Transparent Insulation Materials Research Articles

Preparation of BN@SiO2 nanofiber ceramic aerogel with ultralight, wave-transparent and heat-insulating for microwave sintering furnace

Thermal insulation devices play an extremely important role in enhancing microwave heating efficiency. However, existing wave-transparent insulation materials often exhibit high heat storage, low microwave transmittance at high temperatures, and poor oxidation and thermal shock resistance, hindering high-temperature applications for microwave sintering. To address this issue, we developed an ultralight and wave-transparent BN@SiO2 aerogel, which was fabricated through the in situ growth of SiO2 on the surfaces of BN fibers. The resulting composite aerogel demonstrated excellent high-temperature oxidation resistance and an impressively low density of 0.07g/cm3. Furthermore, the dielectric constant of the BN@SiO2 aerogel ranged from 2.58 to 2.80, and its dielectric loss tangent was as low as 5.13×10−3–7.98×10−3 within the 2–10 GHz frequency range. The successful synthesis of BN@SiO2 aerogel provides new progress and research ideas for the development of wave transparent and thermal insulation materials

Performance Assessment of Novel Transparent Insulation Materials for Integrated Storage Collectors

Transparent insulation structures play a pivotal role in harnessing solar energy efficiently, akin to the greenhouse effect in the atmosphere. This study undertakes a systematic evaluation of a novel sorbitol- or bio-based polycarbonate (bio-PC) for thermal insulation (TI) structures and hot water collector systems. Employing optical and mechanical methods, the bio-PC was comprehensively characterized on the polymer film level. Subsequently, the technical and ecological performance of these structures in various hot water collectors and systems was rigorously modelled and simulated. Results indicated that the novel bio-PC exhibited superior properties compared to conventional materials like cellulose acetate or fossil-based PC, showcasing promising prospects for widespread adoption. Drawing parallels to the greenhouse effect of CO2, the functional principle of transparent insulation structures is rooted in high solar transmittance and infrared absorbance, primarily governed by carbon-oxygen bonds. While fossil-fuel based transparent insulation materials have been prevalent, they suffer from drawbacks such as average infrared absorbance and susceptibility to yellowing. In contrast, the newly introduced bottom-up biopolymer bio-PC, derived from sorbitol derivatives, offers a compelling alternative. The study sheds light on the potentials and limitations of bio-PC for transparent insulation structures in integrated storage or flat plate collectors, aiming to mitigate environmental impacts associated with traditional materials. Future research directions emphasize refining modelling tools and addressing input data deficiencies, particularly for life cycle analysis. Concurrently, efforts are directed towards enhancing simulation accuracy and reliability through concurrent measurements of collector systems equipped with bio-PC-based transparent insulation. This research underscores the critical role of innovative materials in advancing sustainable energy solutions, with bio-PC emerging as a promising candidate in the realm of transparent insulation technology.

Thermal Performance Evaluation of TIM Combined with Residential Windows in Different Climatic Regions in Iran

Windows play a significant role in the increase and loss of heat from the building envelope and determine the quantity, quality, and distribution of daylight. A strategy that involves incorporating transparent insulating materials into a double-glazed window offers the potential to provide combined improvements in thermal and daylighting performance. The thermal properties of transparent insulation materials in windows depend on various factors, such as the type of insulation material, thickness, geometry and insulation structure, location, and orientation of the window, among others. The aim of this research is to optimize three criteria: "thickness," "location of transparent insulation relative to window layers," and "direction of the wall with transparent insulation of the building window." The goal is to minimize thermal loads and reduce energy consumption in residential buildings. To achieve this, a real model was selected, and Design Builder software was used to measure the "heating load," "cooling load," and the sum of these two loads as the "total thermal load" for all three criteria in three cities of Iran with different climates: Tehran (moderate climate), Ahvaz (warm climate), and Tabriz (cold climate). The results of the research showed that for the city of Tehran, 3-inch insulation in the middle of the double-glazed window and the south front is optimal. For the city of Tabriz, 5-inch insulation on the inner surface of the window and the western front is optimal. And for the city of Ahvaz, 3-inch insulation on the outer surface of the window and the eastern front is optimal. It is worth noting that the annual heating load and total annual heating load for all three criteria have the highest values in Tabriz city. Therefore, it is recommended to use HSNPS insulation in transparent windows to reduce energy consumption in Tabriz (cold climate).

A new high-performance flat plate solar collector. Numerical modelling and experimental validation

A new concept of flat plate solar collector (FPC) has been numerically studied for optimization purposes from an energetic and exergetic points of view. The highly efficient results have been achieved by adding transparent insulation materials (TIM) made of plastic and aerogel-silica in the cover. The optimum solution has been prototyped and successfully tested. The numerical simulation and the corresponding analysis are performed with a previously developed numerical simulation tool based on an in-house software platform (NEST). An optimization design has been done using this numerical simulation tool objected to higher performance at the (Tin−Tamb)/Ġ>0.074 range, and a new prototype is fabricated with low-cost materials found in the workshop. The final results are compared with previous prototypes that could collect between 2.5 and 1.4 times higher than standard collectors in summer and autumn, respectively. The new prototype has higher performance at (Tin−Tamb)/Ġ>0.074, which makes it competitive in a high-temperature range. Moreover, with the new layer of aerogel-silica, additional protection against overheating is achieved, as the temperatures of the plastic TIM are limited. The new prototype has higher energetic and exergetic efficiency at high-temperature areas, and the inlet temperature at optimized working conditions is higher than the previous prototype. Finally, the energy efficiency at (Tin−Tamb)/Ġ=0.08 could reach 55% and exergetic efficiency 8%. The manufacturing cost of the FPC prototype with TIM and aerogel-silica is about 160 euros per m2.

Thermal analysis on a novel natural convection flat plate collector with perforated tilted transparent insulation material parallel slats (TIM-PS) in Mediterranean climate

The purpose of this research is the evaluation of heat transfer by natural convection in an innovative flat plate solar collector operating in natural convection mode. The design consists of inclined, perforated slats of transparent insulation material installed between the absorber and the glass cover. Hourly climatic data on the four specific days of solstices and equinoxes was used to investigate the behavior of the novel collector design in the city of Monastir; Tunisia. A comprehensive process, ANSYS FLUENT, was implemented to properly evaluate the thermal performance of the collector. In order to obtain accurate thermal properties of the smart collector façade unit containing the TIM-PS to exploit in the simulation, a validated three-dimensional finite volume model developed using the CFD software was used to solve the conductive, convective and radiative heat transfer properties of the system. We have explored in depth the effect of optical characteristics of the TIM-PS on the collector performance. Present research focuses on the analysis of thermal efficiency profile of flat plate collector with innovative façade in comparison with conventional collector for different climatic conditions. The analysis indicated that innovative façade collector’s efficiency is highly influenced by solar intensity. It was found that TIM-PS façade can effectively reduce the convective heat losses through the front of collector. The simulation results show that perforated tilted TIM-PS offer better performance than conventional façade of collector during all the seasons of the year. Simulations performed for one year predict that with careful selection of the parallel slats properties, the new façade system can generate an efficiency up to 83% in June, 76% in September, 53% in March and 42% in December. The results of the thermal evaluation of this research will help guide the future development of this system, as we have demonstrated that the innovative façade collector can be used all year round. In conclusion, the TIM-PS have great potential and a very wide range of applications in the field of flat plate solar collector.

Optimizing the thermal performance of the window with horizontal transparent insulation slats: A comprehensive analysis and comparative evaluation

Using slats made of transparent insulation material placed within the insulated glass unit (IGU) cavity can effectively reduce convective heat exchange in the gas cavity and improve windows' thermal resistance. A denser slat arrangement in the cavity of the Window with horizontal Transparent Insulation Slats (WTIS) contributes to better convective suppression within the gas-filled cavity. Still, it also raises concerns regarding excessive heat conduction along the slats. Therefore, further investigation is necessary to explore the optimal structure. In this study, we evaluated the thermal performance of WTIS using a validated numerical model and WINDOW7.8, considering various slat spacing, slat thickness, slat width, and cavity thickness. The air-filling and argon-filling cases were discussed. Furthermore, we experimented with testing the thermal performance of WTIS under different temperature conditions and validated the software calculation results. The results demonstrate that reducing the slat thickness and increasing the slat width is beneficial to improve the thermal resistance. The results identified an optimal slat spacing value of WTIS, which depends on both the cavity thickness and slat thickness and increases with their increase. The thermal resistance of optimized argon-filled WTIS is 39.47%-74.07% higher than that of argon-filled IGU.

Optical evaluation of a smart transparent insulation material for window application

Thermotropic (TT) materials can provide dynamic regulation of solar energy and daylight, thus achieving building energy saving and indoor environment improvement. Parallel Slats Transparent Insulation Materials (PS-TIM) when integrated into the cavity of a double-glazed window can increase the thermal resistance of the window system, thus reducing building heating energy consumption. In this study, these two advanced technologies are combined to form a novel TT PS-TIM window system for adaptive daylighting control and enhanced thermal insulation. To achieve this, thermotropic hydrogels such as hydroxypropyl cellulose (HPC) and poly(N-isopropylacrylamide) (PNIPAm) are proposed for integration within polymethyl methacrylate (PMMA) slats between double glass panes. The optical properties of the PMMA-TT slats have been firstly investigated by optical simulations and experiments. Windows integrated with the PMMA-TT slats have been developed and predicted for their daylight performance under different solar incident angles, slat tilt angles and concentrations of HPC/PNIPAm polymer within hydrogel. It was found that the TT PS-TIM window can effectively reduce visible and solar transmittance when the TT material switches from clear (at low temperatures) to translucent (at high temperatures). In addition, the translucent TT PS-TIM window allows less light to be transmitted into the interior space when the slat tilt angle is increased from horizontal to inclined. More uniform daylight distribution in the indoor space can be achieved by increasing the slat tilt angle. The optical investigation results of this research will provide guidance for the further development of this system.

First test field performance of highly efficient flat plate solar collectors with transparent insulation and low-cost overheating protection

The present work demonstrates prototypes of highly efficient flat plate solar thermal collectors prototypes based on transparent insulation materials (TIM) technology for efficiency improvement and an overheating protection system. The design and optimization of the collectors have been numerically carried out using a previously developed simulation tool based on an in-house software platform (NEST) capable of simulating all the entities constituting the system as a whole and using efficient coupling between the elements. Three design variants for the demonstration have been previously tested under laboratory conditions. These collectors are then mounted on the roof of a hospital building. Their performance is comparatively tested along with a conventional flat plate solar collector, under actual meteorological conditions and during long periods. The energy collected is about 2.5 and 1.4 times higher than standard collectors in winter and spring. Thus, due to the long-term exposure of the collectors, aspects such as reliability, durability, energy performance, and correct functioning of the protection system have been analyzed to improve the detected shortcomings for the future generations of the present design.

Parametric investigation on the performance of natural convection flat plate solar air collector with additional transparent insulation material parallel slats (TIM-PS)

The flat plate solar air collector operating in the mode of free convection is an essential element, which contributes to make easier the valorization of solar energy in the residential and industrial sectors. The existing FPCs suffer from comparatively low efficiency and high losses. Being efficient, inexpensive and simple to manufacture, their importance has been increased by the recent intensification of attempts to maximize the profitability of solar energy. To address this challenge, this paper is a numerical investigation of an innovative design and manufacturing approach of a FPC operating with natural convection. A new configuration of FPC, including transparent insulation material parallel slats (TIM-PS), is proposed and investigated. A thorough numerical investigation has been carried out to evaluate the contribution of the TIM-PS in the improvement of the air heating collector performance. The influence of slats’; number, angle of inclination and geometry on the FPC’s performance are studied. This CFD survey yielded the highest optimized and most cost-effective configuration for a vertically mounted collector with seven perforated TIM-PS inclined at +45°. The innovative facade collector can achieve a thermal efficiency around 60% with keeping the lightweight of the collector and the low cost. The peculiarity of this result lies in the combination of perforated and tilted TIM-PS that are investigated in our new study. These results introduce a new design of solar air heater operating in a natural convection mode, designed to be adapted to a range of geographical locations and sunlight conditions.

Numerical investigation of a smart window system with thermotropic Parallel Slat Transparent Insulation Material for building energy conservation and daylight autonomy

Smart window designs have emerged as a means of providing dynamic regulation of solar energy and daylight, enhancing indoor comfort, and achieving building energy conservation. We evaluated a novel window design that integrated a thermotropic (TT) material and Transparent Insulation Material (TIM) and present the investigation in this paper. The Parallel Slat TIM (PS-TIM) structure contained within the window unit provides extra thermal resistance and helps to redirect daylight. The TT material, which is applied to the slats, provides automatic daylight and solar adjustment. Firstly, the TT PS-TIM window system has been characterised thermally and optically. Then, a comprehensive approach including both building energy and daylight simulation packages was used to predict building performance. The effects of geometry (i.e. slat spacing and slat tilt angle) and thermotropic features (i.e. transition temperature and optical properties) on building performance were investigated. The simulation results show that use of TT PS-TIM window system with carefully selected features can simultaneously improve building energy efficiency (up to 22% saving when compared with a conventional double-glazed (DG) window) and attain homogenous daylight distribution with an average Useful Daylight Illuminance, UDI 500–2000 lux, of 52.2%. It was also found that both the geometric configurations and thermotropic features of a TT PS-TIM have significant influence on energy and daylight performance. TT PS-TIM with horizontally placed slats performs better than the unit with tilted slats, in terms of balance between energy efficiency and daylight availability. This research provides design guidance and material development suggestions for integration of this novel window system in buildings.

Performance optimization of flat plate solar collector through the integration of different slats arrangements made of transparent insulation material

Concerns about sustainability of solar energy have resulted in continuous efforts to improve the performance of flat plate solar air collector. The most advanced collector must provide the highest thermal efficiency and satisfy strict requirements for low weight, ease of manufacture and low cost. The purpose of this new study is to examine potential improvements in the performance of flat plate solar air collector. An innovative facade collector, with transparent insulation material (TIM) parallel slats is presented. A numerical modelling of new designed solar air collector was conducted. The performance of this collector was investigated using a three-dimension simulation model, following steady state. Thermal, thermo-hydraulic and exergy efficiencies of the collector containing (TIM-PS) system with different slats; number, height, materials, as well as the slats tilt angle and collector tilt angle (0°,30°,45°,90°) are studied. The CFD predictions show that, the incorporation of TIM-PS decreases the thermal losses, leading to higher efficiencies. This study has realized the most promising and most efficiently optimized design of the 45° tilted collector equipped with 6 TIM-PS tilted by −45°, this new FPC is capable of achieving 81% thermal efficiency. The new design presented in this study, deserves further exploitation as it seems to be a promising alternative for increasing thermal efficiency with a low cost and weight. It could be used in industrial and domestic applications.

Energy and daylight performance of a smart window: Window integrated with thermotropic parallel slat-transparent insulation material

With the increasing awareness of building energy efficiency, indoor environment quality for human wellbeing and working efficiency, efforts have intensified in to inventing intelligent building components. This paper provides a first step in developing a novel multi-effect smart window system, which achieves enhanced energy efficiency and an improved indoor luminous environment by integrating a Transparent Insulation Material (TIM) structure incorporating a Thermotropic material. This system automatically regulates the admittance of solar heat and natural light into the building by responding to a changing environment while taking advantage of the increased thermal resistance and scattered daylight of window integrated TIM. A comprehensive workflow via EnergyPlus and RADIANCE was used to accurately predict the luminous and energy performance of applying the smart window system on a typical south-facing office under selected climates (London, Stockholm, Rome and Singapore). The effect of the optical properties and transition temperature of thermotropic material on building performance was explored in detail. Annual simulation results predict that, with a careful selection of the Thermotropic material properties, installing the TT PS-TIM window system is able to yield up to a 27.1% energy saving when compared with a conventional double glazed window, under the modelled Rome climate. TT PS-TIM windows also provide dynamic daylight control, resulting in increased daylight availability with the percentage of working hours that fall into the UDI500–2000 lx range increasing to 62.3%. The results of this research provide guidance for the next step of the material design and development that seek to balance energy efficiency and solar and daylight control through the use of thermotropic materials.

Integration of transparent insulation shells in linear solar receivers for enhanced energy and exergy performances

This study investigates the performance enhancement of parabolic trough concentrators (PTCs) with transparent insulation material shell (TIMS) of different diameters and thicknesses integrated into evacuated and non-evacuated heat collection elements (HCEs). The results show that non-evacuated TIMS-HCEs have higher energy and exergy efficiencies by up to 62.4 and 63.2%, compared to conventional evacuated HCEs, and by up to 109.2 and 110.9%, compared to conventional non-evacuated HCEs. At high flow rates and low fluid temperatures, the energetic performance of a conventional evacuated HCE is only 6.3% higher than that of the modified non-evacuated one. The modified design also enhances the circumferential temperature uniformity and shows a marginal drop in efficiency when the vacuum is lost. By simulating the PTC performance during four typical days, and without vacuum, the proposed design increased the daily useful heat gain by up to 1.36 and 5.64 kWh, compared to conventional evacuated and non-evacuated HCEs, respectively. Hence, it is proposed as a low-tech alternative to HCE evacuation and as a method of boosting the performance of PTCs operating at low flow rates and high temperatures.

Transparent insulation materials market in Europe

This paper presents the European market of transparent insulation materials as viewed by manufacturers. The objective of the study was to analyse the application of transparent insulation materials in the construction sector across Europe, determine the popularity of various technologies and materials used to manufacture them, the competition among transparent insulation manufacturers, investment in the development of new transparent insulation technologies, and trends in demand for transparent insulation in Europe. The analysis was performed on the basis of a survey of manufacturers. The use of transparent insulation is associated with high cost, yet the potential return on investment in the form of savings over the course of a building’s life-cycle convinces many potential developers to apply these materials. Based on the results of the survey, it can be concluded that European companies follow the increase in energy-efficiency and the transparent insulation market is prosperous, yet differs from country to country. It was observed that the positive perception of indirect heat gain transparent insulation systems was the most prevalent in Germany. The paper also explores the situation on the author’s domestic market – the Polish transparent thermal insulation market.

Experimental and numerical study on the thermal performance of polycarbonate panels

Polycarbonate panels are a specific type of transparent insulation material that can be usefully integrated in building envelope structures. As the applications for such systems are increasing, it was necessary to analyse in detail data for materials which are already available to improve their thermal performance. In this paper the experimental campaign was based on the detailed characterization of the equivalent thermal conductivity parameters of several representative polycarbonate panels. The dependence of the equivalent thermal conductivity on the temperature and different angles of inclination are analyzed. Increasing the angle of the investigated polycarbonate panels changed the thermal conductivity parameters to a very minor degree. On the other hand, the effect of temperature on the thermal properties is proved to be significant and the conversion temperature coefficient is provided in this regard. The computational fluid dynamics (CFD) numerical analysis is employed to validate three-dimensional CFD models and simulate the thermal performance of low-e panels for it to theoretically improve their overall thermal parameters. When applying low-e functionality, depending on the type of polycarbonate panel, the equivalent thermal conductivity was found to range from 0.03750 W/(m·K) to 0.04172 W/(m·K), representing a reduction ranging from 43% to 24%.

Compression and thermal conductivity tests of Cryogel® Z for use in the ultra-transparent cryostats of FCC detector solenoids

The Future Circular Collider (FCC) study includes the design of the detector magnets for the FCC-ee+ (electron-positron) collider, requiring a 2 T solenoid for particle spectrometry, and for the FCC-hh (proton-proton) collider, with a 4 T detector solenoid. For both solenoids and their cryostats, CERN is developing an innovative and challenging design in which the solenoids are positioned inside the calorimeters, directly surrounding the inner tracker. For this purpose, the cryostats must be optimized to have maximum radiation transparency. They are structured as a sandwich of thinnest possible metallic shells for achieving vacuum tightness, supported by layers of low density and highly radiation transparent insulation material, still providing sufficient mechanical resistance and low thermal conductivity. In this respect, thermal and mechanical analysis of innovative insulation materials are currently being carried out. The first material of interest, Cryogel® Z, is shaped as a flexible composite blanket, which combines silica aerogel with reinforcing fibers and a density of 160 kg/m3. It allows a 4 m bore, 6 m long FCC-ee+ detector solenoid cryostat with a total thickness of 250 mm. CERN has investigated the compression of Cryogel® Z under 1 bar equivalent mechanical load and its thermal conductivity between 10 K and room temperature, as well as the critical phenomena of thermal shrinkage and outgassing. We present the test results, as a first overview on the material.

Coupled transparent insulation system with low emissivity solar absorber: An experimentally validated building energy simulation study

A conversion of shortwave to longwave radiation heat transfer in building envelope system represents an substantial part in low-energy design campaing. For that reason, an experimental test sample of a novel solar façade element based on a Transparent Insulation Material (TIM) with a selective and a nonselective absorber was developed. The investigated element is a part of an opaque lightweight structure of a building envelope. The capability of one widely used Building Energy Simulation (BES) tool is analyzed in terms of its ability to model the performance of the TIM façade element. The good consistency between the simulation results and the experimental data obtained specifically via cooling period indicates that the reference simulation model based on high emisivity of solar absorber was reliable when predicting the energy performance of TIM based façade models. However, the low emissivity of solar absorbers in the façade cavity gives rise significant limitations. They were identified concerning the BES calculation methods and modeling principles. The computational results are significantly underestimated in case of low emissivity internal surface. The methodology developed in this study is expected to provide a reference for simulating the thermal and energy performance of TIM-based building elements with different solar absorbers.

First-principles investigation on electronic structure and solar radiation shielding performance of Tl<sub>0.33</sub>WO<sub>3</sub>

<sec>With energy-saving and emission-reduction have become the theme of today's social development, the theoretical design and research of novel transparent heat insulation materials for windows, which can save energy and improve the comprehensive utilization efficiency of solar energy, are particularly crucial.</sec><sec>In this paper, a calculation method based on DFT(density functional theory) is used to study the lattice parameters (the geometric structure of h-WO<sub>3</sub> crystal was optimized by calculation) electronic band structure, formation energy, and optical properties of pure hexagonal phase tungsten trioxide(h-WO<sub>3</sub>) before and after doping with Tl. The calculated results indicate that the lattice volume increases and the total system energy decreases to a negative value after Tl-doped h-WO<sub>3</sub>, while the system has better stability; The electron band structure changes greatly after doping, but the material still maintains n-type conductivity. In the meantime, the optical properties of the material also changed, h-WO<sub>3</sub> had no near-infrared absorption performance before Tl-doping, and Tl<sub>0.33</sub>WO<sub>3</sub> after Tl-doped had strong near-infrared absorption performance. On this basis, the solar radiation shielding performance of h-WO<sub>3</sub> before and after Tl doping has been studied. The results show that pure h-WO<sub>3</sub> has no solar radiation shielding performance, while Tl<sub>0.33</sub>WO<sub>3</sub> thin films after Tl-doped h-WO<sub>3</sub> have high transparency in visible light region and strong absorption in near infrared radiation. The calculation results provide a theoretical basis for the application of transparent thermal insulating material for windows of Tl-doped h-WO<sub>3</sub>.</sec>

Finite element analysis of heat transfer performance of vacuum glazing with low-emittance coatings by using ANSYS

As a new transparent insulation material, vacuum glazing with Low-E (low emittance) coating has drawn more and more attentions thanks to its excellent performances: outstanding thermal and sound insulations, anti-frosting, resisting wind press capacity, and good durability. However, a comprehensive analysis and evaluation on the heat transfer performance of Low-E vacuum glazing are still missing in the current literatures. In this work, the influences of various aspects on the heat transfer performance of Low-E vacuum glazing were analyzed based on the Finite Element Analysis (FEA) method, including thickness of substrate glass, width of the sealing edge, materials and spacing of support pillar array, and insulation frame structure. The simulated results show the following, 1) with the increase of the thickness of the substrate glass, the heat transfer coefficient of the Low-E vacuum glazing rises slowly in a linear trend. The larger the size of the whole piece of the glazing, the more slowly it rises; 2) the Low-E vacuum glazing heat transfer coefficient declines linearly with the decrease of the width of the sealing edge; 3) as the support pillar array spacing increases and the thermal conductivity of the support pillar array decreases, the Low-E vacuum glazing heat transfer coefficient decreases; 4) the use of thermal insulation frame structure can improve the insulation efficiency of the vacuum glazing. Experiments were carried out on a Low-E vacuum glazing, and the heat transfer coefficient of this vacuum glazing was determined by the Building Heat Resistance-III (BHR-III), an equipment for insulation performance testing. The simulated result matches well with the experimental result, with a relative deviation of 2.8%, which confirms the reliability of the simulation result. This work is expected to provide guidance for optimization design of Low-E vacuum glazing and its insulation performance evaluation.

The effect of changing surface emissivity on the natural ventilation rate of a narrow air cavity integrated in a transparent insulation façade

A transparent insulation material (TIM) can be incorporated in a building element in order to improve its thermal performance, including solar heat gain. However, some overheating protection needs to be implemented. The provision of natural ventilation in a façade cavity to avoid overheating, along with other potential techniques, could require a completely different approach to TIM integration in solar façade concepts. This paper concerns an analysis of the effect of different absorber emissivity behind a transparent insulation system. The emissivity changes are primarily studied in order to determine their effects on the overall radiation - natural convection heat transfer through a narrow façade air cavity. A comparative investigation was conducted using experimental full-scale dynamic outdoor tests and the building energy simulation (BES) approach. The thermodynamic response affected by the radiation - natural convection transfer is identified, specifically during the summer peak period, that corresponds to overheating. Depending on the ventilation regime, a low emissivity solar absorber inside a narrow air façade cavity may increase the cooling energy load and temperature response of a façade by 25 and 36%, respectively, in comparison with a high emissivity absorber. When the emissivity of the zone inside the cavity was changed, significant limitations were identified in the BES calculation methods for both vented and unvented cases.