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1
Banionis, Karolis, Jurga Kumžienė, Arūnas Burlingis, Juozas Ramanauskas, and Valdas Paukštys. "The Changes in Thermal Transmittance of Window Insulating Glass Units Depending on Outdoor Temperatures in Cold Climate Countries." Energies 14, no. 6 (March 18, 2021): 1694. http://dx.doi.org/10.3390/en14061694.
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Windows, which have a U-value that is governed by an insulating glass unit (IGU) U-value, must be a building’s only enclosure element, which has no design value concept. The declared U-value, which is calculated or measured with 0 °C of external ambient temperature, is used instead of the design value. For most of a building’s elements, its thermal transmittance with a decrease in the external temperature diminishes a little, i.e., improves. However, for modern window IGUs with Low-E coatings, it is the opposite: the thermal transmittance with a lowering external temperature increases. Therefore, for calculating the peak power for the heating of buildings it is necessary to pay attention to this phenomenon and, therefore, it would be wise to introduce the concept of design U-value for windows, recalculation rules, or affix their declared U-values. This is especially the case in modern times with the prevailing architectural tendencies for enlargement of transparent building elements. For IGUs with Low-E coatings and inert gas fillers, the thermal transmittance depends on the temperature difference between warm and cold environments. When the external temperature is −30 °C instead of 0 °C, the thermal transmittance of the IGU can increase by up to 35%. This study presents the thermal properties of windows’ IGUs depending on the changes in outdoor temperatures by using guarded a hot box climate chamber and presents the proposed simplified methodology for determining the thermal properties of windows’ glass units. The accuracy of the composed simplified methods, comparing the calculated thermal transmittances of IGUs with those measured in the “hot box”, were up to 1.25%.
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Geyer, Christoph, Andreas Müller, and Barbara Wehle. "Measurements of thermal Transmittance of an External massive timber wall in-situ and in the Laboratory." E3S Web of Conferences 172 (2020): 14009. http://dx.doi.org/10.1051/e3sconf/202017214009.
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The thermal transmittance of an exterior massive timber wall was measured in situ in Appenzell, Switzerland according to the standard ISO 9869-1. The measurements were performed with two different measurement sets in parallel. The measurements started in February and stopped at end of April. The measuring data were analyzed using mean values of the thermal transmittance coefficient and of the thermal resistance following the procedure of ISO 9869-1. In order to clarify if the in-situ measurement results show significant deviations from the measurement results of the thermal transmittance obtained in the laboratory, the thermal transmittance of the identical wall construction was measured in the laboratory of Bern University of Applied Sciences in Biel according to the standard EN ISO 8990 for steady state boundary conditions in a guarded and calibrated hot box. The test results will be presented and the measurement setup will be described. The calculation value of the thermal transmittance coefficient of the massive timber wall according to EN ISO 6946 is U = 0.53 W/(m2K). The test results of the thermal transmittance coefficient, U-value of the wall, measured in the hot box, agreed well within a confidence level of 95 % with the calculated value. The in-situ measurement results of the thermal transmittance coefficient of the two measurement sets differ significantly in the order of 8 % referred to the calculated U-value of the wall as the basic amount. Furthermore, both in situ test results of the U-value of the wall show significant deviations from the calculated U-value up to 27 %.
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Flood, Cormac, and Lloyd Scott. "Thermal analysis and post construction verification." International Journal of Building Pathology and Adaptation 38, no. 1 (July 26, 2019): 51–67. http://dx.doi.org/10.1108/ijbpa-12-2018-0098.
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Purpose The residential sector in Ireland accounted for 25 per cent of energy related CO2 emissions in 2016 through burning fossil fuels, a major contributor to climate change. In support of Ireland’s CO2 reduction targets, the existing housing stock could contribute greatly to the reduction of space-heating energy demand through retrofit. Approximately 50 per cent of Ireland’s 2m dwellings pre-date building regulations and are predominantly of cavity and solid wall construction, the performance of which has not been extensively investigated at present. Although commitment to thermal upgrade/retrofit of existing buildings may increase under future government policies, the poor characterisation of actual thermal performance of external walls may hinder the realisation of these targets. Thermal transmittance (U-values) of exterior walls represents a source of uncertainty when estimating the energy performance of dwellings. It has been noted in research that the standard calculation methodology for thermal transmittance should be improved. Implementing current U-value calculation methods may result in misguided retrofit strategies due to the considerable discrepancies between in situ measurements and calculated wall U-values as documented in the case studies carried out in this research. If the method of hygrothermal analysis were to be employed as a replacement for the current standard calculation, it could have significant implications for policy and retrofit decision making. The paper aims to discuss this issue. Design/methodology/approach This research project analysed a case study situated in Dublin, Ireland. The case studies offer an account of the in situ thermal transmittance of exterior walls and link these to hygrothermally simulated comparisons along with more traditional design U-values. Findings The findings of this research identify discrepancies between in situ and design U-values, using measurement, hygrothermal simulation and standard method U-value calculations. The outcomes of the research serve as an introduction to issues emanating from a larger research project in order to encourage researchers to understand and further explore the topic. Originality/value It has previously been highlighted that moisture content is linked to the increase in thermal conductivity of building materials, thus reducing the thermal effectiveness and increasing the elemental U-value. Therefore, it is vital to implement reliable prediction tools to assess potential thermal performance values. This paper presents the findings of a critical instance case study in Dublin, Ireland in which an existing west facing external wall in a semi-detached dwelling was analysed, simulated and measured to verify the elemental wall assembly and quantify thermal transmittance (U-value) incorporating the major criteria required for building performance simulation.
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Bae, Minjung, Youngjun Lee, Gyeongseok Choi, Sunsook Kim, and Jaesik Kang. "Analysis of the Calculation Method for the Thermal Transmittance of Double Windows Considering the Thermal Properties of the Air Cavity." Sustainability 12, no. 24 (December 14, 2020): 10439. http://dx.doi.org/10.3390/su122410439.
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The calculation method for the thermal transmittance (U-value) of double windows as specified by the Korean government (ISO 15099) is often inappropriate. To develop a more suitable calculation method, the thermal properties of the air cavity between the internal and external windows should be considered. Herein, seven cases of double windows were set up. The air cavities were designed in accordance with international standards and computational fluid dynamics (CFD) and used for the calculation of the U-values of the double windows according to ISO 15099 and 10077. All the calculated U-values were compared with experimentally obtained values. In accordance with the ISO 10077-1 method, the thermal resistance of the air cavity calculated using CFD could produce double window U-values that are similar to the experimentally obtained values. In most cases, the difference between the theoretical and experimental U-values was 5% and less than 0.14 W·m−2·K−1, implying that the U-values calculated using CFD and the ISO 10077-1 method are approximately equal to the experimentally obtained U-values. Korean regulations do not include ISO 10077-1 for double-window assessment. However, these criteria can provide a solution in improving the accuracy of the calculation of the overall thermal transmittance of double windows.
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Santos, Lemes, and Mateus. "Thermal Transmittance of Internal Partition and External Facade LSF Walls: A Parametric Study." Energies 12, no. 14 (July 11, 2019): 2671. http://dx.doi.org/10.3390/en12142671.
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Light steel framed (LSF) construction is becoming widespread as a quick, clean and flexible construction system. However, these LSF elements need to be well designed and protected against undesired thermal bridges caused by the steel high thermal conductivity. To reduce energy consumption in buildings it is necessary to understand how heat transfer happens in all kinds of walls and their configurations, and to adequately reduce the heat loss through them by decreasing its thermal transmittance (U-value). In this work, numerical simulations are performed to assess different setups for two kinds of LSF walls: an interior partition wall and an exterior facade wall. Several parameters were evaluated separately to measure their influence on the wall U-value, and the addition of other elements was tested (e.g., thermal break strips) with the aim of achieving better thermal performances. The simulation modeling of a LSF interior partition with thermal break strips indicated a 24% U-value reduction in comparison with the reference case of using the LSF alone (U = 0.449 W/(m2.K)). However, when the clearance between the steel studs was simulated with only 300 mm there was a 29% increase, due to the increase of steel material within the wall structure. For exterior facade walls (U = 0.276 W/(m2.K)), the model with 80 mm of expanded polystyrene (EPS) in the exterior thermal insulation composite system (ETICS) reduced the thermal transmittance by 19%. Moreover, when the EPS was removed the U-value increased by 79%.
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No, Sang-Tae, and Jun-Sik Seo. "Analysis of Window Components Affecting U-Value Using Thermal Transmittance Test Results and Multiple Linear Regression Analysis." Advances in Civil Engineering 2018 (2018): 1–7. http://dx.doi.org/10.1155/2018/1780809.
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Currently, global warming is accelerating, and many countries are trying to reduce greenhouse emission by enforcing low energy building. And the thermal performance of the windows is one of the factors that greatly influence the heating and cooling energy consumption of buildings. According to the development of the window system, the thermal performance of the windows is greatly improved. There are simulations and tests for window thermal performance evaluation techniques, but both are time consuming and costly. The purpose of this study is to develop a convenient method of predicting U-value at the window system design stage by multiple linear regression analysis. 532 U-value test results were collected, and window system components were set as independent values. As a result, the number of windows (single or double) among the components of the window has the greatest effect on the U-value. In this research, two regression equations for predicting U-value of window system were suggested, and the estimated standard errors of equations were 0.2569 in single window and 0.2039 in double window.
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Aversa, Patrizia, Antonio Donatelli, Giuseppe Piccoli, and Vincenza Anna Maria Luprano. "Improved Thermal Transmittance Measurement with HFM Technique on Building Envelopes in the Mediterranean Area." Selected Scientific Papers - Journal of Civil Engineering 11, no. 2 (December 1, 2016): 39–52. http://dx.doi.org/10.1515/sspjce-2016-0017.
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Abstract Although the designed theoretical value of U can be derived from the thermal parameters of layers composing an opaque element, according to ISO 6946:2007, measurements are necessary to confirm the expected behaviour. Currently, the measurements of thermal transmittance based on Heat Flow Meter method (HFM) and according to standard ISO 9869-1:2014 are widely accepted. Anyway, some issues related to difficulties in measurements are present: the roughness of wall surfaces, the proper contact between the heat flow plate and the temperature probes with wall surfaces, undesired changes in weather conditions. This work presents the results obtained in thermal transmittance measurements with a modified HFM method, widely described in this paper. Differences between U-values obtained with the modified HFM method and theoretical ones were in the range 0.6 - 6.5 %. Moreover, the modified HFM method provided a result closer to the theoretical one, when compared to that obtained with standard HFM method (discrepancy with theoretical value were 0.6% and 16.4%, respectively).
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Santos, Paulo, Gabriela Lemes, and Diogo Mateus. "Analytical Methods to Estimate the Thermal Transmittance of LSF Walls: Calculation Procedures Review and Accuracy Comparison." Energies 13, no. 4 (February 14, 2020): 840. http://dx.doi.org/10.3390/en13040840.
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An accurate evaluation of the thermal transmittance ( U -value) of building envelope elements is fundamental for a reliable assessment of their thermal behaviour and energy efficiency. Simplified analytical methods to estimate the U -value of building elements could be very useful to designers. However, the analytical methods applied to lightweight steel framed (LSF) elements have some specific features, being more challenging to use and to obtain a reliable accurate U -value with. In this work, the main analytical methods available in the literature were identified, the calculation procedures were reviewed and their accuracy was evaluated and compared. With this goal, six analytical methods were used to estimate the U -values of 80 different LSF wall models. The obtained analytical U -values were compared with those provided by numerical simulations, which were used as reference U -values. The numerical simulations were performed using a 2D steady-state finite element method (FEM)-based software, THERM. The reliability of these numerical models was ensured by comparison with benchmark values and by an experimental validation. All the evaluated analytical methods showed a quite good accuracy performance, the worst accuracy being found in cold frame walls. The best and worst precisions were found in the Modified Zone Method and in the Gorgolewski Method 2, respectively. Very surprisingly, the ISO 6946 Combined Method showed a better average precision than other two methods, which were specifically developed for LSF elements.
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Gaši, Mergim, Bojan Milovanović, and Sanjin Gumbarević. "Comparison of Infrared Thermography and Heat Flux Method for Dynamic Thermal Transmittance Determination." Buildings 9, no. 5 (May 23, 2019): 132. http://dx.doi.org/10.3390/buildings9050132.
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This paper proposes an alternative experimental procedure that uses infrared thermography (IRT) for measuring the surface temperature of building elements, through which it is possible to approximate the thermal transmittance or the U-value. The literature review showed that all authors used similar procedures that require semi-stationary heat transfer conditions, which, in most cases, could not be achieved. The dynamic and the average methods that are given in ISO 9869 were also used with the IRT and the heat flux method (HFM). The dynamic method (DYNM) shows a higher level of accuracy compared to the average method (AVGM). Since the algorithm of the DYNM is more complicated than that of the AVGM, Microsoft Excel VBA was used to implement the algorithm of the DYNM. Using the procedure given in this paper, the U-value could be approximated within 0–30% of the design U-value. The use of IRT, in combination with the DYNM, could be used in-situ since the DYNM does not require stable boundary conditions. Furthermore, the procedure given in this paper could be used for relatively fast and inexpensive U-value approximation without the use of expensive equipment (e.g., heat flux sensors).
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Ahn, Namhyuck, and Sanghoon Park. "Heat Transfer Analysis of Timber Windows with Different Wood Species and Anatomical Direction." Energies 13, no. 22 (November 19, 2020): 6050. http://dx.doi.org/10.3390/en13226050.
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When assessing the hygrothermal performance of timber windows, it is important to apply the unique thermal conductivity of wood by each wood species as well as an anatomical direction within the same material as they affect the performance and long-term durability of products. A series of heat transfer analyses of window frames using THERM and WINDOW along with measurements on the thermal conductivity of five hardwoods using laser flash apparatus (LFA) was performed to compare and evaluate heat transmittance (U-value) and condensation resistance (CR) of three types of timber and hybrid timber windows. For each window type, 6.1 to 10.3% of the maximum difference in the heat transmittance among cases was calculated. Besides, a linear correlation was found between the U-value and the CR for most cases; thus, the selection of wood species and anatomical direction would improve the hygrothermal performance of timber windows overall. The results also indicated that there were some cases where the overall CR of windows did not improve because the U-value of the glazing system was not sufficiently low.
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Janković, Aleksandar, Biljana Antunović, and Ljubiša Preradović. "ALTERNATIVE METHOD FOR ON SITE EVALUATION OF THERMAL TRANSMITTANCE." Facta Universitatis, Series: Mechanical Engineering 15, no. 2 (August 2, 2017): 341. http://dx.doi.org/10.22190/fume170419017j.
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Thermal transmittance or U-value is an indicator of the building envelope thermal properties and a key parameter for evaluation of heat losses through the building elements due to heat transmission. It can be determined by calculation based on thermal characteristics of the building element layers. However, this value does not take into account the effects of irregularities and degradation of certain elements of the envelope caused by aging, which may lead to errors in calculation of the heat losses. An effective and simple method for determination of thermal transmittance is in situ measurement, which is governed by the ISO 9869-1:2014 that defines heat flow meter method. This relatively expensive method leaves marks and damages surface of the building element. Furthermore, the final result is not always reliable, in particular when the building element is light or when the weather conditions are not suitable. In order to avoid the above mentioned problems and to estimate the real thermal transmittance value an alternative experimental method, here referred as the natural convection and radiation method, is proposed in this paper. For determination of thermal transmittance, this method requires only temperatures of inside and outside air, as well as the inner wall surface temperature. A detailed statistical analysis, performed by the software package SPSS ver. 20, shows several more advantages of this method comparing to the standard heat flow meter one, besides economic and non-destructive benefits.
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Suntharalingam, Thadshajini, Irindu Upasiri, Perampalam Gatheeshgar, Keerthan Poologanathan, Brabha Nagaratnam, Paulo Santos, and Heshachanaa Rajanayagam. "Energy Performance of 3D-Printed Concrete Walls: A Numerical Study." Buildings 11, no. 10 (September 25, 2021): 432. http://dx.doi.org/10.3390/buildings11100432.
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Three-dimensional-printed concrete (3DPC), which is also termed as digital fabrication of concrete, offers potential development towards a sustainable built environment. This novel technique clearly reveals its development towards construction application with various global achievements, including structures such as bridges, houses, office buildings, and emergency shelters. However, despite the enormous efforts of academia and industry in the recent past, the application of the 3DPC method is still challenging, as existing knowledge about its performance is limited. The construction industry and building sectors have a significant share of the total energy consumed globally, and building thermal efficiency has become one of the main driving forces within the industry. Hence, it is important to study the thermal energy performance of the structures developed using the innovative 3DPC technique. Thermal characterization of walls is fundamental for the assessment of the energy performance, and thermal insulation plays an important role in performance enhancements. Therefore, in this study, different wall configurations were examined, and the conclusions were drawn based on their relative energy performance. The thermal performance of 32 different 3DPC wall configurations with and without cavity insulation were traced using validated finite element models by measuring the thermal transmittance value (U-value). Our study found that the considered 3DPC cavity walls had a low energy performance, as the U-values did not satisfy the standard regulations. Thus, their performance was improved with cavity insulation. The simulation resulted in a minimum thermal transmittance value of 0.34 W/m2·K. Additionally, a suitable equation was proposed to find the U-values of 100 mm-thick cavity wall panels with different configurations. Furthermore, this study highlights the importance of analytical and experimental solutions as an outline for further research
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Choi, Doo Sung, and Myeong Jin Ko. "Analysis of Convergence Characteristics of Average Method Regulated by ISO 9869-1 for Evaluating In Situ Thermal Resistance and Thermal Transmittance of Opaque Exterior Walls." Energies 12, no. 10 (May 24, 2019): 1989. http://dx.doi.org/10.3390/en12101989.
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In the last few decades, an average method which is regulated by ISO 9869-1 has been used to evaluate the in situ thermal transmittance (U-value) and thermal resistance (R-value) of building envelopes obtained from onsite measurements and to verify the validity of newly proposed methods. Nevertheless, only a few studies have investigated the test duration required to obtain reliable results using this method and the convergence characteristics of the results. This study aims to evaluate the convergence characteristics of the in situ values analyzed using the average method. The criteria for determining convergence (i.e., end of the test) using the average method are very strict, mainly because of the third condition, which compares the deviation of two values derived from the first and last periods of the same duration. To shorten the test duration, environmental variables should be kept constant throughout the test or an appropriate period should be selected. The convergence of the in situ U-value and R-value is affected more by the length of the test duration than by the temperature difference if the test environment meets literature-recommended conditions. Furthermore, there is no difference between the use of the U-value and R-value in determining the end of the test.
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Rezvani, Fahimeh, and Ignacio Zabalza Bribián. "Calculation and comparative analysis of thermal transmittance (U-value) of Scottish houses from recent centuries." Indoor and Built Environment 28, no. 7 (September 13, 2018): 873–86. http://dx.doi.org/10.1177/1420326x18798885.
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Sadhukhan, Debanjan, Sai Peri, Niroop Sugunaraj, Avhishek Biswas, Daisy Flora Selvaraj, Katelyn Koiner, Andrew Rosener, et al. "Estimating surface temperature from thermal imagery of buildings for accurate thermal transmittance (U-value): A machine learning perspective." Journal of Building Engineering 32 (November 2020): 101637. http://dx.doi.org/10.1016/j.jobe.2020.101637.
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Gullbrekken, Lars, Steinar Grynning, and Jørn Gaarder. "Thermal Performance of Insulated Constructions—Experimental Studies." Buildings 9, no. 2 (February 21, 2019): 49. http://dx.doi.org/10.3390/buildings9020049.
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Buildings that are designed to meet high-energy performance requirements, e.g., passive houses, require well-insulated building envelopes, with increased insulation thicknesses for roof, wall and floor structures. We investigate whether there are differences in the efficiency of thermal insulation materials at different moisture levels in the insulation and if there is a larger or smaller risk of natural convection in wood-fibre based insulation than in mineral wool. The work has mainly been performed by use of laboratory measurements included permeability properties and full-scale measurements of thermal transmittance of mineral wool and wood-fibre insulated constructions. In addition, calculations have been used to calculate resulting effects on the thermal performance of constructions. Results showed that the thermal conductivity was unaffected by moisture in the hygroscopic range. The air permeability was found to be approximately 50% higher for the wood-fibre insulation compared to mineral wool insulation. Measurements showed that the largest U-values and Nusselt numbers were found for the wall configuration. Calculation of the U-value of walls showed that in order to achieve the same U-value for the wood-fibre insulated wall as the mineral wool, it is necessary to add 20 mm insulation to the 250 mm wall and approximately 30 mm for the 400 mm wall.
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Khartabil, Ahmad, and Samer Al Martini. "Thermal Transmission Properties of Sustainable Concrete with Supplementary Cementitious Materials." Key Engineering Materials 853 (July 2020): 142–49. http://dx.doi.org/10.4028/www.scientific.net/kem.853.142.
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Understanding the thermal properties of a construction material is necessarily to evaluate its heat transfer resistance that has a major contribution to the energy-efficiency required to achieve sustainable structure. Thermal properties are evaluated through three main parameters namely: thermal conductivity, thermal resistivity and thermal transmittance. The aforementioned parameters are commonly referred as K-value, R-value, and U-value respectively. Recent regulations by Dubai municipality enforced to use sustainable concrete in construction. This is by replacing cement with supplementary cementitious materials (SCMs), such as grand granulated blast furnace slag (GGBS) and fly ash. The use of grand granulated blast furnace slag (GGBS) at relatively high percentage replacement became a typical practice in ready-mixed concrete industry in Dubai. As such, it is essential to characterize the thermal properties of this sustainable concrete. The current paper investigates the thermal properties of sustainable concrete mixtures incorporating supplementary cementitious materials, air entrainment additives, polypropylene and hybrid synthetic fiber. K-value, R-value and U-value are evaluated in accordance with ASTM C518. Additionally, hardened density of all investigated mixtures are measured. The results show that the foamed concrete has better heat transfer resistance than that for the non-air entrained mixture.
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Klõšeiko, Paul, Reimo Piir, Marti Jeltsov, and Targo Kalamees. "Thermal bridge effect of vertical diagonal tie connectors in precast concrete sandwich panels: an experimental and computational study." E3S Web of Conferences 172 (2020): 08001. http://dx.doi.org/10.1051/e3sconf/202017208001.
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The purpose of this work was to quantify the thermal bridge effect of vertical diagonal tie connectors in precast concrete sandwich panels (PCSPs). Special interest was in cases where the use of rigid insulation (e.g. PIR) would leave air gaps between insulation boards and diagonal ties, thus intensifying the thermal bridge. A climate chamber experiment using 5 different joint types was performed to gather reference data for CFD model validation. In the experiment, natural convection was observed in joints where no additional insulation was used, i.e. in air cavities. Significantly larger heat fluxes were measured in these cavities compared to insulated joints. The thermal bridging effect was evaluated for a typical PCSP (thermal transmittance without thermal bridges U = 0.11 W/(m²·K)) using CFD software taking into account 3D heat conduction and convection. Simulation results indicate that diagonal ties without adjacent air cavities increased the average thermal transmittance (U-value) of the envelope by 8%, diagonal ties with a 6 mm air cavity – 19...33% and diagonal ties with a 10 mm air cavity – 45...56%. In conclusion, it was found that the joints in insulation caused by diagonal ties affect the overall thermal performance of the building envelope significantly when efforts are not made to fill the air cavities around the connectors.
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de Rubeis, Tullio, Giovanni Pasqualoni, Domenica Paoletti, and Dario Ambrosini. "Thermal Characterization of Different Insulating Materials via Experimental Analysis in a Guarded Hot Box." Tecnica Italiana-Italian Journal of Engineering Science 65, no. 2-4 (July 30, 2021): 230–35. http://dx.doi.org/10.18280/ti-ijes.652-414.
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The thermal characterization of building envelope materials is a crucial phase in understanding the building energy performance, and it is commonly evaluated through the thermal transmittance, often synthetically indicated as U-value. There are several ways to experimentally assess the U-value of insulating materials and multi-layers systems, usually defined by means of experimental in-situ heat flux measurements, where, however, a considerable variation of the boundary conditions may occur, making the measurement difficult. In this work, the experimental thermal characterization of different insulating materials applied to an X-lam wall is presented. The analysis is carried out using a Guarded Hot Box, which allowed to reproduce real, repeatable, and controlled operating conditions. Two different insulating materials were selected: expanded polystyrene (EPS) with graphite and hemp. The experimental tests were carried out by imposing a temperature difference reproducing the common operating conditions (0°C in cold chamber and 20°C in hot chamber). Steady-state conditions (constant temperature in the chambers) have been imposed to determine the thermal properties of the multi-layer systems. The tests, lasted 72 hours each, showed U-values equal to 0.15 W/m2K ± 3.1% for EPS with graphite and 0.19 W/m2K ± 3.1% for hemp.
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Gaspar, Katia, Miquel Casals, and Marta Gangolells. "Influence of HFM Thermal Contact on the Accuracy of In Situ Measurements of Façades’ U-Value in Operational Stage." Applied Sciences 11, no. 3 (January 22, 2021): 979. http://dx.doi.org/10.3390/app11030979.
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Accurate information on the actual thermal transmittance of walls is vital to select appropriate energy-saving measures in existing buildings to meet the commitments of the European Green Deal. To obtain accurate results using the heat flow meter (HFM) method, good thermal contact must be made between the heat flow meter plate and the wall surface. This paper aimed to assess the influence of the non-perfect thermal contact of heat flow meter plates on the accuracy of in situ measurement of the façades’ U-value when a film was applied to avoid damage to the wall surface. Given the fact that to avoid harm to the wall surface, the laying of a film is a usual procedure in the installation of equipment during the building’s operational stage. The findings show that deviations between measured U-values when an HFM was installed directly on the wall surface and when an HFM was installed with a PVC film were found to differ significantly from the theoretical effect of including a PVC film during the monitoring process.
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Memon, Saim, Farukh Farukh, and Karthikeyan Kandan. "Effect of Cavity Vacuum Pressure Diminution on Thermal Performance of Triple Vacuum Glazing." Applied Sciences 8, no. 9 (September 19, 2018): 1705. http://dx.doi.org/10.3390/app8091705.
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Long-term durability of the vacuum edge seal plays a significant part in retrofitting triple vacuum glazing (TVG) to existing buildings in achieving progress towards a zero-energy building (ZEB) target. Vacuum pressure decrement with respect to time between panes affects the thermal efficiency of TVG. This study reports a 3D finite element model, with validated mathematical methods and comparison, for the assessment of the influence of vacuum pressure diminution on the thermal transmittance (U value) of TVG. The centre-of-pane and total U values of TVG are calculated to be 0.28 Wm−2 K−1 and 0.94 Wm−2 K−1 at the cavity vacuum pressure of 0.001 Pa. The results suggest that a rise in cavity pressure from 0.001 Pa to 100 kPa increases the centre-of-pane and total U values from 0.28 Wm−2 K−1 and 0.94 Wm−2 K−1 to 2.4 Wm−2 K−1 and 2.58 Wm−2 K−1, respectively. The temperature descent on the surfaces of TVG between hot and cold sides increases by decreasing the cavity vacuum pressure from 50 kPa to 0.001 Pa. Nonevaporable getters will maintain the cavity vacuum pressure of 0.001 Pa for over 20 years of life span in the cavity of 10-mm wide edge-sealed triple vacuum glazing, and enable the long-term durability of TVG.
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Aguilar-Santana, Jorge Luis, Hasila Jarimi, Mariana Velasco-Carrasco, and Saffa Riffat. "Review on window-glazing technologies and future prospects." International Journal of Low-Carbon Technologies 15, no. 1 (December 5, 2019): 112–20. http://dx.doi.org/10.1093/ijlct/ctz032.
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Abstract Windows are one of the significant indicators of the energy efficiency of a building and have undergone extensive research since the last decades. This paper reviews the performance of various window technologies covering the physical and optical properties of traditional windows and advanced window technologies. In window technologies, one of the most critical parameters is its thermal transmittance value or also known as U-value. In this paper, we discuss the relationship between the physical and optical parameters of the different types of windows and its U-value. Additionally, this paper will also provide interested readers with a wide range of information, including the research gaps in window technologies. Among the main conclusions, we found that, although several advancements have been achieved in this field in the last decade, further research is needed to develop window technologies that not only have high insulating properties but also can generate power.
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Choi, Bo-Eun, Ji-Hyun Shin, Jin-Hyun Lee, Sun-Sook Kim, and Young-Hum Cho. "Establishment of Passive Energy Conservation Measure and Economic Evaluation of Fenestration System in Nonresidential Building of Korea." International Journal of Polymer Science 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/8681737.
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ECO2 (building energy efficiency rating program) and passive energy conservation measures (ECMs) were established as a basic study for targeted methodologies and decision support systems development in Korea to meet national regulations. The primary energy consumption and economic evaluation of nonresidential buildings was performed. Passive ECMs were classified as planning and performance elements. The planning elements are the window-to-wall ratio (WWR) and horizontal shading angle. The performance elements are the thermal transmittance (U-value) of the walls, roof, and floor and the U-value and solar heat gain coefficient (SHGC) of windows. This study focused on the window-to-wall ratio and the U-value and solar heat gain coefficient of windows. An economic efficiency database for the constructed alternatives was built; the target building was set and the Passive ECM List for the target building was derived. The energy consumption evaluation and economic evaluation were performed for each of the constructed alternatives, and a methodology for guiding energy efficiency decisions was proposed based on the performance evaluation results, and the optimal Passive ECM List for the target building was derived.
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Respondek, Zbigniew. "Heat Losses through Insulated Glazing Placed Horizontally or Diagonally." Key Engineering Materials 828 (December 2019): 1–8. http://dx.doi.org/10.4028/www.scientific.net/kem.828.1.
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Heat transfer through insulating glass units is a complex phenomenon. Heat exchange occurs here through conduction, convention and radiation. In practical calculations of heat losses in buildings, the declared value of the thermal transmittance (U) is most often taken into account, which is valid for vertical panes. Currently, more and more horizontal and diagonal glass partitions are made. The aim of the article is to analyze, on the basis of the adopted calculation model, the influence of the angle of glazing slope on the thermal transmittance in different weather conditions. The different wind speed and the possibility of radiative cooling were taken into account. Radiative cooling is a phenomenon manifested by a drop in temperature on the surface of horizontal and diagonal building partitions below the external air temperature. It occurs at night under a cloudless sky. It was found that in the case of horizontal or diagonal glazing heat losses increase significantly, which affects the energy balance of the building. Radiative cooling, especially in windless weather, is an additional unfavorable factor.
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Viljanen, Klaus, Xiaoshu Lü, and Jari Puttonen. "Hygrothermal Behaviour of Ventilation Cavities in Highly Insulated Envelopes." E3S Web of Conferences 172 (2020): 07003. http://dx.doi.org/10.1051/e3sconf/202017207003.
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This article presents long-term experimental studies on the moisture safety in the ventilation cavities of highly insulated (HI) structures. The tested HI-walls had thermal transmittances of 0.11-0.13 W/m2K. A wall with a thermal transmittance of 0.23 W/m2K represented the baseline wall in the test. In addition to walls, an HI-roof of a newly built house with a U-value of 0.08 W/m2K was measured. The results indicate that, in the ventilation cavity, the relative humidity of an HI-wall exceeds 1-7% of the humidity measured from the baseline wall during winter, which coincides with the 0.4-1.5ºC lower temperatures observed in the HI-walls. The mold risk in the ventilation cavities of the walls is low, as the value of the mold index (MI) remains below one, which indicates small amounts of microscopic mold only on surfaces. However, at the bottom of the cavity, the MI value reaches 1.4 due to lower temperatures. In the HI-roof, the MI values are between 1.0 and 2.0 in the middle of the cavity in winter. The reasons for the higher mold risk of the roof are the humid weather, the built-in moisture of the roof and the low heat flux from inside. The study confirms that, in the future, warmer weather and increased humidity can increase moisture risks in the ventilation cavities. The results support the use of materials that are more resistant to mold in the outer parts of structures.
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Tejedor, Blanca, Eva Barreira, Vasco Peixoto de Freitas, Tomasz Kisilewicz, Katarzyna Nowak-Dzieszko, and Umberto Berardi. "Impact of Stationary and Dynamic Conditions on the U-Value Measurements of Heavy-Multi Leaf Walls by Quantitative IRT." Energies 13, no. 24 (December 15, 2020): 6611. http://dx.doi.org/10.3390/en13246611.
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Infrared thermography (IRT) has become a commonly applied non-destructive testing method for assessing building envelopes. Like any diagnosis tool, IRT requires an appropriate experience and principle understanding, mainly when the method is used for quantitative analyses. The challenges of the IRT often deal with the dynamic properties of building partitions. Climatic conditions have a certain variability, and the accumulated energy storage in the building components can affect their temperature as well as the calculated thermal performance. This paper aims to analyze how stationary and dynamic regimes of a quantitative IRT test could impact the measured thermal transmittance of heavy multi-leaf walls. Investigation in two European countries with different climatic conditions are reported. In this way, it is discussed which boundary conditions should be guaranteed to provide reliable information about a building envelope using quantitative IRT. In order to check the quality of the measurements, the heat flux meter (HFM) method was also implemented, following the ISO 9869. The research revealed that it could be possible to use short-lasting tests in the climatic conditions of Southern Europe, while long-term tests should be implemented in Northern European countries where climatic conditions are less regular.
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Baek, Sanghoon, and Sangchul Kim. "Potential Effects of Vacuum Insulating Glazing Application for Reducing Greenhouse Gas Emission (GHGE) from Apartment Buildings in the Korean Capital Region." Energies 13, no. 11 (June 2, 2020): 2828. http://dx.doi.org/10.3390/en13112828.
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Korea has set a goal of reducing greenhouse gas emissions (GHGEs) to levels 37% below the “business as usual (BAU)” level by 2030, and the building sector, in particular, aims to reduce GHGEs by 45,000,000-ton CO2-eq by 2020. In order to reach this goal, it is crucial to reduce GHGEs that result from energy consumption in apartment buildings, which account for approximately 65% of all buildings in the capital region where the population is concentrated. Moreover, as apartment buildings not only have high window-to wall area ratios, but also use insulating glazing (IG) with low thermal performance, an advanced window system with low heat transmittance (U-value), such as a concrete structure, is necessary for effective GHGE reduction. Therefore, this study aims to evaluate the GHGE reduction effects from replacing existing IG vacuum insulating glazing (VIG) with low U-values in the apartment housing located in the capital region. The analysis revealed the possibility of a GHGE reduction by 45%–79% with the application of commercial VIG with U-values of 0.7 W/m2·K in lieu of the existing IG with U-values ranging from 1.2 to 3.3 W/m2·K for all apartment buildings located in the capital region. Furthermore, GHGEs could be reduced by 82%–93% by replacing the existing IG with VIG with U-values of 0.2 W/m2·K.
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Ávila-Delgado, Jorge, María Dolores Robador, José Antonio Barrera, and Madelyn Marrero. "Influencia del acristalamiento sobre los parámetros y la calificación energética de acuerdo con la orientación del edificio y los porcentajes de aberturas de fachada = The influence of glazing over the parameters and energy rating according to the building orientation and the façade openings percentages." Anales de Edificación 2, no. 1 (April 7, 2016): 34. http://dx.doi.org/10.20868/ade.2016.3196.
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Resumen Es bien conocida la importancia de los cristales en la demanda de energía del edificio, ya que la envolvente térmica es lo más importante. En este trabajo se ha realizado un estudio de la influencia de la transmitancia térmica (factor U) y el factor solar (valor g) de tres tipos diferentes de acristalamiento en la calificación energética. Se ha realizado el análisis en una vivienda unifamiliar situada en la ciudad de Sevilla, España, con diferentes hipótesis, en concreto seis porcentajes de apertura que van desde 10 a 60% considerado por el Código Técnico de la Edificación español, y cuatro orientaciones según las direcciones cardinales. Para los tipos de zona climático y acristalamiento considerados, el valor del parámetro g tiene mayor incidencia en el rendimiento energético que la transmitancia térmica. Se ha establecido qué orientación proporciona mayor ahorro de energía, independientemente de la demanda de calefacción y enfriamiento y de la calificación energética. Además, hay que considerar los valores ideales de ambos parámetros para cada orientación con el fin de mejorar la calificación energética. Por lo tanto, al seleccionar un tipo de acristalamiento, sería importante tener en cuenta los mejores valores de los parámetros "T" y "g" para cada orientación con el fin de obtener menor gasto de energía. Abstract It is well known the significant impact of glazing over the building energy demand making it the thermal envelope’s most important part. A study of the influence of thermal transmittance (U-factor) and solar factor (g-value) of three different glazing types over the parameters and energy rating are shown in this paper. A single-family dwelling located in Seville city, Spain, has been analyzed to which a set of hypotheses, six opening percentages ranging from 10 to 60% considered by the Spanish Building Code on its simplified option, and different combinations, four orientations matching the cardinal directions, has been applied. For the climate zone and glazing types considered, the g-value parameter has a higher incidence on the global demand and energy rating than thermal transmittance. It is established which orientation greater energy savings can be achieved independently for heating, cooling demand and energy rating. Also the ideal values for both parameters that should be considered in each orientation in order to improve the energy rating. Therefore, when selecting a type of glazing it would be important to consider the best “U” and “g” parameter values together for each orientation in order to get the lowest energy demand possible.
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Huang, Chih Hong, Wan Ting Hong, Ta Wui Cheng, Yeou Fong Li, and Hsin Hua Tsai. "A Building Envelope Coating Provides Radiative-Cooling Effect for Subtropics." Key Engineering Materials 853 (July 2020): 209–14. http://dx.doi.org/10.4028/www.scientific.net/kem.853.209.
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The primary source of heat in building envelopes in subtropical regions is solar radiation. As global warming worsens, the building insulation is receiving an increasing amount of attention.We developed a coating material with radiative cooling potential and conducted an experiment on a reduced scale to investigate the radiative-cooling performance of bare concrete and concrete coated with UU500, an inorganic insulation coating, under artificial daylight and after the daylight lamps were turned off. The results indicate that UU500 has radiative-cooling effects. We calculated the thermal transmittance coefficient Ui of the coating and presented a radiative cooling coefficient Ex to modify the U-value formula defined in ISO 9869-1: 2014. Coatings with higher Ex values should be promoted and developed to provide the materials industry with a better theoretical foundation for coating development, which enlightened a new approach for building energy saving strategy.
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Gumbarević, Sanjin, Bojan Milovanović, Mergim Gaši, and Marina Bagarić. "Application of Multilayer Perceptron Method on Heat Flow Meter Results for Reducing the Measurement Time." Engineering Proceedings 2, no. 1 (November 14, 2020): 29. http://dx.doi.org/10.3390/ecsa-7-08272.
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To reduce the impact on climate change, many countries have developed strategies for the building sector with a goal to reduce the energy demands and carbon emission of buildings. As most buildings that exist today will very likely exist in foreseeable future, many buildings will need to undergo major renovations. One of the most important parameters in determining the transmission heat losses through the building envelope is the U-value, i.e., thermal transmittance, and it is simply the rate of heat transfer per unit temperature. Since the U-value is one of the most important parameters regarding building energy performance, envelope elements that do not perform well in terms of transmission heat losses must undergo a renovation processes. The in-situ U-value of building elements is usually determined by the Heat Flux Method (HFM). One of the issues of current application of the HFM is the measurement duration. This paper explores the possibilities of reducing the measurement time by predicting the heat flux rate using a multilayer perceptron (MLP), a class of artificial neural network. The MLP uses two input layers that are the interior and exterior air temperatures, and the output layer that is the predicted heat flux rate. The predicted value is trained by comparing the predicted heat flux rates with the measured values, and by rearranging the neural network parameters (weights and biases) in corresponding neurons by minimizing the mean squared error defined for trained values (measured versus predicted heat flux rates). The use of MLP shows promising results for predicting the heat flux rates for the analyzed cases (4 days HFM results) when the training is performed on 2/3 or 1/2 of the overall measurement time. The application of the MLP could be in reducing the in-situ measurement time when determining heat losses through building elements in shorter time periods.
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Tejedor, Blanca, Kàtia Gaspar, Miquel Casals, and Marta Gangolells. "Analysis of the Applicability of Non-Destructive Techniques to Determine In Situ Thermal Transmittance in Passive House Façades." Applied Sciences 10, no. 23 (November 24, 2020): 8337. http://dx.doi.org/10.3390/app10238337.
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Within the European framework, the passive house has become an essential constructive solution in terms of building efficiency and CO2 reduction. However, the main approaches have been focused on post-occupancy surveys, measurements of actual energy consumption, life-cycle analyses in dynamic conditions, using simulation, and the estimation of the thermal comfort. Few studies have assessed the in situ performance of the building fabric of passive houses. Hence, this paper explores the applicability of non-destructive techniques—heat flux meter (HFM) and quantitative infrared thermography (QIRT)—for assessing the gap between the predicted and actual thermal transmittance of passive house façades under steady-state conditions in the Mediterranean climate. Firstly, the suitability of in situ non-destructive techniques was checked in an experimental mock-up, and, subsequently, a detached house was tested in the real built environment. The findings revealed that both Non-Destructive Testing (NDT) techniques allow for the quantification of the gap between the design and the actual façades U-value of a new passive house before its operational stage. QIRT was faster than the HFM technique, although the latter was more accurate. The results will help practitioners to choose the most appropriate method based on environmental conditions, execution of the method, and data analysis.
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Carlos, Jorge S. "OPTIMAL WINDOW GEOMETRY FACTORS FOR ELEMENTARY SCHOOL BUILDINGS IN PORTUGAL." Journal of Green Building 13, no. 1 (January 2018): 185–98. http://dx.doi.org/10.3992/1943-4618.13.1.185.
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INTRODUCTION With respect to thermal performance, windows are the weakest component of the building envelope, essentially because the U-value is usually higher than the opaque envelope. This would allow the highest heat conductance of the building envelope. However, it also helps buildings to gain useful solar heat during winter. Therefore, it has been generally accepted that passive buildings would have small windows towards the poles and large windows facing the equator (Persson, Roos, and Wall 2006). In spite of this guideline, large or fully glazed facades have been used in modern architecture. The intensive use of air conditioning is the result of overheating and high thermal loss problems, which otherwise would lead to thermal discomfort. This extensive use of large windows associated with high energy consumption has motivated researchers to study this building component. Window areas were investigated by Persson et al. (Persson, Roos, and Wall 2006) on 20 terraced houses with larger windows facing the equator and built in Gothenburg. The building envelope was well insulated and fitted with energy efficient windows. It was found that energy efficient windows do not have a major influence on the heating demand in the winter, but it is relevant for the cooling need in summer. Therefore, reduced indoor illuminance due to small windows can be solved by enlarging them in order to obtain relevant daylighting conditions. When efficient windows are designed for a warm climate, as in Mexico, reducing heat flux and solar transmittance indoors was the best option for energy savings (Aguilar et al. 2017). However, reducing solar transmittance influences the indoor illuminance, which was not analyzed.
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Huang, Baofeng, and Wensheng Lu. "Experimental Investigation of the Multi-Physical Properties of an Energy Efficient Translucent Concrete Panel for a Building Envelope." Applied Sciences 10, no. 19 (September 29, 2020): 6863. http://dx.doi.org/10.3390/app10196863.
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The multi-physical properties of the building envelope play a major role in the energy efficiency of buildings. Translucent concrete panels (TCPs) with various volumetric ratios of optical fibers (OFs) were cast. To understand the multi-physical properties of the TCP for the building envelope, compressive strength, thermal and light transmittance tests were carried out. The compressive strength test showed that TCP with light-weight mortar (LWM) has higher strength compared to that with normal-weight mortar (NWM), but it did not exhibit an apparent ductile behavior. The U-values of the plain panel were 4.25 and 5.45 W/(m2 K) for TCPs with the LWM and NWM, respectively. The existence of the OFs improved the thermal insulation property. The K-values of the LWM TCP were smaller than that of the common façade, which proved its excellent energy-efficient performance. The solar heat gain coefficients (G-values) of the two tested TCP types—LWM and NWM—were 0.198 and 0.242, respectively. The visible light transmission test showed that the light transmitted by the TCP was proportional to the density of the OFs in a matrix of concrete. The experimental light acceptance angle of the OF was close to the computational value (35 °C). Therefore, all the experimental results demonstrated that TCPs can improve the energy efficiency of buildings.
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Pracucci, Alessandro, Sara Magnani, and Oscar Casadei. "The Integration of Vacuum Insulated Glass in Unitized Façade for the Development of Innovative Lightweight and Highly Insulating Energy Efficient Building Envelope—The Results of Eensulate Façade System Design." Designs 4, no. 4 (September 24, 2020): 40. http://dx.doi.org/10.3390/designs4040040.
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The European Commission has identified the building industry as one of the key sectors to achieve its 2020 strategy to create conditions for smart, sustainable, and inclusive growth. In this frame, the aim of Horizon 2020′s Eensulate project is the development of innovative lightweight and highly insulating energy efficient unitized building façades, suitable for both new and existing buildings. The Eensulate façade module integrates two components developed within the project: Vacuum Insulated Glass (VIG) for architectural purposes, with a U-value of 0.3 W/sqm∙K; a highly insulating foam for automated manufacturing and insulation for the spandrel part. This article presents the Eensulate façade system design simulations and achievements related to VIG integration to solve issues that emerged by the utilization of its innovative components (sealant thermal bridge and getter strips). VIG design and testing have gradually changed the façade module and consequently, façade components have been progressively designed to achieve the expected target of 0.641 W/sqm∙K for thermal transmittance. The results demonstrate that the target can be achieved by aluminum profiles, Ethylene Propylene Diene Monomer (EPDM) thermal bridge, and additional insulating components, obtaining a new product for unitized façades able to reduce energy consumption in buildings with large glass surfaces.
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Zingre, Kishor T., Kiran Kumar D. E. V. S., and Man Pun Wan. "Analysing the Effect of Substrate Properties on Building Envelope Thermal Performance in Various Climates." Energies 13, no. 19 (October 1, 2020): 5119. http://dx.doi.org/10.3390/en13195119.
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Existing regulations on the thermal efficiency of building envelope assemblies are based on the steady state thermal properties of substrate materials. Heat transfer mechanisms of passive heat curbing methods such as phase change materials and cool materials, which are dynamic in nature, are currently not being accounted for. The effectiveness of thermo-physical and solar radiation properties of building materials (i.e., solid homogeneous layers without air gap) in reducing the heat gain into a building in a hot climate could be well understood with the equivalent thermal resistance (Req) concept. A simple and easy-to-use mathematical derivation (i.e., to estimate the instantaneous heat flux across an envelope assembly) is proposed in this paper to understand the mechanism of equivalent R-value (i.e., reciprocal of thermal transmittance, U-value) due to solar radiation properties of passive substrate materials. The model is validated against field experiments carried out at two apartment units of a residential building. The Req due to high outer surface solar radiation properties (i.e., by applying a cool coating) is dynamic as it varies with the weather conditions. The effect of a substrate material’s solar radiation and thermo-physical properties on the overall roof thermal performance is investigated using the Req model for four cooling dominated climates around the globe, having different diurnal conditions and sky temperatures. Increasing the outer surface’s solar reflectance (from 10% to 80%) reduces net heat gain through the flat roof during both daytime and nighttime. In contrast, adding only thermal resistance (from 5 mm to 75 mm thick polyurethane) or volumetric heat capacity (by adding 5 mm thick phase change material) to the building envelope brings down heat gain during the day, but not in the night. Thermal insulation is found to be the second effective property, followed by thermal mass irrespective of different diurnal conditions and sky temperatures across the climates.
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Mounir, Soumia, Youssef Maaloufa, Khabbazi Abdelhamid, and Khalid El Harrouni. "Characterization of Thermal Inertia and Footprint Carbon of Clay-Wool, Clay-Cork, and Clay-Plastic Composites." Key Engineering Materials 886 (May 2021): 213–27. http://dx.doi.org/10.4028/www.scientific.net/kem.886.213.
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Passive solutions in the concept of energy efficiency play an important role in reducing energy consumption, and emissions of CO2. However, controlling the parameters of walls, and roof thermal Inertia is the perfect way to ensure comfort inside houses. In this paper, an investigation of thermal inertia behavior, and energy efficiency of clay with natural, and industrial additives: cork, wool, and waste of plastic. The use of those materials will improve the comfort of the inhabitants of the cold area who suffer from the hard climatic conditions, not just the block’s clay will be extracted from the same area but also they will be sun backed, the thing which will reduce the huge energy consumption of brickyard. A study of the energy efficiency of those materials was done using TRNSYS, and an evaluation of their environmental impact was evaluated by calculating their emissions in terms of CO2. The results obtained indicate an important characteristic in term of thermal Inertia, for a value of thermal transmittance of U= 0.55 W.m-2.K-1, we need 0.9m thickness of wall using the heavy concrete, however, if we use clay, we gain 69 %, clay-plastic we gain 79 %, clay cork, we gain 87 %, and by clay-wool, we earn 89 % in term of the wall’s thickness. For the delay of the heat flow of a wall of 25 cm, we could assure a delay of above 11h instead of just 2h for the heavy concrete. Concerning the heating need during a year during the cold season, the clay presents a need for 1500 KJ.h-1. Concerning the footprint carbon, the composite clay-cork has a negative footprint carbon; however, the clay and clay-wool present a low carbon emission near zero when the clay-plastic and the heavy concrete present the highest value of emissions.
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Salvalai, Graziano, and Marta Maria Sesana. "EXPERIMENTAL ANALYSIS OF DIFFERENT INSULATED FAÇADE TECHNOLOGIES IN SUMMER CONDITION." Journal of Green Building 14, no. 4 (September 2019): 77–91. http://dx.doi.org/10.3992/1943-4618.14.4.77.
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At the present, the ventilated façade is one of the most widely used and most innovative systems characterized by different energy saving features, but due to its complexity, the real performances are difficult to predict by numerical analysis. This work shows the results of the monitoring campaign conducted on two Cross Laminated Timber (CLT) test boxes equipped with different thermal coat technologies to realize the performances comparisons. In particular, the investigation focus on the evaluation of surface temperatures of the different wall layers and the indoor air temperature for: i) a micro ventilated façade and ii) two different ETICS solutions. The monitoring campaign has been conducted during the summer season on walls with equivalent thermal transmittance (U-value) and different thermal capacity. In detail, the experimental work has been performed to estimate the Isotec® wall micro ventilated façade performance in comparison with two traditional ETICS technology: the first one realized with EPS and the second one with high density rock wool insulation. The results show that due to the shading effect provided by the external layer, the temperature within the cavity of the ventilate façade is reduced by 8–10 °C, reducing the cooling loads through the wall by 30–40% with respect to ETICS with EPS. The shading and the ventilation effects balance the presence of thermal insulation with less heat capacity; consequently, it validates the good quality of Isotec® as wall technology with performances comparable to ETICS solution with high density rock wool insulation.
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Jurelionis, Andrius, and Edmundas Isevičius. "CFD PREDICTIONS OF INDOOR AIR MOVEMENT INDUCED BY COLD WINDOW SURFACES/VĖSIŲ LANGŲ PAVIRŠIŲ SUKELIAMO ORO JUDĖJIMO TYRIMAI PASITELKIANT KOMPIUTERINIO MODELIAVIMO METODUS." JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 14, no. 1 (March 31, 2008): 29–38. http://dx.doi.org/10.3846/1392-3730.2008.14.29-38.
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During the past decades, large windows and glazed façades have become an important part of modern architecture and they are designed frequently in both public and residential buildings. However, besides the positive effect of such a design on building occupants, large windows may cause thermal discomfort. Cold inner window surface may generate draught in the occupied zone. Thermal comfort in rooms is usually assessed by measuring air temperature, relative humidity, air velocity and heat transfer due to radiation. In this study computational fluid dynamics (CFD) methods have been used to investigate these phenomena. Air movement caused by cold vertical window surfaces was evaluated and its impact on thermal comfort conditions in rooms have been outlined. Windows of different constructions and having different heat transmission coefficients were modelled (2.4, 1.6 and 1.0 W/m2K). CFD predictions showed that even in cases of low window thermal transmittance coefficient (U value), thermal discomfort conditions may appear in the room if the height of the window is more than 2.0 meters. Santrauka Dideli langai ir stiklo fasadai tapo neatsiejama šiuolaikiškos architektūros dalis. Jie projektuojami ne tik visuomeniniuose, bet ir individualiuose namuose. Nekalbant apie teigiamus tokios architektūros aspektus, didelių matmenų langai gali tapti šiluminio diskomforto priežastis. Už patalpos orą vėsesnis vidinis stiklo paviršius sukelia žemyn nukreiptą oro srautą, kuris tam tikru greičiu patenka į žmonių gyvenamąją arba darbo zoną. Vėsių stiklo paviršių sukeltų oro srovių intensyvumas priklauso nuo lango šiluminių savybių, jo konstrukcijos bei šildymo prietaisų įrengimo vietų. Dažniausiai mikroklimato sąlygos patalpose vertinamos matuojant oro temperatūrą, santykinį drėgnį, oro judrumą ir šilumos mainus spinduliavimu. Straipsnyje pristatomas tyrimas, kuriam buvo pasitelktas kompiuterinis oro judėjimo modeliavimas (skaitiniai skysčių ir dujų dinamikos metodai). Buvo tiriama oro judėjimo patalpose priklausomybė nuo langų bei stiklo fasadų konstrukcijų ir šiluminių savybių. Modeliuojant įvertinti trys langų tipai, kurių šilumos perdavimo koeficientų vertės: 2,4; 1,6 ir 1,0 W/m²K. Rezultatai parodė, kad net ir mažiausiai šilumai laidūs langai gali sukelti neleistiną oro judėjimą patalpose, jei jų aukštis viršija 2 metrus.
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Hernández-Garfias, Enrique, Carolina del Carmen Pérez-Sánchez, Temani Durán-Mendoza, Juan Guzmán-Ceferino, and Manuel González-Pérez. "Caracterización Térmica De Vidrios Con Recubrimientos Metálicos." European Scientific Journal, ESJ 17, no. 21 (June 30, 2021): 305. http://dx.doi.org/10.19044/esj.2021.v17n21p305.
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Por la situación climática de las últimas décadas, las normas internacionales que regulan a los materiales de construcción son cada vez más estrictas. Actualmente, el vidrio es uno de los materiales de construcción más utilizados a nivel global y existen normas para evaluar su rendimiento térmico y así conocer su eficiencia para ahorrar energía. El Coeficiente de Transferencia de Calor (U) y el Coeficiente de Ganancia de Calor Solar (CGCS) son los principales parámetros térmicos que se utilizan para verificar si el rendimiento del material es satisfactorio en función de las normas vigentes y el mercado de vidrios. Para determinar estos parámetros se hicieron pruebas al exterior con un calorímetro solar diseñado y desarrollado para este fin. En este trabajo se evaluaron cinco muestras de vidrio: una muestra de vidrio claro (referencia) y cuatro muestras con recubrimientos de ZnO:Cu y ZnO:Ag en distintas concentraciones y número de capas aplicadas, los cuales fueron desarrollados con el objetivo de reducir la ganancia de calor. Los resultados de la evaluación mostraron diferencias poco significativas entre la muestra de referencia y las muestras con recubrimientos. Por lo cual, se sugiere realizar modificaciones durante el desarrollo o la aplicación de los recubrimientos que permita mejorar las características de ganancia térmica.
Due to the climatic situation of the last decades, the international standards that regulate construction materials are increasingly strict. Currently, glass is one of the most used building materials in the world, and there are standards to evaluate its thermal performance and thus know its efficiency to save energy. The Thermal Transmittance (U-value) and the Solar Heat Gain Coefficient (SHGC) are the main thermal parameters used to verify if the performance of the material is satisfactory according to current standards and the glass market. To determine these parameters, outdoor tests were carried out with a solar calorimeter designed and developed for this purpose. In this work, five glass samples were evaluated: one clear glass sample (reference) and four samples with ZnO: Cu and ZnO: Ag coatings in different concentrations and number of applied layers, which were developed to reduce heat gain. The results of the evaluation showed not very significant differences between the reference sample and the samples with coatings. Therefore, it is suggested to carry out modifications during the development or application of the coatings to improve the thermal gain characteristics.
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Hassan, Osama A. B. "Effect of foundation designs of passive house on the thermal bridges at the ground." Journal of Engineering, Design and Technology 14, no. 3 (July 4, 2016): 602–13. http://dx.doi.org/10.1108/jedt-09-2014-0059.
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Purpose This paper aims to understand the effect of different foundation designs of passive house on the resultant thermal bridges, at the junction between a wall and a slab on grade. Design/methodology/approach The linear thermal transmittances of some newly developed foundations of passive house are determined. The investigated foundation designs are L-element, U-element and foundation with foam glass technique. Findings It is found that the special design of passive house foundation can considerably influence the heat flow through thermal bridges. In this context, it is proposed a new foundation design of passive house, which has relatively low heat loss through thermal bridges. The results are compared with the “default” ISO values used to evaluate the effect of thermal bridges in typical buildings. It is found that there is large difference between the calculated linear thermal transmittances at the investigated foundations of passive house as compared to typical buildings. Practical implications The results can hopefully be used to improve the energy efficiency of the passive house. Social implications Sustainable solution of buildings. Originality/value A new foundation design of passive house is suggested to reduce heat loss through thermal bridges.
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Zaccaro, Francesco, John Richard Littlewood, and Carolyn Hayles. "An Analysis of Repeating Thermal Bridges from Timber Frame Fraction in Closed Panel Timber Frame Walls: A Case Study from Wales, UK." Energies 14, no. 4 (February 23, 2021): 1211. http://dx.doi.org/10.3390/en14041211.
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Calculating Repeating Thermal Bridges (RTBs) for Timber Frame (TF) closed panels that could occur in Offsite Manufactured (OSM) Modern Methods of Construction (MMC), such as exterior walls for nearly-to-zero operational energy dwellings to be constructed in Wales, United Kingdom (UK) is discussed in this paper. Detailed calculations for linear RTBs due to the TF components are often neglected when evaluating thermal transmittance (known as U-values hereafter). The use of standard TF fractions does not allow the designer to perceive their detrimental impact on RTBs and consequent U-values for exterior walls. With the increase of the thermal performance of exterior walls and as such lower U-values due to ever-tightening Building Regulations, specifically related to the energy use and carbon emissions from the space heating of dwellings, then the impacts of RTBs requires more investigation. By not calculating the potential of linear RTB at the design stage could lead to a performance gap where assumed U-values for exterior walls differ from manufacture to onsite. A TF detail from the Welsh manufacture has been chosen as a case study, to develop and apply a methodology using manufacturing drawings to evaluate TF fraction and their effect on the thermal performance.
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Kumar, Ashok, Rajesh Deoliya, and P. S. Chani. "Insulating Materials for Energy Saving in Buildings." Key Engineering Materials 632 (November 2014): 1–14. http://dx.doi.org/10.4028/www.scientific.net/kem.632.1.
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Insulation is considered one of the effective solutions to achieve energy savings in buidings. Better insulation having low thermal conductivity contributes significantly to new construction and retrofitting existing buildings. The Energy Conservation Building Code and National Building Code of India define the prescriptive and mandatory requirements for the U-factor and R-values for different climates but the way to achieve these values is left to the designers. As none of the walling and roofing assemblies in buildings fulfill the criteria for overall thermal transmittance, the study deals with determining the thermal conductivity of sustainable walling materials and prefab roofing technologies as well as insulating materials using Guarded Hot-Plate Apparatus. The MATLAB program is developed for computing the U-values and for predicting the desired retrofit insulation thicknesses to make different materials and roofing assembly combinations comply the Code requirements in different climatic regions of India. The results of the study are used for computing the performance with and without insulation using DesgnBuilder software for improving energy efficinecy of the buildings in composite climate in India.
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Cui, Hai Hong. "Research on Amending the Energy Efficiency Provisions in the Building." Applied Mechanics and Materials 568-570 (June 2014): 1991–94. http://dx.doi.org/10.4028/www.scientific.net/amm.568-570.1991.
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The purpose of this paper is to identify the main requirements of the Building Regulations Part L1A for new dwellings. An explanation of the technical basis for energy rating is given including how they are calculated, how fuel costs are used, the role of the standard occupancy pattern, and an appreciation of the Building Research Establishment Domestic Energy Model (BREDEM). The aims and requirements of the European Directive on the Energy performance of Buildings and its implementation for new and existing domestic buildings is also considered. Design/methodology/approach – The requirements of Part L1A of the Building Regulations are developed. These relate to the thermal properties of the building fabric including insulation, thermal bridging, air tightness and glazing, the efficiency and responsiveness of heating and hot water systems, ventilation and lighting. The methodology for calculating thermal transmittance coefficients (U-values) is also demonstrated.
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Strandberg-de Bruijn, Paulien, Anna Donarelli, and Kristin Balksten. "Full-scale Studies of Improving Energy Performance by Renovating Historic Swedish Timber Buildings with Hemp-lime." Applied Sciences 9, no. 12 (June 18, 2019): 2484. http://dx.doi.org/10.3390/app9122484.
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With an increased focus on reducing greenhouse gas emissions, energy saving is of great importance in all sectors of society. EU directives set targets for member states to reduce energy use in buildings. Energy saving in historic buildings requires special measures, balancing energy-saving renovations against the preservation of heritage values. Traditional constructions are open to vapor diffusion and generally work differently from modern constructions. Modern materials in traditional constructions sometimes damages the original material as they are usually diffusion-tight. The aim of this study was to investigate whether hemp-lime could be used as an insulation material to improve the energy efficiency of historic timber building envelopes with a rendered façade in Sweden. The objective was to determine the actual energy savings for space heating. An additional objective was to determine the actual thermal transmittance and to study thermal buffering through in-situ measurements in a full-scale wall renovated with hemp-lime. Two full-scale wall sections were constructed at the Energy and Building Design laboratory at Lund University: A traditional post-and-plank wall with a lime render (80 mm), and a post-and-plank wall with a hemp-lime render (90 mm). Energy use for space heating was monitored continuously over a period of one year. The wall with a hemp-lime render required 33% less energy for space heating than the traditional post-and-plank wall with a lime render. This was accomplished without changing the framework, appearance or material in the render and without drastically changing the hygric properties of the façade. From the gathered data, the thermal transmittance (U-values) for both walls was calculated using two different methods, one based on material properties and the other based on energy use data. For both walls, thermal transmittance based on actual energy use data during the heating period was lower than what was expected from their material properties. This indicates that more material properties than thermal conductivity and material thickness need to be taken into account when performing energy use calculations. With hemp-lime, a renovation can be accomplished without damaging the timber structure and wooden slats, and it can be done with local traditional materials and building methods with no difference in appearance to a traditional lime render. This allows for heritage values to be preserved, while also allowing the building to comply with modern standards and with increased thermal comfort and reduced energy use.
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Pihelo, Peep, and Targo Kalamees. "Commissioning of thermal performance of prefabricated timber frame insulation elements for nZEB renovation." MATEC Web of Conferences 282 (2019): 02004. http://dx.doi.org/10.1051/matecconf/201928202004.
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The current study contains a commissioning of thermal performance of highly insulated building envelope, located in cold and humid Estonian climate. The focus is on the renovation of old apartment building to nearly-zero energy building with prefabricated timber frame insulation elements with designed thermal transmittances U=0.10-0.12 W/(m2∙K). Air tightness, heat flux and temperatures were measured after renovation. Results of commissioning are showing some deviations from designed values, possibly caused by internal convection, improper tightening of joints of elements and poor quality of sealing of layers which must be kept airtight. The results have shown that analysis of designed solutions before, during and after renovation is worthwhile. Thorough inspection and strict rules of quality control on work site are essential for high-quality, sustainable outcomes of renovation with timber frame insulation elements and to guarantee designed thermal performance.
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Blanco, Jesús M., Yokasta García Frómeta, Maggi Madrid, and Jesús Cuadrado. "Thermal Performance Assessment of Walls Made of Three Types of Sustainable Concrete Blocks by Means of FEM and Validated through an Extensive Measurement Campaign." Sustainability 13, no. 1 (January 4, 2021): 386. http://dx.doi.org/10.3390/su13010386.
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The thermal behavior of three different walls, made with and without by-products, is assessed by means of the Finite Element Method, aiming to evaluate its performance in terms of the sustainable construction of the blocks. Results were compared to those obtained from an experimental campaign, aiming at validation of the model. The by-products used for the blocks were “lime sludge” and “sawdust”, whose performance was compared against the traditional blocks made of concrete as a reference, aiming to demonstrate its sustainability, showing decreases of the thermal transmittance up to 10.5%. Additionally, following the same methodology, the thermal behavior of these above-mentioned blocks but now with added internal insulation made of “recycled cellulose” was assessed, showing higher decreases up to 25.5%, increasing sustainability by addressing an additional reduction in waste, so the right combination of using by-products and the insulating filler in their cavities has been revealed as a promising way of optimizing the walls, offering a relevant improvement in energy savings. Finally, when comparing the U-values of the blocks made of concrete without insulation versus those made of by-products, with insulation, improvements up to 33.3% were reached. The adaptation of the procedure through a moisture correction factor was also incorporated.
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Aguilar-Santana, Jorge Luis, Mariana Velasco-Carrasco, and Saffa Riffat. "Thermal Transmittance (U-value) Evaluation of Innovative Window Technologies." Future Cities and Environment 6, no. 1 (2020). http://dx.doi.org/10.5334/fce.99.
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"95/04037 Critical thermal transmittance (U) value for the design of green buildings." Fuel and Energy Abstracts 36, no. 4 (July 1995): 287. http://dx.doi.org/10.1016/0140-6701(95)95641-h.
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"A New Metre for Cheap, Quick, Reliable and Simple Thermal Transmittance (U-Value) Measurements in Buildings." Sensors 17, no. 9 (September 3, 2017): 2017. http://dx.doi.org/10.3390/s17092017.
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Dutta, Arindam, and Akash Samanta. "Determining Factor/s of Window Glazing Regarding Reduction in Electrical Energy Consumption." Journal of Energy Resources Technology 142, no. 3 (October 16, 2019). http://dx.doi.org/10.1115/1.4044888.
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Abstract Among all building envelops, windows are typically the weakest barrier to heat ingress. The building energy consumption of any conditioned building located in the tropical country is deeply governed by the amount of heat gain inside the building because heating ventilation and air-conditioning (HVAC) system is a major energy consumer. Hence, it can be easily inferred that the energy consumption of a building can be reduced through judicial selection of window glasses. This paper illustrated the importance of thermal transmittance (U-value) and solar heat gain coefficient (SHGC) value of window glazing in detail and also demonstrated the energy savings potential of various types of commercially available windowpanes. The electric energy savings potential of various types of windowpanes such as tinted, reflective, single glazing, and double glazing glasses have been analyzed through eQUEST energy simulation software for a building, situated in the tropical region of India. Building architectural data and all other information regarding HVAC, lighting, etc. have been collected during the energy audit and trained in the eQUEST simulation for further analysis. The calibration of simulation model has been done using actual monthly electricity consumption data of the case building. This study depicts the percentage decrease in electrical energy consumption due to retrofitting of various commercially available window glasses compared with base building. The study also compares the importance of main two determining factor(s) U and SHGC value behind the judicial selection of proper window glazing.