Moderate Indoor Research Articles

The response of clay plaster to temperature and RH sinusoidal variations

Hygroscopic finishing materials can be used to moderate indoor humidity levels; they have the capacity to adsorb and release moisture from and to the surrounding air, depending on the indoor relative humidity levels. To determine the moisture buffering properties of materials several protocols have been introduced. However, testing procedures are based on a time-response method, where humidity variations are under a square wave function and temperature remains constant. Therefore, the ability of these methods to simulate material behaviour under real conditions, where cyclical humidity variations are more gradual, and temperature is variable, has been called into question. The aim of this study is to perform a standard moisture buffering test, by substituting the step-variation method, with a sinusoidal humidity function at different temperatures. Clay has been used to perform the tests in a climatic chamber, where a small increase of relative humidity have been set, in order to obtain a quasi-sinusoidal curve. The relative humidity variation are limited by low humidity (33% RH) and high humidity (75% RH) and temperature variation between 18 °C and 28 °C. Materials tested present a lag in the response to the peak relative humidity to peak mass gain, which suggests an alternative way to consider the rate of sorption and the moisture storage function. The significance of the paper is to develop a laboratory test that can be more readily compared with the behaviour real buildings, which operate under more of a sine waveform

Imaging Individual Differences in the Response of the Human Suprachiasmatic Area to Light.

Circadian disruption is associated with poor health outcomes, including sleep and mood disorders. The suprachiasmatic nucleus (SCN) of the anterior hypothalamus acts as the master biological clock in mammals, regulating circadian rhythms throughout the body. The clock is synchronized to the day/night cycle via retinal light exposure. The BOLD-fMRI response of the human suprachiasmatic area to light has been shown to be greater in the night than in the day, consistent with the known sensitivity of the clock to light at night. Whether the BOLD-fMRI response of the human suprachiasmatic area to light is related to a functional outcome has not been demonstrated. In a pilot study (n = 10), we investigated suprachiasmatic area activation in response to light in a 30 s block-paradigm of lights on (100 lux) and lights off (< 1 lux) using the BOLD-fMRI response, compared to each participant's melatonin suppression response to moderate indoor light (100 lux). We found a significant correlation between activation in the suprachiasmatic area in response to light in the scanner and melatonin suppression, with increased melatonin suppression being associated with increased suprachiasmatic area activation in response to the same light level. These preliminary findings are a first step toward using imaging techniques to measure individual differences in circadian light sensitivity, a measure that may have clinical relevance in understanding vulnerability in disorders that are influenced by circadian disruption.

Metal-organic framework MIL-100(Fe) as a novel moisture buffer material for energy-efficient indoor humidity control

Metal-organic frameworks (MOFs) are a new class of porous materials composed of a three-dimensional network of metal ions held in place by multidentate organic molecules. MIL-100(Fe) (molecular formula: Fe3O(H2O)2OH(BTC)2), as one kind of MOFs, has an excellent performance of water sorption due to the large specific surface areas and high porosity. The paper proposes an innovative application of MIL-100(Fe) as a new kind of moisture buffer material to control the indoor humidity passively. MOFs can moderate indoor moisture fluctuation, which will greatly reduce the energy consumption of HVAC systems and improve the building energy efficiency. In the paper, microstructure and moisture characterizations of MIL-100(Fe) have been carried out. The moisture buffer value (MBV) of MIL-100(Fe) has been measured and compared to the typical building materials. The results show that MIL-100(Fe) can absorb up to 15 g m−2·RH−1 at 8 h, which is 33 times higher than the laminated wood. A novel lumped model for building latent load simulation has been developed. The energy saving potential by using MOFs in a typical office in different climates was calculated. The results show that a 5 m2 MOF wall panel can remove most of the latent load in dry and moderate climates without any energy input; MOFs can be regenerated by night ventilation. In the hot and humid climate, the MOF materials can remove 73.4% of the latent load, and can be easily regenerated by using low-grade energy.

Indexes for passive building design in urban context – indoor and outdoor cooling potentials

In this paper, we propose a practical approach for decision-making regarding passive cooling design for buildings in dense urban contexts. For non-cooled buildings under temperate climates, assessment of summer thermal discomfort determines the usual passive cooling design together with fossil energy and GHG savings at earth scale. However, passive cooling techniques for indoor climate can be also valuable for local environment impacts, especially urban heat islands’ mitigation. Lack of simple representative criteria and complexity of simulation outputs constitute a barrier for the development of passive cooling. Based on a study of a generic commercial building, we analyzed several designs with Sankey diagram and we developed two performance indexes. This chart synthesis of complex output data allows a direct comparison of design solutions. This analysis gives hints for better designer understanding of urban climate and building interactions for the studied passive cooling solutions: cool roofing, nocturnal natural ventilation and rooftop PV system as shading device. Our results show that nocturnal natural ventilation is efficient to moderate indoor overheating compared to the "cool roof". In addition, cool roofs reduce anthropogenic heat transferred to urban environment. PV panels as shading device mitigate summer discomfort and produce energy that increase building energy efficiency through the year. We defined two Key Performance Indexes (KPIs) to define cooling potential of both indoor and urban environment. These KPIs obtained for different temperate climates highlight new prospects for the design of efficient urban designs with controlled environmental impacts and decision process of stakeholders.

Total body skin temperature of runners during treadmill exercise

The aim of this study was to investigate the time evolution of total body skin temperature during running exercise on treadmill. A group of physically active subjects performed two different treadmill exercises, at graded load and at constant load, for a duration of 30 min, in a moderate indoor environment. Thermal maps of the anterior and posterior body regions were gathered, before, during and after the exercise, by means of infrared thermography. Skin temperature of total body was calculated as a combination of individual measurements taken over several body regions. Within the limits due to the relatively small size of the sample group, results typically show a fall in total body skin temperature during the early stages of treadmill exercise. As the exercise progresses, the dynamics of the skin temperature response is affected by the type of exercise, showing a further decrease during the graded load exercise and a slight increase during the constant load exercise. Regionally averaged skin temperatures were found to be lower than total body skin temperature over the most peripheral body regions less involved in running (upper limbs) and comparable with or higher than total body skin temperature over calves and thighs.

Development and hygric and thermal characterization of hemp-clay composite

This study investigates the use of clay as binder in hemp composite and compares hemp–clay composite to hemp–lime concrete. The clay is produced from washing mud from gravels production site. Two clay drying temperature are used. The thermal properties are measured with a hot wire method and the hygric characterization is based on the measurement of Moisture Buffer Value. Performances obtained on clay blocks, hemp–clay composite and hemp–lime composite are compared. The results show that the two clay drying temperatures do not impact on the thermal conductivity nor on the moisture buffer value of clay blocks. Hygric and thermal performances of hemp–clay and hemp–lime composites with the same density are close. These materials act as excellent hygric regulators. Performances measured separately on hemp and clay underline an interesting synergetic effect in the case of hemp–clay composite leading to a higher ability to the moisture buffering. Such material can be advantageously used in buildings to moderate indoor humidity variations.

Application analysis of theoretical moisture penetration depths of conventional building material

Due to the significant impact of indoor humidity on indoor air quality, human comfort, and energy consumption, many researchers have investigated the use of various hygroscopic materials to moderate indoor humidity levels and save energy. The results show that the indoor relative humidity of the room with hygroscopic materials is more stable and moderate. Hygroscopic materials can be also used to reduce the energy consumption of heating, ventilation, and air-conditioning system. Although many laboratory measurements and numerical simulation studies have been done for hygroscopic materials, there is little study on moisture penetration in materials with limited thickness in practical engineering application. Moisture penetration depth has great influence on material moisture parameters and indoor humidity simulation model, such as effective moisture penetration depth model. In this article, a theoretical moisture penetration depth model is developed, and the theoretical moisture penetration depths of conventional building materials are calculated. The results show that when the wall material thickness is below the 1/e theoretical moisture penetration depth, the proportional relationship between the moisture buffer value and the square root of time is not kept. When the wall material thickness is thinner than its theoretical moisture penetration depth, ignoring the material thickness might cause significant error in indoor moisture content calculation using effective moisture penetration depth model.

Indoor Humidity Environment in Huizhou Traditional Vernacular Dwellings of China in Summer

A three-month field measurement of temperature and humidity was carried out in order to analyze the indoor humidity environment in a Huizhou traditional vernacular dwelling compared with that in a modern dwelling during summer. The results showed that the average relative humidity in the traditional vernacular dwelling over 83% was slightly higher than the corresponding value around 75% in the modern dwelling. The humidity fluctuation appeared stable in wing-room due to the moisture buffering effect of the internal timber wood while the humidity variation was drastic in bedroom with well air-tightness due to frequent application of air-condition. The dependency of indoor humidity on the outdoor humidity was strong resulted from a great effect of natural ventilation in the traditional vernacular dwelling with a correlation coefficient of 0.8. Although humidity was high, the thermal comfort was acceptable with the comfortable time near 60% in the traditional vernacular dwelling during summer. It is supposed to apply synthetic hygroscopic materials on the basis of the timber wood with ventilation to moderate indoor humidity in modern architectures in Huizhou area.

Phase Change Humidity Control Material and its Application in Buildings

The synthesis of novel phase change humidity control material (PCHCM) was achieved by using composite microencapsulated phase change material (MPCM) and hygroscopic material. The PCHCM composite can moderate indoor hygrothermal fluctuations by absorbing or releasing both heat and moisture. The MPCM was synthesized by the microencapsulated phase change material (PCM) with SiO2 shell. The diatomite was used as hygroscopic material.The morphology of MPCM and PCHCM were measured by scanning electron microscopy (SEM). The thermal properties of the new composites were analyzed with differential scanning calorimetry (DSC). The thermal gravimetric analysis (TGA) was used to study the thermal stability. Both the moisture transfer coefficient and moisture buffer value (MBV) of the PCHCM were measured by two bottle method. The DSC results show that the super-cooling degrees of microcapsule and PCHCM are lower than pure PCM. Both the moisture transfer coefficients and the MBV of PCHCM are higher than pure hygroscopic materials.The influence of PCHCM on indoor hygrothermal environment and building energy consumption was also studied. The results show that the PCHCM can effectively regulate the indoor temperature and relative humidity, thus own a potential energy saving rate of 18% for the test building in research. The overall hygrothermal performance of PCHCM is better than the simple combination of two separate layers of PCM and hygroscopic materials. The PCHCM could be used as an innovative passive material to improve the building energy efficiency.

A Moisture Penetration Depth Model of Building Hygroscopic Material

Due to the significant impact of indoor humidity on Indoor Air Quality, human comfort and energy consumption, many researchers have investigated the use of various hygroscopic materials to moderate indoor humidity levels and save energy. The results show that the indoor relative humidity of the room with hygroscopic materials is more stable and moderate. Although many laboratory measurements and numerical simulation studies have been done for hygroscopic materials, there is little study on moisture exchange between materials with limited thickness and indoor air. The EMPD model is widely used due to its fast solution time and reasonable accuracy. However, it is not suitable when the hygroscopic material is thin and limited. In this paper, a double effective moisture penetration depth (DEMPD) model is described and developed. An application analysis of the proposed DEMPD model is presented. The results show that the DEMPD model can well simulate the moisture exchange between hygroscopic material with limited thickness and indoor air while the traditional EMPD model shows a great deviation.

Lifetime of organic photovoltaics: Linking outdoor and indoor tests

A comprehensive outdoor study of polymer solar cells and modules for duration of one year was conducted. Different sample geometries and encapsulations were employed in order to study the spread in the lifetimes. The study is a complimentary report to previous work that focused on indoor ageing tests. Comparison of the indoor and outdoor lifetimes was performed by means of the o-diagram, which constitutes the initial steps towards establishing a method for predicting the lifetime of an organic photovoltaic device under real operational conditions based on a selection of accelerated indoor tests. Acceleration factors were determined using the ISOS-protocols, which enabled reproducible data acquisition between different laboratories and operators within the OPV community. A semi-automatic filtering method was employed for processing data acquired in outdoor tests. It was found that the lifetime of the samples tested under outdoor conditions was somewhere between the lifetimes of samples measured in accelerated indoor test conditions of damp heat and light soaking (ISOS-D-3 and ISOS-L-2) and in moderate indoor test conditions (shelf life and high temperature storage). The presented results reveal that while the accelerated ageing studies reveal days and weeks of lifetime for the studied samples, in outdoor real operational conditions the samples demonstrate stability up to months and seasons.

Effects of graduated compression stockings on skin temperature after running

High skin temperatures reduce the thermal gradient between the core and the skin and they can lead to a reduction in performance and increased risk of injury. Graduated compression stockings have become popular among runners in the last years and their use may influence the athlete's thermoregulation. The aim of this study was to investigate the effects of graduated compression stockings on skin temperature during running in a moderate indoor environment. Forty-four runners performed two running tests lasting 30min (10min of warm-up and 20min at 75% of their maximal aerobic speed) with and without graduated compressive stockings. Skin temperature was measured in 12 regions of interest on the lower limb by infrared thermography before and after running. Heart rate and perception of fatigue were assessed during the last minute of the running test. Compression stockings resulted in greater increase of temperature (p=0.002 and ES=2.2, 95% CI [0.11–0.45°C]) not only in the body regions in contact (tibialis anterior, ankle anterior and gastrocnemius) but also in the body regions that were not in contact with the garment (vastus lateralis, abductor and semitendinosus). No differences were observed between conditions in heart rate and perception of fatigue (p>0.05 and ES<0.8). In conclusion, running with graduated compression stockings produces a greater increase of skin temperature without modifying the athlete's heart rate and perception of fatigue.

Comparison of conventional and green building materials in respect of VOC emissions and ozone impact on secondary carbonyl emissions

Building materials (BMs) are major contributors to indoor emission sources of volatile organic compounds (VOCs). In this study, 8 kinds of BMs (including conventional and green) for ceiling, cabinetry, and flooring commonly used indoors were tested in a 216 L chamber. Primary emissions of carbonyls (C1 to C8 aldehydes and ketones) at 48 h were 75–673 μg m−2 h−1 from conventional BMs, and 62–151 μg m−2 h−1 from green BMs. Primary emissions of BTEX at 48 h were 59–264 μg m−2 h−1 from conventional BMs, and 37–56 μg m−2 h−1 from green BMs. Ozone initiated molar yields of carbonyls were 0.10–2.36 from conventional BMs, and 0.13–0.86 from green BMs. Secondary emissions of carbonyls were 7–150 μg m−2 h−1 from conventional BMs, and 4–73 μg m−2 h−1 from green BMs. Green BMs had lower emissions than conventional analogs, especially for wooden flooring and gypsum board. BMs with mineral content are the most promising materials in this study, given moderately high ozone deposition velocity but generating the least byproducts. Secondary emissions determined in this study demonstrate that moderate indoor ozone concentrations may lead to increased concentrations of carbonyls, especially formaldehyde and acetaldehyde that potentially increase adverse chronic health effects.

The potential benefits of retrofitting thermal mass into New Zealand houses

This article reports on a study undertaken to investigate the effectiveness of thermal mass to moderate indoor air temperatures and to reduce energy demand when it is introduced into existing timber frame residential buildings. The research investigated characteristics of the existing New Zealand housing stock and how energy is used in those dwellings. Six different house typologies were defined and computer models created. Different combinations of thermal mass retrofits were assigned to each house type with variations also involving heat pumps. In all, the investigation produced 72 different scenarios, each of which was modelled for thermal performance using IES VE software. General trends indicate that thermal mass retrofits are more effective in older houses, with more recent dwellings generating little improvement on average annual indoor temperatures. This is most likely a consequence of the higher insulation levels required in the newer houses as well as lower infiltration rates. In a sense, these newer houses start from a higher performance level and the introduced thermal mass provides relatively smaller improvements. The research concludes that, while thermal mass is an integral part of passive solar design, insulation is much more important, particularly in houses where smaller areas of glazing limit the extent to which the sun can charge the mass. A useful outcome of the project is a set of cases that can help inform residential owners about different passive retrofit options and the associated benefits to costs.

Fluid Balance and Sodium Losses During Indoor Tennis Match Play

This study assessed fluid balance, sodium losses, and effort intensity during indoor tennis match play (17 ± 2 °C, 42% ± 9% relative humidity) over a mean match duration of 68.1 ± 12.8 min in 16 male tennis players. Ad libitum fluid intake was recorded throughout the match. Sweat loss from change in nude body mass; sweat electrolyte content from patches applied to the forearm, calf, and thigh, and back of each player; and electrolyte balance derived from sweat, urine, and daily food-intake analysis were measured. Effort intensity was assessed from on-court heart rate compared with data obtained during a maximal treadmill test. Sweat rate (M ± SD) was 1.1 ± 0.4 L/hr, and fluid-ingestion rate was 1.0 ± 0.6 L/hr (replacing 93% ± 47% of fluid lost), resulting in only a small mean loss in body mass of 0.15% ± 0.74%. Large interindividual variabilities in sweat rate (range 0.3-2.0 L/hr) and fluid intake (range 0.31-2.52 L/hr) were noted. Whole-body sweat sodium concentration was 38 ± 12 mmol/L, and total sodium losses during match play were 1.1 ± 0.4 g (range 0.5-1.8 g). Daily sodium intake was 2.8 ± 1.1 g. Indoor match play largely consisted of low-intensity exercise below ventilatory threshold (mean match heart rate was 138 ± 24 beats/min). This study shows that in moderate indoor temperature conditions players ingest sufficient fluid to replace sweat losses. However, the wide range in data obtained highlights the need for individualized fluid-replacement guidance.

Assessing the moisture buffering performance of hygroscopic material by using experimental method

It is widely known that the problem of low or high indoor humidity environment has various adverse effects on occupant’s health, durability of the building envelope and energy consumption. In order to create comfortable and healthy indoor environment, it is necessary to maintain the indoor humidity steady in a correct level. Hygroscopic interior material can adsorb and desorb moisture from surrounding air, adopting this material is an energy-efficient way to moderate indoor humidity variations and thus it has been applied as finishing materials in some buildings. However, there is no criterion to evaluate the moisture buffering effect of applying hygroscopic material. In this research investigation, a series of experiments with different applying parameters were designed and carried out in a climate-controlled test chamber. The purpose of this study is to quantitatively evaluate the moisture buffering effect by applying hygroscopic material, as well as to understand the humidity distribution of a hygroscopic material furnished room. Experimental results showed that the effects of moisture adsorption/desorption decreased exponentially when the ambient air change rate per unit area of hygroscopic material increased.

Modeling the effect of hygroscopic curtains on relative humidity for spaces air conditioned by DX split air conditioning system

The use of hygroscopic materials for moisture buffering is a passive way to moderate the variation of indoor humidity. Through absorption and desorption, surface materials in the indoor environment, such as curtains, carpets and wall paper, are able to dampen the moisture variations. The moisture buffering capacity of these materials may be used to improve the relative humidity of the indoor environment at reduced energy costs. The objectives of this paper are threefold. The first objective is to derive a theoretical model for the transient moisture transfer between a curtain system and the indoor air for the case where the curtain is placed in front of a wall. The second objective is to conduct experiments inside environmental chambers to validate the theoretical model and to test the ability of curtains to moderate indoor humidity. It is shown that the experimental results for the curtain moisture uptake and the relative humidity inside the chamber compared well with the model simulation results. The third and final objective is to test and evaluate the model under “real environment conditions” for a case study of a hygroscopic cotton curtain, placed in a “typical” office space in the city of Beirut with an area of 25 m 2 that uses direct expansion (DX) air conditioning system. It is found that hygroscopic curtains maintain humidity of less than 65% during part load operation compared to the upper limit of 70% relative humidity when no curtain is used. On the other hand, it is found that the energy use, as determined by the daily electrical power consumption of the DX system, is almost the same for the two cases, (with and without a curtain), where approximately 20 kWh of energy input is required 13 kWh of sensible energy and 7 kWh of latent energy.

Testing and modelling of a novel ceiling panel for maintaining space relative humidity by moisture transfer

Radiant ceiling panels are preferred over all-air systems because of their ability to lower energy consumption and maintain better comfort conditions. One disadvantage is their inability to moderate indoor humidity. To overcome this limitation, a new panel that can transfer heat and moisture is being developed. This research determines the performance of this panel under different temperature and humidity conditions. The effectiveness of the panel ranges from 15% to 28%, depending on the conditions. A computational fluid dynamics model of the panel has been developed using the commercial software, FLUENT. Good agreement is seen between experiments and the model for most cases. Comparing the change in humidity ratio of the air, the average difference is 5%.

Positioning Accuracy Improvement With Differential Correlation

The success of satellite navigation in the mass consumer market will depend greatly on its performance in deep urban and moderate indoor environments. The signal obstructions in these environments lead to low signal-to-noise ratios, which substantially degrade the positioning accuracy of GPS and Galileo receivers. New ranging techniques are required to increase the positioning accuracy to an acceptable level for pedestrian navigation in urban and indoor environments. Differential correlation is such a new ranging technique. It can replace the state-of-the-art noncoherent integration with very little implementation overheads. It improves performance as it utilizes the statistical properties of GPS and Galileo signals. This paper analyzes the resulting positioning accuracy for GPS and Galileo receivers when differential correlation is utilized. The probability density functions for early-late code discrimination with differential correlation are algebraically derived in closed form. The resulting positioning accuracies are presented for signals with binary phase shift keying (BPSK) and binary offset carrier (BOC) modulation in a large variety of reception conditions. The results indicate that differential correlation can replace noncoherent integration for all relevant configurations of GPS and Galileo receivers. It increases the accuracy of the measured receiver-to-satellite distances by 40% to 77% when compared to noncoherent integration.

A model for managing and evaluating solar radiation for indoor thermal comfort

Thermal comfort of people occupying indoor spaces depends, to a large extent, on the direct component of solar radiation incident on the human body. In turn, even the diffuse component of the solar radiation could affect the thermal sensations of people. Despite this evidence, at the present there is a lack in the availability of simple and reliable methods capable of taking into account the influence of the solar radiation on thermal balance in the human body. In this work a comprehensive method is presented for the computation of the mean radiant temperature of people in thermal moderate indoor environments in the presence of solar radiation. The effects produced on the amount of solar radiation entering rooms in the presence of shadowing devices are also analysed. Finally, an application of the method is provided for a non-parallelepiped room equipped with a south window: results are shown in terms of the mean radiant temperature. A simple evaluation of thermal comfort conditions, referring to the present international standards, is also provided. The model can be easily linked to the computerized methods for analyzing the thermal behaviour of buildings, and is intended as a support for the thermal comfort evaluation methods.