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This study focuses on the development and characterization of a novel composite material based on flue gas desulfurization (FGD) gypsum modified with functionalized nanocellulose. The incorporation of 0.1 wt% nanocellulose into the FGD gypsum matrix resulted in significant improvements in mechanical strength, water resistance, and thermal insulation properties. The flexural and compressive strength of the optimized composite increased by 32 % and 27 %, respectively, compared to the control sample. The water absorption decreased by 22 %, and the softening coefficient increased from 0.72 to 0.85, indicating enhanced water resistance. The thermal conductivity of the composite was reduced by 31 %, showcasing its potential as an energy-efficient building material. SEM analysis revealed a refined microstructure with improved interfacial bonding between the nanocellulose and gypsum matrix, while FTIR spectroscopy confirmed the presence of chemical interactions between the components. The moisture buffering capacity of the composite was also superior, with a 38 % higher moisture buffering value than the control sample. These findings highlight the potential of functionalized nanocellulose as a reinforcing agent in FGD gypsum-based composites, offering a promising solution for the development of high-performance, eco-friendly building materials.

This study focuses on the development and characterization of a novel composite material based on flue gas desulfurization (FGD) gypsum modified with functionalized nanocellulose. The incorporation of 0.1 wt% nanocellulose into the FGD gypsum matrix resulted in significant improvements in mechanical strength, water resistance, and thermal insulation properties. The flexural and compressive strength of the optimized composite increased by 32 % and 27 %, respectively, compared to the control sample. The water absorption decreased by 22 %, and the softening coefficient increased from 0.72 to 0.85, indicating enhanced water resistance. The thermal conductivity of the composite was reduced by 31 %, showcasing its potential as an energy-efficient building material. SEM analysis revealed a refined microstructure with improved interfacial bonding between the nanocellulose and gypsum matrix, while FTIR spectroscopy confirmed the presence of chemical interactions between the components. The moisture buffering capacity of the composite was also superior, with a 38 % higher moisture buffering value than the control sample. These findings highlight the potential of functionalized nanocellulose as a reinforcing agent in FGD gypsum-based composites, offering a promising solution for the development of high-performance, eco-friendly building materials. [ABSTRACT FROM AUTHOR]

The increasing requirements concerning the consideration of the environmental impact of building materials, along with the simultaneous preservation and enhancement of building thermal parameters, have led to a surge in interest in insulations based on organic or recycled materials. Despite the growing interest in these materials, there remains a scarcity of scientific studies regarding their hygrothermal properties. Within the scope of the research described in the text, the insulation properties of loose-fill materials (hemp shives, cellulose fibers, loose wood wool, and mineral wool as a reference) in wooden frame walls were analyzed. The authors simulated walls with the same U value filled with these materials using Delphin 6.1 software. The simulation time was 3 years, considering the appropriate climatic conditions of Olsztyn and different microclimatic conditions inside the rooms. Insulations made of natural organic can absorb and reveal moisture to the internal environment, while mineral wool transports the moisture to the outside, which may cause condensation problems. Insulations made of hemp shives or wood wool do not increase the level of accumulated moisture over time, which results in thermal stability. In contrast, cellulose and mineral wool store more moisture, which in wet conditions increases the heat flux by 6.9% and 5.2%, respectively. [ABSTRACT FROM AUTHOR]

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The management of indoor humidity through equipment consumes massive energy, leading to the growing interest in passive regulation of indoor humidity via moisture buffering. Numerous factors may impact the performance of interior finishing material during moisture regulation, thus identifying the dominant parameters is critical for moisture buffering effect optimization. This study analyzes the influence of five moisture and surface parameters, which are directly related to the moisture transfer of the interior finishing layer, on the thermal loads in a typical office building under typical climates in China. The analysis employs scatter plots and sensitivity indices based on Sobol's method. The results show that the material thickness plays a decisive role under different climates. The importance of sorption isotherm varies with climates and load types. The vapor diffusion resistance factor of the material only affects the latent heat loads, while the effect of the surface vapor transfer resistance is negligible. Finally, this study puts forward suggestions for interior finishing material selection to achieve low-load performance based on the characteristics of parameter combinations.

The internal structures and the hygroscopicity of bio-based boards consisting of giant reed (Arundo donax L.) and hazelnut shells as bio-aggregates, and a sodium silicate solution as the adhesive, were investigated. The aim was to evaluate the influence of each material (the bio-aggregates and adhesive) and their distributions in the boards on the final performance. By carrying out X-ray computed tomography, the internal structures and the porosities of the boards were determined, allowing important considerations of their hygroscopicity. The voids' percentages were between 26% and 36% of the total volume of the composites. Both the materials and the composites demonstrated high hygroscopicity. In particular, the mixtures of the bio-aggregates and the sodium silicate allowed reaching a moisture buffering value of 7.44 g/(m2%RH) for the A. donax-based composite, 3.86 g/(m2%RH) for the hazelnut-shell-based composite, and 4.65 g/(m2%RH) for the mixture-based composite. Besides the identification of the contributions of the materials, a detailed discussion of the assessed properties was carried out to use these bio-based boards in vernacular historic construction. The results show how the aggregate type and the adhesive content affected the final behavior, demonstrating the importance of a conscious material choice. Furthermore, helpful information for the future development of these types of bio-based boards and their possible optimization was provided. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study is devoted to assessing the hygroscopic and durability properties of a clay composite with the addition of a natural polymer. Modified polymer-retrograded starch hydrogel (RSH) of various concentrations (2.5, 5.0, 7.5, and 10.0%) and heating times (3 and 5 h) were used as clay stabilizers. The introduction of retrograded starch tends to increase the drying rate of clay composites at the early period of 0–4 days without the formation of shrinkage defects. Moisture uptake increased by 29% (from 140 to 180 g/m2) over the control clay composite without RSH. The hysteresis rate of the clay samples modified with RSH decreased by half (from 0.3 to 0.15%), but the hygroscopic properties were better. The use of RSH polymer increased the durability (water erosion resistance) of the clay composite. The obtained composite has great potential for indoor use due to its high moisture-regulating and durability properties. [ABSTRACT FROM AUTHOR]

Building simulation software can provide a reliable prediction of the building environmental response, however, in historical building simulations the uncertainty increases due to the lack of information and the incorrect choice of the numerical model. In this work, the moisture buffering effect is investigated using two different models in EnergyPlus software. The analysis shows that the selection of the moisture buffering calculation method highly affects the simulation results and the set-up of some input variables during the calibration phase. In detail, the use of the Effective Capacitance model could overestimate the effects of the infiltration in terms of mixing ratio, leading to the adoption of a lower value of air change rate for the model validation (about 3 times in the case study analysed). Such phenomena particularly affect historical buildings, generally characterized by massive structures and many furnishings.

Silica aerogel composites reinforced with reclaimed cotton fibers obtained from textile industry wastes are here presented. These fibers were obtained from fabric leftovers of textile clothing industry, using only mechanical processes for reverting wasted fabric scraps to elementary fibers. The syntheses were carried out following environmentally friendly solutions. The post-gelation silylation/washing steps were performed applying ethyl acetate, recognized as a non-hazardous solvent. The tetraethyl orthosilicate-based aerogel composites were developed with a co-precursor having a non-hydrolysable bulky branch, isobutyltriethoxysilane, aiming to reduce brittleness and increase hydrophobicity. The aerogel matrix composition used here, reinforcement conception and modification solvent are being presented for the first time in the literature. The composites, manufactured in small cylindrical-shape (diameter ~3 cm) and disk-shape (diameter ~9 cm and ~14 cm) were silylated with hexamethyldisilazane and ambient pressure dried. Thermal conductivities were assessed by non-stationary and steady-state methods, the later yielding values 25–37% lower, achieving a value as low as 21 ± 3 mW m–1 K–1. The composites exhibit a high degree of flexibility conferred by the embedded cotton fibers, that imparted as well good acoustic insulation, since at frequencies near 1300 Hz, the sound absorption coefficient is 0.8. Cotton fibers are well known by their moisture buffering. By taking advantage of that water adsorption/desorption, the thermal regulation ability of the aerogels is studied here as a novel application for these materials. At 85% of relative humidity, silica aerogel composites with ~15 wt% of cotton fibers adsorbed 2.6 wt% of moisture and the process reversibility was confirmed. Highlights: Cotton-silica aerogel composites reinforced with waste fibers obtained from fabric scraps. Reclaimed industrial cotton fibers mechanically processed, without detrimental chemicals. A non-hazardous solvent, ethyl acetate, used for the first time for aerogel manufacturing. Multifunctional silica-aerogel composite: moisture regulator and thermal/acoustic barrier. [ABSTRACT FROM AUTHOR]

In Southern European countries, due to the specific climate, economy and culture, a permanent heating practice during winter is not widely adopted. This may have a significant effect on the performance of indoor coating materials, typically tested considering hygrothermal conditions in the range of 33–75% relative humidity (RH) and 20–25 °C, which are common in continuously heated buildings. In this study, the indoor climate of four bedrooms located in Lisbon, Portugal, was monitored under operational conditions. Based on the data monitored in the case studies, characteristic ranges of indoor hygrothermal conditions were defined and compared to those considered in standard test procedures. In addition, numerical simulations were adopted to compare the hygroscopic performance of four plasters under operational conditions observed on-site. Results show that the four rooms, intermittently heated or unheated, do not provide comfort conditions over 50% of the wintertime, with temperatures lower and RH higher than the ones recommended by the standards. The MBVs resulting from simulations (under operational conditions) are qualitatively in agreement with the MBVs obtained under standard testing conditions. Nonetheless, future studies are recommended to evaluate if standard tests are quantitatively representative of the hygroscopic performance of coating materials in the Southern European scenario. [ABSTRACT FROM AUTHOR]

In recent years, moisture buffering materials for interior finishing have received much attention for their ability to regulate indoor humidity passively. It is necessary to investigate the potential of such materials' moisture buffering performance before application because the effect is highly climate and material dependent. However, existing studies in China lack a comprehensive overview of the moisture buffering potential of different interior finishing materials throughout the large country with a wide spectrum of climates. This paper aims to outline the moisture buffering potential for office buildings in various climates in China through numerical methods. Specifically, simulations in 15 representative Chinese cities are conducted with five interior finishing materials under two heating, ventilation, and air conditioning (HVAC) scenarios. The results show that the moisture buffering materials hold a general potential to regulate indoor humidity conditions and reduce buildings' HVAC load. Such benefits are evident in the mild climate but weak in humid areas. The moisture buffering effect also displays significant seasonal variations and could worsen indoor humidity conditions in some cases, indicating the importance of utilizing moisture buffering materials properly. In addition, although moisture buffering materials can reduce the HVAC load, the reduction is limited, within 3 kWh/m2, in most simulated cases. The energy-saving benefits of moisture buffering materials should thus not be over-emphasized. Finally, suggestions are put forward to instruct the choice of interior finishing material according to climate and buildings' HVAC scenarios. [ABSTRACT FROM AUTHOR]

Hygroscopic material can moderate the indoor humidity variation due to its moisture buffering effect. This effect would change when used as interior finish mainly due to air exchange and wall moisture transfer. The author focused on clarifying the extent of the wall''s influence on indoor moisture buffering and building humidity environment. A room model was established and the situation of no wall moisture transfer was simulated by adding a vapour barrier between the interior finish and the wall. Comparing this result with wall moisture transfer, the moisture buffering effect of the wall can be quantitatively analysed. The results verify that the buffering effect and the humidity environment, especially the seasonal buffering, change with the wall moisture transfer. The wall has great impacts on buffering in the cases of thin interior finish, high moisture production and low ventilation. Because the layer under the hygroscopic material also has buffering capacity, the difference of using various thicknesses of material is not obvious. Frequent ventilation reduces the buffering effect but improves the RH optimality. [ABSTRACT FROM AUTHOR]

This study investigated the development of fly ash geopolymer composites with rice husk, aiming to create sustainable building materials with improved sound absorption, thermal insulation, and hygric properties, while maintaining adequate mechanical strength. Rice husk was incorporated as bio-lightweight aggregate at various volume fractions (40 %-70 %). The results showed that compressive strength decreased with increasing rice husk, and the R40 and R50 mixes remained suitable for non-load-bearing applications (0.83–0.33 MPa). On the contrary, sound absorption increased, with the R50 mix showing the highest performance (noise reduction coefficient of 0.60). Moisture buffer value significantly improved, particularly in the 40 %-60 % mixes classified as "good" by the NORDTEST method. The R50 mix demonstrated the most balanced moisture regulation (MBV of 1.23 g/m².%RH), potentially benefiting indoor air quality and energy efficiency in building applications. Furthermore, thermal conductivity decreased with increasing rice husk content; the R40 and R50 mixes exhibited promising thermal insulation properties (0.230–0.195 W/m∙K). These findings suggest that fly ash geopolymer-rice husk composites are attractive and sustainable building materials for non-load-bearing applications, offering significant advantages in acoustics, moisture control, and thermal performance. • Geopolymer-rice husk composites with enhanced sound absorption, thermal insulation, and hygric properties were made. • The composites are suitable for non-load-bearing applications. • The optimum noise reduction coefficient was 0.60, MBV of 1.23 g/m².%RH, thermal conductivity of 0.195 W/m∙K. [ABSTRACT FROM AUTHOR]

Moisture buffering describes the use of materials with high water-vapour sorption capacity to provide humidity control in interior spaces. Established models of the moisture dynamics of buffering are derived from conventional Fickian vapour-diffusion equations. We describe an alternative analysis using a Sharp-Front formulation. This yields a similar expression for the moisture effusivity, several consistent scalings and a new definition of the moisture penetration depth. Features of the model are compared with some published experimental data. A new sorption buffer index is a measurable experimental property that describes the water-vapour buffer strength of the material.

Building simulation software can provide a reliable prediction of the building environmental response, however, in historical building simulations the uncertainty increases due to the lack of information and the incorrect choice of the numerical model. In this work, the moisture buffering effect is investigated using two different models in EnergyPlus software. The analysis shows that the selection of the moisture buffering calculation method highly affects the simulation results and the set-up of some input variables during the calibration phase. In detail, the use of the Effective Capacitance model could overestimate the effects of the infiltration in terms of mixing ratio, leading to the adoption of a lower value of air change rate for the model validation (about 3 times in the case study analysed). Such phenomena particularly affect historical buildings, generally characterized by massive structures and many furnishings. [ABSTRACT FROM AUTHOR]

Buildings are subjected to the indoor environment, especially in non-controlled climates. Temperature and humidity variations might effect or even damage materials sensitive to moisture. For this reason, it is important to understand the response of hygroscopic materials to variable indoor environmental conditions. Existing methods looked into the dynamic sorption capacity of materials, by analysing the impact of only humidity fluctuations, with temperature usually considered non-influential or non variable. However, temperature fluctuations may impact the moisture capacity of the materials, as materials properties might substantially vary with temperature. Moreover, in existing protocols, the humidity variations are considered to be varying under square wave fluctuations, which may not be applicable in environments, where the indoor is influenced by daily and seasonal climate variations, which presents more complex fluctuation. In this study, a simulation method that can predict the impact of environmental condition on materials under simultaneous temperature and humidity fluctuations was developed. Clay and gypsum plaster were analysed in the numerical model and results were then validated with experimental data. Materials were subjected to either sinusoidal and triangular temperature and RH variations and different cycle time intervals. The investigation of sinusoidal and triangular environmental variations pushed to a better understanding of materials response to different environments and to the improvement of the simplified model. The development of a simplified model can realistically predict the potential future impact of climate changes on buildings without the use of complex and memory demanding computational methods. [ABSTRACT FROM AUTHOR]

Environmental issues and health-benefitting design strategies have raised interest in natural and renewable building materials, resulting in an increased focus on the use of wood in built environment. The influence of wooden materials on measured and perceived indoor environment quality (IEQ) has gained attention during the past few decades, with a growing number of studies having explored the issue. This review was conducted to examine and summarise the body of research on the influence of wooden interior materials on IEQ, with an emphasis on the following themes: emissions of chemical compounds, moisture buffering of indoor air, antibacterial effects, acoustics, and psychological and physiological effects. This review found that wooden interior materials exert mainly positive or neutral effects on IEQ, such as moderating humidity fluctuations of indoor air, inducing positive feelings in occupants, and inhibiting certain bacteria. Negative effects on IEQ are limited to volatile organic compounds emitted from wood. The odour thresholds of some aldehydes and terpenes are low enough to affect the perceived IEQ. Additionally, concentrations of formaldehyde and acrolein may under certain conditions cause adverse health effects. Further studies are needed to better understand these phenomena and take advantage of the beneficial effects while hindering the unpleasant ones. [ABSTRACT FROM AUTHOR]

This study investigates the impact of surface coating on the humidity control capability of porous hygroscopic material, and proposes a dual-scale correlation method for moisture buffering (MBV). First, the findings indicate that the primary factors that influence the negative effects of coatings are the moisture response ability of the material and the temperature and relative humidity difference in the measuring environment. As these factors increase, the impact of the coating on the wet physical properties decreases, such as the moisture buffering effect, the deviation can be reduced from 28% to 3%. Furthermore, this research considers the moisture resistance of the air layer on the material surface as the main reason for the deviation between the ideal MBV model and the measured value. And an optimized ideal MBV model is proposed in this study, which demonstrates improved accuracy and is better suited for calculating MBV of materials. Finally, this study presents a dual-scale method that correlates the material-scale results obtained from laboratory tests with the full-scale results obtained from application simulations. Research and sensitivity results indicate that this dual-scale method is effective and reliable. Moreover, the impact of the coating on the actual indoor humid environment is acceptable when the comfortable requirements are not high. In conclusion, this study establishes a research foundation for simulating and applying coupled coatings on hygroscopic materials, facilitating enhanced passive control of indoor humidity environment and improved building energy efficiency. • The impact of coating is effected by wet-physical properties and test conditions. • An ideal moisture buffering optimization model is proposed. • A dual-scale correlation method between material-scale and full-scale is proposed. [ABSTRACT FROM AUTHOR]

In Southern European countries, due to the specific climate, economy and culture, a permanent heating practice during winter is not widely adopted. This may have a significant effect on the performance of indoor coating materials, typically tested considering hygrothermal conditions in the range of 33–75% relative humidity (RH) and 20–25 °C, which are common in continuously heated buildings. In this study, the indoor climate of four bedrooms located in Lisbon, Portugal, was monitored under operational conditions. Based on the data monitored in the case studies, characteristic ranges of indoor hygrothermal conditions were defined and compared to those considered in standard test procedures. In addition, numerical simulations were adopted to compare the hygroscopic performance of four plasters under operational conditions observed on-site. Results show that the four rooms, intermittently heated or unheated, do not provide comfort conditions over 50% of the wintertime, with temperatures lower and RH higher than the ones recommended by the standards. The MBVs resulting from simulations (under operational conditions) are qualitatively in agreement with the MBVs obtained under standard testing conditions. Nonetheless, future studies are recommended to evaluate if standard tests are quantitatively representative of the hygroscopic performance of coating materials in the Southern European scenario.

• Development of novel hemp shiv based composites with low thermal conductivity of 0.05 W/mK. • Enhanced vapour permeability and excellent moisture buffering value up to 3.6 g/m2 RH. • Pre-treatment of hemp shiv leads to high water resistance reducing water absorption by 123%. • The composites have low density (175–240 kg/m3) and show good mechanical performance. This study focuses on the development of advanced water resistant bio-based composites with enhanced hygrothermal performance for building applications. The highly porous structure of hemp shiv is responsible for low thermal conductivity and allows the material to adapt to varying humidity conditions providing comfortable indoor environment. However, the pore network and the hydrophilic nature of hemp shiv affects the compatibility and durability of the material in presence of excess moisture conditions. In this work, novel hemp shiv composites were prepared in a starch based or silica based matrix and characterised for their hygroscopic, thermal and mechanical properties. The hemp shiv based composites were resistant to water yet permeable to vapour and showed excellent moisture buffering capacity when compared to conventional hemp-lime composites. The composites prepared were light weight with low thermal conductivity values of 0.051–0.058 W/mK and showed good mechanical performance. Hemp shiv composites with superior hygrothermal characteristics have immense potential as robust thermal insulation building materials. [ABSTRACT FROM AUTHOR]

• Silica based hydrophobic coating for hemp shiv. • Coating significantly enhances the water resistance of hemp shiv. • The moisture buffering property of hemp shiv was retained after coating. • Effect of coating on physical and chemical properties of hemp shiv were studied. This study focuses on the surface treatment of an extremely hydrophilic natural plant material, hemp shiv, using a functionalised silica based coating to provide hydrophobicity while retaining its moisture buffering ability. The chemical composition and physical structure of bio-based materials results in their extremely hydrophilic behaviour. In this work, a simple one step coating process was used to enhance the water-repellence of hemp shiv without compromising its ability to adsorb and release moisture. The coating modified the morphology and surface roughness of hemp shiv providing a hydrophobic surface having a water contact angle of 118° and reduced the bulk water absorption by 250% over 24 h. Mercury intrusion porosimetry (MIP) showed that the treatment refined the pore size distribution of hemp shiv, reducing the size of larger pores but not completely blocking the smaller pores thereby allowing hemp shiv to buffer moisture. Fourier-transform infrared spectroscopy (FTIR) revealed the chemical composition was modified by the coating, reducing the hydroxyl groups. Hemp shiv aggregates treated with functionalised silica based coating show potential for the development of robust lightweight building materials with enhanced hydrophobicity. [ABSTRACT FROM AUTHOR]

Plaster has, from ancient times, been used as a decorative material. However, the advances in materials engineering such as thermal and moisture control provide new opportunities. Superabsorbent polymers (SAPs) have been found to possess passive moisture control that may find utilization in modern buildings. However, the main drawback is associated with a limited number of applicable SAPs due to mechanical strength loss. In this regard, concurrent utilization of cellulose fibers may provide additional benefits linked with the reinforcing of plaster structure and preservation of superior hygric properties. In this regard, this study investigates the combined effect of SAP and cellulose fibers on the material properties of cement-lime plaster in terms of its mechanic, thermal, and hygric properties. To access the capability of such modified plasters to control the interior moisture fluctuations, the moisture buffering value is determined. Obtained results show the effect of both applied admixtures on material performance, whilst the synergic effect was most obvious for humidity control accessed through the moisture buffer coefficient.

The humidity level of indoor air is an important factor influencing the air quality and energy consumption of buildings, as well as the durability of building components. Indoor humidity levels depend on several factors, such as moisture sources, air flow, and the adsorption/desorption properties of materials. The moisture-buffering characteristics of building materials that are in contact with indoor air may help moderate the variations of indoor humidity, especially in the summer and winter. In this study, the moisture adsorption/desorption properties of building materials were investigated experimentally and numerically. These properties can be used to characterize the ability of building materials to exchange moisture with the indoor environment. This study indicates that a building material surface resistivity was the main factor creating variations of moisture buffering.

Buildings are subjected to the indoor environment, especially in non-controlled climates. Temperature and humidity variations might effect or even damage materials sensitive to moisture. For this reason, it is important to understand the response of hygroscopic materials to variable indoor environmental conditions. Existing methods looked into the dynamic sorption capacity of materials, by analysing the impact of only humidity fluctuations, with temperature usually considered non-influential or non variable. However, temperature fluctuations may impact the moisture capacity of the materials, as materials properties might substantially vary with temperature. Moreover, in existing protocols, the humidity variations are considered to be varying under square wave fluctuations, which may not be applicable in environments, where the indoor is influenced by daily and seasonal climate variations, which presents more complex fluctuation. In this study, a simulation method that can predict the impact of environmental condition on materials under simultaneous temperature and humidity fluctuations was developed. Clay and gypsum plaster were analysed in the numerical model and results were then validated with experimental data. Materials were subjected to either sinusoidal and triangular temperature and RH variations and different cycle time intervals. The investigation of sinusoidal and triangular environmental variations pushed to a better understanding of materials response to different environments and to the improvement of the simplified model. The development of a simplified model can realistically predict the potential future impact of climate changes on buildings without the use of complex and memory demanding computational methods.

Highlights • Moisture buffering improves indoor air quality and hygrothermal comfort. • The lack of a globally agreed method makes comparisons difficult. • Dynamic sorption properties should be quantified by in situ testing. • Modelled moisture buffering does not fully represent the performance. • A novel method of full scale moisture buffering is required. Abstract It is important to control indoor humidity level in buildings as it influences occupant's health and comfort. Hygroscopic building materials present great potential to passively regulate air humidity due to their ability to adsorb and desorb moisture. In recent years researchers have focused on this capacity, referred to as Moisture Buffering, as it has the potential to improve indoor thermal comfort and reduce HVAC usage and their consequent energy consumption. However, building designers generally do not consider this property an important factor, due to its unclear influence and difficulty in the quantification of its effects in real buildings. Therefore, it is complicated to develop an appropriate laboratory scale testing. The aim of this paper is to investigate the challenges related to moisture buffering measurement and to examine the approaches adopted by researchers. The significance of this study is to identify discrepancies between existing methods in the evaluation of the dynamic adsorption properties and presents areas for further development in testing. [ABSTRACT FROM AUTHOR]

Highlights • Internal gains in higher performance homes have a larger impact on total loads. • 5th, 50th, and 95th percentile internal gain profiles generated stochastically. • Latent internal gains can account for 50% of the latent load in humid climates. • Dehumidification equipment sized based on median internal loads may be undersized. Abstract Residential building codes and voluntary labeling programs are continually increasing the energy efficiency requirements of residential buildings. Improving a building's thermal enclosure, installing the ductwork in conditioned space, and improving the building's airtightness results in significant reductions in externally-driven sensible and latent cooling loads. As a building's efficiency is improved, occupant-related internal gains become a larger portion of the building sensible and latent loads. Additionally, internal gains are highly uncertain compared to other load components. In this study, we use a stochastic approach to simulate occupant-related internal gains and compare the internal gains to other sensible and latent heat sources in four house efficiency levels in 10 U.S. climates using whole-building energy simulation software. We compare the expected range in occupant-related internal gains to other building characteristics such as cooling set point, air infiltration rate, and mechanical ventilation rate. We show that in high-efficiency homes, sensible internal gains vary from less than 10% to greater than 40% of the building sensible load under peak total cooling conditions depending on climate and internal gain profile. Likewise, latent internal gains vary from less than 10% to more than 60% of the building latent load under peak total cooling and peak dehumidification conditions depending on climate and internal gain profile. [ABSTRACT FROM AUTHOR]

Abstract Libraries and archives house a majority of cultural heritage objects. The main purpose of libraries and archives is to provide suitable indoor climate conditions for preservation of their collection. In general, a large bulk of hygroscopic material is present which aids stable indoor climate conditions. Limited disturbances due to visitor presence occur in repositories and excludes to a large extent thermal comfort requirements. Library archives show potential of more tolerant setpoint control with permissible fluctuations. Little research is present into dynamic setpoint control and intermittent conditioning in libraries and archives. The aim of this study is to explore the possibility for intermittent conditioning and dynamic setpoint control on the energy impact and microclimate behavior in a library case study in The Netherlands. By means of a hygrothermal monitoring campaign from August 2016 to August 2017 the current indoor climate has been assessed under regular conditions and intervention periods (summer and winter) where the air handling unit was turned off. Both temporal and spatial measurements provided important information on microclimate behavior of the investigated repositories. A validated multi-zone model was used to investigate multiple setpoint strategies. Results show the potential of intermittent conditioning depending on whether dynamic setpoint conditions are used during operational hours (e.g. ASHRAE climate classes). If static conditions are applied, energy demand increases significantly, however, under dynamic setpoint control significant energy savings are possible. The lifetime multiplier is used to assess the chemical risks. The majority of investigated setpoint strategies show increased chemical risk. Highlights • Exploring different climate control strategies on the energy impact and microclimate behavior in a library environment. • Extensive hygrothermal monitoring used to assess the indoor climate under regular conditions and intervention periods. • Validation of multi zone numerical model is executed to investigate intermittent conditioning and dynamic setpoint control. • Resulting indoor climate conditions are assessed for collection preservation by using specific risk assessment method. [ABSTRACT FROM AUTHOR]

Highlights • Construction wastes were used to produce high moisture buffering capacity. • Addition of H 2 O 2 dramatically enhanced the mortars' moisture buffer value. • Fly ash-based mortars presented low thermal conductivity. Abstract In this study, lightweight waste-based geopolymeric mortars were evaluated for the first time regarding their potential to passively adjust indoor relative humidity (RH) levels. Geopolymer mortars were prepared using a mixture of fly ash (FA) and metakaolin (MK) as a binder, in a proportion of 75:25 wt% (FA:MK), construction and demolition waste as the fine aggregate and a pore forming agent in varying amounts. The results showed that the addition of a pore-forming agent to the compositions considerably increased the moisture buffer value (MBV) of the mortars, that is, from 0.80 (reference mortar) to 5.61 g/m2 Δ%RH (mortar with highest porosity). The moisture buffering capacity shown by these eco-friendly mortars is higher than values reported for other binder materials and can be classified as excellent (MBV > 2 g/m2 Δ%RH). The porous FA-based mortars also presented low thermal conductivity (as low as 0.19 W/m∙K), which suggests that these innovative binders could be simultaneously used for indoor moisture buffering and as low thermal conductivity materials. [ABSTRACT FROM AUTHOR]

Passive humidity control in buildings can be achieved by incorporating materials that have a moisture-buffering capacity. Such materials absorb moisture at peak-moisture times and give off the stored-up moisture at low moisture times, thereby stabilizing the relative humidity of an interior. The advantages of this phenomenon include energy savings and the improvement of both thermal comfort and perceived air quality. It is necessary to investigate different materials for their moisture-buffering capabilities. In this work, the moisture-buffering potential of American clay and magnesium oxide (MagO) boards was investigated. This was done through a field study that monitored twin buildings under different operation scenarios. One was set as the reference building, and its interior was finished with gypsum, owing to the usage of this material as a common industry practice. The second building was set as the test building and was covered with American clay and MagO boards. The operational congruency of the buildings was checked, and then, three tests were conducted to simulate the interior finishes of a building, ventilation effects, and occupancy density. It was found that the American clay exhibited a better moisture buffering potential than gypsum, especially in the comparison of as-built surface conditions. Further, the experimental results also showed that the moisturebuffering potential of MagO boards may be comparable to that of gypsum, and a coating of vapor-open MagO boards is beneficial for humidity regulation. [ABSTRACT FROM AUTHOR]

Graphical abstract Thermal conductivity measurement. Highlights • The hygrothermal properties of bamboo particles are studied. • Novel binders from natural resources are used for building bio-insulation materials. • Influence of high relative humidity on durability of bamboo particles is investigated. • Thermal insulation of bio-materials is evaluated under different humidity conditions. Abstract Bio-insulating materials are well known to reduce the environmental impact of constructions and are able to regulate the indoor temperature and humidity of buildings. This study investigates the influence of high-absorbing bio-glues based on a protein and lignin compound on moisture transfer and storage as well as on thermal performance of bamboo particleboards. The investigations are based on the moisture buffer value, vapor permeability, isothermal vapor sorption and thermal conductivity. Simultaneously, the mechanical properties and mold growth of these materials, manufactured for the study, are also investigated. The results demonstrate excellent moisture buffer capacity, from 2.13 to 3.26 g/(m2·%RH). The vapor sorption isotherm results exhibit the materials’ high moisture storage, and the vapor permeability behaves like commercial bio-insulating materials. The thermal conductivity of particleboards shows a low value, in accordance with their density and variation in moisture content. In addition, the results indicate mold appearance on the surfaces of specimens after 14 days exposure to 84% relative humidity. Moreover, a comparison of the hygrothermal characterizations between bamboo particleboards and fiberboards (Nguyen et al., 2017) is carefully made to highlight the exceptional features of those bio-boards. [ABSTRACT FROM AUTHOR]

Increasing insulation levels and improved windows are reducing sensible cooling loads in high-efficiency homes. This trend raises concerns that the resulting shift in the balance of sensible and latent cooling loads may result in higher indoor humidity, occupant discomfort, and stunted adoption of high-efficiency homes. This study utilizes established moisture-buffering and air-conditioner latent degradation models in conjunction with an approach to stochastically model internal gains. Building loads and indoor humidity levels are compared for simulations of typical new construction homes and high-efficiency homes in 10 US cities. The sensitivity of indoor humidity to changes in cooling set point, air-conditioner capacity, and blower control parameters are evaluated. The results show that high-efficiency homes in humid climates have cooling loads with a higher fraction of latent loads than the typical new construction home, resulting in higher indoor humidity. Reducing the cooling set point is the easiest method to reduce indoor humidity, but it is not energy efficient, and overcooling may lead to occupant discomfort. Eliminating the blower operation at the end of cooling cycles and reducing the cooling airflow rate also reduce indoor humidity and with a smaller impact on energy use and comfort. [ABSTRACT FROM AUTHOR]

Moisture buffering of building materials has a significant impact on the building's indoor humidity, and building energy simulations need to model this buffering to accurately predict the humidity. Researchers requiring a simple moisture-buffering approach typically rely on the effective-capacitance model, which has been shown to be a poor predictor of actual indoor humidity. This paper describes an alternative two-layer effective moisture penetration depth (EMPD) model and its inputs. While this model has been used previously, there is a need to understand the sensitivity of this model to uncertain inputs. In this paper, we use the moisture-adsorbent materials exposed to the interior air: drywall, wood, and carpet. We use a global sensitivity analysis to determine which inputs are most influential and how the model's prediction capability degrades due to uncertainty in these inputs. We then compare the model's humidity prediction with measured data from five houses, which shows that this model, and a set of simple inputs, can give reasonable prediction of the indoor humidity. [ABSTRACT FROM AUTHOR]

The modern society pays growing attention on global environmental issues, public safety, and individual health, which highlights the necessity of exploring sustainable, energy-saving, flame-retardant, and anti-mildew materials for building applications. Herein, by in-situ preparing copper phytate-hierarchically porous MOF-199 hybrid (PCuM) in natural wood (W) via simple phytate induced defect engineering strategy, we reported a multifunctional low fire-hazard wood composite (PCuM-W). The phytate anion not only acted as a modulator to generate hierarchical porosity in MOF-199, but also offered high flame retardancy due to its six phosphorus groups. The copper phytate anchored on the cell wall exhibited charring and graphitizing effects and enhanced the flame retardancy and smoke suppression performance of wood. By pyrolysis, a hierarchically porous MOF-199-derived carbon formed and offered a considerably enhanced catalytic activity towards the conversion of CO. With a weight percent gain of only 13.5%, the fire growth index, total smoke production, and maximum CO production rate of PCuM-W were 74.2%, 85.4%, and 33.3% lower than that of W, respectively, showing outstanding fire-hazard-reducing efficiency that surpassed most of its counterparts. Furthermore, due to the hierarchical porosity and antimicrobial property of PCuM, PCuM-W showed excellent moisture-buffering ability and mildew resistance. This work brings guidelines for fabricating hierarchically porous MOFs to realize multifunctional materials via phytate induced defect engineering. [Display omitted] In-situ prepared copper phytate-hierarchically porous MOF-199 hybrid (PCuM) in wood. Phytate anions offered flame retardancy and created hierarchical porosity in PCuM. 74.2% and 85.4% reduced fire growth index and total smoke production of PCuM-W. PCuM-derived CuO-embedded hierarchical porous carbon catalyzed the conversion of CO. Excellent moisture-buffering ability (2.09 g/m2·RH) and mildew resistance. [ABSTRACT FROM AUTHOR]

• On the production of eco-efficient mortars to passively improve indoor comfort. • Study of five different waste fractions from an invasive plant: Acacia dealbata. • The biomass addition to gypsum plastering mortars enhance their hygroscopicity. • A MANOVA shows the statistical significance of each addition on mortars. • The highest moisture buffering is performed by the mortar with 10% vol. of bark. Hemihydrate gypsum is a very eco-efficient binder. Gypsum plasters were commonly used in the past and should be still chosen nowadays for being an eco-efficient choice. However, their hygroscopicity and contribution to act as moisture buffer are not very high. The present study analyses the hygrothermal behaviour of mortars based on gypsum and modified with the addition of residual biomass of A. dealbata , an invasive species in Portugal. Five different fractions of the plant were tested as additions for mortars, at incorporation levels of 5% and 10% by volume, with the purpose of enhancing the moisture buffering of the plasters without jeopardizing other properties. The study found that the addition of A. dealbata increases their hygroscopic behaviour. In some cases (bark fraction) the Moisture Buffering Value of the reference mortar is triplicated, and the behaviour is comparable with high hygroscopic plasters as clay-based ones. However, biological colonization must be controlled. [ABSTRACT FROM AUTHOR]