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• Wind-driven rain (WDR) quantification experimentally on 2 case buildings. • Effect of WDR on hygrothermal conditions in internally insulated masonry studied. • Numerical simulations to determine WDR effect on hygrothermal performance. • WDR models were found to overestimate WDR deposition. • Direct influence of WDR events on RH behind insulation was not detected. An inevitable measure when energy retrofitting historic buildings in Europe, is the reduction of building envelope heat loss. On preservation-worthy facades where external insulation is not an option, installation of internal insulation is gaining pace. The historic buildings in Denmark are often constructed with solid masonry facades and wooden decks. The internal insulation may, however, entail potential hygrothermal risks in walls and embedded wood. Measures such as vapour barriers and capillary active insulation materials are continuously evolving and the subject of much current research. The hygrothermal conditions are of great importance for the durability of the building constructions, and for the health and wellbeing of occupants. Wind-driven rain (WDR) is a central factor contributing to water penetration and moisture loads of the exterior walls. Numerous studies have shown that WDR loads influence the moisture conditions in masonry walls and embedded wooden beams, and can even affect interior relative humidity. In the present paper WDR loads on existing façades in a cold temperate climate were determined by measurements and compared to a semi-empirical model. Simultaneously, the hygrothermal conditions within internally insulated walls with exposed brick and embedded wooden beams were monitored. Furthermore, numerical simulations were implemented for clarification of WDR impact. Hygrothermal simulations and previous studies, inevitably show that high WDR loads result in higher moisture content behind the interior insulation. Results from the field measurements of WDR however, cannot directly be referred to the moisture content measured in walls behind interior insulation or beam ends. However, fluctuations in external air humidity proved to be influential on condiditons in the construction. Implementation of a semi-empirical model for calculations of WDR agreed with previous studies in predictions being too conservative when compared to measured WDR. [ABSTRACT FROM AUTHOR]

Highlights • The new type straw block that can be used in solar greenhouse is invented. • The hygrothermal environment of solar greenhouse with new wall is favorable. • The pH of new type straw block is high and mycelia were hard to grow on it. • The new type straw block can recycle straw material and protect clay resource. Abstract New types of straw block (types I and II straw blocks) were developed and applied in the north wall of solar greenhouses. The hygrothermal and fungistatic properties of the new types of straw block were researched, and the thermal and wet environment of a solar greenhouse with a north wall formed from new types of straw block (STG) was measured. The thermal properties of the new types of straw block north wall (ST) were higher than those of a porous clay block north wall (CL). The pH values of the extracted liquids of the types I and II straw blocks were 13 and 11.5, respectively, making it difficult for mycelia to grow on these blocks. At the depths of 0, 80, 160 and 240 mm, the temperatures of ST were 0.5, 0.6, 0.8 and 1.2℃ higher than those of CL, respectively. Compared to the solar greenhouse with a porous clay block north wall (CLG), the air temperature of STG was 0.5℃ higher during nighttime, and the average relative humidity was 5.3% lower during nighttime. The research shows that the STG has better thermal and wet environment characteristics, and it is durable and suitable for the growth of crops. [ABSTRACT FROM AUTHOR]

Highlights • Performances of retrofitted educational building is investigated. • Thermal resistance, moisture-related risks and IEQ are investigated. • Thermal resistance could be estimated under winter period. • Overall safe behavior is observed despite some mold growth risks. • Hygrothermal comfort is achieved in the classroom. Abstract This paper deals with the performance of a high school building renovated with prefabricated ventilated façade elements through a field experimental study under oceanic climate. Temperature, relative humidity and heat flux were measured at different points of the renovated façade, while temperature, relative humidity and CO 2 concentration were monitored within a classroom. The performance of the renovated building is discussed based on the analysis of two years of measurement data. The experimental results show that the measured in situ thermal resistance of prefabricated ventilated façade elements could be evaluated reliably only under winter period and that it is higher than the design one. Secondly, we note that the application of exterior thermal insulation does not lead to major moisture related pathology on retrofitted building envelope. Only small mold growth risks may exist close to hygroscopic material in relation with solar radiation. Last, we observe that hygrothermal comfort is achieved most of the teaching time, whereas CO 2 concentration exceed critical threshold levels every day. [ABSTRACT FROM AUTHOR]

Highlights • Gypsum boards added with porous materials and phase change materials were prepared. • Hygrothermal performance of specimens was analyzed based on ISO 12,571 and 12,572. • Thermal conductivity of specimens was lower than conventional gypsum board. • Water vapor resistance factor was higher than gypsum board after impregnation of PCM. • There were no moisture problems of gypsum boards with porous materials and PCM. Abstract Gypsum board is widely used as a finishing material, and it is mixed with functional materials to improve the comfort level of indoor air, provide thermal insulation, and satisfy moisture properties. In addition, Phase change material (PCM) is also used as a functional material to reduce energy consumption. Recently, there have been many studies on improving moisture problems, such as condensation and mold growth. Therefore, the hygrothermal behavior of building materials must be carefully considered to reduce the risk of moisture problems. The objective of this study was to improve the thermal and moisture performance of gypsum board, and achieve energy savings by adding porous material and PCM. The characteristics of functional gypsum board (FGB) with expanded vermiculite (EV), expanded perlite (EP), nano carbon material (C300), and n -octadecane (PCM) were analyzed by fourier transform infrared (FTIR) spectroscopy for structural stability. The thermal conductivities of the various FGBs were analyzed by TCi thermal conductivity analyzer, and their hygroscopic properties were analyzed based on ISO 12,571 and 12,572. In addition, the hygrothermal performance of walls applied with FGB was evaluated using Wäme und Feuchte instationär (WUFI) simulation; the wall composition was concrete wall. As a result, the thermal conductivities of FGB were decreased by 15%, compared with the conventional gypsum board. In the case of moisture properties, the water vapor resistance and water content of FGB were increased, compared with the conventional gypsum board (SR). However, the simulation results showed that there were no moisture problems, such as condensation, mold growth, or structural damage. [ABSTRACT FROM AUTHOR]

Highlights • Silica and aerogels age when exposed to temperature and humidity. • Full microstructural characterizations of several commercial silica and aerogel are provided. • Surface chemistry and texture modifications are observed. • Specific ageing conditions provide the background for describing ageing mechanisms. • Evolution mechanisms and durability are assessed for precipitated, fumed, hydrophobized and aerogel silica. Abstract Several commercial silica powders (precipitated, fumed, hydrophobized) and aerogels were aged in climatic chambers. Four different conditions of temperature [50–70°C] and relative humidity [70–90%RH] were used to identify the influence of both parameters and the underlying mechanisms. Samples were characterized by sorption measurements (nitrogen and water) giving access to the evolution of specific surface area (BET), pore size distribution (BJH) and hydrophilicity. Structurally, a common trend along with silica ageing is the reduction of the specific surface area and a shift in the pore size distribution (loss of the smallest mesopores). However, the ageing scenario and intensities observed differ according to the type of silica (precipitated, fumed, hydrophobic, aerogels). On the one hand, the hydrophilicity of a precipitated silica decreases with ageing due to the reduction of the specific surface area. On the other hand, the hydrophilicity of a fumed silica first increases then decreases with ageing, as a result of two competing effects: the increase of local hydrophilicity (siloxane hydrolysis) and the decrease of the specific surface area. Surface chemistry appears to be a key parameter governing the extent of these evolutions: a precipitated silica is more sensitive than a fumed silica whereas the hydrophobic silica studied exhibited the strongest resistance. Therefore, the main mechanism of structural evolution, probably implying mass transfer in a dissolution/precipitation process, requires water on the surface of silica and thus hydrophilic groups to adsorb it. Short term ageing (24 days) on precipitated and fumed silicas showed that temperature is the most important parameter in activating a mechanism, the intensity of which is thereafter (96 days) governed by relative humidity. The significant influence of humidity was also observed for aerogels, for which the ageing scenario and intensity appears to be product specific. [ABSTRACT FROM AUTHOR]

Abstract Historical dwellings make up a significant fraction of the French building stock and require substantial retrofitting to reduce their energy consumption and improve their thermal comfort. In the city center of Cahors, France, the old medieval dwellings are considered as valuable cultural heritage and internal insulation is often the only insulation technique that can be used when the architectural value of the exterior façade is to be preserved. However, internal insulation may have an impact upon the hygrothermal performance of the wall, leading to lowered drying capacity, with possible interstitial condensation and mold growth. Hygrothermal models may be used to assess the risk of failure, but the accuracy of the results depends on how reliable the input data is, including external boundary conditions, which may vary significantly in dense medieval cities such as Cahors. In this study, a Geographical Information System model of Cahors is used to develop EnergyPlus models of individual dwellings. The boundary conditions output by these models are, in turn, used to model the hygrothermal performance of façades with different internal insulations, using the hygrothermal tool Delphin. The Delphin outputs are then analyzed with the VTT model, a mold growth assessment model. Results highlight a quantitative correlation between some urban morphology characteristics and the hygrothermal performance of refurbished walls, with some configurations raising the risk of damage patterns. We find that bio-based insulation presents a better hygrothermal performance than mineral wool in most of the configurations. [ABSTRACT FROM AUTHOR]

Highlights • An experimental assessment of the impact of the perlite content on the thermal performance of plaster is here presented. • Analyses have been carried out through laboratory, in-situ measurements and heat and moisture transfer simulations on a real case study. • The embodied energy and embodied carbon have been assessed for different percentages of perlite content. Abstract In the last few years, thermal insulating plasters have started to be an attractive solution for the insulation of already existing wall structures, especially old masonry ones, where refurbishment interventions can involve the replacement of damaged plasters. Intensive research efforts are being made to reduce the thermal conductivity and the environmental impact of these materials by optimizing their mixtures (combination of lightweight aggregates, binders and additives). In the present study, the hygrothermal performance and environmental impact of the different perlite-based plasters that are currently being developed have been investigated. A series of analyses has been carried out, at a material scale, by means of heat flow meter apparatus, to determine the relationship between the perlite content and the thermal properties. Moreover, the effect of the moisture content on λ has been analyzed, and the embodied energy and embodied carbon of the four mixtures have been assessed using both the cradle-to-gate and the cradle-to-site approaches. Furthermore, in-situ measurements have been conducted at a demonstration site, at a component scale, and a series of heat and moisture transfer simulations has been carried out to evaluate the actual thermal behaviour of the plaster under real operating conditions. The thermal conductivity values of the four plaster mixtures ranged from between 0.118 W/mK and 0.059 W/mK, thus demonstrating that the perlite concentration had a significant impact on the reduction of thermal conductivity and that the embodied energy of the applied material (5 cm thickness) decreased as the perlite content increased. Moreover, the results of the measurements on the demonstration building and the hygrothermal simulations have revealed that the thermal insulating plaster is able to reduce the U-value of the wall. However, an increase of 26–30% of the actual thermal conductivity should be considered when the material is exposed to real operating conditions. [ABSTRACT FROM AUTHOR]

Highlights • Disaggregated materials from green roofs substrates. • Impact of water content on the thermo-acoustic performance. • Raining processes can highly influence the thermal performance. • Final acoustic absorption and insulation is influenced when increasing the water. • The conditioning at 90% RH does not produce significant differences of the final acoustic behavior. Abstract Green roofs can be considered as effective and esthetically appreciated passive tools for energy saving systems in buildings. In particular, the effect of evapotranspiration and the large thermal inertia of such solutions, represent highly attractive properties to be implemented in advanced building envelope components. Although these properties are deeply influenced by external factors such as weather conditions, and greenery dynamics, the materials used in substrate and drainage layers are too commonly assumed as constant thermal insulation layers depending only on their physical properties and water content. In particular, common disaggregated materials used in internal layers of extensive green roofs, generally are characterized by a highly complex matrix, and consequently, such materials usually lack of realistic thermal-acoustic properties evaluation. The main objective of the study is to investigate the impact of water content on the thermo-acoustic performance of different disaggregated materials from green roofs substrates commonly used in Mediterranean climates. In particular, the TPS method was used to assess the effect of humidification and raining processes on the final performance of the considered samples. An extensive acoustic characterization was also developed, based on the acoustic transfer function method. Results show that raining processes can highly influence the thermal performance of such materials, which depending on their density, can even triple their thermal conductivity value and achieve twice the volumetric specific heat at ambient conditions. Furthermore, the acoustic characterization procedure showed that the biggest modification on the final acoustic absorption and insulation capability, i.e. about 20 dB when the 80 mm samples, was produced by increasing the water content of the system from 10% to 30% RH. On the contrary, the conditioning at 90% RH does not produce significant differences of the final acoustic behavior of the substrates. [ABSTRACT FROM AUTHOR]

Highlights • Thermal conductivity decreases with the addition of plant aggregates. • Earth material is highly water vapour permeable. • Sorption–desorption isotherms are assessed with DVS and saturated salt solution methods. • MBV of earth-based materials is excellent. Abstract Earth is a material presenting good hygric properties, which is an important point as comfort and indoor air quality have become major issues. Nowadays, the energy efficiency of a construction is also crucial, but the thermal insulation provided by an earth brick is quite low. Therefore, some plant aggregates were added to lighten the material, thus decreasing its thermal conductivity. The hygrothermal properties of seven formulations made of earth with 0, 3 or 6% by weight content of barley straw, hemp shiv or corn cob were assessed. The properties determined were thermal conductivity, specific heat capacity, water vapour permeability, and sorption–desorption isotherms measured with the saturated salt solution and DVS methods. The theoretical MBV was also calculated. The study showed a large decrease in thermal conductivity when a large volume of plant aggregates was added while plant aggregates incorporation conversely affected the thermal inertia parameters. Concerning water vapour permeability, as earth is a very permeable material, the addition of plant aggregates did not improve this property. The sorption capacity of bio-based earth materials was slightly increased in comparison with earth alone. Finally, the calculated MBV showed the excellent buffering capacity of this kind of material, with and without plant aggregates. [ABSTRACT FROM AUTHOR]

Phase change humidity control material (PCHCM) is a new kind of composite made of high performance phase change material (PCM) microcapsules and hygroscopic materials (e.g. diatomite etc.). The PCHCM composite can moderate the indoor hygrothermal conditions by absorbing or releasing both heat and moisture, and consequently effect the sensible and latent heat load of buildings. In this research, a novel model for analyzing the hygrothermal performance of the PCHCM in built environment is developed and validated by experiments. The new model is then applied to investigate the impact of PCHCM on indoor hygrothermal conditions and building energy consumption in an office building under different climates (Beijing, Paris, Atlanta, and Guangzhou). The simulation results show that PCHCM has a great impact on the building energy performance in Paris and Atlanta climates, which have a large temperature and humidity difference between day and night. The maximal potential energy saving rate could be up to 19.57% in Paris. The model and analysis will provide a guidance for the application of PCHCM in different climate conditions. [ABSTRACT FROM AUTHOR]

Straw bale construction can be utilised to deliver energy efficient and low carbon buildings, however there are concerns over the durability of straw. The water sorption property is a critical factor in the degradation behaviour of straw and other lignocellulosic materials. Typically, either wheat or rice straw is utilised for bale construction, however, this variation is not considered. This paper presents the sorption property of wheat and rice straw and the micro-structure that affect the sorption property. Although the surface and cross-sectional structure of the two straw species are different at micro scale, the sorption isotherms were not significantly different. This study on the water sorption property of rice and wheat straw allows for the assessment of durability within a wall construction. This impact of this research will be the growth in low carbon energy efficient straw bale construction with confidence over its long term durability characteristics. [ABSTRACT FROM AUTHOR]

In heritage buildings with solid masonry walls, where external insulation is not an option, insulating internally is an alternative way to improve indoor climate and reduce energy consumption and heat loss through external walls. This study presents results from hygrothermal measurements performed in four different buildings in Denmark where internal insulation has been installed. The buildings are all heritage buildings from 1877–1932 and of solid masonry walls. The insulated façades differ in orientation, surface treatments, location, and insulation system. The insulation materials used are phenolic foam and polyurethane (PUR) foam, with calcium silicate channels in a grid of 40 × 40 mm. Measurement results and hygrothermal assessments indicate that a vapour barrier does not contribute positively to the performance of the system and the more vapour open, the better performance on solid masonry. However, the performance is highly dependent on other parameters like insulation thickness and surface treatment, and above all: the external hygrothermal loads. Therefore, before the application of internal insulation, every case should be carefully assessed in order to find the most suitable solution with regards to both thermal and hygrothermal performance. [ABSTRACT FROM AUTHOR]

Current insulation materials in the construction market, which are predominantly inorganic materials, have a high performance in relation to heat transfer, i.e. high R-values, but the environmental impacts in their production processes are significant. The use of bio-based natural fibre materials such as cork, cotton, wood fibre, hemp, etc. with their lower embodied energy, moisture buffering capacity and, consequently, improved Indoor Environmental Quality have received increasing focus in both research and application, particularly amongst environmentally-conscious clients and designers. In this study a natural fibre material in the form of wood waste is examined experimentally to assess its suitability for use as a thermal insulation material, without the addition of any binder, within a timber frame wall construction. The wood waste is from primary production sources using untreated material. According to our experimental results, the thermal conductivity values of wood waste with different densities, ranged from 0.048 to 0.055 W/mK. These values are slightly higher than commonly used inorganic based insulation materials, although comparable to other natural insulation materials in the market, but have the economic advantage of being a low-cost by-product. The values relating to the material hygric performance including the water vapour diffusion resistance factor, water vapour permeability, and water absorption coefficient were also determined and presented, which will help facilitate future hygrothermal modelling. [ABSTRACT FROM AUTHOR]

Since water is inextricably linked with life, its presence in green building constructions is an inevitable aspect in the process of hygrothermal behaviour analysis. Water content in the substrate of green structures is a variable phenomenon throughout a year. During this period it has a strong influence on the building's hygrothermal behaviour. The WUFI simulation tool analyses hygrothermal behaviour of the tested extensive green roof in the climatic conditions of East Slovakia (Košice). The presented simulation scenarios are aimed at assessing the influence of water in the green roof substrate on the roof membrane temperature and the fluctuation of heat fluxes through the roof during summer period (June 1–August 31). Presence of water and its movement through capillary forces is an essential aspect of hygrothermal behaviour and cannot be neglected in the simulation process. Water in the tested green roof substrate has reduced the average daily heat flow across the roof by 11%, which significantly contributed to lowering its summer overheating. Calculated water content in the substrate was influenced by the selected initial water content condition for up to two-thirds of the simulated period's length. [ABSTRACT FROM AUTHOR]

Gypsum board as a wall and ceiling finishing material can be used to reduce building energy consumption. To optimally use gypsum board as building material, methods are needed to reduce mold and condensation that frequently found on the material and inner surfaces of the board. The influence of gypsum board on hygrothermal behavior of building needs to be confirmed first. The objective of this study was to reduce gypsum boards’ thermal conductivity and improve their moisture properties. Their effect on the hygrothermal behavior and performance of buildings were then evaluated. Specifically, gypsum board was applied to a concrete wall in this study. Porous materials such as expanded vermiculite (EV), expanded perlite (EP), and three xGnP of different surface areas (C-300, C-500 and C-750) were used to improve the thermal and moisture performance of the gypsum board. Gypsum boards’ density, thermal conductivity, water vapor resistance factor, and water content of gypsum board by relative humidity were then evaluated. The influence of hygrothermal behavior of walls when gypsum boards adding porous materials were used as interior finishing materials on concrete wall were then examined. [ABSTRACT FROM AUTHOR]

Three wall panels of identical calculated U-value were simultaneously assessed in a large dual environmental chamber under a number of steady state and dynamic hygrothermal boundary conditions. This study used large-scale wall elements under identical controlled conditions in order to eliminate uncontrollable variables normally encountered in full-scale studies. The following panels were tested: Mineral Wool Panel, Wood Fibre Panel and the Biond Panel (an assembly of wood fibre and hemp-lime). Within the limits of the error range of the calculation, the measured U-value was same for all test panels when assessed under steady state and dynamic hygrothermal boundary conditions. It was however observed that in a boundary condition simulating intermittent heating, the Biond panel showed the highest heat storing and releasing capability whereas the Mineral Wool Panel showed the lowest. In terms of moisture management, the Biond panel exhibited the highest moisture dampening ability within the panel structure. Higher thermal and hygric inertia of the Biond panel may be useful in mitigating overheating of dwellings and reducing interstitial condensation. [ABSTRACT FROM AUTHOR]

A building materials’ properties have a great influence on its energy performance, and this is particularly true of the hygrothermal properties of the insulation material. The variation in moisture content generated by weather conditions can have a strong impact on heat transport. The phenomena involved are very complex and difficult to fully simulate numerically, particularly when the moisture variation occurs under exposure to rain. In the case of the medium density expanded cork agglomerate that is increasingly used without any coating as an external thermal insulation layer of buildings, these phenomena can be particularly relevant. Thus, this paper evaluates the importance of varying moisture content on the thermal behavior of a wall covered with uncoated medium density cork agglomerate when exposed to rain. A simple analytical model that simulates the heat transfer phenomenon was used to quantify its importance by comparing the mathematical results with those obtained experimentally. Steady and unsteady state conditions were simulated. For comparison purposes, winter and summer environmental conditions for both dry and wet weather were assumed. The results show that the thermal behavior of the wall is only affected in the rainy period, until the first few hours when the expanded cork board starts to dry. When rain is simulated, the temperature of the water has a key effect on the wall's behavior. The moisture transport phenomenon and changes in the hygrothermal material properties are almost entirely confined to the upper layers of expanded cork board and to the rainy period. [ABSTRACT FROM AUTHOR]

A method for synthesizing representative weather data for future climate out of regional climate models (RCMs) was introduced previously for the energy simulation of buildings (Nik, 2016). The method suggests creating one typical and two extreme data sets based on the distribution of the outdoor dry bulb temperature (T drybulb ). This article extends the application of such weather data in the hygrothermal simulation of buildings by simulating a pre-fabricated wooden frame wall. To investigate the importance of considering moisture and rain conditions in creating the representative weather files, two more groups of weather data are synthesized based on the distribution of the equivalent temperature (T equivalent ) and rain. Moisture content, relative humidity, temperature and mould growth rate are calculated in the façade and insulation layers of the wall for several weather data sets. Results show that the synthesized weather data based on T dry bulb predict the hygrothermal conditions inside the wall very similar to the original RCM weather data and there is no considerable advantage in using the other two weather data groups. This study confirms the applicability of the synthesized weather data based on T dry bulb and emphasizes the importance of considering extreme scenarios in the calculations. This enables having distributions more similar to the original RCM data while the simulation load is decreased enormously. [ABSTRACT FROM AUTHOR]

Wall finishes with high solar reflectance and thermal emittance, commonly known as cool walls, can reduce the exterior surface temperatures of façades, and consequently the building cooling energy needs and power demand, and lower the sensitivity to degradation. Aging, though, may affect their performance. To investigate this risk, we exposed for four years in Milan, Italy, two series of façade finish coats, white and beige, facing north and south, in vertical and vertical-sheltered position, and we measured their solar spectral reflectance and thermal emittance before and after aging. The solar reflectance of the white finish coats drops from 0.75 to 0.55 in four years, and from 0.46 to 0.38 for the beige coats, while the thermal emittance is unchanged. Then, for a typical residential building with white walls, we computed that the cooling energy needs increase with walls aging by 5% and 11%, respectively, with or without exterior wall insulation. The exterior surface temperature is increased even by 6 °C, and the number of sudden surface temperature variations in one hour is boosted. Finally, the moisture content in the external layers is reduced, showing the impact on the heat and mass balance because of the uncertainty in solar absorption due to aging. [ABSTRACT FROM AUTHOR]

Taking the integrated gaseous contaminants and moisture adsorption potential of desiccant material, a new heat pump assisted solid desiccant cooling system (HP-SDC) was proposed based on the combination of desiccant rotor with heat pump. The HP-SDC was designed for dehumidification, cooling and air purification aimed at improving indoor air quality and reducing building energy consumption. The heat and moisture transfer in adsorption desiccant rotor was theoretical modelled with one-dimensional partial differential equations. The theoretical model was validated with experimental measurements, and the results showed the model could be used to predict the heat and moisture transfer in desiccant rotor. The air thermal conditioning process and energy consumption of HP-SDC was then experimental measured under varied outdoor thermal environments. Results showed that compared to conventional ventilation system, the energy performance of HP-SDC was more efficient mainly due to high efficient air purification capacity, reduction of cooling load and raised evaporation temperature. The energy performance of HP-SDC was sensitive to outdoor humidity ratio. Further improvements of HP-SDC energy efficiency are suggested to be focused on low regeneration temperature desiccant rotor and more efficient high temperature refrigerant. [ABSTRACT FROM AUTHOR]

Hemp shives is a lightweight material known for its insulating properties. Associating these bio-fibers with plant-based matrix instead of a mineral binder in insulation applications is of ecological interest. This article describes the study of a low environmental impact 100% plant-based material made solely from wheat starch and hemp shives. The hemp/starch ratio (H/S) influence and hemp shive size are studied. Samples are evaluated in terms of physical properties, mechanical behaviour and hygrothermal properties through an experimental approach. Results show that increasing 0–5 mm hemp shive proportion from 15% to 30% leads to a significant enhancement of the mechanical and hygric characteristics due to the load transfer and porosity. However, when the H/S ratio increases, mechanical and hygrothermal characteristics decrease slightly. Finally, the hemp-starch agro-material with H/S equal to 8 and 30% of 0–5 mm hemp shive seems to be the optimal composition between the studied samples. [ABSTRACT FROM AUTHOR]

Cities often show nighttime air temperatures higher by 3–4 °C than adjacent non-urban areas. This yields to cooling loads in average higher by 13% for urban than rural buildings. Here we assess the hygrothermal performance and the heating and cooling loads of a reference building representative of the Italian stock. We compare its performance calculated with hourly urban weather data (2002–2008) with the performance of the same building using a rural dataset instead. Milan’s Urban Heat Island reduces the heating loads by 12% and 16%, for the non-insulated and insulated building, respectively, while the cooling loads are increased by 41% and 39%. The urban building also shows dehumidification loads 74–78% lower than the rural building. Moreover, during the 2003 heat wave, the indoor air temperature is computed to be 1.5 °C–2.2 °C higher in a non-conditioned urban building than in the rural one. This increases the wakefulness, occupants’ vulnerability to overheating, and impacts the overall hygrothermal performance. Our findings highlight the need of a different design concept for urban with respect to non-urban buildings, even though they are, by law, in the same climate zone. [ABSTRACT FROM AUTHOR]

Green roofs enjoy a good reputation concerning comfort in summertime, energy savings, rain water retention and durability. However, applied on moisture sensitive substrates like timber constructions, their high thermal inertia and limited drying potential may lead to failure, especially in case of insufficient design or workmanship. As the conditions below the greenery cannot be evaluated by dew point calculations, only a more detailed simulation allows for a realistic prediction of the hygrothermal performance of the components. This contribution introduces a new hygrothermal green roof model based on field and laboratory tests. In difference to previous models it focuses on the moisture and temperature conditions beneath the greenery using more simple approaches for the plant cover but more detailed approaches for the moisture balance in the drainage and growth media. Therefore material data for moisture storage, vapor diffusion and liquid transport were determined in the laboratory and adapted to the built in situation by the help of additional field tests. The model is validated by the help of measured temperature conditions beneath the green roof test fields, as well as concerning the moisture conditions in the critical layers of sensitive timber roofs! The validation shows that the performance of the green roof can be well reproduced throughout the whole year and under all climate conditions including rain water absorption and storage, evaporation and freezing influences. Thus it can be used for both, moisture and energy performance simulations of roofs with greenery under different climatic conditions. [ABSTRACT FROM AUTHOR]

This article focuses on the experimental investigation of hygrothermal behavior of hemp concrete (HLC) and straw rape concrete (SLC) walls. An experimental device has been developed which makes it possible to analyze several hygrothermal behaviors of building wall under static and dynamic conditions. The monitoring of kinetic of temperature and relative humidity within the wall shows the strong coupled of heat and mass transfer. In case under dynamic conditions, the condensation and evaporation phenomena lead to the damping of variation of temperature within the wall. In addition, the air permeability test and infrared tomography analysis have been done. The both walls have high air permeability and some heterogeneous zones have been highlighted. [ABSTRACT FROM AUTHOR]

The carried scientific research regarding evaluation the hygrothermal effects of integration the vegetation into the building envelope was influenced with the differences in necessity to use air-conditioning in the houses, which are not surrounded with vegetation in horizontal structure and which have such vegetation during the summer time. The experimental testing is based on the precise measurements of the relative humidity and temperature, which were carried close to the building plaster in the place without influence of vegetation and between the wall and vegetation. Vegetation on the house, which was used for experimental purposes, is made up of the vine species with a thickness of 40 cm in the place where measurement was carried. Although the investigation takes longer, the paper aims to one month to show the summer time. The mathematical modelling of the obtained data was realized using the numerical as well as the statistical methods The paper aims especially on modelling the differences in relative humidity and temperature of the air and between the wall and vegetation. The dependence of temperature differences was expressed as a piecewise function using the method of Least squares of multiple regression as statistical method. Also the proportional energy to that which might be saved daily instead of its use for air-conditioning in the house was determined. The measurements as well as the used methods: showed sufficient accuracy. [ABSTRACT FROM AUTHOR]

In this paper a new dynamic simulation model for the building energy performance analysis of multi-enclosed thermal zones, where rigid air temperature and humidity conditions must be kept, is presented. The model was implemented in a suitable computer code (DETECt 2.3.1) developed for research scopes. Such simulation model allows the hygrothermal analysis of buildings with multi-enclosed thermal zones surrounded by larger ones (e.g. display glass cases with valuable artefacts in museum halls, neonatal intensive care units for premature and full-term newborn babies in hospitals wards, etc.). For this purpose, a novel control algorithm, based on a model reference adaptive control scheme, enabling the online adaptation of the control gains, is implemented. Rigid air temperature and humidity conditions can be guaranteed also in case of sudden and rapid variations of hygrothermal loads. Through such new tool innovative techniques and operative strategies for obtaining energy efficiency and indoor comfort of special building spaces can be studied. In order to show the capabilities of the tool and the robustness of the adaptive algorithm, as well as the potentiality of the proposed multidisciplinary approach to the energy-related behaviour in buildings (based on building energy modelling and simulation and control theory), two meaningful case studies have been developed. In particular, they refer to the museums and hospital indoor spaces where enclosed thermal zones have to be kept under stringent hygrothermal conditions. [ABSTRACT FROM AUTHOR]

The IEA agency in its annex 41 deals with the modelling of heat, air and moisture (HAM) transfer in whole buildings. In its words, coupling among these phenomena is crucial for future energy optimization of buildings. Computational fluid dynamics (CFD) is difficult and costly to use for everyday practice. Instead, popular building energy simulation software tools (BES) use simplified models popularly known as multi-zone models. Historically the thermal methods were developed separately from the multi-zone airflows and with different purposes. In well-known multi-zone flow software-tools like CONTAM [1] or COMIS [2] , the airflow is decoupled from the thermal problem. BES try to gather those separated efforts and couple both heat and the airflow phenomena using different strategies [3] . All this separated development and the increase in computation capacity, has led to a point where improvements are needed [3] . After a critical review of recent hygrothermal zone models, we present a proposal of a simplified zone model for the air–water mixture dynamics which can be used in BES. The resulting dynamical state variables are the zone dry temperature, absolute humidity, total pressure and dry air mass content. This means that, in contrast with other literature models, we employ three intensive and one extensive variable respectively. Moreover, the reference height level inside the zone cannot be chosen arbitrarily. The dynamic is obtained by using zone energy balance, balances of dry air and water mass content and the Equation of State for the wet air mixture. The zone can store dry air and water, therefore their density can change with time inside the volume. Inside the zone a hydrostatic pressure field is assumed with no kinetic energy storage. The resulting model is a made up of three non-linear ordinary differential equations and one algebraic equation. The model is automatically capable of dealing with wet air saturation conditions by using a special control signal α control . [ABSTRACT FROM AUTHOR]

Vernacular architecture is closely and traditionally linked to energy efficiency due to its adaptation to climate and location. The main purpose of this paper is to diagnose the hygrothermal behaviour inside the vernacular housings of the Jerte Valley ( Valle del Jerte) , located in the Spanish Central System mountain range ( Sistema Central ). This region is widely characterised by a Mediterranean continental mountain climate with medium-sized mountains and presents two distinguished six-month periods: one is warm and dry, whereas the other is cold and rainy. The objective of the aforementioned diagnosis is to promote the preservation of buildings and its energy refurbishment. As a starting point, a study that associates the region’s monthly climate data with the thermal comfort has been developed. Afterwards, a regional building type has been defined for further use by an energy simulation program in order to measure the hygrothermal behaviour of the envelope. Finally, these results have been related both to thermal comfort and bioclimatic strategies. The results suggest that, during the warm period, indoor conditions are comfortable without the need for an additional energy supply. Nevertheless, in the cold period, indoor conditions are warmer than outdoor conditions, but an additional external energy supply will be required to achieve the comfort zone. Accordingly, it is determined that the refurbishment solutions used for those constructions must maintain intact the bioclimatic strategies that benefit summer conditions. However, strategies that give rise to winter conditions without changing its summer behaviour must be improved. [ABSTRACT FROM AUTHOR]

The rate of glazed area to floor area and to sun-exposed wall area of a room is one of the main relationships in energetically optimized architecture. This paper shows the results of the hygrothermal and lighting behaviour on autumn period, of a Primary School which was monitored for a year. It was selected from a universe of 60 school prototypes located in Resistencia, a hot-humid mid-latitude city in the Northeast of Argentina. The measurements were compared with simulations through Simedif, Ecotect and its Radiance interface, in real occupation conditions. A root mean square error of 0.6 °C was obtained. Then the thermal behaviour of the building with an optimized envelope by regulating its glazed areas was simulated for the same period of autumn. Better hygrothermal comfort conditions were verified with the optimization proposal, as well as higher levels of illuminance and uniformity in the spatial distribution of natural light, which would be reflected in an electrical consumption saving for lighting. Consequently, this study will contribute to determining criteria for sizing suitably glazed areas to achieve wellness conditions, which are not covered in full in the current Planning and Building Codes, for school buildings in Resistencia. [ABSTRACT FROM AUTHOR]

• A novel MOF-MPCM composite was prepared for indoor hygrothermal control. • Biomass-derived green MOF MIL-160(Al) was synthesized for moisture buffering. • The MOF-MPCM composite can moderate both heat and moisture simultaneously. • The MOF-MPCM has a significant impact on the energy performance of buildings. • The potential energy saving by using MOF-MPCM could be up to 35.2%. Space cooling (including dehumidification) is the fastest-growing use of energy in buildings. Materials that have high thermal and moisture buffer capacities can passively mitigate indoor temperature and humidity fluctuations, thus reducing the demand for air conditioning and improving building energy efficiency. Here, we report a novel metal–organic framework (MOF) based microencapsulated phase change material (MPCM) composite. The new MOF-MPCM is a dual-function material that can simultaneously absorb/release heat and moisture from surrounding air and passively regulate the indoor hygrothermal environment. MIL-160(Al), a novel green and biomass-derived MOF material with excellent sorption performance and large-scale production potential, was prepared for moisture buffering. MPCM containing an n -octadecane core and polymethylmetracrylate shells were synthesized for temperature control. Physicochemical and hygrothermal properties of MOF-MPCM composite were characterized by SEM, XRD, DVS, DSC, and TGA techniques, etc. A HAM-Enthalpy model was developed to study the impact of MOF-MPCM on the indoor hygrothermal environment and building energy performance in different climates. Seven cities around the world (i.e., Singapore, Hong Kong, Phoenix, Denver, Barcelona, London, and Beijing) were selected as the representative climate locations. The simulation indicates that MOF-MPCM can effectively mitigate indoor temperature and moisture variations and cut down the energy consumption of air conditioning systems, especially in hot-dry, temperate, and continental climates with large diurnal air temperature and humidity variations. The maximum energy-saving potential could reach 35.2% in Phoenix. The study provides guidance for the further improvement and application of dual-function MOF-MPCM composite in different climates. [ABSTRACT FROM AUTHOR]

There is an interest in increasing the energy efficiency of residential housing and sometimes achieving net-zero structures. Effective materials such as spray urethane offer benefits in terms of greater thermal resistance as well as reduction in uncontrolled air leakage. Increased envelope resistance without greatly increasing wall thickness can be a positive feature for a low-energy structure. In this paper, potential hygrothermal performance of five wall panels with different insulation configurations is studied by field experimentation. The five configurations of insulation materials are fibreglass, spray foam, fibreglass with Structural Insulated Sheathing, spray foam EPS rigid insulation, and fibreglass with EPS insulation. The panels are installed side-by-side in a test house; thermocouples and relative humidity sensors are installed. The thermal performance of the panels, humidity levels inside wall cavities, and risk of mold growth are investigated. For further investigation, four homes are constructed, each with one of four potential wall configuration, and studied under occupancy. The experimental results from the building science “building physics” point of view are obtained: wood stud is a thermal bridge on north walls but a thermal mass on west walls; and air cavity in spray foam wall does not generate negative heat convection but increases wall insulation. [ABSTRACT FROM AUTHOR]

The goal of this paper is to identify the effects of in-pore transport of liquid water and water vapor as well as phase changes on the hygrothermal behavior of earthen buildings. Indeed, one of the main assets used to promote these constructions is their role in moisture buffering hence temperature and relative-humidity quality controlling. However, there is no clear consensus yet concerning the impact of these phenomena on the global energy performance of the buildings. A coupled model is therefore proposed in this paper, based on heat and mass balances inside the earthen walls, in order to clarify this question. This model considers separately the kinematics of each phase (e.g. liquid water, vapor, dry air and solid matrix), in interaction with each other. It also takes into account the impact of pore water confinement on the liquid-to-vapor phase change, in particular on the resulting latent heat released or absorbed. The model is successfully compared to experimental results on instrumented full-scale rammed earth wall subjected to temperature cycles. It eventually allows identifying the singular hygrothermal behavior of earth material by testing the range of applicability of the simplifying assumptions which are commonly made in function of the permeability of the tested material. [ABSTRACT FROM AUTHOR]

Innovative and efficient ways to carry out numerical simulations are worth of investigation to reduce the computational complexity of building models and make it possible to solve complex problems. This paper presents a reduced order model, based on Proper Generalised Decomposition (PGD), to assess 2-dimensional heat and moisture transfer in walls. This model is associated with the multizone model Domus using an indirect coupling method. Both models are co-simulated to perform whole-building hygrothermal simulation, considering 2D transfer in walls. The whole-building model is first validated with data from the IEA Annex 41. Then, a case study is considered taking into account a 2-zones building with an intermediary shared wall modelled in 2 dimensions to illustrate the importance of the technique to analyse the hygrothermal behaviour of the wall. It has been highlighted that the whole model enables to perform more precisely analyses such as mould growth on the internal surface. In addition, important theoretical numerical savings (90%) are observed when compared to the large original model. However, the effective numerical savings are not so important (40%) due to the limitations of the co-simulation method. [ABSTRACT FROM AUTHOR]

A coupled heat and moisture transfer 1D-model is developed to simulate the hygrothermal behavior of a coated hemp concrete wall. The hysteretic behavior of each layer (hemp concrete and plasters) is included in the modeling whereas a perfect hygrothermal contact is assumed between each layer. The numerical results are first compared to experimental ones obtained on a facility specially designed to measure mass variations as well as temperature and relative humidity fields within a coated sample. The comparison gives satisfactory results and underlines the influence of the hygrothermal properties, but also of plaster's thickness. Furthermore, it is observed experimentally that coating layers reduce moisture transfer and, thus, moisture buffer value of multilayered materials. A second comparison is performed with experimental data measured on a multilayer wall subjected to climatic variations. It was found that including the hysteresis in the modeling improve the prediction of the relative humidity field within a wall subjected to isothermal and non-isothermal conditions. However, it requires knowing the hygrothermal history of the wall in order to set initial moisture content of each layer. [ABSTRACT FROM AUTHOR]

Passive Houses are buildings which provide comfortable indoor conditions at an extremely low heating and cooling load. The peak daily average heating and cooling loads are typically below 10 W/m 2 and annual useful energy demands are below 15 kW h/(m 2 a). The Passive House standard was originally developed in Germany. In this paper we show by hygro-thermal dynamic simulation that it is possible to realize residential Passive Houses in all of the world's relevant climate zones, represented here by Yekaterinburg, Tokyo, Shanghai, Las Vegas, Abu Dhabi, and Singapore. The window quality, insulation levels, and mechanical services all depend on the climate as well as on the building's shape and orientation. The resulting annual energy demand for space conditioning of the Passive Houses is 75 to 95% lower than that of a traditionally insulated building of the same geometry. In humid climates like Shanghai or Singapore, special attention must be paid to humidity aspects. In climates which are hot and humid all year long, the total useful energy demand for sensible and latent cooling may exceed 70 kW h/(m 2 a) even in a Passive House. Finally, it is shown that the architectural quality is not compromised by the Passive House requirements. [ABSTRACT FROM AUTHOR]

Innovative and efficient ways to perform numerical simulations are worth investigations to reduce the computational complexity of building models and permit to solve complex problems. This paper proposes a Proper Generalised Decomposition (PGD) model reduction technique for heat and moisture multizone modelling. First, the transient multizone problem is written using PGD formalism and solved in a non-incremental way to assess hygrothermal fields. The computational complexity and accuracy of results of the reduced-order model and the large original model are compared, highlighting that the fields are precisely represented with the PGD resolution. The complexity of the reduced-order model is lower, offering interesting numerical savings, particularly when the number of the building zones increases. The second advantage of the method is for solving parametric problems. Two illustrations are proposed. The first considers a climate and ventilation flow rates parametric multizone problem. The PGD model analyse the behaviour of building zones as a function of these two extra-parameters. For the second, an initial condition and source-term PGD parametric solution is computed. It is then coupled with a wall model to perform whole-building hygrothermal simulation. For both studies, the model represents accurately the hygrothermal fields in the different zones with important computational savings. [ABSTRACT FROM AUTHOR]

Existing buildings account for 40% of total green gas emission in the atmosphere [1,2] . Historic and heritage buildings are part of this building stock, and the need for improving their energy performance, despite the derogations for officially protected ones, is supported for achieving the European 2020 Energy Strategy aims [3] . However, when dealing with these buildings, not only are the intervention measures constrained by possible architectural preservation requirements, but also the preparatory building diagnosis itself: only non-destructive and non-invasive monitoring techniques are, reasonably, allowed. Therefore, during onsite energy auditing, ad-hoc monitoring protocols should be adopted. In this study, an indirect non-invasive envelope monitoring, for evaluating brick masonry hygrothermal behavior, has been proposed and applied in a heritage building in Antwerp (Belgium). The suggested method is aimed at onsite evaluating the thermal performance of buildings traditional masonry and at quantifying the extent of its alteration due to the moisture distribution variation. Areas detected as wet during iterative passive infrared thermography and environmental monitoring, showed thermal transmittance values more than three times higher than the dry ones on the same masonry surface. [ABSTRACT FROM AUTHOR]

In Europe and worldwide several legislations are adopting comfort models that include the variability of occupants behaviour based on the external climate conditions. The latest adaptive comfort methods consider outdoor temperature not only as a steady variable but also as the representation of occupants past thermal history. The paper presented deals with a summer environmental monitoring carried out in a Sardinian earth building. These traditional houses are very often without AC systems and the control of summer conditions is based mainly on natural ventilation. By the use of adaptive comfort model, the different thermal performance between the upper and lower floor of the two storey building are investigated. Different models have been implemented, some included in current technical standards, some other still experimental. The results show the capability of the case-study to provide comfort conditions, but only in the lower floor. The upper floor that traditionally was used as a depository and now hosts the bedrooms shows overheating problems. The change of use, in this case, is the main cause of the bad performance, as highlighted by the microclimatic survey. [ABSTRACT FROM AUTHOR]

The selection of a thermal comfort model for establishing indoor optimal hygrothermal conditions during the hot period has a major impact on energy consumption of Net Zero Energy Buildings in hot climates. The objective of this paper is to compare the influence of using different thermal comfort models for zero energy buildings in hot climates. The paper compares the impact of applying Fanger's model, Givoni's model, the ASHRAE 55 adaptive comfort model and the EN 15251 adaptive comfort model on energy consumption and comfort performance. Using both the building performance simulation tools ZEBO and EnergyPlus for energy simulation, an existing prototype of a residential apartment module is used to evaluate energy performance and thermal comfort in two parametric series. The first one is the result of coupling natural ventilation and mechanical cooling and the second one is guided coupling natural ventilation, mechanical cooling and ceiling fans. This study shows that the percentage of energy consumption difference meeting the comfort criteria according to ISO 7730 in comparison to EN 15251, ASHRAE 55 or Givoni's model varied up to 16%, 21% and 24.7%, respectively for the presented case study. More energy savings can be expected for buildings in hot climates with greater cooling demands. [ABSTRACT FROM AUTHOR]

The thermal and flow performances in a single spiral-type ground heat exchanger in one-week operation were numerically simulated by considering the coupled thermal and moisture migration model for backfill and soil fields. The main factors involved Reynolds number (3000–10000), inlet temperature (30–40 °C), initial volumetric moisture content (6.95–20.8%), backfill materials (native sand, and sand/kaolin blend with 5% adding ratio of kaolin), spiral diameters (0.4–0.8 m), spiral pitches (0.1–0.8 m) and operation modes. The thermal performance of the heat exchanger without considering the coupled thermal and moisture migration model in unsaturated soil could be overestimated in long-term operation. The average temperatures in the blend enhanced by about 2% compared with the sand field, but the change degrees for the moisture content in the blend field were about 33% lower than that in the sand field, which imply that the kaolin additive could simultaneously enhance the thermal migration and water-holding capacity of the sand. The heat transfer rate of the heat exchanger in the blend enhanced by 24–36% with widening the spiral diameter from 0.4 to 0.8 m or narrowing the spiral pitch from 0.8 to 0.1 m, while the pressure drop rose by 50–92% and 4–5 times, respectively. 3-h-on/3-h-off mode among three intermittent operation modes (12-h-on/12-h-off, 6-h-on/6-h-off and 3-h-on/3-h-off) for the blend was more effective one to urge the soil temperature restoration. The intermittent operation mode should be also a feasible technique for prompting the thermal performance of the ground heat exchanger. [ABSTRACT FROM AUTHOR]

• Optimizing environment control system for underground sleeping space. • Thermal comfort, air quality and energy consumption were considered. • The influences of inlet air velocity, temperature and angle were investigated. • The CFD-GA method was proposed to optimize key design parameters. As one of the main functions of urban underground spaces, underground shelter can be utilized for prevention/mitigation of disasters. In underground shelter, narrow sleeping spaces are recommended due to cost-effective and space-saving charcteristics. However, it is challenging to create a satisfied indoor environment with narrow sleeping spaces because of the limited space, high density of occupants and complex physical fields. In this study, an environmental control system was proposed for narrow sleeping spaces with multiple occupants, and numerical simulations were adopted in design and optimization process. Firstly, a numerical strategy (including turbulence modeling, meshing method and experimental validation) was proposed for the environment control system. Secondly, the validated numerical model was adopted to investigate the influences of key design parameters (such as inlet air velocity, temperature, air supply angle and airflow pattern) on indoor environment and energy consumption of narrow sleeping spaces with airflow pattern of "Up-supply and Down-return". Thirdly, the CFD-GA (Genetic Algorithm) method was utilized to optimize multiple design parameters of the environment control system. The optimal results indicated that all of the indexes (predicted percentage dissatisfied [PPD], percentage dissatisfied of draft sensation [PD] and carbon dioxide [CO 2 ] concentration) satisfied the requirement of standards, and its energy consumption was much lower than other design conditions. Compared to the "Up-supply and Down-return" airflow pattern, the "Down-supply and Up-return" airflow pattern produced higher PD values and caused stronger draft sensation. Overall, the numerical strategy and CFD-GA optimization method is able to provide proper design of indoor environment control for the underground narrow sleeping space, from the perspectives of thermal comfort, air quality and energy saving. [ABSTRACT FROM AUTHOR]

Mould growth on building materials is a complex phenomenon involving various causes environmental conditions including temperature and relative humidity, nutrients, exposure time. Environmental conditions and nutrient are closely related to physical properties of building materials. Thus, the appropriate selection of building materials is very important for prevention of adverse health effects due to mould growth. The aim of this study is to determine the influence of the hygric properties of interior finishing materials on the mould growth. This paper presents the results of mould growth risk evaluation with variation of hygric properties of interior finishing materials using hygrothermal and bio-hygrothermal simulation approaches. An experimental study was conducted to characterize the hygric properties of wallpapers which are used mainly as interior finishing material in residential buildings. Six types of wallpapers and two type of hygric properties (water vapour transmission property and moisture storage function) were selected for the study. WUFI Plus was selected for a whole building hygrothermal simulation. The results from the hygrothermal simulation were used for the assessment of mould growth risk using a biohygrothermal calculation model, WUFI-Bio. The simulation results show the clear correlation between the mould growth rates and the hygric properties of wallpapers. [ABSTRACT FROM AUTHOR]

A selection of hygroscopic salts and desiccant matrices (Salt In Matrix, SIM) were chosen from the part I of this research through characterisation of their pore structure and hygrothermal functional properties as candidate materials for a novel open thermal energy storage (TES) system. The aim of the paper was to analyse the candidate materials performance under controlled, large scale experimental tests. This was achieved through hygrothermal cyclic behaviour tests and energy and exergy analysis. Zeolite provided the highest temperature lift of all candidates due to the high amount of vapour adsorption and its fast reaction kinetics however, after the initial period (1–2 h), the moisture adsorption rate and thus heat generation decrease sharply. Zeolite also showed a sharp drop in performance over the four cycles as it requires a higher regeneration temperature (>180 °C) than that used (100 °C) for this research. SIM-3a (Vermiculite–CaCl 2 ) was found to be the most promising candidate for open TES systems due to its high heat generated and rapid mass uptake at higher relative humidity levels. [ABSTRACT FROM AUTHOR]

Interior insulation is often the only possible post-insulation technique to improve the thermal performance of single leaf masonry walls. As a result of potential damage patterns such as frost damage, interstitial condensation and mould growth however, there is often some reluctance to adopt this technique. To fully exploit the capacity for energy savings offered by interior insulation while avoiding hygrothermal failure, a reliable risk assessment is extremely important. This requires a probabilistic approach, since the uncertainty of all influencing parameters might result in widely varying results. As, so far, no real methodology is available to select the interior insulation system and thickness resulting in the best balance between energy savings and hygrothermal risks, this paper presents a decision tool based on a Monte Carlo analysis. Additionally, the influence of the rain load and some masonry characteristics is discussed. In the study, both vapour tight interior insulation systems and a capillary active insulation system are considered. Overall, vapour tight systems tend to be preferable for structures that are resistant to frost damage. For buildings sensitive to frost damage or when wooden beam ends are present, however, capillary active systems are shifted forward. [ABSTRACT FROM AUTHOR]

Previous work by the same authors has shown that in mixed-humid climates, tight, super-insulated residential structures can experience high humidity events in summer months. Standard, commercially available vapor compression-based air conditioners struggle to control humidity in such structures with low cooling loads. Therefore a desiccant-assisted heat pump system for tight, super-insulated residential structures is proposed. This paper first reviews solid desiccant cooling cycles. Then a hybrid desiccant cooling cycle is explained and a prototype machine based on the cycle is described. The machine, known as HAWC (hybrid air/water conditioner), accomplishes cooling, dehumidification, ventilation, and domestic hot water heating. This paper models the HAWC within the framework of dynamic building energy modeling software and concludes that a refined version of the HAWC prototype is capable of completely eliminating high humidity events in the summer time while still saving energy as compared to a traditional HVAC system. [ABSTRACT FROM AUTHOR]

In this paper a new methodology for the comprehensive evaluation of the thermal condition of environment based on operative temperature thermal levels, so called decitherms, is presented. It allows an assessment based on the perception of the environment by man. It stems from the impact of the environment on human psyche as described by the Weber–Fechner law. One of its strengths is that it takes into account the fact that a decrease in operative temperature is perceived the more strongly at lower temperatures. The concept of the decitherm allows a direct numerical comparison with decibels, used for noise evaluation, and with deciodors, used for odor assessment, and additionally the total environment can be assessed by adding the individual levels multiplied by corresponding impact factors. Further, concrete values for SBS can be estimated, rating of air-conditioning systems efficiency defined and the degree of danger to man whether by overheating (hyperthermia) or undercooling (hypothermia) can be estimated. This methodology has already been used in the preparation of European standard prEN 4666:2011 Aerospace Series, Aircraft integrated air quality and pressure standards, criteria and determination methods. [ABSTRACT FROM AUTHOR]

In this study, we present a recently patented insulating rendering based on silica-aerogels. It is mainly developed for exterior thermal insulation applications. In addition to new buildings, it can be used for retrofitting existing ones since it has a high insulation performance and its application is easy, compatible with the traditional masonry facades, and using the well-known ordinary techniques. The objectives are to examine the hygrothermal performance of walls with this rendering and to compare different thermal insulation configurations. The methodology followed is developing a numerical model, then conducting an experimental set-up on a test-cell having the rendering on its south wall to validate the numerical model under real weather conditions. Different exterior wall structures are examined: no insulation, exterior insulation using this rendering, interior insulation, and interior and exterior insulation. Six assessment criteria are used: assembly water content, drying rate, mold growth, condensation risk, ASHRAE-160 criterion, and heat losses. Results show that interior thermal insulation systems can cause several moisture problems: inability to dry out over the years, condensation risk, etc. Adding the aerogel-based rendering on the exterior surface of the un-insulated or the already internally insulated walls reduces significantly or even removes the moisture risks. Also, it reduces significantly the wall heat losses. [ABSTRACT FROM AUTHOR]

Bio-based building materials such as hemp concrete have been used successfully in building construction due to their thermal and environmental properties. Since they are also hygroscopic, modeling their hygrothermal behavior is also relevant for appropriate building design. In this work, heat and moisture transfer is investigated numerically by accounting for hysteresis and phase change effects. Input physical properties and their dependency on temperature and moisture content were determined by laboratory experiments. To validate the model, two extended cyclical adsorption/desorption experiments were first performed on an instrumented hemp concrete sample. One of the tests was conducted according to the Nordtest protocol. In the third experiment, a hemp concrete wall was monitored under various boundary conditions. The comparison of numerical results with experimental data gave satisfactory results for all the experiments, regarding mean moisture variation, local temperature and relative humidity variations. Lastly, we conclude on the use of a hysteresis model for hygroscopic materials. [ABSTRACT FROM AUTHOR]

This paper details the dynamic simulation of a small, super insulated Passivhaus residential structure, namely The Ohio State University's entry into the 2011 Solar Decathlon competition. This study explores the use of a conventional vapor compression conditioning system as well as the effects of occupant behavior on the parameters affecting comfort within the structure. It adds to the current literature on the subject by presenting a simulation of a Passivhaus and its HVAC system in a mixed climate where cooling and dehumidification are traditionally required. Furthermore it adopts a simulation tool which acts on time scales significantly less than 1 h. It is concluded that the house, while energy efficient, has difficultly controlling moisture levels. In the summer season it is too humid, and in the winter it is too dry. The study concludes that conventional HVAC equipment cannot fully address the moisture and indoor air quality issues that are a result of new building techniques with stringent air infiltration and insulation standards. [ABSTRACT FROM AUTHOR]

The novel building materials continue to emerge, but there is not enough research on their performance. To explore the hygrothermal characteristics of the aerogel-enhanced foam precast concrete wall panels, a mathematical model was established and verified by experiments. The heat and moisture transfer performance parameters were tested by experiments, and the functional relations of related parameters have been fitted. Two typical cities in China, Shanghai in hot summer and cold winter area (HSCW) and Beijing in cold area (CA) were taken as examples. The hygrothermal characteristics of wall panels were numerically calculated for 5 years. The results show that the internal temperature and humidity of the wall panels in the two regions showed irregular periodic changes. The heating and cooling loads of the wall panel were calculated by the coupled heat and moisture transfer model and heat transfer model, respectively. Under the conditions of considering the eastward solar radiation and ignoring the radiation, the comparison of the results of the same model shows that the cooling load deviation in Shanghai is more than 55%, while the deviation in Beijing is as high as 62.4%. While the maximum deviation of the heating load between the two areas is only about 9.5%. Secondly, the results of the two models under the same working conditions are compared, and the maximum deviation of the cooling load in the two areas is only 11.2%. The maximum heating load deviation is only 4.1%, and the minimum is 1.34%. In addition, the impact of solar radiation on the cooling load in two climate zones far exceeds the heating load, and it has a greater impact on Shanghai. [ABSTRACT FROM AUTHOR]