal insulation properties of foamed phosphogypsum-based cementitious materials was studied. The results show that when the content of phosphogypsum is 60 %, the water-binder ratio is 0.300, the content of fly ash is 30 %, and the content of quicklime is 8 %, the mechanical and thermal insulation properties of phosphogypsum-based cementitious materials are the best. Although the porosity of physical foaming specimens is lower than that of chemical foaming specimens, the mechanical and thermal insulation properties of physical foaming specimens are better than those of chemical foaming specimens. The larger the pore diameter and the more connected the pore, the more serious the stress concentration of the specimen under compression, resulting in the decrease of the compressive strength. In addition, the porosity increases with the increase of foaming agent content, but the thermal conductivity does not decrease significantly with the increase of porosity. The reason is that with the increase of foaming agent content, the pore diameter also increases, which reduces the thermal resistance of the specimen and affects the further reduction of the thermal conductivity. This study can provide a theoretical basis for the practical engineering application of phosphogypsum as thermal insulation building materials.

Life cycle assessment (LCA) of thermal insulation materials: A critical review

Thermal insulation of buildings is a key factor in reducing the environmental impact of the building sector by lowering the energy demand of buildings for heating and cooling. The choice of material for the thermal insulation has become more important with the rising need for sustainability. Life cycle assessment (LCA) is a common tool to assess the environmental impact of products or services. This study reviews the available literature on LCA of building thermal insulation materials in a structured literature review. The aim was to provide an overview over the literature, critically assess the methodology used as well as the results of the LCAs, especially to identify the potential of renewable based thermal insulation. This review covered 47 studies on building thermal insulation materials in total and developed a pedigree matrix to assess the quality of the articles. The results show at times significant methodological issues and a lack of transparency on the implementation of methods within the LCA framework. For the comparative LCA results, the review suggests that among the market leading materials, EPS, Stone wool, and Glass wool are highly similar in their impact. Other materials such as XPS or PUR show overall higher impacts in the majority of categories. The results further suggest that renewable based materials tend to have a lower environmental impact, but are not necessarily better. The main cause of impact for non-renewable organic materials is the raw material and for inorganic materials the production process, while the most common main driver of impacts for renewable based materials are binders and additives. This highlights further potential for improvement for the environmental impact of renewable based thermal insulation materials by lowering the need for additives.

Preparation and Sound Insulation Performance of Polystyrene Building Flame Retardant and Thermal Insulation Building Materials.

In this study, magnesium hydroxide (MH) was modified by sodium dodecylbenzene sulfonate (SDBS) to prepare modified magnesium hydroxide (MMH) flame retardant, which was mixed with polystyrene (PS) to obtain flame retardant PS composite plate. The micromorphology, mechanical properties, thermal stability, and flame retardancy of flame retardant PS composite plate were analyzed. The experimental results show that MMH is well dispersed in PS matrix, PS-MMH-3 has the best tensile strength and elongation at break, the limit oxygen index (LOI) is 44.3% higher than that of pure PS, and the combustion rate is slow, indicating that PS-MMH-3 has good flame retardant properties.

Optimization of the thermal conductivity test for building insulation materials under multifactor impact

The thermal conductivity of building materials is an important parameter in building thermal engineering and energy conservation. When building thermal insulation materials are placed in the real environment, they are affected by dynamic temperature and humidity conditions, and most materials have certain moisture content. However, moist materials have a different thermal conductivity than dry materials, and an inaccurate estimation of thermal conductivity will cause errors in the energy conservation calculation of the building envelope. To accurately measure the thermal conductivity under a controllable environment and reduce energy conservation calculation errors, the effects of the measuring apparatuses, drying temperature, specimen size, specimen moisture content, ambient temperature and humidity on the thermal conductivity of the building thermal insulation materials are studied. The sensitivity of thermal conductivity to various influencing factors is analyzed, and the thermal conductivity value of moist building thermal insulation materials is determined as the basis to select or design products for building envelopes. In addition, the test method of thermal conductivity for building thermal insulation materials is optimized.

Fabrication and Evaluation of Proper Building Thermal Insulation Materials

Fabrication and Evaluation of Proper Building Thermal Insulation Materials