Thermal Insulation Capacity Research Articles

Low-temperature flux synthesis of potassium hexatitanate whiskers: Growth mechanism and applications in high-temperature infrared thermal insulation

Potassium hexatitanate whiskers (PHWs, K2Ti6O13)are a promising functional material with high thermal insulation capacity. In this study, PHWs were successfully synthesized using the flux method at temperatures ranging from 725 °C to 1100 °C. The crystal growth mechanism of PHWs in the KCl flux follows a series-parallel pattern. The synthesized PHWs have a near-infrared reflectivity (NIR) exceeding 95%, and the cause of high reflectivity was theoretically analyzed based on the Kubelka-Munk equation. The high temperature stability of near-infrared reflectivity and the thermal stability of the PHWs were further assessed using TG-DSC, XRD, SEM, and UV–VIS-NIR analysis. It was found that PHWs prepared at 800 °C begin to decompose into TiO2 at approximately 1375 °C. Nevertheless, the near-infrared reflectivity remains stable even after heat treatment. Additionally, PHWs were prepared as a composite thermal insulating coating, showing thermal conductivity between 0.177 and 0.569 W/(m K) across the temperature range of 200 °C to 900 °C. The temperature difference between the hot and cold surfaces of the composite coating was significantly greater compared to the control groups at various temperatures, with a p-value of less than 0.01 in the paired t-test. This result demonstrates the great application potential of PHWs as a high-temperature near-infrared thermal insulation material.

Evaluation of thermal insulation capacity and mechanical performance of a novel low-carbon thermal insulating foam concrete

The use of building insulation materials is an effective measure to reduce building energy consumption. To improve the sustainability of insulation materials, desert sand (DS) was used to replace part of the binder, and rice husk ash (RHA) was incorporated to further improve the performance of foamed concrete. The fresh properties, strengths, thermal properties and thermal insulation function of DS-based foamed concrete (DSFC) were systematically investigated. The use of DS and RHA to replace part of Portland cement (PC) and fly ash reduces the flowability of the mixture when the water/binder (PC, fly ash, DS and RHA) ratio is constant. Although the incorporation of DS into foamed concrete increases its density and thermal conductivity, it improves the volume stability of the sample. The strength of specimen with DS decreases due to the low reactivity of DS, which also reduces the content of hydration products. Further incorporation of RHA not only improves the matrix strength by increasing the C-S-H content but also improves the pore structure of the DSFC by increasing the yield stress of the paste. The joint application of DS and RHA effectively reduces the heat storage coefficient and thermal inertia index of DSFC, which is beneficial to improve the thermal insulation capacity of buildings and reduce energy consumption. Incorporating DS and RHA can effectively improve the environmental and economic benefits of the foamed mixture, and the unit strength cost and carbon emission per cubic meter of the 5%–10% RHA-modified samples are reduced by 20.3%–39.1% and 20.2%–38.9%, respectively, compared with the DS35. This research provides a new approach and theoretical basis for building energy saving and external wall insulation.

Transformation of Fly Ash-Based Oxide Particles into a Functional Silica-Alumina Aerogel and Its Potential Application as an Anti-icing Surface.

Lightweight, surface hydrophobic, highly insulating, and long-lasting aerogels are required for energy conservation and ice-repellent applications. Here, we present the conversion of fly ash to a silica-alumina aerogel (SAA) by utilizing its high silica content. The extracted silica component replaces expensive precursors typically used in conventional aerogel production. Ice adhesion performance was compared to that of polypropylene (PP), an insulating commodity polymer. First, we removed some salt impurities and heavy metals via water and alkaline washing protocols. Then, we produced SAA via the ambient pressure drying method by using trimethylchlorosilane (TMCS) as an adhesion promoter. The newly produced SAA has a surface area of 810 m2 g-1 and shows hydrophobic properties with a contact angle of 140 ± 5°. The thermal conductivity of SAA is 0.0238 W m-1 K-1 with C P = 1.1922 MJ m-3 K-1. The ice adhesion strength of the PP substrate was calculated as 188.30 ± 51.24 kPa, while the ice adhesion strength of the SAA was measured as 1.21 ± 0.40 kPa, which was about 150 times lower than that of PP. This indicated that SAA had icephobic properties since ice adhesion strength was less than 10 kPa. This study demonstrates that fly ash-based SAA can be utilized as an economical material with a large surface area and exceptional thermal insulation capacity and is free of harmful compounds (heavy metals), making it potentially suitable as an anti-ice thermal insulation material.

Mechanical Properties and Durability of Composite Cement Pastes Containing Phase-Change Materials and Nanosilica.

Escalating global surface temperatures are highlighting the urgent need for energy-saving solutions. Phase-change materials (PCMs) have emerged as a promising avenue for enhancing thermal comfort in the construction sector. This study assessed the impact of incorporating PCMs ranging from 1% to 10% by mass into composite Portland cement partially replaced by fly ash (FA) and nanosilica particles (NS). Mechanical and electrochemical techniques were utilized to evaluate composite cements. The results indicate that the presence of PCMs delayed cement hydration, acting as a filler without chemically interacting within the composite. The combination of FA and PCMs reduced compressive strength at early ages, while thermal conductivity decreased after 90 days due to the melting point and the latent heat of PCMs. Samples with FA and NS showed a significant reduction in the CO2 penetration, attributed to their pozzolanic and microfiller effects, as well as reduced water absorption due to the non-absorptive nature of PCMs. Nitrogen physisorption confirmed structural changes in the cement matrix. Additionally, electrical resistivity and thermal behavior assessments revealed that PCM-containing samples could reduce temperatures by an average of 4 °C. This suggested that PCMs could be a viable alternative for materials with thermal insulation capacity, thereby contributing to energy efficiency in the construction sector.

Weathering resistance of novel sustainable prefabricated thermal insulation wall

External walls, serving as the primary medium for heat exchange between the building and the external environment, has its thermal loss comprising the largest proportion of building energy consumption. Therefore, enhancing the thermal insulation capacity of the wall is of great significance in reducing building energy consumption. In this paper, a novel sustainable prefabricated expanded polystyrene (EPS) thermal insulation wall panel with irregular column frame structures was developed. And weathering tests combined with finite element simulations were conducted to investigate its weathering performance and degradation patterns. The results revealed that In the weathering test, the panel surfaces did not exhibit apparent water seepage cracks, powdering, hollowing, peeling, etc. There was no occurrence of facing brick detachment or damage. The outer surface concrete of the wall panel experienced resistance during normal thermal expansion and contraction, generating compressive stress during expansion and tensile stress when contracted. In addition, the bond strength of the specimens decreased by 8.1% after the thermal-rain cycles, 5.1% after the thermal-cold cycles, and 12.1% after the freeze-thaw cycles. In the numerical simulations, the temperature stress at various positions on the concrete wall had a noticeable mutual restraining effect on the force deformation of the nearby concrete. There was a significant risk of cracking in the middle and around the opening, particularly in the lower part of the wall panel. This study serves as a basis for the degradation analyses and optimization design of the sandwich insulation wall panels for sustainability.

Sustainable construction materials for low-cost housing: Thermal insulation potential of expanded SBR composites with leather waste

In recent years, there has been a growing interest in improving energy efficiency and thermal comfort in low-income housing, especially in regions prone to extreme climatic conditions. Conventional construction materials such as bricks and concrete exhibit shortcomings in energy efficiency, resulting in high indoor temperatures. This scenario not only impacts residents' well-being but also increases energy consumption, especially for air conditioning systems, potentially straining the electrical infrastructure in hot climate areas, leading to power outages and adverse consequences for the community and local industry. This study proposes an innovative and sustainable solution: the use of expanded styrene-butadiene rubber (SBR) with micronized leather shavings, possessing thermal insulation properties. The thermal insulation capacity of the composites was evaluated using heat flow methods, hot/cold plate heat flow analysis, and impedance tube acoustic method. The SBR/Leather waste composite at 20 phr emerges as a viable, promising, and sustainable alternative, exhibiting significant thermal insulation capacity with a thermal conductivity of 0.073 Wm-1.K−1 and temperature attenuation close to 15 °C, potentially enhancing comfort and quality of life in urban areas. The thermal insulation results of the other composites also surpassed traditional construction materials such as building boards, plywood, fiberglass, asphalt roofing, and cement tiles. The study demonstrates the feasibility of reusing leather as a reinforcing filler in rubber-based foams to produce thermal insulation materials, offering a sustainable solution to mitigate urban heating and improve quality of life in cities.

Enhancing Thermal Insulation of Poly(β-Hydroxybutyrate) Composites with Charring-Foaming Agent-Coated Date Palm Wood

Date palm fiber (DPF) holds great potential for composite materials, but its flammability limits its practical applications. In this study, DPF was modified using a pad-drying method to impregnate it with a 5 wt.% solution of ammonium dihydrogen phosphate (ADP). These treated fibers were then utilized to fabricate poly(β-hydroxybutyrate)- (PHB-) based composites. The resulting thermal insulators were comprehensively evaluated for their flammability, physical, mechanical, and thermophysical properties, as well as morphological and thermal stability characteristics. The findings revealed a significant reduction in flame spread and smoke suppression; however, the concentration used is not sufficient to achieve the desired rating grades. The thermal insulation capacity of the modified fiber composites was substantially enhanced, particularly with the 40% PHB/DPF-ADP composite displaying the lowest thermal conductivity at 0.0564 W/m.K. Moreover, the presence of gaps and voids at the interface led to a reduction in tensile strength to 4-7 MPa. Additionally, the modified fiber composites exhibited significantly reduced water absorption (~0.76%), attributed to the formation of a highly water-resistant substance containing a furan compound. This work provides a simple and effective approach for achieving durable flame retardancy and long-term thermal insulation performance, offering promising opportunities for the practical application of biobased PHB composites.

Experimental investigation on transpiration cooling of ammonium carbonate in porous composite structure at high-temperature

This paper presents and experimental investigation of a novel transpiration cooling concept using ammonium carbonate as the solid coolant. Ammonium carbonate is a promising solid transpiration coolant with stable physicochemical properties at room temperature, high heat absorption by decomposition, and no solid residual after decomposition. In order to enhance the load-bearing properties of the thermal protection structure, alumina and zirconia ceramic foams with high porosity and large pore size were used as the coolant carrier, and the foam layer could still provide thermal insulation capacity after the coolant was exhausted. The transpiration cooling experiment were conducted with a stainless-steel wire mesh porous panel as the heated surface of the cooling structure within the high-temperature radiant apparatus, and the cooling performance was compared with that of hydrogel and a passive thermal protection structure. The results indicated that the thermal protection effect using the transpiration cooling technique has a significant advantage over the passive thermal protection method. The maximum cooling efficiencies of the ammonium carbonate cooling structure were up to 6.5 % and 33.7 % for the surface and bottom, respectively. In the transpiration cooling system without coolant injection force, the addition of a thin foam layer can extend the cooling time of ammonium carbonate from 981 s to 1800 s. However, this approach is detrimental to the cooling performance of the hydrogel. Influenced by the huge heat absorption of ammonium carbonate, the difference in heat transfer between alumina and zirconia foams within the cooling structure can be negligible.

Hygrothermal Properties and Performance of Bio-Based Insulation Materials Locally Sourced in Sweden.

In recent years, there has been a paradigm shift in the building sector towards more sustainable, resource efficient, and renewable materials. Bio-based insulation derived from renewable resources, such as plant or animal fibres, is one promising group of such materials. Compared to mineral wool and polystyrene-based insulation materials, these bio-based insulation materials generally have a slightly higher thermal conductivity, and they are significantly more hygroscopic, two factors that need to be considered when using these bio-based insulation materials. This study assesses the hygrothermal properties of three bio-based insulation materials: eelgrass, grass, and wood fibre. All three have the potential to be locally sourced in Sweden. Mineral wool (stone wool) was used as a reference material. Hygrothermal material properties were measured with dynamic vapour sorption (DVS), transient plane source (TPS), and sorption calorimetry. Moisture buffering of the insulation materials was assessed, and their thermal insulation capacity was tested on a building component level in a hot box that exposed the materials to a steady-state climate, simulating in-use conditions in, e.g., an external wall. The tested bio-based insulation materials have significantly different sorption properties to stone wool and have higher thermal conductivity than what the manufacturers declared. The hot-box experiments showed that the insulating capacity of the bio-based insulators cannot be reliably calculated from the measured thermal conductivity alone. The results of this study could be used as input data for numerical simulations and analyses of the thermal and hygroscopic behaviour of these bio-based insulation materials.

Sandwich-Structured Mxene/Waste Polyurethane Foam Composites For Highly Efficient Electromagnetic Interference, Infrared Shielding and Joule Heating.

Electromagnetic interference (EMI) shielding and infrared (IR) stealth materials have attracted increasing attention owing to the rapid development of modern communication and military surveillance technologies. However, to realize excellent EMI shielding and IR stealth performance simultaneously remains a great challenge. Herein, a facile strategy is demonstrated to prepare high-efficiency EMI shielding and IR stealth materials of sandwich-structured MXene-based thin foam composites (M-W-M) via filtration and hot-pressing. In this composite, the conductive Ti3C2Tx MXene/cellulose nanofiber (MXene/CNF) film serves as the outer layer, which reflects electromagnetic waves and reduces the IR emissivity. Meanwhile, the middle layer is composed of a porous waste polyurethane foam (WPUF), which not only improves thermal insulation capacity but also extends electromagnetic wave propagation paths. Owing to the unique sandwich structure of "film-foam-film", the M-W-M composite exhibits a high EMI shielding effectiveness of 83.37dB, and in the meantime extremely low emissivity (22.17%) in the wavelength range of 7-14µm and thermal conductivity (0.19W m-1 K-1), giving rise to impressive IR stealth performance at various surrounding temperatures. Remarkably, the M-W-M composite also shows excellent Joule heating properties, capable of maintaining the IR stealth function during Joule heating.

Multifunctional graphene/Ti3C2Tx MXene aerogel inlaid with Ni@TiO2 core-shell microspheres for high-efficiency electromagnetic wave absorption and thermal insulation

The demand for high-performance electromagnetic wave absorbing (EMA) materials featured with strong attenuation ability, extended absorption bandwidth and ultralight property is imperative yet remains challenging. Herein, a three-dimensional hierarchically porous reduced graphene oxide (rGO)/Ti3C2Tx MXene aerogel embedded with Ni@TiO2 core–shell microspheres was prepared via directional freeze-drying followed by a mild annealing process. The divergence in structure and multicomponent dielectric/magnetic features bring about optimized impedance matching characteristic, multiple polarization and loss pathways, collectively contributing to the excellent absorption performance. As a result, the Ni@TiO2/MXene/rGO (NTMRG-2) aerogel exhibits optimized EMA capability with a maximal effective absorption bandwidth (EABmax) of 6.48 GHz at a lower loading level of 5 wt% in the supporting matrix, covering the whole Ku band. Additionally, it achieves a minimum reflection loss (RLmin) of −71.4 dB with a matching thickness of 2.04 mm. Moreover, the aerogel also exhibits an ultra-light density of 5.58 mg cm−3, superior thermal insulation capacity (close to air) and hydrophobicity, underscoring its potential for multiple applications in various scenarios.

Heat storage and release in binary paraffin-hexadecyl amine composites for solar greenhouses in cold climates

Traditional solar greenhouses in cold regions of China often suffer from poor thermal insulation and storage capacity, resulting in inefficient use of solar energy resources and reduced crop production efficiency. Therefore, it is crucial to explore methods to enhance the thermal conditions within these greenhouses. This paper proposes incorporating a “binary paraffin hexadecyl amine” phase change material into concrete, creating a novel composite material for use in a phase change thermal storage concrete slab. This approach can effectively address the previously mentioned issues. Two solar greenhouses were constructed to directly observe the material's impact on the thermal environment within a greenhouse. One greenhouse was equipped with the phase-change thermal storage slab, while the other served as a control greenhouse without the slab. Temperature field test was conducted on both greenhouses, and the obtained test data demonstrated the temperature regulation advantages of the phase-change greenhouses. Tomatoes were concurrently cultivated in both structures, and a temperature test was conducted to assess the phase-change heat-storage slab's influence on temperature regulation. The results indicate that, compared to similar studies, the phase-change heat-storage slab employed in this study demonstrates superior temperature regulation capabilities. It raises the average greenhouse temperature by 4.2 °C during winter, storing 8.85 × 104 kJ/m3 of heat per unit volume, which is 1.5 to 2.8 times higher than existing materials in the same category. In sunny conditions, the phase-change greenhouse exhibited a 4.9 °C reduction in maximum indoor temperature during the day and a 3.5 °C increase in minimum indoor temperature at night compared to the control greenhouse. This indicated that the phase-change heat storage slab acted as a heat buffer, effectively regulating the temperature inside the solar greenhouse. Tomatoes experienced a 26.6 % increase in effective accumulated temperature, resulting in maturation period occurring 13.04 % earlier compared to the control greenhouse.

Properties and Durability of Cementitious Composites Incorporating Solid-Solid Phase Change Materials

This paper investigates the properties and durability of cementitious composites incorporating solid-solid phase change materials (SS-PCM), an innovative heat storage material. Mortars with varying SS-PCM contents (0%, 5%, 10%, 15%) were formulated and characterized for rheological, structural, mechanical, and thermal properties. Durability assessment focused on volume stability (shrinkage), chemical stability (carbonation), and mechanical stability (over thermal cycles). Mortars with SS-PCM exhibited significant porosity and decreased mechanical strength with higher SS-PCM content. However, thermal insulation capacity increased proportionally. Notably, the material’s shrinkage resistance rose with SS-PCM content, mitigating cracking issues. Despite faster carbonation kinetics in SS-PCM mortars, attributed to high porosity, carbonation appeared to enhance long-term mechanical performance by increasing compressive strength. Additionally, SS-PCM composites demonstrated superior stability over thermal cycles compared to reference mortars.

Insulating materials for the construction of houses with natural fibers of Yucca spp., Agave lechuguilla and Super absorbent synthetic fibers

The building physics aspects for thermal insulation in building construction are presented in brief. Different demands are placed on the thermal insulation material. In addition to the thermal insulation capacity, the price and the regional availability are important. From this perspective the use of fiber plants occurring in the semi-desert (semi-arid) zones of Mexico and an industrial waste material is being investigated.

Fabrication and characterization of lignocellulosic coconut and energy reed straw-reinforced methylene diphenyl diisocyanate-bonded sustainable insulation panels

The use of renewable environmental resources and plastics that can be returned to the biological cycle shows a new direction in the application of composite building materials. This study investigated the potential and strengthening effects of developing composite panels from coconut materials (CM) and reed straw (RS) particles in the presence of methylene diphenyl diisocyanate (MDI). Five composite panels with 100:0, 60:40, 50:50, 40:60, and 0:100% proportions were produced. The nominal density was 600 kg/m3 and the dimensions were 400 × 400 × 8 mm3. The panels were produced by hot-pressing for a total of 10 min at a maximum pressure of 7.2 MPa and at 135 degrees, and then slowly cooled at room temperature. The following experiments were performed: mechanical, physical and morphological properties, thermal conductivity, FTIR (Fourier transform infrared spectroscopy), and EDX (Energy disruptive X-ray). The study gave the following results: the thermal conductivity of the coir and reed panels is competitive with the thermal insulation capacity of similar natural-based insulation materials, and is close to the values of other mineral and plastic-based insulation materials. The values of thermal conductivity coefficient ranged from 0.08 to 0.10 W/(mK). Only reeds (MDI_1) boards have better results than coconut materials. Among the mechanical properties, flexural strength and internal bonding strength increased proportionally with the increase in the amount of coconut. The Young's modulus reached its maximum in the case of a 50–50% coir-reed mixture. The best values of the panels are: 6.33 MPa for flexural strength, 1.83 GPa for Young's modulus and 0.36 MPa for internal bonding strength. The morphological recordings confirmed the proper mixing and binding of the lignocellulosic materials in the composite. FTIR tests proved the successful chemical interactions. The findings support the possibility of creating a promising, environmentally friendly building material.

Influence of recycled concrete powder and CO2 curing on the properties of thermal insulation mortars

Recycled concrete powder (RCP) is a promising supplementary cementitious material, its application in thermal insulation materials is however very limited. In this study, the influence of RCP substitution on the properties of insulation mortars was investigated. The results showed that as the RCP content increased, the compressive strength and thermal conductivity of insulation mortars decreased by 39.8% and 16.8%, owing to the increasing volumes of porous paste and internal air voids. Note that the mortar containing a high content (50 wt%) of RCP struggled to meet the strength requirements of the specification. Therefore, CO2 curing was further employed here to alleviate the strength loss and successfully increased the compressive strength by 11%∼38%. It was found that since the CaCO3 particles formed and densified the microstructure (confirmed by the porosity test), the strength reduction derived from the RCP substitution was compensated for. Consequently, insulation mortars incorporating 50% RCP after CO2 curing for 7 days exhibited satisfactory compressive strength (∼ 0.22 MPa) and relatively low thermal conductivity (∼ 0.048 W/(m∙K)). The mortars showed improved aesthetic appearance and excellent thermal insulation capacity in both hot and cold environments. This study proposed a successful approach to combining reutilization of RCP and CO2 curing in insulation mortar generation, which effectively improved the sustainability of materials.

Eliminating trade-offs between optical scattering and mechanical durability in aerogels as outdoor passive cooling metamaterials.

Passive cooling is a promising approach for reducing the large energy consumption to achieve carbon neutrality. Foams/aerogels can be considered effective daytime cooling materials due to their good solar scattering and thermal insulation capacity. However, the contradiction between the desired high solar reflectivity and mechanical performance still limits their scalable production and real application. Herein, inspired by the "Floor-Pillar" concept in the building industry, a multi-structure assembly-induced ice templating technology was used to construct all-cellulosic aerogels with well-defined biomimetic structures. By using cellulose nanofibers (CNFs) as pillars and cellulose nanocrystals (CNCs) as floors and methyltrimethoxysilane (MTMS) as a crosslinking material, an all-cellulosic aerogel (NCA) exhibiting high mechanical strength (mechanical strength = 0.3 MPa at 80% compression ratio, Young's modulus = 1 MPa), ultralow thermal conductivity (28 mW m-1 K-1), ultrahigh solar reflectance (97.5%), high infrared emissivity (0.93), as well as excellent anti-weather function can be achieved, exceeding the performance of most reported cellulosic aerogels. Furthermore, the mechanisms of the improved mechanical strength and stimulated superior solar reflectance of NCA were studied in detail using finite element simulations and COMSOL Multiphysics. As a result, the NCA can achieve a cooling efficiency of 7.5 °C during the daytime. The building energy stimulus demonstrated that 44% of cooling energy can be saved in China annually if the NCA is applied. This work lays the foundation for the preparation of biomass aerogels for energy-saving applications.

Влияние длительного естественного старения теплоизоляционных минераловатных материалов на физико-химические и термические превращения

Purpose. The article studies physico-chemical and thermal transformations of mineral wool thermal insulation of natural ageing. The subject of the study is thermal insulation materials of natural ageing, and the object of the study is their physicochemical and thermal characteristics. The aim of the work is to establish physicochemical and thermal transformations of mineral thermal insulation of natural ageing. The research is aimed at identifying features of physico-chemical and thermal transformations of thermal insulation based on mineral fibers and organic binders in the ageing process. Methods. A set of precision physicochemical methods such as X-ray phase analysis (XRF), infrared spectroscopy and thermal analysis methods (TG, DTG, DSC) was used. Findings. The results of studying mineral thermal insulation (service life of 60 years) revealed characteristic changes in the structure of the material. The XRF method established that the ageing process of mineral wool materials is caused by occurring microdefects and disruption of material fibers structure organization. Changes in thermal insulation phase state have thermal fluctuation of kinetic nature of material mechanical destruction. The IR spectroscopy method identified changes in the areas of characteristic absorption bands: 2 800–2 200, 2 000–1 600 and 1 295–1 005 cm–1 caused by chemical destruction of organic binder in mineral thermal insulation. The nature of thermal transformations of the material was established, a tendency towards a decrease in the threshold temperatures for mass loss start due to destructing polymer binder was revealed. It is noted that natural ageing may result in loss of fire resistance of thermal insulation systems, as well as in intensificating smoldering combustion of thermal insulation. Research application field. The results are of interest to builders, designers, fire safety engineers and can be used in regulatory and technical as well as in reference literature on fire safety. Conclusions. During the ageing process irreversible physical and chemical changes occur in the structure of thermal insulation, leading to loss of thermal stability of the material and to a possible increase in the intensity of latent smoldering combustion. Technical obsolescence of the material leads to decreasing fire resistance limits of various thermal insulation systems due to loss of thermal insulation capacity and integrity.

Moisture Performance Requirements for Insulation in Exterior Wood-Frame Walls without a Vapour Barrier

An increased interest has been observed, especially among architects, in constructing the building envelope without using a vapour barrier membrane of polyethene (PE) foil. An increasing interest in biogenic building materials has also been expressed, as their use, besides storing embedded carbon, can reduce greenhouse gas emissions, replacing nonrenewable building components. Further, building envelope construction without a vapour barrier reduces expenses and the difficulty of the work process, especially around joints and penetrations. This study aims to determine the most important material properties of biogenic thermal insulation materials that influence the moisture-robustness of exterior wood-frame walls constructed without a vapour barrier. A literature study was performed to examine which material parameters have the most influence on the moisture conditions in an exterior wall without a vapour barrier. Hygrothermal simulations of lightweight exterior walls were performed to investigate the significance of variations in material properties (e.g., equilibrium moisture content and vapour diffusion resistance) and determine their necessary characteristics when used as thermal insulation material in an exterior wall without a vapour barrier in internal humidity class 3 (defined in EN ISO 13788). The moisture-robustness of the construction is assessed based on the risk of mould growth in the layer between the thermal insulation and wind barrier. The study suggests that the moisture capacity of the available common biogenic thermal insulation materials does not significantly affect the overall moisture performance of the wall. Simulations demonstrate that, for the thermal insulation layer in internal humidity class 3, at least one of the following requirements must be met to ensure moisture-robustness in exterior walls without a vapour barrier: (I) high diffusion resistance of the thermal insulation and (II) high moisture capacity of the thermal insulation material at relative humidity between 60% and 90%. Commercial biogenic thermal insulation materials on the market do not meet the latter requirement.

Is bedding material a more effective thermal insulator than trap cover for small mammal trapping? A field experiment

Live trapping is a key technique for conducting ecological studies on small mammals. All-metal live traps are popular in monitoring schemes owing to their tested performance, lightweight design (aluminium) and foldability. However, capture represents a stressful situation for small mammals, particularly during cold seasons, when individuals are susceptible to cold weather starvation resulting from low temperature and insufficient food to maintain body temperature. Metal live traps provide limited protection against cold temperatures, and it is often recommended to use covers to buffer external temperature fluctuations and prevent entry of moisture. Here, we compared the insulative performance of a PVC cover designed for Sherman traps and of bedding material, using data loggers to record temperature and humidity inside traps. We conducted different experiments simulating field conditions (traps at night with a heat source inside) and different treatments (cover, bedding material) to test the thermal insulation capacity of three models of widely used commercial traps: Longworth, Sherman, and Heslinga. Our findings indicated that Longworth and Sherman traps were better insulated against ambient air temperature fluctuations than Heslinga traps (+2.0 °C warmer on average). Bedding material was paramount in reducing relative humidity and increasing thermal insulation capacity of traps (+3.1 °C), an effect that was strengthened when a PVC cover was additionally used (+4.2 °C). The covered traps prevented the direct entrance of rain and dew (reducing damp bedding), provided camouflage (reducing thefts), and improved thermal and humidity conditions of traps (potentially increasing survival of captive small mammals). Our results suggest that using covers and bedding materials can improve thermal and humidity conditions within live traps, thus reducing the metabolic costs of thermoregulation and increasing survival chances for trapped small mammals during cold seasons.