Hot Box Method Research Articles

3D printing for energy optimization of building envelope – Experimental results

The building sector is a major contributor to the world's energy consumption, exhibiting an ever-increasing trend. Heat losses through the building envelope constitute the most significant factor. Furthermore, the construction process has seen limited technological advancements in recent years, remaining heavily reliant on manual labor. Additive manufacturing emerges as a promising approach, with applications in the building sector on the rise. However, research on the thermal performance of 3D-printed components remains limited. Despite its recent introduction in the construction industry, 3D printing has yet to attain a level of maturity commensurate with other established methods.This paper aims to reduce this gap by analyzing 3D-printed blocks from a heat transfer perspective. The article introduces two key innovations. Firstly, it explores the design of various internal geometries and air gaps aimed at minimizing heat flux exchange between block surfaces. Secondly, it presents an experimental study conducted with a custom-designed setup tailored for testing 3D printed blocks. The blocks are constructed using recyclable plastic material and feature different internal geometries based on hexagonal cells. While the plan size of the cells remains consistent, their vertical structures vary as follows: 1) Block 1: Hexagonal air cavities without horizontal partitions. 2) Block 2: Hexagonal air cavities with three horizontal partitions, dividing the cells vertically into four parts. 3) Block 3: Honeycomb structure characterized by three horizontal partitions and staggering along the vertical axis.Their performance was experimentally evaluated using the Hot Box method, heat flow meter sensors, and infrared thermography. The results demonstrated reductions of up to 11.5 % in terms of thermal transmittance (U-value) with the inclusion of horizontal partitions. Starting from a U-value of 1.22 ± 0.04 W/m2K (Block 1), a transmittance of 1.08 ± 0.04 W/m2K was achieved for the honeycomb structure with horizontal partitions (Block 3).

Promising biomass waste–derived insulation materials for application in construction and buildings

AbstractCurrent insulation materials applied in construction engineering and the building industry are generally petrochemical-based polymers and recycled thermal insulation materials. The environmental effects of these materials’ production processes are substantial, despite their high thermal insulation performance. Consequently, the researchers conclude that it is essential to develop and produce insulating materials with superior thermal properties, minimal environmental impact, and a reasonable cost. The study concentrated on the application of insulation materials derived from biomass in the development of thermal insulation. The purpose of this review is to investigate and develop the possibilities of using biomass wastes as renewable and eco-friendly thermal insulation materials for construction engineering and the building industry. The thermal conductivity of those materials was measured using the hot plate and hot box methods, two of the most widely used hot processing methods. With a relatively low thermal conductivity (< 0.100 W·m−1·K−1), this review provides critical scientific insight into potential building insulation materials derived from biodegradable and abundant resources. It was observed that these materials are appealing for use in building and construction because they have a number of potential advantages from technical, economic, environmental, and green credentials perspectives. The collection of information enables some conclusions regarding the different biomass waste–derived insulation materials that have already been investigated and identifies gaps in the literature. Finally, the scope of commercialization pathways and future research directions to validate the proposed material alternatives’ claim for commercial-scale applications has been identified in this review. Graphical Abstract

Research on Thermal and Heat Insulation Properties of Aerogel Heat-Insulating Reflective Coatings

This study aims to investigate the heat and thermal insulation mechanisms of aerogel heat-insulating reflective coatings. Two working conditions, the hot box method and the open environment at the hot end, were simulated using a gypsum board as the substrate. We conducted thermal tests on blank panels, composite panels with aerogel heat-insulating reflective coatings, and XPS-insulated composite panels for two operating conditions. And the thermal insulation power calculation was carried out for the reflective and barrier materials. The test results show that the air temperature differences between the hot and cold ends of the blank, aerogel coating, and XPS boards under the hot box method were 28.8 °C, 38.2 °C, and 55.2 °C, respectively, and that the air temperature differences between the cold ends of the coating and XPS panels under the natural environment heating condition were 24.2 °C and 24 °C, respectively. Theoretical calculations show that the aerogel heat-insulating reflective coatings produce a net radiative cooling power of 145.9 W/m² when the surface of the specimen is at the same temperature as the ambient temperature. The heat flux powers of the aerogel coating board and XPS panel were 9.55 W/m² and 1.65 W/m² when the temperature difference between the two surfaces on both sides of the specimen was 10 °C, respectively.

A new method for measuring thermal resistance of building walls and analyses of influencing factors

The thermal resistance of the building wall is one of the most important parameters of thermal performance, it will impact the building energy consumption and indoor thermal comfort directly and greatly. The present methods for thermal resistance measurement of building walls are mainly derived from the heat flow meter method and the hot box method, which require a rigorous measurement environment and tedious measurement steps. In this paper, a new method to measure the thermal resistance of the building walls based on the analytical solution was proposed. Firstly, a board was placed on the interior surface of a wall, and an analytical solution of the heat transfer process in the building wall along with the board was obtained. Then the temperature of the interface between the wall and the board was measured. Finally, the thermal resistance of the wall could be calculated based on the analytical solution and the measured temperature values. The new method was also verified in this research. It was found that no matter the single-layer or the multi-layer walls, the relative errors were all less than 10%. When the thermal resistance of the building wall is low, a board with low thermal conductivity such as fiberboard could be used. When the thermal resistance of the building wall is high, the flat glass is a good choice. The temperature values of the interface at the moments of 70 h and 75 h are suitable to calculate the thermal resistance of the building wall.

In Situ Thermal Transmittance Assessment of the Building Envelope: Practical Advice and Outlooks for Standard and Innovative Procedures

Different standard methods for the assessment of the thermal performance of the building envelope are used: analogy with coeval building, theoretical method, heat flow meter measurement, simple hot box, infrared thermography, and thermometric method. Review papers on these methods, applied in situ and in laboratory, have been published, focusing on theory, equipment, metrological performance, test conditions and data acquisition, data analysis, benefits, and limitations. However, steps forward have been done and not been deepened in previous works: in fact, the representative points method and the weighted area method have been proposed, too, whilst artificial intelligence and data-driven methods have begun to prove the reliability also in the U-value prevision using available datasets. Considering this context, this work aims at updating the literature background considering exclusively in situ methods. The work starts from bibliometric and scientometric analysis not previously conducted: this helped to group the methods and to sketch the innovations and the future perspectives. Indeed, from the bibliometric and scientometric literature analysis what emerged was (i) the richness of the background on this topic, especially in the recent years, (ii) two macro-groups (methods with and without measurements), and (iii) the importance of paper keywords (otherwise, interesting papers are eluded by the output of simple database queries). The method study that followed aims at providing (i) a broader view of the thermal transmittance (U-value) assessment procedures, including the utmost recent applications, proposal, and outlooks in this field, (ii) the understanding on the fundamental theories of the techniques, (iii) practical advice for building-envelope assessment, focusing on the advantages and limitations useful for professionals and researchers involved in the energy audit, conservation, or refurbishment of building stock, (iv) the identification of the interconnection between the techniques that often rely on one another, and (v) final remarks and future perspective of the procedures, which embrace the use of artificial intelligence (AI). From the topic analysis, as a result, it emerged that this is an open field for future research, especially with the implementation of AI, which requires good datasets and trials on the models’ architectures, in terms of input layer, number of hidden layer and neurons, and percentage of data to be employed for model training and testing.

Thermal performance characterization of supply-air double windows: A new guarded hot box protocol and numerical modelization

The window area constitutes a significant part of the façades of heritage buildings in French cities. An effective way to improve window performance as well as preserve the appearance of heritage buildings is to retrofit old single-glazed windows into supply-air double windows by putting a secondary window inside the existing window. For window renovation, the U-value is an important indicator. To accurately identify the U-values (i.e., the Ueq value, Uuse value and Uloss value) of supply-air double windows, a new guarded hot box (GHB) method was firstly proposed which improved the GHB setup and calibration/testing procedure. Based on GHB experiments, the thermal performance of different window configurations was identified and compared. The results showed that U-value reductions were in the range of 59.2%-80.8% by renovating a single-glazed window into a supply-air double window. Moreover, the window U-value was compared to the center-of-glass U-value, which is often used in building codes to simulate building energy consumptions. It was found that the deviations between the window U-value and the center-of-glass U-value were in the range of 21.6%-45.5% for different window configurations. The GHB experimental data were further utilized to validate a three-dimensional computational fluid dynamic (CFD) model. Based on the validated model, a parametric study was performed to investigate the impacts of different window configuration parameters on U-values. The results showed that the location of Low-E coating, coating emissivity and air flow rate had significant effects on U-values. In addition, it was found that improving the thermal conductivity performance of the internal window frame was more important than the external window frame.

Review of the Experimental Methods for Evaluation of Windows’ Thermal Transmittance: From Standardized Tests to New Possibilities

One of the most important parameters that indicate the energy performance of a window system is the thermal transmittance (U-value). Many research studies that deal with numerical methods of determining a window’s U-value have been carried out. However, the possible assumptions and simplifications associated with numerical methods and simulation tools could increase the risk of under- or over-estimation of the U-value. For this reason, several experimental methods for investigating the U-value of windows have been developed to be used either alone or as a supplementary method for validation purposes. This review aims to analyze the main experimental methods for assessing the U-value of windows that have been published by national and international standards or as scientific papers. The analysis criteria include the type of the test in terms of boundary conditions (laboratory or in situ), the part of the window that was tested (only the center of glazing or the entire window), and the data analysis method (steady-state or dynamic). The experimental methods include the heat flow meter (HFM) method, guarded hot plate (GHP) method, hot box (HB) method, infrared thermography (IRT) method, and the so-called rapid U-value metering method. This review has been set out to give insights into the procedure, the necessary equipment units, the required length of time, the accuracy, the advantages and disadvantages, new possibilities, and the gaps associated with each method. In the end, it describes a set of challenges that are designed to provide more comprehensive, realistic, and reliable tests.

Thermal Performance of Slotted Light Steel-Framed Composite Wall

In this study, calibrated hot box and finite element simulation methods were used to study the influence of a slotted web on the thermal performance of a lightweight steel stud composite wall. By comparing the results from the simulations and experiments, the accuracy of the finite element method was verified; this method was then used for parameter analyses. The results showed that the wall’s thermal transfer coefficient is inversely proportional to increases in the length of the slot and height of the stud web, leading to improvements in the thermal insulation effect; vice versa, the wall thermal transfer coefficient increases when the slot transverse spacing and stud thickness increase, and the insulation effect correspondingly worsens. The stud spacing influences the insulation performance of the wall by changing the proportion of studs within a certain wall. The greater the proportion of studs, the greater the stud thermal bridging, the faster the thermal loss, and the worse the insulation effect of the wall. In practice, the height of the stud web can be set as required. Preferably, for practical applications, the number of rows of slots is 5–7, the length of the slots is 70–80 mm, the transverse distance of the slots is 6–8 mm, the thickness of each stud is 1 or 1.2 mm, and the distance of each stud is 600 mm.

Thermophysical Properties of Sawdust and Coconut Coir Dust Incorporated Unfired Clay Blocks

Sawdust and coconut coir dust are agro-wastes/by-products which are suitable for use as raw materials to manufacture unfired clay blocks due to their excellent physical and mechanical properties. A limited number of studies have been conducted on the utilisation of these agro-wastes in clay block production, and they have mostly been devoted to investigating the physicomechanical properties, with less attention given to the thermal properties. Moreover, the majority of the studies have used chemical binders (cement and lime) in combination with agro-waste, thus increasing the carbon footprint and embodied energy of the samples. Furthermore, no research has been performed on the thermal performance of these agro-wastes when incorporated into clay blocks at the wall scale. Therefore, to address these limitations, the present study developed unfired clay blocks incorporating sawdust and coconut coir dust (0, 2.5, 5, and 7.5% by weight), without the use of chemical binders, and evaluated their thermal performance, both at the individual and wall scales. The experiments were divided into two phases. In the first phase, individual sample blocks was tested for basic thermal properties. Based on the results of the first phase, small walls with dimensions of 310 mm × 215 mm × 100 mm were built in the second phase, using the best performing mixture from each waste type, and these were assessed for thermal performance using an adapted hot box method. The thermal performance of the walls was evaluated by measuring the heat transfer rate from hot to cold environments and comparing the results to the reference wall. The results showed that thermal conductivity decreased from 0.36 W/mK for the reference sample, to 0.19 W/mK for the 7.5% coconut coir dust sample, and 0.21 W/mK for the 7.5% sawdust sample, indicating an improvement in thermal insulation. Furthermore, the coconut coir dust and sawdust sample walls showed a thermal resistance improvement of around 48% and 35%, respectively, over the reference sample wall. Consequently, the findings of this study will provide additional essential information that will help in assessing the prospective applications of sawdust and coconut coir dust as the insulating material for manufacturing unfired clay blocks.

Multi-cell, triple pane, vacuum insulated glazing

A novel Triple Pane Vacuum Insulated Glazing (TPVIG) architecture consisting of three panes of glass separated by two offset grids is described. The grids are made of frit-coated fibers fused with the glass panes in a vacuum to create many independent hermetic cells. Unlike traditional VIGs, which are separated by support pillars, these cells significantly increase the redundancy in sealing, and the additional bonds formed by the grid lines reduce the stresses on the edge bonds thereby increasing VIG reliability. A numerical thermal analysis was conducted to determine the thermal performance of the VIG and suggested U-values below 0.5 W/m2-K (greater than R = 11.4 hr-ft2-°F/Btu) can be obtained. A prototype of the VIG unit consisting of three glass panes (5.7 mm, 1.1 mm and 5.7 mm thick with low-e coating on two surfaces) was fabricated and tested for thermal performance using the hot box method. The experimental center of glass U-value for the VIG was found to be 0.42 W/m2K (R = 13.2 hr-ft2-°F/Btu). This U-value is about four times lower than a typical Argon filled double pane window.

Thermal insulation potential of wood-cereal straws/plaster composite

Nowadays, it is important, even necessary, to develop building materials from renewable resources. In this context, the use of low-cost natural fibers in the manufacture and reinforcement of materials is of great interest from an economic and environmental point of view. Present paper investigated the use of plaster loaded with two untreated plant fibers, Wood Fiber (WF) and cereal Straw Fiber (SF), in order to use them in thermal insulation applications of buildings. Composite materials based on Wood Fiber Plaster (WFP), Straw Fiber Plaster (SFP) and Wood-cereal Straw plaster (WSFP) were prepared with varying densities (0 %; 5 %; 10 %; 15 %; 20 % by volume). Their thermo-physical characteristics were characterized from the chemical structure (FTIR), crystallinity (XRD), thermal conductivity (Hot Box Method), thermal diffusivity (Flash Method) and the water uptake (ASTM D570) point of views. Two linear correlations concerning thermal conductivity and thermal diffusivity of WSFP, WFP and SFP samples have been established. Results show that the incorporation of wood fibers and cereal straw fibers reduce the thermal conductivity as well as thermal capacity, effusivity and the weight of composite materials. The comparison between other composite materials show that proposed composite is good competitor vs. materials used in insulation.

How Do Temperature Differences and Stable Thermal Conditions Affect the Heat Flux Meter (HFM) Measurements of Walls? Laboratory Experimental Analysis

In recent years, experimental tests related to building components through laboratory facilities have relatively matured. The techniques are based on one-dimensional heat transfer by creating a permanent temperature difference over a specimen to control heat fluxes. The three main methods are the Guarded Hot Box (GHB) method, the Calibrated Hot Box (CHB) method, and the Heat-Flow Meter method (HFM). The HFM method is the most widely applied technique for measuring on-site U-values of building components and several scientific works stressed the need for high temperature differences between the environments, suggesting 10 °C or 15 °C. However, temperature stability and high temperature gradients are difficult to obtain, especially for Mediterranean climatic conditions. Starting from this, an experimental study was conducted through a GHB apparatus, setting temperature differences from 2 °C to 20 °C between the hot and cold chambers. Heat flow measurements were performed to compute the thermal conductance of a specimen characterized by a known stratigraphy, thus highlighting the effect of the low thermal gradient on data acquired by the heat flow sensor. It was found that, even for low temperature differences (2 °C) maintained by ensuring stable thermal conditions, the experimental results are comparable with those obtained for higher and usual temperature differences (20 °C).

Thermal characterization of soil-cement bricks using mining tailings

Soil-cement bricks are earth construction materials that have been gaining prominence due to their environmental advantages. The Brazilian Technical Standard NBR 8491 establishes physical and mechanical procedures to characterize these bricks. However, the thermal characterization is an important assessment, since it is related to the building’s thermal performance. The objective of this study is to thermally characterize a panel of soil-cement bricks produced with mining tailings. For such, its absorptance (α) was evaluated using the ALTA II spectrometer, and its thermal transmittance (U) and thermal resistance (RT) through the hot box method (ISO 9869). The results enabled the calculation of the thermal capacity (CT), thermal lag (φ) and solar factor (FSO) of the panel, which were compared to the Brazilian Technical Standards NBR 15575-4 and NBR 15220 for Bioclimatic Zone 8. As a result, the soil-cement body panel showed values of α = 0.71, U = 2.47 Wm-2K-1, CT = 273.4 kJm-2K-1, φ = 6.02 h and FSO = 6.81%, meeting the requirements established in the first standard, but failing to attend the second. To comply with the Brazilians specifications, it is suggested to paint bricks with lighter colors focusing on decreasing its absorptance value. Thus, soil-cement bricks may be an environmental alternative to dispose of the waste generated during the mining process, contributing to sustainability.

Measuring the effective thermal resistance of ventilated air-spaces behind common wall assemblies: theoretical uncertainty analysis and recommendations for the hot box method modifications (ASHRAE 1759-RP)

A well-designed ventilated wall that incorporates air-space behind cladding can reduce energy use for conditioning buildings by adding a thermally resistive layer. The scarcity of thermal performance data and standardized test methods is a particular barrier for practitioners to implement ventilated air gaps behind the facades. The current standardized test method to evaluate the thermal performance of a wall structure, such as ASTM 1363-19, does not consider the effect of the ventilated air-space behind external claddings. Therefore, testing and design recommendations are required to account for the impact of ventilation airflow on the thermal resistance of vertical air-spaces behind common cladding materials. In this study, the theoretical uncertainty analysis of the effective thermal resistance of the ventilated cavity is performed for a steady-state condition. The results revealed that temperature sensors with an absolute uncertainty of ±0.18 (±0.1 °C) and heat flux sensors with a relative uncertainty of 3% or lower are required to capture a wide range of the effective thermal resistance of the ventilated air gap. Thereafter, based on the uncertainty of temperature and heat flux measurements, the modifications of the ASTM C1363-19 test method to account for the airflow effects on the thermal performance of the wall assembly are proposed. A detailed description of the experimental setup is provided, and protocols for collecting, analyzing, and evaluating data are suggested. An example demonstrating how the proposed method can be practically used to measure the thermal resistance of a ventilated air-space is also presented.

Thermal Resistance of Insulated Precast Concrete Sandwich Panels

Many nations are already working toward full implementation of energy efficiency in buildings known as Green Building. In line with this perspective, this paper aims to develop a thermally efficient precast concrete sandwich panels (PCSP) for structural applications. Therefore, an experimental investigation was carried out to determine the thermal resistance of the proposed PCSP using Hotbox method and the results were validated using finite element method (FEM) in COMSOL Multiphysics Software. The PCSP were designed with staggered shear connectors to avoid thermal bridges between the successive layers. The staggered connectors are spaced at 200 mm, 300 mm and 400 mm on each concrete layer, while the control panel is designed with 200 mm direct shear connection. In the experimental test, four (4) panels of 500 mm × 500 mm and 150 mm thick were subjected to Hotbox Test to determine the thermal resistance. The result shows that thermal resistance of the PCSP with staggered shear connection increases with increase in spacing. The PCSP with 400 mm staggered shear connectors indicates the best thermal efficiency with a thermal resistance (R value) of 2.48 m2K/W. The thermal performance was verified by FEA which shows less than 5% error coupled with a precise prediction of surface temperature gradient. This indicates that, with conventional materials, thermal path approach can be used to develop a precast concrete building with better thermal resistant properties. Hopefully, stakeholders in the green building industry would find this proposed PCSP as an alternative energy efficient load bearing panel towards sustainable and greener buildings.

Experimental Investigation of Thermal Conductivity from Insulation Based on Rice Hulks: Guarded and Calibrated Hot Box Method

In developing countries, large quantities of agricultural residues associated with harvests are generated, given that agriculture is one of the most important economic activities. The valorization of these residues for the construction sector could contribute to the improvement of energy efficiency in buildings. Through passive techniques, the construction of insulating thermal-acoustics panels, blocks, and aggregate for reinforced concrete can improve the energy efficiency. In this study, an experiment was performed to measure thermal conductivity of the Agricultural-Thermal Insulation Panel (ATIP) based on rice hulks. These Agricultural-Thermal Insulation Panels were elaborated follow a standard process to compaction of the rice hulks to be employed as insulation material with a panel dimension of 200x200x34.5(mm3). A “Hot Box” configuration was used to obtain the thermal conductivity of the panels, using different temperature gradients between hot and cold chambers.

Numerical and experimental investigation of heat transfer across semi-transparent horizontal screen layers

Estimating the total heat flux passing through layers of materials is commonly used to determine the performance and potential of thermal isolation for general building design. The thermal properties of building glazing have been studied theoretically and experimentally for several decade. In this study, an enhanced algorithm for calculating the heat transfer through semi-transparent screens was developed and validated via published data and in-site experiments in order to analyze thermal properties of different screen materials and their combinations under more realistic conditions. The proposed algorithm allows to simplify the linearization of a nonlinear system, which is solved by inverting a tridiagonal matrix. Overall heat transfer coefficients (U-values) for single and multiple thin-screens were calculated numerically and measured using the hot-box method. The building insulating materials such as glass, polymers, aluminium films, and selected commercial thermal screens were examined. The cross-validated results indicated good agreement between calculated, measured and previously published results demonstrating the abilities of the method to predict new data for materials and their combinations that have not yet been estimated. Moreover, the algorithm allows to adopt the experimentally validated results to real ambient conditions by applying relevant scaling methods. The following results demonstrate the insulation properties of various commercial thermal screens. It is found that U-values reduce by 30% and 15% for the combination of a glass screen with an additional layer of a transparent infra-red (IR) radiation absorbing screen and a polyethylene screen, respectively. In comparison, the contributions of an additional screen containing aluminium foil strips could reduce the U-value by about 80% and 70% for polyethylene and glass cover screen, respectively. It was confirmed that low-emissivity materials have a more significant effect on reducing the U-value than insulating materials with IR-absorbing properties. The approach is valid for investigating the performance of thermal insulation in different enclosures, glazing in buildings, or moveable thermal screens in greenhouses.

Determination of the impact of environmental temperature on the thermal conductivity of polyisocyanurate (PIR) foam products

Polyisocyanurate (PIR) foam is a thermal insulation material increasingly used in construction and industry, with significantly lower thermal conductivity than others due to its fine structure and low conductivity blowing gases. The results of previous studies have shown that the thermal conductivity of PIR can increase due to exchange of the blowing gas with environmental gases during the operation, and when the material enters low temperature environments, where blowing gas condensation occurs. However, the conditions contributing to thermal conductivity increase of PIR haven't been sufficiently investigated, therefore detailed studies of thermal properties of PIR products were performed. Aging procedures with differently prepared PIR samples were performed in a climatic chamber, the thermal conductivities were measured by the heat flow meter and by Hot-box methods. The largest increase in thermal conductivity (up to 15%) was determined for samples stored at high temperatures (up to +70 °C), the changes in thermal conductivity are smaller for samples with diffusion-tight facings and higher - for thin and cut from the core of product samples. The aging at negative temperature has no effect on the thermal conductivity, however, the thermal conductivity of material at a mean -20 °C temperature increased by up to 20% compared to standard thermal conductivity. It was noticed that determined changes for the tested material are significantly smaller than those described in previous studies, so the results of this study will contribute to a wider use of PIR products and more accurate assessment of the energy performance of buildings.

Effect of Iron (III) Oxide Powder on Thermal Conductivity and Diffusivity of Lime Mortar.

One of the challenges in construction is the improvement of energy efficiency of buildings. Development of construction materials of low thermal conductivity is a straightforward way to improve heat isolating capability of an enclosure. Lime mortar has a number of advantageous and peculiar properties and was widely used until the “irruption” of Portland cement. Currently, lime mortar is still used in restoration of traditional buildings or, according to the urban regulations, in catalogued constructions. The goal of the present study is the improvement of the heat isolating capability of lime mortars. The strategy of this work is the addition of iron (III) oxide powder, which is one of the possible components forming the cements, to a base lime mortar. The reason to choose Fe2O3 was two-fold. The first reason is low thermal conductivity of Fe2O3 compared to lime mortar. The second reason is that the low solubility and small size of iron (III) oxide particles have an effect on the thermal conductivity across the lime particles. The effect of iron (III) oxide powder on the thermal conductivity has been experimentally determined by the hot-box method. It has been found that the insulating capacity and thermal inertia of lime mortar is improved significantly by the addition of Fe2O3 powder, increasing the energy saving of the enclosure.

Comparison of thermal insulation performance of vacuum insulation panels with EPS protection layers measured with different methods

For reducing the energy use of buildings, the application of insulation materials can be a possible solution to improve energy efficiency. However, with the continuously tightening regulations, thicker and thicker insulations should be used (e.g., up to 20–25 cm in Hungary and about 40–50 cm in the Nordic countries) to fulfil the directives. In the past decades, developmental research started to focus on both decreasing the thickness and decreasing the thermal conductivity of materials parallels. With this research direction, the investigations of the new type of insulation materials took place. The use of materials having thermal conductivity with less than 0.020 W/mK spread over. These materials are the so-called super insulation materials. Besides Vacuum Insulation Panels (VIPs), aerogel-based materials belong to this group, too. This paper will present laboratory tests executed on two altered types of protected Vacuum Insulation Panels: a one side and a 2 side protected VIP, also called Vacuum Insulation Sandwich (VIS). The first one, type “A” contains 20 mm thick laminated fumed silica, covered with 10 mm thick expanded polystyrene on one side, while type “B” was the one where the 10 mm thick laminated fumed silica core was packed between two 10 mm thick EPS slabs. Firstly, thermal insulation performance was investigated by the so-called guarded hot-box method for U-value, where the samples were placed on a solid brick wall. Furthermore, the thermal insulation performance of protected VIPs was also tested with Hukseflux heat flux plates. To reveal the applicability limits caused by the thermal bridges infrared thermography images (IR) were taken, too. From the images and the measurement results, a theory was formed regarding the heat flow directions inside the encapsulated panels. The current article emphasizes the equivalent thermal conductivity for the assessment of the thermal protection performance of vacuum insulation panels. The paper states that by using VIPs at least, 70% reduction can be reached in the U-value compared to the value of the solid brick wall. Moreover, the paper points out that the use of EPS protection layer on both sides of the VIP has a promising effect by reducing the thermal bridges. Furthermore, the VIP protected with EPS slabs on both sides results in less equivalent thermal conductivity.