Pub Date : 2023-01-31DOI: 10.1177/17442591221150250
Roberto Garay-Martinez, B. Arregi, M. Lumbreras
There are several research methods for the on-site assessment of U-values that aim to avoid the use of surface heat flux measurements and rely on tabulated or empirically developed correlations to define this parameter. This works performs a detailed process to estimate indoor surface heat transfer coefficients based on several experimental campaigns over building walls. Data is filtered out to remove periods with large temperature variations and/or unstable convective conditions due to HVAC. A statistical analysis is conducted, and the outcomes used to test the validity of U-value estimation approaches. The outcomes show that the actual surface heat transfer coefficients are in the range of reference works, but variations in the range of up to 2 W/m2 K are found. Uncertainty levels associated to the estimation of surface heat transfer coefficient are in the range 60% for instantaneous values while this is reduced down to 12%–20% for 8-h averages. Variations and uncertainty levels are higher for low temperature gradient situations, which are considered to be very likely for modern insulation levels. It is concluded that methods seeking to avoid the use of surface heat flux measurements need to develop much deeper knowledge in this field to gain accuracy and reliability.
{"title":"Surface heat transfer coefficients in building envelopes: Uncertainty levels in experimental methods","authors":"Roberto Garay-Martinez, B. Arregi, M. Lumbreras","doi":"10.1177/17442591221150250","DOIUrl":"https://doi.org/10.1177/17442591221150250","url":null,"abstract":"There are several research methods for the on-site assessment of U-values that aim to avoid the use of surface heat flux measurements and rely on tabulated or empirically developed correlations to define this parameter. This works performs a detailed process to estimate indoor surface heat transfer coefficients based on several experimental campaigns over building walls. Data is filtered out to remove periods with large temperature variations and/or unstable convective conditions due to HVAC. A statistical analysis is conducted, and the outcomes used to test the validity of U-value estimation approaches. The outcomes show that the actual surface heat transfer coefficients are in the range of reference works, but variations in the range of up to 2 W/m2 K are found. Uncertainty levels associated to the estimation of surface heat transfer coefficient are in the range 60% for instantaneous values while this is reduced down to 12%–20% for 8-h averages. Variations and uncertainty levels are higher for low temperature gradient situations, which are considered to be very likely for modern insulation levels. It is concluded that methods seeking to avoid the use of surface heat flux measurements need to develop much deeper knowledge in this field to gain accuracy and reliability.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"200 1","pages":"62 - 91"},"PeriodicalIF":2.0,"publicationDate":"2023-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75912453","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-26DOI: 10.1177/17442591221150257
D. Khovalyg, Alexandre Mudry, T. Keller
The traditional sequential design of building elements, where every element performs only one dedicated function, carries significant embodied energy. Thus, modular pre-fabricated load-bearing elements could overcome the disadvantages of the current carbon-intensive construction practice and go beyond; as such, lightweight glass fiber-polymer composite profiles could be more advantageous in performance. Cellular structures of such profiles can be advantageous for adding water channels for active heating and cooling indoors and for fire protection. Therefore, the development of such a modular active building slab referred to as P-TACS (Prefabricated Thermally-Activated Fiber-Polymer Composite Slab) is explored in this work. The structural performance of a proposed P-TACS design is verified in terms of serviceability and ultimate limit states. The addition of local carbon fiber inclusions allows for an increase in the span of the slab to 10 m and a more uniform surface temperature. Thermal performance of the structurally optimized geometrical configuration is analyzed by, first of all, determining water parameters based on the 1D approach partially adopted from the standard radiant systems analysis and, secondly, by a detailed 2D thermal analysis using ANSYS Fluent numerical simulations. The hydraulic and thermal performance comparison of the novel P-TACS design with two standard radiant systems (ESS Type A and RCP) reveals that the P-TACS design outperforms the standard embedded surface system ESS Type A, both for floor heating and cooling case. In addition, the response time of P-TACS is three times faster compared to the ESS response time. The main advantage of the P-TACS is in lower mean water temperature, compared to traditional embedded radiant systems (e.g., EES type), required for conditioning the space, potentially resulting in lower operational energy use. The fire outbreak scenario is considered to complete the analysis, and the measures to switch water flow from nominal to fire scenario are proposed.
{"title":"Prefabricated thermally-activated fiber-polymer composite building slab P-TACS: Toward the multifunctional and pre-fabricated structural elements in buildings","authors":"D. Khovalyg, Alexandre Mudry, T. Keller","doi":"10.1177/17442591221150257","DOIUrl":"https://doi.org/10.1177/17442591221150257","url":null,"abstract":"The traditional sequential design of building elements, where every element performs only one dedicated function, carries significant embodied energy. Thus, modular pre-fabricated load-bearing elements could overcome the disadvantages of the current carbon-intensive construction practice and go beyond; as such, lightweight glass fiber-polymer composite profiles could be more advantageous in performance. Cellular structures of such profiles can be advantageous for adding water channels for active heating and cooling indoors and for fire protection. Therefore, the development of such a modular active building slab referred to as P-TACS (Prefabricated Thermally-Activated Fiber-Polymer Composite Slab) is explored in this work. The structural performance of a proposed P-TACS design is verified in terms of serviceability and ultimate limit states. The addition of local carbon fiber inclusions allows for an increase in the span of the slab to 10 m and a more uniform surface temperature. Thermal performance of the structurally optimized geometrical configuration is analyzed by, first of all, determining water parameters based on the 1D approach partially adopted from the standard radiant systems analysis and, secondly, by a detailed 2D thermal analysis using ANSYS Fluent numerical simulations. The hydraulic and thermal performance comparison of the novel P-TACS design with two standard radiant systems (ESS Type A and RCP) reveals that the P-TACS design outperforms the standard embedded surface system ESS Type A, both for floor heating and cooling case. In addition, the response time of P-TACS is three times faster compared to the ESS response time. The main advantage of the P-TACS is in lower mean water temperature, compared to traditional embedded radiant systems (e.g., EES type), required for conditioning the space, potentially resulting in lower operational energy use. The fire outbreak scenario is considered to complete the analysis, and the measures to switch water flow from nominal to fire scenario are proposed.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"43 1","pages":"686 - 707"},"PeriodicalIF":2.0,"publicationDate":"2023-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84235808","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-20DOI: 10.1177/17442591221144785
Ahmad Deeb, F. Benmahiddine, J. Berger, R. Belarbi
Current hygrothermal behaviour prediction models neglect the hysteresis phenomenon. This leads to a discrepancy between numerical and experimental results, and a miscalculation of buildings’ durability. In this paper, a new mathematical model of hysteresis is proposed and implemented in a hygrothermal model to reduce this discrepancy. The model is based on a symmetry property between sorption curves and uses also a homotopic transformation relative to a parameter s ∈ [ 0 , 1 ] . The advantage of this model lies in its ease of use and implementation since it could be applied with the knowledge of only one main sorption curve by considering s = 0 , in other words, we only use the axisymmetric property here. In the case where the other main sorption curve is known, we use this curve to incorporate the homotopy property in order to calibrate the parameter s .The full version of the proposed model is called Axisymmetric + Homotopic. Furthermore, it was compared not only with the experimental sorption curves of different types of materials but also with a model that is well known in the literature (CARMELIET’s model). This comparison shows that the Axisymmetric + Homotopic model reliably predicts hysteresis loops of various types of materials even with the knowledge of only one of the main sorption curves. However, the full version of Axisymmetric + Homotopic model is more reliable and covers a large range of materials. The proposed model was incorporated into the mass transfer model. The simulation results strongly match the experimental ones.
{"title":"Development of a hysteresis model based on axisymmetric and homotopic properties to predict moisture transfer in building materials","authors":"Ahmad Deeb, F. Benmahiddine, J. Berger, R. Belarbi","doi":"10.1177/17442591221144785","DOIUrl":"https://doi.org/10.1177/17442591221144785","url":null,"abstract":"Current hygrothermal behaviour prediction models neglect the hysteresis phenomenon. This leads to a discrepancy between numerical and experimental results, and a miscalculation of buildings’ durability. In this paper, a new mathematical model of hysteresis is proposed and implemented in a hygrothermal model to reduce this discrepancy. The model is based on a symmetry property between sorption curves and uses also a homotopic transformation relative to a parameter s ∈ [ 0 , 1 ] . The advantage of this model lies in its ease of use and implementation since it could be applied with the knowledge of only one main sorption curve by considering s = 0 , in other words, we only use the axisymmetric property here. In the case where the other main sorption curve is known, we use this curve to incorporate the homotopy property in order to calibrate the parameter s .The full version of the proposed model is called Axisymmetric + Homotopic. Furthermore, it was compared not only with the experimental sorption curves of different types of materials but also with a model that is well known in the literature (CARMELIET’s model). This comparison shows that the Axisymmetric + Homotopic model reliably predicts hysteresis loops of various types of materials even with the knowledge of only one of the main sorption curves. However, the full version of Axisymmetric + Homotopic model is more reliable and covers a large range of materials. The proposed model was incorporated into the mass transfer model. The simulation results strongly match the experimental ones.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"70 1","pages":"567 - 601"},"PeriodicalIF":2.0,"publicationDate":"2023-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85009052","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-17DOI: 10.1177/17442591221145470
Kazuma Fukui, S. Takada
The sorption property of porous building materials in the hygroscopic region (sorption isotherm) is an important input to hygrothermal simulation. In this study, we proposed efficient and accurate protocols to obtain sorption isotherms using the static desiccator method. We developed a calculation model for three-dimensional simultaneous heat and moisture transfer in a material corresponding to the measurement specified in ISO 12571. Using an international database of the material properties, we conducted numerical simulations of the sorption process for five types of materials. The evolution of the amount of adsorbed moisture in a specimen and the time to reach equilibrium during the measurement were calculated under various humidity levels and specimen dimensions. According to the simulated results, we improved timing and interval for weighting the specimen to confirm the attainment of equilibrium for each type of a material and for each humidity level from the viewpoint of efficiency and accuracy. Meanwhile, the influence of size of a specimen on the time necessary to obtain the results was quantitatively demonstrated. Moreover, it was demonstrated that the method used for the determination of the attainment of equilibrium provided in ISO 12571 can underestimate the moisture content of materials with low moisture content and vapor permeability, and a policy to reduce risks of the underestimation was proposed.
{"title":"Study on efficient and accurate protocols of measuring sorption isotherm of porous building materials using three-dimensional hygrothermal simulation","authors":"Kazuma Fukui, S. Takada","doi":"10.1177/17442591221145470","DOIUrl":"https://doi.org/10.1177/17442591221145470","url":null,"abstract":"The sorption property of porous building materials in the hygroscopic region (sorption isotherm) is an important input to hygrothermal simulation. In this study, we proposed efficient and accurate protocols to obtain sorption isotherms using the static desiccator method. We developed a calculation model for three-dimensional simultaneous heat and moisture transfer in a material corresponding to the measurement specified in ISO 12571. Using an international database of the material properties, we conducted numerical simulations of the sorption process for five types of materials. The evolution of the amount of adsorbed moisture in a specimen and the time to reach equilibrium during the measurement were calculated under various humidity levels and specimen dimensions. According to the simulated results, we improved timing and interval for weighting the specimen to confirm the attainment of equilibrium for each type of a material and for each humidity level from the viewpoint of efficiency and accuracy. Meanwhile, the influence of size of a specimen on the time necessary to obtain the results was quantitatively demonstrated. Moreover, it was demonstrated that the method used for the determination of the attainment of equilibrium provided in ISO 12571 can underestimate the moisture content of materials with low moisture content and vapor permeability, and a policy to reduce risks of the underestimation was proposed.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"32 1","pages":"541 - 566"},"PeriodicalIF":2.0,"publicationDate":"2023-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80453299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-12DOI: 10.1177/17442591221145514
Chao Jiang, Yan Zhou, Kai Li, Difang Wei
This paper investigates the case building’s cooling effect, energy saving, and carbon sequestration with green facade and green roof. The west and east GF is covered with wisteria, and the GR is planted with different kinds of vegetables. The cooling effect of the GF and GR is analyzed by field test. The cooling energy saving of the GF and GR is deeply discussed with EnergyPlus software simulation. Carbon sequestrations of the GF and GR are calculated considering both plant photosynthetic and energy saving with the field test and simulation. The results show that the average external surface temperature reduction of the west GF, east GF, and GR is 4.5°C, 4.2°C, and 9.7°C on sunny days, 1.3°C, 1.3°C, and 1.4°C respectively on cloudy days. The total cooling energy saving of the GF and GR is 4.75 kWh/m2. The cooling energy saving of the GR with seven kinds of vegetables varies from 529.6 to 2936.3 kWh, which is related to the LAI and height of vegetables. The daily cooling energy saving in hot sunny weather scenario is almost three times that in cool sunny. The carbon sequestration ability per planted GF area is 1.4 kg C/m2, and per planted GR area with seven different vegetables varies from 0.88 to 2.21 kg C/m2, in which the strongest is peanut, and the weakest is lettuce. At last, the cooling energy savings of GF in different orientations on hot, warm, and cool sunny days are discussed, which is shown that the cooling energy saving effect of the different oriented GF mainly depends on the received solar radiation amount in this orientation. The results of this research can provide some assistance in improving the design of the building GR and GF.
本文对该案例建筑采用绿色立面和绿色屋顶的降温效果、节能效果和固碳效果进行了研究。西边和东边的GF覆盖着紫藤，而GR则种植着各种蔬菜。通过现场试验分析了GF和GR的冷却效果。通过EnergyPlus软件仿真，对GF和GR的冷却节能进行了深入探讨。通过田间试验和模拟计算，同时考虑植物光合作用和节能，计算了GF和GR的固碳量。结果表明:晴天时西GF、东GF和GR的平均外表面温度降低4.5°C、4.2°C和9.7°C，阴天时分别降低1.3°C、1.3°C和1.4°C。GF和GR合计制冷省电4.75 kWh/m2。7种蔬菜GR的制冷节能值在529.6 ~ 2936.3 kWh之间，与蔬菜的LAI和高度有关。炎热晴朗天气下的日制冷节能量几乎是凉爽晴朗天气下的3倍。GF种植面积的固碳能力为1.4 kg C/m2, 7种不同蔬菜的GR种植面积的固碳能力在0.88 ~ 2.21 kg C/m2之间，其中花生最强，生菜最弱。最后讨论了不同朝向GF在炎热、温暖和凉爽晴天的制冷节能效果，表明不同朝向GF的制冷节能效果主要取决于该朝向接收的太阳辐射量。研究结果可为改进建筑GR和GF的设计提供一定的帮助。
{"title":"Impact of green roof and green facade on building thermal performance and carbon sequestration in subtropical climate of China","authors":"Chao Jiang, Yan Zhou, Kai Li, Difang Wei","doi":"10.1177/17442591221145514","DOIUrl":"https://doi.org/10.1177/17442591221145514","url":null,"abstract":"This paper investigates the case building’s cooling effect, energy saving, and carbon sequestration with green facade and green roof. The west and east GF is covered with wisteria, and the GR is planted with different kinds of vegetables. The cooling effect of the GF and GR is analyzed by field test. The cooling energy saving of the GF and GR is deeply discussed with EnergyPlus software simulation. Carbon sequestrations of the GF and GR are calculated considering both plant photosynthetic and energy saving with the field test and simulation. The results show that the average external surface temperature reduction of the west GF, east GF, and GR is 4.5°C, 4.2°C, and 9.7°C on sunny days, 1.3°C, 1.3°C, and 1.4°C respectively on cloudy days. The total cooling energy saving of the GF and GR is 4.75 kWh/m2. The cooling energy saving of the GR with seven kinds of vegetables varies from 529.6 to 2936.3 kWh, which is related to the LAI and height of vegetables. The daily cooling energy saving in hot sunny weather scenario is almost three times that in cool sunny. The carbon sequestration ability per planted GF area is 1.4 kg C/m2, and per planted GR area with seven different vegetables varies from 0.88 to 2.21 kg C/m2, in which the strongest is peanut, and the weakest is lettuce. At last, the cooling energy savings of GF in different orientations on hot, warm, and cool sunny days are discussed, which is shown that the cooling energy saving effect of the different oriented GF mainly depends on the received solar radiation amount in this orientation. The results of this research can provide some assistance in improving the design of the building GR and GF.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"35 1","pages":"602 - 629"},"PeriodicalIF":2.0,"publicationDate":"2023-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78387677","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-01DOI: 10.1177/17442591221142506
Mosha Zhao, H. Künzel, S. Mehra
According to existing measurements and simulation results, the indoor thermal comfort in traditional wooden buildings (still remaining in a large amount) in the Chinese Hot-Summer-Cold-Winter zone is very poor in winter. However, few studies can be found regarding the energy retrofitting of their wooden enclosures, which is increasingly regarded as essential for improving indoor thermal comfort and maintaining built heritage. Therefore, this study demonstrates a method based on parametric study applying the widely validated WUFI®Plus software to help design hygrothermally functional insulation systems for this area. The parametric study was conducted on the example of traditional exterior wooden walls in Tongren in southern China. Five parameters were investigated, including internal and external insulation systems, vapor-open (mineral wool) and vapor-tight (XPS) insulation materials, a U-value of 0.8 W/(m2K) as well as a lower U-value of 0.24 W/(m2K) for the insulated walls, different capabilities and positions of an additional vapor control layer, as well as different cooling/dehumidification conditions in the warm period of a year. It has been found in this study that, if possible, a lower U-value than the current Chinese design standard for energy efficiency of buildings (0.8 W/(m2K) should be preferred for energy retrofitting. This can limit the yearly duration of a high internal surface relative humidity over 80% shorter than 30 days without any dehumidification devices. Besides, this study provides some feasible wall configurations with instructions on their limitations to guide future work regarding the design of insulated building components and the operation of renovated traditional wooden buildings.
{"title":"Design hygrothermally functional wooden insulation systems: A parametric study for mixed climate","authors":"Mosha Zhao, H. Künzel, S. Mehra","doi":"10.1177/17442591221142506","DOIUrl":"https://doi.org/10.1177/17442591221142506","url":null,"abstract":"According to existing measurements and simulation results, the indoor thermal comfort in traditional wooden buildings (still remaining in a large amount) in the Chinese Hot-Summer-Cold-Winter zone is very poor in winter. However, few studies can be found regarding the energy retrofitting of their wooden enclosures, which is increasingly regarded as essential for improving indoor thermal comfort and maintaining built heritage. Therefore, this study demonstrates a method based on parametric study applying the widely validated WUFI®Plus software to help design hygrothermally functional insulation systems for this area. The parametric study was conducted on the example of traditional exterior wooden walls in Tongren in southern China. Five parameters were investigated, including internal and external insulation systems, vapor-open (mineral wool) and vapor-tight (XPS) insulation materials, a U-value of 0.8 W/(m2K) as well as a lower U-value of 0.24 W/(m2K) for the insulated walls, different capabilities and positions of an additional vapor control layer, as well as different cooling/dehumidification conditions in the warm period of a year. It has been found in this study that, if possible, a lower U-value than the current Chinese design standard for energy efficiency of buildings (0.8 W/(m2K) should be preferred for energy retrofitting. This can limit the yearly duration of a high internal surface relative humidity over 80% shorter than 30 days without any dehumidification devices. Besides, this study provides some feasible wall configurations with instructions on their limitations to guide future work regarding the design of insulated building components and the operation of renovated traditional wooden buildings.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"26 1","pages":"474 - 509"},"PeriodicalIF":2.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74581981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-01DOI: 10.1177/17442591221142496
P. Huttunen, J. Vinha
Building physical simulation software rely on assumptions regarding the local equilibria in materials’ pore systems, which may be unjustified for certain materials. While local hygrothermal non-equilibrium has still been in focus in some previous studies, it has been unclear how significant factor it may be when modeling real structures. In case of wood, the non-equilibrium is related to the slowness of intrusion of water molecules into the hygroscopic cell walls. Including local non-equilibrium in macroscopic model requires separate variables for pore air vapor and adsorbed moisture, and modeling the local mass transfer between pore air and adsorbed moisture requires effective material parameters, whose experimental determination is not straightforward. Commercially available sorption balances can be used to record data, which can be used in the parameter estimation. In this type of problem of parameter estimation from time-dependent data the mathematical challenge is to find global optimum from different solutions, which yield similar values for objective function. This difficulty can be overcome by using statistical inversion approach, which we applied in studying low-density woodfibre material (LDF). Dynamic sorption parameters were finally applied in numerical analysis of a laboratory test assembly. Based on the results, our conclusion is that the slowness of sorption is obvious in small LDF sample, which is exposed to changing humidity, but with the studied material the sorption seem to happen fast enough so that local non-equilibrium may have only slight effects in modeling of real structures.
{"title":"Dynamic water vapor sorption in wood-based fibrous materials and material parameter estimation","authors":"P. Huttunen, J. Vinha","doi":"10.1177/17442591221142496","DOIUrl":"https://doi.org/10.1177/17442591221142496","url":null,"abstract":"Building physical simulation software rely on assumptions regarding the local equilibria in materials’ pore systems, which may be unjustified for certain materials. While local hygrothermal non-equilibrium has still been in focus in some previous studies, it has been unclear how significant factor it may be when modeling real structures. In case of wood, the non-equilibrium is related to the slowness of intrusion of water molecules into the hygroscopic cell walls. Including local non-equilibrium in macroscopic model requires separate variables for pore air vapor and adsorbed moisture, and modeling the local mass transfer between pore air and adsorbed moisture requires effective material parameters, whose experimental determination is not straightforward. Commercially available sorption balances can be used to record data, which can be used in the parameter estimation. In this type of problem of parameter estimation from time-dependent data the mathematical challenge is to find global optimum from different solutions, which yield similar values for objective function. This difficulty can be overcome by using statistical inversion approach, which we applied in studying low-density woodfibre material (LDF). Dynamic sorption parameters were finally applied in numerical analysis of a laboratory test assembly. Based on the results, our conclusion is that the slowness of sorption is obvious in small LDF sample, which is exposed to changing humidity, but with the studied material the sorption seem to happen fast enough so that local non-equilibrium may have only slight effects in modeling of real structures.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"3 21 1","pages":"399 - 424"},"PeriodicalIF":2.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90156098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-01DOI: 10.1177/17442591221142501
N. Reuge, F. Collet, S. Prétot, S. Moisette, M. Bart, O. Style, A. Shea, C. Lanos
The hygrothermal behavior of a bio-based multilayered wall has been studied by numerical simulations. The key point of these research investigations was to properly describe the hygrothermal transfers occurring inside the studied wall solution. In previous work, the case of the wall subjected to a given real climate (Wroughton HIVE demonstrator, UK, Feb 2018) has been investigated. The present work, focused on the moisture regulation capacity of the wall, considers an improved kinetics model of sorption, different layer configurations, one additional climate (Bordeaux, FR, Apr 2008) and the effect of indoor cyclic loads. Compared to the classical approach, the local kinetics approach results in prediction of stronger and steeper hygric dynamics with larger relative humidity variations at small time scales. The study of the different wall configurations allows to determine the best one in terms of moisture damping: the vapor control membrane is advantageously removed provided the OSB3 12 mm layer is replaced by an OSB4 18 mm layer. Moreover, the simulations show that the Moisture Buffer Value characteristic of each material layer is not a sufficient criterion to evaluate hygric performance of the wall; strong hygric interactions occur with the layer’s permeability independently of its sorption capacity. Finally, water content hysteresis phenomena are studied and it appears that under usual operating conditions, they can be ignored by adjusting the layers’ permeabilities for adequate fits on the Moisture Buffer Value tests.
{"title":"Hygrothermal transfers through a bio-based multilayered wall: Modeling study of different wall configurations subjected to various climates and indoor cyclic loads","authors":"N. Reuge, F. Collet, S. Prétot, S. Moisette, M. Bart, O. Style, A. Shea, C. Lanos","doi":"10.1177/17442591221142501","DOIUrl":"https://doi.org/10.1177/17442591221142501","url":null,"abstract":"The hygrothermal behavior of a bio-based multilayered wall has been studied by numerical simulations. The key point of these research investigations was to properly describe the hygrothermal transfers occurring inside the studied wall solution. In previous work, the case of the wall subjected to a given real climate (Wroughton HIVE demonstrator, UK, Feb 2018) has been investigated. The present work, focused on the moisture regulation capacity of the wall, considers an improved kinetics model of sorption, different layer configurations, one additional climate (Bordeaux, FR, Apr 2008) and the effect of indoor cyclic loads. Compared to the classical approach, the local kinetics approach results in prediction of stronger and steeper hygric dynamics with larger relative humidity variations at small time scales. The study of the different wall configurations allows to determine the best one in terms of moisture damping: the vapor control membrane is advantageously removed provided the OSB3 12 mm layer is replaced by an OSB4 18 mm layer. Moreover, the simulations show that the Moisture Buffer Value characteristic of each material layer is not a sufficient criterion to evaluate hygric performance of the wall; strong hygric interactions occur with the layer’s permeability independently of its sorption capacity. Finally, water content hysteresis phenomena are studied and it appears that under usual operating conditions, they can be ignored by adjusting the layers’ permeabilities for adequate fits on the Moisture Buffer Value tests.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"233 1","pages":"425 - 454"},"PeriodicalIF":2.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76975788","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-12-23DOI: 10.1177/17442591221140470
S. Roels, Astrid Tijskens
Since timber frame constructions can help to reduce CO2-emissions and lower the embodied energy of buildings, the market share of timber-based buildings is growing across Europe. Unfortunately, timber frame constructions are found to be susceptible to moisture damage, such as interstitial condensation, mould growth and wood rot. To avoid moisture damage, a correct design of the wall composition is crucial, with special emphasis on the ratio between vapour resistance of wind and vapour barrier. Given that experimental investigations are time-consuming and expensive, numerical tools are common to assess the hygrothermal behaviour of building components. And although timber frame constructions are inherently two- or even three-dimensional due to the embedded wooden elements, most often, 1D-simulations focussing on the basic configuration with insulation between wind and vapour barrier are conducted. This paper investigates to what extent neglecting the embedded wooden elements influences the risk assessment of the wall. Three different wall configurations have been considered and their hygrothermal response, as predicted by 1D- and 2D-numerical simulations, are compared. Variability of the exterior climate is included by using four distinct different climate regions. Contrary to common assumptions, buffering of moisture in wooden elements does not always lower the risk on moisture damage, but might even increase it. While the predicted risk on mould growth was found to be similar between 1D and 2D-simulations, the opposite was found for the risk on interstitial condensation. Mainly for cold climates and wall configurations with hardly any other hygric buffering capacity, levels of interstitial condensation were found to be significantly higher when taking the wooden elements into account in the numerical simulations. Hence, care should be taken when assessing the reliability of timber frame walls based on 1D-simulations only.
{"title":"The impact of wooden studs on the moisture risk of timber frame constructions","authors":"S. Roels, Astrid Tijskens","doi":"10.1177/17442591221140470","DOIUrl":"https://doi.org/10.1177/17442591221140470","url":null,"abstract":"Since timber frame constructions can help to reduce CO2-emissions and lower the embodied energy of buildings, the market share of timber-based buildings is growing across Europe. Unfortunately, timber frame constructions are found to be susceptible to moisture damage, such as interstitial condensation, mould growth and wood rot. To avoid moisture damage, a correct design of the wall composition is crucial, with special emphasis on the ratio between vapour resistance of wind and vapour barrier. Given that experimental investigations are time-consuming and expensive, numerical tools are common to assess the hygrothermal behaviour of building components. And although timber frame constructions are inherently two- or even three-dimensional due to the embedded wooden elements, most often, 1D-simulations focussing on the basic configuration with insulation between wind and vapour barrier are conducted. This paper investigates to what extent neglecting the embedded wooden elements influences the risk assessment of the wall. Three different wall configurations have been considered and their hygrothermal response, as predicted by 1D- and 2D-numerical simulations, are compared. Variability of the exterior climate is included by using four distinct different climate regions. Contrary to common assumptions, buffering of moisture in wooden elements does not always lower the risk on moisture damage, but might even increase it. While the predicted risk on mould growth was found to be similar between 1D and 2D-simulations, the opposite was found for the risk on interstitial condensation. Mainly for cold climates and wall configurations with hardly any other hygric buffering capacity, levels of interstitial condensation were found to be significantly higher when taking the wooden elements into account in the numerical simulations. Hence, care should be taken when assessing the reliability of timber frame walls based on 1D-simulations only.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"11 1","pages":"455 - 473"},"PeriodicalIF":2.0,"publicationDate":"2022-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86347197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-12-22DOI: 10.1177/17442591221136274
Jonas Dürr, A. Geissler, C. Hoffmann
An enormous range of building materials that is almost impossible to keep track of is available. The trend toward building densification in cities continues apace. Coupled with climate change, a situation is emerging that poses ecological as well as economic risks in terms of living comfort in public, urban spaces. Building designers need help (tools) to be able to address a wide range of requirements within their planning. The development of the Multi-Criteria Decision-Making (MCDM) model BASK (engl. “Construction Materials for Cities in Climate Change”) is presented. The goal of the model is to assist building designers in determining surface materials for wall, ground and roof construction and help determine the best compromise between environmental, economic, and building practice criteria. Currently available criteria are heat stress, visual reflectance, CO2 equivalents, electricity production, retrofitability, sound absorption, construction costs, and life span. The criteria can be weighted by the designer, resulting in a customized ranking of construction systems that best meets the designer’s prioritized criteria. The design of BASK basically allows for an extension of the criteria. The version of BASK described in this paper includes 10 construction systems covering a wide range of construction types focused on walls. The tool requires technical data for materials considered in construction systems included, which are made available via a data base. The scope of construction systems can also be extended in the future. Based on the restricted set of construction systems the results of a sensitivity analysis and initial validation are given.
{"title":"Development of a Multi-Criteria Decision-Making model to assist building designers in the choice of superficial construction systems in urban areas","authors":"Jonas Dürr, A. Geissler, C. Hoffmann","doi":"10.1177/17442591221136274","DOIUrl":"https://doi.org/10.1177/17442591221136274","url":null,"abstract":"An enormous range of building materials that is almost impossible to keep track of is available. The trend toward building densification in cities continues apace. Coupled with climate change, a situation is emerging that poses ecological as well as economic risks in terms of living comfort in public, urban spaces. Building designers need help (tools) to be able to address a wide range of requirements within their planning. The development of the Multi-Criteria Decision-Making (MCDM) model BASK (engl. “Construction Materials for Cities in Climate Change”) is presented. The goal of the model is to assist building designers in determining surface materials for wall, ground and roof construction and help determine the best compromise between environmental, economic, and building practice criteria. Currently available criteria are heat stress, visual reflectance, CO2 equivalents, electricity production, retrofitability, sound absorption, construction costs, and life span. The criteria can be weighted by the designer, resulting in a customized ranking of construction systems that best meets the designer’s prioritized criteria. The design of BASK basically allows for an extension of the criteria. The version of BASK described in this paper includes 10 construction systems covering a wide range of construction types focused on walls. The tool requires technical data for materials considered in construction systems included, which are made available via a data base. The scope of construction systems can also be extended in the future. Based on the restricted set of construction systems the results of a sensitivity analysis and initial validation are given.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"4 1","pages":"513 - 540"},"PeriodicalIF":2.0,"publicationDate":"2022-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74398028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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