Search

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 • 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]

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 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]

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]

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]

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]

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]

Highlights: [•] Open stores have to match an important thermal load due to the infiltration air. [•] This situation is harder with intense pedestrian traffic and in warm humid climates. [•] Climatic separation and advanced hygrothermal control systems enables energy savings. [•] Modern air curtains can keep suitable indoor air temperature and humidity conditions. [•] Energy savings in commercial buildings with these systems exceeds 30%. [ABSTRACT FROM AUTHOR]

• Effects of driving forces on hygroscopic conditions are investigated. • Indoor humidity showed different degrees and tendencies according to moisture driving forces. • Humidity ratios differed by 0.01%–38.78% according to driving forces. • The EMPD model can produce differences of 4.4%–51.2% in thermal loads. To more accurately evaluate the indoor hygrothermal environment of a building, control the indoor temperature and humidity, evaluate the thermal comfort of occupants, and select the capacity of the heating, ventilation, and air conditioning (HVAC) system, moisture transfer from and into architectural materials should be considered. However, the most widely used commercialized software ignores the moisture effect from envelopes or adopts a simplified model based on the difference in humidity ratios between hygroscopic materials and interior zone air. In this study, the effects of the driving forces of hygrothermal models were identified and quantified. The calculated results show that the indoor humidity changes differed when the moisture effect by moisture adsorption and desorption was considered in the models. Because the simplified effective moisture penetration depth (EMPD) model uses differences in the humidity ratio as a driving force, the calculated results of the indoor humidity ratio exhibit relatively constant tendencies. However, the thermodynamic chemical potential model corresponds to a detailed heat, air, and moisture transfer (HAM) model that uses the water potential as a driving force; this model can consider the moisture effect based on temperature and humidity changes. Therefore, the humidity ratios calculated using the detailed thermodynamic HAM model show differences of 0.01%–38.78%, and the difference in relative humidity between building materials and indoor air becomes smaller; these results are comparable to those of the simplified model. Finally, the adoption of a simplified model can result in differences in the sensible heat load of 4.4%–13.8% and latent heat load of 16.1%–51.2%. Thus, this study confirmed that a coupled HAM model, which uses the water potential as a driving force, can be employed to accurately simulate the hygrothermal behavior of building envelopes. [ABSTRACT FROM AUTHOR]

• Adhesive used for ETICS provides moisture within the wall and increases moisture transfer resistance. • Simulated temperature and relative humidity profiles agree with the measured ones. • Using bio-based insulation may reduce the condensation risk. • The ventilated cladding system design is of high importance regarding the condensation risk. This work focuses on the hygrothermal behavior of three external thermal insulation systems: one ETICS including EPS insulation and two ventilated cladding systems including either mineral or biobased insulation. These systems were applied on a rendered hollow concrete wall and tested simultaneously between two climatic chambers. Thermocouples, humidity sensors and heat flux sensors allow investigating the hygrothermal behavior of the retrofitted wall at different stages: just after the application of insulations systems, during safe and critical use. The measured data are compared to numerical results obtained by solving a heat and moisture transfer model. Results highlight the key role of adhesive on ETICS, which provides a significant moisture source during the application and forms an additional moisture transfer resistance within the wall. Results on ventilated cladding systems show that using biobased insulation may delay and even prevent the risk of interstitial condensation. The comparison between numerical and experimental results is satisfying for temperature and heat flow density, but underline the sensitivity of relative humidity to the sorption capacity of hygroscopic building materials. In addition, the systems design has a great influence on the condensation risks. [ABSTRACT FROM AUTHOR]