This article reports the variations in volatile organic compound (VOC) emission rates from Scots pine wood under varying relative humidity (RH) conditions. The experiment encompassed both heartwood and sapwood, involving recently sawn (“new”) wood, and aged (“old”) wood that had been stored indoors for 15 years. Individual specimens were placed in climate chambers, wherein specific RH levels were maintained in the following sequence: 20%, 40%, 60%, 80%, 60%, 40%, and 20%, 1 month each. VOC samples were systematically collected at the end of each RH period and analyzed using TD-GC-MS system. The results demonstrate a direct relationship between RH levels and VOC emission rates in all specimen categories. Old wood indicated significantly lower emission rates compared to new wood, with distinct differences in emitted compound composition. As the experiment progressed, the initial differences between old and new specimens diminished, reaching minimum difference by the last measurement. Aldehydes were among the two most prevalent compound groups in all sample types. Terpenes were the most abundantly emitted group during the first VOC collection. However, their emissions subsequently declined, followed by an increase in all main chemical groups at 80% RH. Additionally, more polar compounds were emitted as RH increased. This study contributes to the discussion regarding the suitability of standard emission tests performed in fixed 50 ± 5% RH for hygroscopic materials. More attention should be given to the influence of RH on VOC emissions to ensure a comprehensive understanding of wood material’s emission behavior.

Moisture is a crucial factor regarding degradation of building materials, and hygrothermal simulations are essential tools for analysing and predicting moisture content and durability of buildings under dynamic conditions. This article focusses on the development of a Danish moisture reference year, based on climate data from the period 2001 to 2019. The reference year was created as a “one-fits-all” for hygrothermal simulations and to ensure better representation of the Danish climate conditions. Traditionally reference years from nearby locations in Germany and Sweden have been used. The reference year was created according to EN ISO 15927-4:2006; the raw climate data was statistically analysed, and representative months were selected. This process resulted in five reference years, with focus on different types of constructions and exterior claddings. The new reference years were compared with reference years from nearby locations, as well as with the raw Danish climate data over a 9-year period. The analysis includes comparison of the climate parameters, and validation through dynamic simulations in WUFI and DELPHIN. In WUFI, simulations were made for typical wall and roof constructions, whereas DELPHIN simulations were made for three calibrated models from an earlier project, of internally insulated solid masonry walls. The results indicate that the five new Danish reference years were quite similar in many aspects (regardless of the chosen primary and secondary climate parameters) and provided a reliable representation of Danish climate conditions. For the hygrothermal simulations, a good correlation was generally observed between results from simulations using the Danish reference years and simulations based on raw climate data.

A dynamic insulation material is a smart material that can be used for designing adaptive dynamic building wall systems, which actively control the energy and mass transfer between the outside environment and the indoor of the building. In this work, an optimization methodology is implemented to design customized dynamic insulation materials for building wall elements. Two different locations are chosen as case studies: Sauce Viejo (Argentina) and Frankfurt (Germany). By analyzing the relationship between the heat flux and the thermal gradient to which the wall is exposed, it is shown that the wall element must behave as a thermal switch to optimize the energy performance of the system. It is found that an optimized thermal switch could reduce undesired heat loads of a building wall element between 8% and 10% in comparison with a typical insulation material and it has a better capability to evacuate the heat in order to reduce internal heat gains, showing that a thermal switch can be good candidate for designing energy-efficient building wall elements.

This study investigates the influence of waste tire rubber (WTR) on the liquid-phase moisture transport properties in cement mortar under ambient conditions—an area that is still insufficiently explored in current literature. While most studies have focused on mechanical performance, this work integrates capillary absorption testing with a liquid-phase moisture transfer model calibrated using experimental data to quantify sorptivity and water diffusivity. Seven mortar mixtures were prepared: one control (no WTR), three with WTR powder replacing 7%, 14%, and 21% of sand by volume, and three with rubber aggregates at the same replacement levels. The study systematically compares the effects of WTR in both powder and aggregate forms on key parameters such as sorptivity, water diffusivity, accessible porosity, and compressive strength. Capillary absorption tests provided empirical data for model calibration and analysis of liquid-phase moisture transfer behavior. Results showed that WTR substitutions up to 14% reduced accessible porosity by 18.03% and sorptivity by up to 351%, attributed to the hydrophobic nature of rubber, which impedes capillary flow. However, at a 21% replacement level, both porosity and sorptivity increased, while compressive strength declined—indicating that high WTR content compromises mechanical integrity and limits suitability for structural use. Water diffusivity exhibited two regimes: a low-diffusivity phase (<0.01 mm 2 /s) under partial saturation, and a higher-diffusivity phase at near-saturation, consistent with dual-regime moisture transfer models. WTR incorporation led to more tortuous pore structures, which reduced water ingress and improved moisture resistance. WTR powder was more effective than rubber aggregates in reducing sorptivity and porosity, particularly at replacement levels up to 14%. WTR powder at replacement levels up to 14% improved moisture resistance, suggesting its potential use in non-structural cement elements such as renders and plaster coatings. The results clarify how WTR particle morphology influences pores connectivity and liquid-phase moisture transfer, supporting its potential for enhancing durability in moisture-sensitive, non-load-bearing cement applications.

HAM models have proven their value for analyzing moisture-related pathologies by assessing hygrothermal responses to environmental exposure. In this study, a coupling between CFD and HAM is developed to capture spatial wetting and drying effects, which allows to identify façade degradation patterns. Wind-driven rain (WDR) and evaporation significantly influence the hygrothermal performance and durability of façades, particularly in heritage and renovation. In traditional HAM modeling, WDR and convective heat transfer coefficients (CHTC) are often simplified by applying generic, uniform values across the façade. However, this approximation fails to account for the spatial and temporal variations in WDR and neglects the significant variations in CHTC due to the surrounding velocity flow field. These oversimplifications can limit the validity and accuracy of hygrothermal predictions. This study presents a novel approach by externally coupling CFD simulations with HAM modeling to capture the spatial distribution of WDR and CHTC on building façades. Steady Reynolds-averaged Navier-Stokes equations and Eulerian-multiphase simulations are performed to calculate the wind flow and the rain trajectories with turbulent dispersion of raindrops. Using a cubic low-rise building as a case, the coupled model evaluates the effects of wind and rain exposure on façade deterioration, including frost degradation, salt crystallization, and algae growth. Results indicate that conventional approaches tend to underestimate critical rain loads, while drying potential is overestimated. It highlights how spatial variations in WDR and drying influence degradation mechanisms, emphasizing the need for more detailed spatial analyses. This integrated method provides valuable insights into risks posed by moisture exposure and drying dynamics, offering practical applications for targeted renovation strategies and improved preservation of building materials.

Blue brick is a traditional material used in China’s historical architecture, which is subjected to different degrees of moisture-related degradation after experiencing hundreds of years of exposure to the natural environment. It is of great significance to study the hygrothermal properties of the historical blue bricks for the conservation and restoration of these heritage structures. This study carried out a comprehensive measurement and characterization of the historical blue bricks from Linqing, which are extensively utilized in many World Cultural Heritage Sites in China. The thermal properties and pore structure of the bricks are first investigated. Sorption isotherm and pressure plate tests are conducted to obtain the equilibrium moisture content in the hygroscopic and overhygroscopic ranges, respectively. The moisture transport characteristics are further assessed by water vapor transmission test, capillary water absorption test, and drying test. A material characterization is further conducted to acquire the moisture storage and moisture transport functions of the bricks. The results show that the historical blue bricks exhibit a large discrepancy in the porosity, thermal properties, moisture storage and transport properties due to the difference in their pore structures. By reproducing the drying and capillary water absorption processes by HAM simulations, the derived liquid water conductivity functions and vapor diffusivity functions of the blue bricks are further calibrated. The complete hygrothermal properties of the historical blue bricks achieved in this research contribute to a solid material data input for heritage protection and renovation.

Due to the significant energy consumption and carbon emissions associated with the building sector, the development of sustainable and energy-efficient construction materials is of great interest. This article presents the physicochemical properties of miscanthus, its cultivation and growth, applications in the construction domain, and the challenges and limitations posed by the chemical composition of this lignocellulosic material. Thus, the objective is to present a state of art on miscanthus, by providing a solid foundation for the elaboration of plant based thermal insulation composite material to be used in construction. It has been proved that the low thermal conductivity of miscanthus (0.05 W/(m. K)), its high porosity, lightweight and other environmental advantages (renewability and sustainability) make of it and of the miscanthus-based materials promising candidates in the building insulation industry.

This study explores the development of empirical relationships for the critical transport performance parameters, pressure rise and entropy generation in peristaltic flow of Bingham fluid through curved channel. The aim is to study structural fluid dynamics to evaluate the interaction between fluid transport and channel geometry by considering effects of curved channel structure on pressure distribution, and heat losses and hence improving efficiency. To do so a consistent correlations of input parameters like curvature, Bingham number, and Brinkman number and the corresponding output responses is developed using a combination of Response Surface Methodology (RSM) and Artificial Neural Networks (ANNs). Numerical solutions of the governing equations are obtained using MATLAB’s bvp4c solver, ensuring precise modeling of the flow dynamics. Optimiality is ensured by parameter sensitivity analysis and residual assessments reveal that the Bingham number has a significant impact on pressure rise, while the curvature parameter plays a pivotal role in entropy generation. Although the Brinkman number has minimal effect on pressure rise, its influence on entropy generation exhibits a complex, parameter-dependent behavior. The developed models are rigorously validated, showing strong predictive accuracy with low error margins and high correlation coefficients across training, testing, and validation phases. The findings of this research offer critical insights into optimizing peristaltic flow in practical, non-Newtonian fluid systems, contributing to the advancement of fluid management technologies and systems efficiency.

UV germicidal irradiance has gained significant popularity as a disinfection technology since the COVID-19 pandemic. Challenges remain in accurately characterizing the in-duct irradiance distribution of UVC lamps under varying air parameters, introducing uncertainty in exposure and efficiency estimations. This study experimentally characterizes irradiance of 222 and 254 nm UV lamps in a conduit using a 9-point average method. Irradiance measurements are recorded from five sides at each point, and a correction factor is proposed to account for spectrometer detection angle overlaps. Results indicate that the 254 nm lamp output increases by 18% with an air temperature rise from 25°C to 35°C but decreases by 21% as air velocity rises from 0.5 to 2 m/s. In contrast, the 222 nm lamp shows negligible sensitivity to changes in air temperature or velocity. Relative humidity variations (25%–60%) did not significantly affect either lamp’s output. In addition, the 222 nm lamp generates minimal ozone and total volatile organic compounds (TVOCs) during operation in stagnant air. The particle tracking simulation results revealed higher velocity fluctuations in proximity to the installed 222 nm lamp than the 254 nm lamp due to the larger lamp geometries. Experimental UVGI efficacy tests targeting airborne E . coli inactivation, combined with comprehensive life cycle analysis, demonstrated that the 254 nm lamp offers superior cost-effectiveness and sustainability for continuous in-duct air disinfection. These findings provide practical insights for optimizing UVC systems for air disinfection applications.

This article aims to investigate the link between lab-measured material properties and whole building performance of rammed earth (RE) walls through characterization at laboratory scale and numerical simulations using combined heat and moisture transfer models at whole building (WB) scale. RE buildings are known as an energy-efficient solution in hot climates and are low-carbon construction since local unfired earth is used as construction material. Nevertheless, the behavior of such buildings under different internal and external loads needs additional investigations. The present study explores the use of unstabilized RE walls, with and without the use of painting, three bio-stabilized RE and conventional concrete walls for comparison. The simulation includes climate conditions from Central Europe and North Africa, along with typical residential and tertiary occupancy scenarios. To identify the contribution of RE materials in controlling the indoor climate, the investigation covers a total of 24 configurations of six wall materials, two locations, and two occupancy scenarios. Results are analyzed by comparing heating demand, summer thermal comfort, and relative humidity levels. Furthermore, the hygrothermal properties of bio-stabilized RE are experimentally determined, to confirm the choice of using only moisture-dependent parameters. Experimental investigations focus on the influence of temperature on sorption isotherm, hysteresis, adsorption kinetics, and moisture buffer value (MBV). The results of this investigation show that thermal properties measured at the material scale seem to have a direct link with results at the whole building scale for heating demand and summer thermal comfort for uninsulated walls, while a more complex behavior is related to the hygroscopic properties, due mainly to the combined effect of the kinetics of adsorption and vapor permeability of the material.