Relative Humidity Fluctuations Research Articles

Performance analysis of human respiratory system based on the second law of thermodynamics.

The purpose of this study is to develop a comprehensive thermodynamic model of the human respiratory system and quantify the effects of inspiratory air temperature, relative humidity (RH), lung capacity and O2 fluctuation in metabolic reaction on the human respiratory system under three different physiological conditions, i.e. rest, moderate level of physical activity and extreme level of physical activity. Therefore, a second law-based analysis has carried out for the human respiratory system. It is observed that exergetic efficiency decreases by 21% and 16.5% during moderate and extreme level of activity respectively as compared to the physical condition of rest. The respiratory efficiency also increases with the increase in inspiratory air temperature and RH. For a given inspiratory air temperature, an increase in lung volume leads to a reduction in the efficiency. Increase in TV with a high airflow rate gives a higher magnitude of efficiency, such a situation appearing when a person's lung compliance harmed due to diseases. The respiratory efficiency decreases up to 2% with the increase in O2 percentage. The efficiency of the respiratory system is in maximum during rest followed by an extreme and moderate level of activity. However, with the controlled supply of O2, the efficiency of the human respiratory performance increases with the decrease in O2 percentage. Due to partial oxidation of glucose at a reduced O2 level, exergy input from the metabolic reaction is less leading to increased exergetic efficiency.

3D digital image correlation system for monitoring of changes induced by RH fluctuations on parchment

One of the most common sources of damage in Cultural Heritage Objects (CHO) such as parchment, oil paintings and historical textiles is relative humidity (RH) changes which cause inplane and out-of-plane displacements of their surfaces. The best suited method which enables full-field, non-contact displacements measurement with high resolution and sufficient range, is 3D Digital Image Correlation (3D DIC). However, the standard version of DIC requires applying random, good contrast speckle pattern at a surface of the object under investigation. Such requirement is not acceptable for CHOs. In this paper, we analyze the possibility to apply 3D DIC method for monitoring of displacements in selected groups of CHOs without modifying their surface i.e. based on their natural texture. The selection of the data capturing conditions and analysis parameters can lead to successful non-invasive monitoring of CHOs’ behavior. The samples studied herein are historical parchments subjected to controlled RH changes that impose inplane and out-of-plane displacements variations in time.

Unexpected three-state hydrochromism of a donor-acceptor self-complex with fluctuations in relative humidity.

Water in our environment is ever present, particularly in our atmosphere, from which it may be adsorbed by materials hygroscopically. At the molecular level, the binding of water molecules to various materials is driven by weak interactions but can have profound effects on physical properties, including the donor-acceptor interactions in charge transfer (CT) salts. Herein we present the unexpected three-state hydrochromatic switching of a bipyridinium-based donor-acceptor self-complex with changes in relative humidity (RH) and subsequent stable hydrate formation. RH is typically an overlooked variable that can vary greatly. These findings suggest that care should be taken to consider fluctuations in RH when characterizing the solid state optical band gap and CT absorption bands for organic donor-acceptor CT salt complexes.

Influences of high-reflective mulching membrane coupled with a drip sub-irrigation system on temperature and humidity of the soil

The present study deals with an original application of RR materials to the agriculture sector, evaluating the effectiveness of a high-reflective mulching membrane treated with glass micro-spheres and coupled with a drip sub-irrigation system. An experimental facility, in which this technology is exploited, has been set up in Perugia (Italy). Influences of the mulching membrane on hygrothermal properties of the soil were evaluated through humidity and temperature sensors during the monitoring campaign. Data from unmulched field section was used as a reference case. The effectiveness of this technology was evaluated by focusing on three days that are representative of as much weather conditions. The monitoring campaign conducted from April to May 2021 has demonstrated that the high-reflective mulching membrane can reduce the temperature and relative humidity fluctuations throughout the day. In addition, the mulching membrane can reduce the soil temperature at different depths (i.e. 0.05 m, 0.10 m, and 0.15 m). The highest soil temperature reduction was found equal to 8.95°C at 0.15 m. Basing on such preliminary results, a more detailed and extended monitoring campaign will be performed in summer conditions.

Temperature and humidity monitoring to identify ideal periods for liquefaction on Earth and Mars – data from the High Andes

During an almost two week-long field campaign in the Atacama Desert high altitude region of Ojos del Salado volcano, temperature (T) and relative humidity (RH) values were monitored on the surface and <1–5 cm sized rocks, focusing on the night-time values. The aim was to identify and evaluate potential temporal characteristics of daily T and RH changes, searching for ideal periods for deliquescence that has recently been proposed for Mars. Although the atmospheric pressure on Mars is much lower than on Earth, and the atmosphere is drier in general, the huge daily temperature fluctuation there could produce elevated humidity values at night-time; this aspect has thus been analysed on Earth at a desert location, where because of the high elevation night-time cooling is very strong, just like on Mars. Different nearby surface locations showed the same temporal T/RH characteristics, but evident variations were observed between different days. Strong fluctuations could be observed on 10–20 minute long temporal scales, that might influence the deliquescence process, and should be accounted for in future missions aiming to analyse this process on Mars. Night-time periods were favourable for deliquescence. Among the modelled Mars-relevant salts [CaCl2, Ca(ClO4)2, Mg(ClO4)2, NaCl] the longest durations of possible deliquescence were for CaCl2, Ca(ClO4)2 and Mg(ClO4)2, ~7–12 hours for one day. The duration for deliquescence showed some increase along with the rising elevation, due to the decreasing night-time temperature. Thus despite the low humidity on Mars, the cold nights may cause elevated RH towards deliquescence. The Atacama Desert locations analysed are a useful analogue of the deliquescence process on Mars. Fluctuation in RH was observed in night-time, suggesting that similar variability might be present on Mars, and that should be considered in the future, including in evaluating how fast the microscopic liquid formation progresses. Night-time slope winds expected on Mars might have a strong impact on the local T/RH conditions. A more detailed analysis in the future should focus on identifying and separating regions with and without much of the expected night-time fluctuation

About the influence of environmental conditions on the distribution of the SARS-CoV-19 virus in Ukraine

Taking into account that climate and atmospheric processes can, to a certain extent, affect viral epidemics, the dynamics of the rates of infection with the SARS-CoV-19 virus was analyzed in comparison with a number of climate factors (temperature, precipitation, humidity, etc.) in the territory Kiev, Dnepropetrovsk, Odessa and Khmelnytsky regions as well as the city of Kiev during April—August 2020. To assess the impact of environmental conditions on the process of virus infection, the index of confirmed cases (ICC) was introduced.It is shown that in the spring, in particular, in May, the ICC index increased with a cold snap and decreased with a warming. In summer, the ICC index decreased with an increase of temperature with a delay of infection by 5—7 days, which is apparently associated with the incubation period of the virus (5—14 days). In particular, there was no increase in ICC values at high temperatures (over 30 °C). The relative humidity of the atmosphere air and the dew point temperature are more closely related to the efficiency of virus transmission. Thus, in spring, with an increase in relative humidity, an increase in the values of the ICC index was observed, and vice versa, with a decrease in relative humidity, the ICC index decreased. In summer, at high air temperatures and fluctuations in relative humidity, the ICC index mainly decreased, with the exception of a few weather situations. A decrease in the amount of atmospheric precipitation in April-August 2020 in Ukraine affected the activity of aerosol transmission of viruses (air-dust transport prevailed). At the same time, it was found that an increase of the ICC index during rainy periods correlates with the number of days with precipitation (less — with the amount of precipitation), while there is a delay in the growth of infection rates by several days. Analysis of the possible effect of precipitation acidity on the survival of the SARS-CoV-19 virus indicates the absence of a significant effect of this factor on the dissemination of viral infection. The presented results of the analysis of data on infection with the SARS-CoV-19 virus in Ukraine indicate a certain dependence of this process on climatic factors and are important for the assessment of the risks of infection and related diseases.

Investigation on the use of hygrothermal modelling for paper collections

Dynamic simulation is increasingly adopted in the preventive conservation of cultural heritage as an advanced method to investigate strategies for mitigating the climate-induced degradation. The conservation of paper collections is strongly interrelated with the relative humidity of the air, as organic-hygroscopic materials act as buffers on relative humidity fluctuations while being vulnerable to moisture-induced damage. In the dynamic simulation of the microclimate within library and archival storage facilities, it is thus fundamental to include the hygrothermal interaction between the building and its hygroscopic content. The hygroscopic behaviour of paper collections can be modelled by hygrothermal tools such as those of the HAM-family (Heat, Air and Moisture), used to simulate simultaneous heat and mass transfers through porous envelope materials. This research aims at investigating the use of the HMWall model coupled with the software IDA ICE (Indoor Climate and Energy) to simulate of the 1-D heat and moisture transfer through a single wall made of paper. A literature survey was carried out to collect the available hygrothermal properties of modern and historical papers. Sensitivity analysis was used to identify the most relevant hygrothermal parameters in the simulation of moisture gradients across the paper wall. Moreover, the number of sub-layers in the paper wall model was found to significantly affect the internal distribution of moisture gradients. The use of the HMWall model was then tested in the simulation of the hygroscopic behaviour of a single paper wall in both steady-state and transient conditions. Finally, a simplified model able to preserve the accuracy of the results was proposed with the purpose of reducing the computation effort that a high-resolution model could involve if implemented in whole buildings. This study represents the first step towards the application of the HMWall model for the simulation of the indoor climate of library repositories.

Trend Analysis of Temperature and Humidity in Kwara State, Nigeria

Abstract This paper examines the trend analysis of temperature and relative humidity in Kwara State. Climatic data on annual mean temperature (minimum and maximum) and relative humidity for 40 years (1978-2017) were collected from Nigerian Meteorological Agency (NIMET) Ilorin. Semi-Average method, Mann- Kendull statistics and regression method were used to analyse the trend in temperature and relative humidity. The Standardized Anomaly Index (SAI) was also used to examine the changes in temperature and humidity over the period of 1978-2017. The result of the analysis indicates that temperature (minimum and maximum) and relative humidity exhibit an upward trend. This implies that temperature and relative humidity increase over the period of 1978-2017. The Mann-Kendull statistics values show that there is no significant difference in the values of temperature (minimum and maximum) and relative humidity. The result of the Standardized Anomaly Index (SAI) also revealed that the values of temperature and humidity fluctuated around the long –term mean. About 50% of the annual average relative humidity falls above the long term average while 40% of the annual mean maximum temperature falls above the long term average. It can therefore, be deduced that there is the possibility of increment in the values of temperature and relative humidity which could cause a serious challenge to human health and climate change. The study therefore, suggests that increase and fluctuations in temperature and relative humidity should be a critical factor in designing strategies to mitigate the effect of climate change on the environment and human health.

Perturbations of atmospheric surface layer characteristics during the annular solar eclipse on 26 December 2019 over a semi-arid region Anantapur in southern India

The Annular Solar Eclipse (ASE) occurred on December 26, 2019, which was visible at most of the South Indian subcontinents with greater than 80% obscurity, particularly during the morning hours, and it played a crucial role in the atmospheric dynamics. For the first time, the ground-based measurements have used to investigate the fluctuations of air temperature, relative humidity, atmospheric pressure, wind speed and direction, UV-A radiation, and turbulence parameters on solar eclipse day over a semi-arid region, Anantapur, in Southern India. The Surface Layer (SL) meteorological parameters have abruptly changed on eclipse day (December 26, 2019) as compared to the control day (December 27, 2019). During eclipse day, the near-surface air temperature was significantly decreased (1.12 °C), and relative humidity increased (14.63%) after 60 min of the beginning of the eclipse, which mainly due to cooling the surface. The atmospheric pressure has reduced by 0.9 hPa during the eclipse period, and the winds speed also reduced to 0.92 ms−1 due to the stabilization of Atmospheric Boundary Layer (ABL) and cooling in the SL. The turbulence parameters, including those are Sensible Heat Flux (SHF), Momentum Flux (MF), and Turbulent Kinetic Energy (TKE) have also reduced from 99.37 to 0.91 Wm-2, 0.38 to 0.03 Nm−2, and 1.47 to 0.37 m2s-2, respectively during the eclipse day, which mainly due to eclipse cooling effect diminishing the turbulence in Atmospheric Surface Layer (ASL). The lowest values (0.18 ms−1) of friction velocity were observed during the eclipse day, and the Monin–Obukhov stability parameter showed a significant variation in the atmospheric from weakly unstable to neutral conditions during the eclipse day. The vertical wind speed showed downdrafts during the eclipse and even after the eclipse due to subsidence of air. The investigation revealed that the ABL dynamic process and turbulence processes are affected due to cut off of solar radiation and make the SL cooling.

Temperature and relative humidity in a palaeontological collection: the buffering effect of microenvironments

Adequate values of environmental parameters are crucial for the long-term preservation of the fossils in a palaeontological collection. In particular, incorrect or fluctuating temperature (T) and relative humidity (RH) can affect glued or repaired materials, induce the proliferation of mould, provoke mechanical breakage, recrystallization or mineral decay. From April 2015 to March 2017, six hygrothermometers were incorporated in selected microenvironments of the Palaeontological Collection at the Facultad de Ciencias, Universidad de la República at Montevideo, Uruguay. The main aim of this study was to test the buffering effect of different enclosures compared to the ambient environmental parameters (AMB). The selected storage units were a mobile rack of shelves (C1), a cardboard box inside C1 (C2), a lidded plastic polypropylene box inside C1 (C3), a drawer in a non sealed cabinet (P), and a drawer inside a tightly sealing cabinet (G1). Maximum and minimum values of T and RH were manually gathered on a weekly basis. Linear graphs and statistical analysis (i.e. mean values, standard deviation and Kruskall-Wallis non-parametric variance analysis) were used to compare the measurements obtained. Regarding both T and RH, the more extreme values and fluctuation of these parameters were achieved in the ambient. With respect to T, all enclosures protected from Tmax variations as lower Tmax were recorded inside enclosures. With respect to RH, only C3 and G1 showed significantly lower values of RHmax than ambient values. Additionally, C3 and G1 showed an almost constant amplitude between maximum and minimum values which indicates that specimens were less exposed to fluctuations in RH. The results herein obtained show that to minimize the impact of environmental instability, it is safer for specimens to substitute cardboard by plastic containers, and closed storage units are better than open ones. In addition, sealed containers and cabinets protect the specimens from other agents of deterioration such as dust and pests.

English

In Northern Ghana, harvesting of the bulk of paddy, which is cultivated under rain-fed conditions, coincides with the harmattan season. This season is characterized by low relative humidity and dry weather conditions which hasten drying and increase the tendency of the paddy to crack during milling. The farmers also store paddy for longer periods in anticipation of higher price in the open market, thus the paddy may deteriorate as a result of fluctuations in seasonal temperature and relative humidity. This study assessed the effects of fertilizer application regimes and storage duration on cracking and breaking during milling in 4 aromatic rice varieties. Across the varieties, grains that showed signs of cracks will eventually break during milling, and grain susceptibility to cracking significantly (P<0.05) increased when stored beyond 30 days. Gbewaa rice recorded significantly (P<0.05) higher cracking (49.2%) followed by Amankwatia (43.9%), CSIR-AGRA (40.4%) and Exbaika (40.3%). Fertilization regime of 2 basal applications and 2 topdressings at panicle initiation and booting-heading stages resulted in grains that were well-filled and thick to resist drying and cracking. Key words: Aromatic varieties, nitrogen fertilizer, straight-milling, paddy cracking, consumer taste. &nbsp

Geothermal Technology for Sustainable Climate Control in an Historic House

ABSTRACT This paper discusses integration of twenty-first-century direct-exchange geothermal technology with nineteenth-century heat supply infrastructure to provide climate control at The Breakers, Newport, Rhode Island, U.S.A. In 1892, Cornelius Vanderbilt II built an 11,600 m2 Italian Renaissance style summer residence equipped with the most modern domestic technology available. This house retains original architectural finishes, furnishings, and a decorative arts collection, to give visitors insight into America’s Gilded Age. The mansion’s original design relied upon the ocean setting for its natural ventilation during summer occupancy; a convection heat system maintained the building through winter. A century later, risks to the collection due to extreme fluctuations in temperature and relative humidity along with rising energy costs prompted a climate modification feasibility study. The expense and complexity of conventional systems were deemed prohibitive, intrusive, and unsustainable. A high-efficiency geothermal heat pump system was chosen because it could generate conditioned, filtered air, re-use historic convection heat shafts, and significantly offset heating costs. Since going online in 2018, the system has stabilized the interior environment and considerably reduced fuel consumption. Discussion will include challenges encountered through design, installation and start-up, and assessment of environmental data.

An assessment of the contribution of air pollution to the weathering of limestone heritage in Malta

Malta is known for its limestone megalithic temples of which many are inscribed on the UNESCO World Heritage List. A variation of this limestone was historically, and until very few years ago, a primary building material in Malta. The temples are subject to various environmental influences which until recently have led to several collapses due in part to serious stone surface and infill loss. As a protection measure, open-sided shelters have been built over three of these temples. This work assesses the degrading influence of air pollution (nitrogen dioxide, ozone, particle matter, sulfur dioxide, and acidity in rain) on the temples, in combination and comparison with the influence of other environmental factors (relative humidity, temperature, precipitation, moisture, sea salt, wind) and in this respect evaluates the potential protective effect of the shelters. The variation in air pollution weathering of limestone exposed outdoor in Malta was calculated by exposure–response functions from the ICP-materials programme and compared with measured values, and its contribution to the deterioration of the temples was evaluated. The difference between urban and rural locations in Malta, in the first year of atmospheric chemical weathering of limestone due to air pollution, was found to be about one micrometer loss of stone surface. This is probably less than the annual variations due to the influence of natural climatic factors, and small compared to the present annual variations in continental Europe. The deposition of sea salt and presence of salts on and in the limestone megaliths and changes in salt-crystallization events due to relative humidity fluctuations, inside and outside the shelters, will account for more of the variations in the first year of weathering of Globigerina limestone than variations in air pollution. The deterioration will also be related to temperature (including condensation events), wind parameters and rainfall, as well as ground water replenished from areas beyond the shelter.

Physicochemical characteristics of PM2.5 particles during high particulate event (HPE) in school area

Observations of fine particulate matter (PM2.5) and meteorological parameter (temperature, relative humidity and wind speed) fluctuations during a high particulate event (HPE) in Sekolah Kebangsaan Bayan Lepas, Malaysia have been conducted for three days (48 hrs). Selected sample spot of collected PM2.5 particles with high concentration was chosen to investigate the physicochemical characteristics using Field Emission Scanning Electron Microscope coupled with Energy Dispersive X-ray (FESEM-EDX). The results show that the 24 h average concentration ± standard deviation of PM2.5 (81.87 μg m−3 ± 31.83) exceeded the limit suggested by Malaysia Ambient Air Quality Standard (MAAQS-2020) and United State Environmental Protection Agency (USEPA) which is 35 μg m−3. The diurnal variations of PM2.5 concentration fluctuated significantly during HPE. Results from Pearson correlation shows that relative humidity gives the most significant influence towards PM2.5 concentration (r = 0.410; p < 0.01) followed by wind direction (r = -0.306, p < 0.01), temperature (r = -0.262., p<0.01) and wind speed (r = -0.206; p < 0.01). From a morphological and elemental analysis, it shows that PM2.5 particles collected on a filter consist of two possible sources, natural and anthropogenic sources. The element components found in the natural particles were C, O, Na, Al, Si, S, K and Fe. The major components were C, O, Al, and Si with weight percentages were 18%, 39%, 9%, and 22%. Dominant elements in anthropogenic particles were C (41%) and a significant amount of K (3%) are found which considered as biomass burning soot. Besides that, the particles also consist of O, Na, Al, Si, and Cl. In summary, particles from natural and anthropogenic sources are dominant in the ambient PM2.5 during HPE.

Influence of Superabsorbent Polymers on Moisture Control in Building Interiors

Moisture loads in building interiors are accompanied by a deterioration of the indoor air quality. Such a phenomenon may induce serious health risks for building inhabitants as well as degradation of furnishing. Unfortunately, the employment of additional heat, ventilation and air conditioning (HVAC) devices does not comply with the sustainability principle due to increased energy consumption, thus cannot be viewed as an efficient solution. This study deals with the use of superabsorbent polymers (SAP) in cement-lime plasters, thus extends the current state of knowledge and outlines further possible development of novel moisture responsive plasters since lightweight aggregates do not provide the desired performance. To be specific, this paper contemplates the experimental analysis of novel plasters modified by 0.5, 1 and 1.5 wt. % of SAP to obtain input parameters for computational modeling. Based on the obtained outputs, the incorporation of SAP admixture resulted in a substantial increase in moisture transport properties including the water absorption coefficient and water vapor diffusion properties. The performed computational modeling revealed a considerable reduction of relative humidity fluctuations, thus mitigation of potential health issues associated with undesired moisture content in building interiors. Achieved results indicate that the SAP enhanced plasters have substantial passive moisture buffering performance and thus may contribute to the improvement of indoor air quality.

Preparation and characterization of metal-organic framework /microencapsulated phase change material composites for indoor hygrothermal control

Building materials with high thermal and hygric inertia can moderate the fluctuation of indoor temperature and relative humidity, and thus can improve the indoor thermal comfort and reduce the building energy consumption passively. In this study, a novel hygrothermal control material was prepared based on Metal-Organic Frameworks (MOFs) and microencapsulated phase change material (MicroPCM). The new MOF/MicroPCM composite has a dual functionality of adsorption and desorption of both heat and moisture, can offer an accurate passive control of the indoor hygrothermal environment. N-octadecane was encapsulated by polymethylmetracrylate (PMMA) as MicroPCM for the thermal buffering. MIL-100(Fe) was prepared by the hydrothermal reaction method as the humidity buffering material. A series of hygrothermal control composite materials were obtained by grinding MicroPCM and MIL-100(Fe). Physicochemical properties of the synthesized materials were characterized by SEM, TEM, XRD, FTIR, N2 physisorption, Water vapor sorption isotherm, DSC and TGA techniques. Hygrothermal properties of the composites were analyzed in comparison to pure MicroPCM and MIL-100(Fe). The thermal and humidity buffering behavior of the composites containing 50% MicroPCM was analyzed by numerical simulations. The results show that the composites possess an excellent thermal and humidity buffer capacity, which can be used for building energy-saving and improving thermal comfort.

Fracture saturation in paintings makes them less vulnerable to environmental variations in museums

Understanding paintings as physical systems is fundamental for advancing environmental specifications that would allow for effective management of museum environments in terms of reducing energy use and carbon emissions while maintaining high standards of collection care. The current environmental specifications were derived using the criterion of the crack initiation in undamaged, usually new, material. In reality, historical paintings exhibit complex crack patterns called craquelures. The present paper analyses painted wood which is among the category of cultural objects most vulnerable to relative humidity and temperature fluctuations and frequently found in museum collections of various kinds. Fracture toughness determined experimentally for the most brittle component of pictorial layer—the ground layer (gesso) is used as a ‘failure criterion’. Comparison of energy release rate—calculated for the model of the gesso laid on a wooden substrate using finite element analysis—with the structure toughness, allowed the fracture saturation expressed as the ratio of spacing between cracks S to gesso layer thickness t to be determined for various combinations of the gesso stiffness and geometries of structural flaws at which cracks initiate. For flat geometry of a panel painting and panel thickness of 40 mm, representing the worst-case, largest stresses in the gesso layer, the fracture saturation occurs when S/t is larger than 5, even if flaws in the gesso layer are present. The paper shows that the fracture saturation significantly changes vulnerability of paintings to climate variations—a panel painting with developed craquelure network is significantly less vulnerable to climate variations than an undamaged one.

Effect of hygrothermal behaviour of earth brick on indoor environment in a desert climate

This study describes the experimental testing of the hygrothermal properties of the earth brick and the numerical analysis of the hygrothermal behaviour of a residential building in a desert climate in order to evaluate the effect of the earth brick on the indoor environment. The hygrothermal properties, i.e. thermal conductivity, specific heat capacity, equilibrium moisture content and water vapour permeability, were characterized to be used in the following numerical simulation of indoor environment. The numerical analysis was conducted by whole building simulations using EnergyPlus which can be used to simulate the indoor climate in buildings. An existing residential building was monitored for two days in summer in order to validate the accuracy of the model. The simulated results showed that compared with the fired brick, the earth walls reduce the amplitude of both indoor air temperature and relative humidity fluctuations, especially the maximum of relative humidity, due to both thermal inertia and moisture capacity of the earth bricks. Besides, the heating energy consumption results of the earth brick rooms were significantly lower than the fired brick rooms during the heating period.

Programmable passive actuation for adaptive building façade design using hygroscopic properties of wood

ABSTRACT This paper exploits the hygroscopic properties of wood and its passive response to fluctuation of relative humidity to develop a framework for programmable actuation in adaptive building façade design. This responsive shape shifting mechanism is specifically employed for the embedded actuation of dynamic shading configurations. Utilizing the hygroscopic properties of wood in adaptive shading devices embraces passive motion with a low-cost and low-tech approach, as a response to rapid climatic changes. Using physical experiments and image analysis, changes in the deflection and angle of curvature of wood samples in response to fluctuation in relative humidity were measured and tracked. A set of controlled hygroscopic parameters affecting the motion response of wood were deduced, including the fixation position, fixation type, and percentage and location of isolated areas of wood samples, thus achieving more control of response behavior and multiple shading percentages. A parametric script was developed using Grasshopper graphical algorithm editor and Ladybug environmental plugin to simulate shading configurations for the identified control parameters in the summer and winter solstices for an adaptive façade prototype.

Precise humidity control materials for autonomous regulation of indoor moisture

Indoor relative humidity is an important parameter to determine indoor air quality, occupants’ thermal comfort and building energy consumption. As recommended by ASHRAE, the appropriate indoor relative humidity range for a healthy and comfortable indoor environment is between 40% and 65% RH. In order to meet the requirements, the most commonly used method is mechanical dehumidification/humidification system by using electricity. However, this approach is energy consuming. In this paper, a novel precise humidity control material (PHCM) based on Metal-Organic Frameworks (MOFs) is synthesized and its application in built environment is investigated. This material has an S-shape isotherm, high porosity and very high water vapor uptake of 1.62 g/g at 80% RH. It can rapidly adsorb moisture as the indoor relative humidity exceeds 60%, and release moisture as relative humidity drops below 45%. Unlike the conventional desiccants, e.g. zeolites, silica gel etc., MOF-PHCM can autonomously control indoor relative humidity within the desired comfort range at room temperature. Hygrothermal properties of the new material are measured. Numerical simulations have been carried out to study the effect of MOF-PHCM on indoor hygrothermal conditions and building energy consumption in five different climates worldwide (i.e. hot desert, semi-arid, Mediterranean, temperate, and humid subtropical). The results show that MOF-PHCM can effectively control indoor relative humidity fluctuations and reduce building energy consumption in most climates without any additional energy input. MOF-PHCM can be easily regenerated by either night ventilation (e.g. in hot desert, semi-arid, Mediterranean climates) or heating system powered by low-grade energy (e.g. in humid climates).