Decreased humidity improves cognitive performance at extreme high indoor temperature

In this study, we examined the cognitive performance of subtropically acclimatized subjects at an extreme high indoor temperature and the effect of decreased humidity on the cognitive performance at the high temperature. Forty-eight healthy subjects experienced the three exposure conditions: 26°C/relative humidity (RH) 70%, 39°C/RH50%, and 39°C/RH70% in a climate chamber. During 140-minute-long exposures to each thermal condition, they were required to perform cognitive tests that assess the perception, spatial orientation, concentration, memory, and thinking abilities. Meanwhile, their heart rate, core temperature, skin temperature, blood pressure, and body weight were measured and subjective responses, that is, thermal comfort, perceived air quality, and acute health symptoms were investigated. At the relative humidity of 70%, increasing indoor temperature from 26°C to 39°C caused a significant decrease in the accuracy of these cognitive tests. However, when the relative humidity decreased from 70% to 50% at 39°C, the accuracy of the cognitive tests increased significantly. Accordingly, the physiological and subjective responses of the subjects changed significantly with the changes in indoor temperature and humidity, which provided a basis to the variation in the cognitive performance. These results indicated that decreasing indoor humidity at extreme high temperature could improve the impaired cognitive performance.     

Use of personalized ventilation for improving health,comfort, and performance at high room temperature and humidity

The effect of personalized ventilation (PV) on people's health, comfort, and performance in a warm and humid environment (26 and 28°C at 70% relative humidity) was studied and compared with their responses in a comfortable environment (23°C and 40% relative humidity). Thirty subjects participated in five 4‐h experiments in a climate chamber. Under the conditions with PV, the subjects were able to control the rate and direction of the supplied personalized flow of clean air. Subjective responses were collected through questionnaires. During all exposures, the subjects were occupied with tasks used to assess their performance. Objective measures of tear film stability, concentration of stress biomarkers in saliva, and eye blinking rate were taken. Using PV significantly improved the perceived air quality (PAQ) and thermal sensation and decreased the intensity of Sick Building Syndrome (SBS) symptoms to those prevailing in a comfortable room environment without PV. Self‐estimated and objectively measured performance was improved. Increasing the temperature and relative humidity, but not the use of PV, significantly decreased tear film quality and the concentration of salivary alpha‐amylase, indicating lower mental arousal and alertness. The use of PV improved tear film stability as compared to that in a warm environment without PV.     

Effect of initial conditions,boundary conditions and thickness on the moisture buffering capacity of spruce plywood

In this paper, the moisture buffering capacity of spruce plywood is measured by recording the change in mass of a test specimen when the air relative humidity is changed between 33% RH and 75% RH. The aim is to represent diurnal cycles in indoor humidity with 33% RH maintained for 16 h and 75% RH maintained for 8 h. Measurements are taken using two different apparatuses, which provide different convective transfer coefficients between the air and the plywood, and the results are compared to a numerical model for validation. The validated numerical model is then used to investigate the effect of initial conditions, boundary conditions and thickness on the moisture buffering capacity of plywood. The results show that the buffering capacity of plywood depends on the initial conditions and thickness of the plywood as well as the surface film coefficient and humidity cycle.     

The relationship between indoor and outdoor temperature,apparent temperature,relative humidity,and absolute humidity

Many studies report an association between outdoor ambient weather and health. Outdoor conditions may be a poor indicator of personal exposure because people spend most of their time indoors. Few studies have examined how indoor conditions relate to outdoor ambient weather. The average indoor temperature, apparent temperature, relative humidity (RH), and absolute humidity (AH) measured in 16 homes in Greater Boston, Massachusetts, from May 2011 to April 2012 was compared to measurements taken at Boston Logan airport. The relationship between indoor and outdoor temperatures is nonlinear. At warmer outdoor temperatures, there is a strong correlation between indoor and outdoor temperature (Pearson correlation coefficient, r = 0.91, slope, β = 0.41), but at cooler temperatures, the association is weak (r = 0.40, β = 0.04). Results were similar for outdoor apparent temperature. The relationships were linear for RH and AH. The correlation for RH was modest (r = 0.55, β = 0.39). Absolute humidity exhibited the strongest indoor‐to‐outdoor correlation (r = 0.96, β = 0.69). Indoor and outdoor temperatures correlate well only at warmer outdoor temperatures. Outdoor RH is a poor indicator of indoor RH, while indoor AH has a strong correlation with outdoor AH year‐round.     

Window/door opening‐mediated bedroom ventilation and its impact on sleep quality of healthy,young adults

This work examined window/door opening as means of bedroom ventilation and the consequent effect upon occupants’ sleep, using data from 17 healthy volunteers. Bedroom CO₂ level, temperature, and relative humidity were measured over 5 days, for two cases: open window or door (internal, bedroom door), and closed window and door. Participant filled questionnaires and sleep diary provided subjective measure of sleep quality. Actigraphy objectively monitored the participants during sleep. Additionally, a FlexSensor, placed under pillows of participants, detected movement during sleep. Average CO₂ level for the Open conditions was 717 ppm (SD = 197 ppm) and for Closed conditions was 1150 ppm (SD = 463 ppm). Absolute humidity levels were similar for both conditions, while Open conditions were slightly cooler (mean = 19.7°C, SD = 1.8°C) than Closed (mean = 20.1°C, SD = 1.5°C). Results showed significant correlations (P < .001) between actigraphy data and questionnaire responses for: sleep latency (r = .45), sleep length (r = .87), and number of awakenings (r = .28). Of all analyzed sleep parameters, questionnaire‐based depth of sleep (P = .002) and actigraphy‐based sleep phase (P = .003) were significantly different between Open and Closed conditions.     

Increasing the indoor humidity levels in buildings with ventilation systems: Simulation aided design in case of passive houses

In modern societies, people spend about 90 percent of their time inside buildings. The challenge of building physics is to ensure that buildings are planned, constructed and built to provide a comfortable and healthy working and living environment. As construction style has changed during recent years, the planning phase has to be much more precise and the need of simulation programs that respond to every little change arises. An increasing problem in Austria is the indoor humidity. In the field of renovated buildings with airtight new building envelopes, mould growth due to high indoor relative humidity (RH) is a persistent problem. On the other hand, in recently realized Austrian passive houses with an air treatment system, the low humidity level of the indoor air is a problem with which scientists have been struggling for some time. It has been observed in numerous measurements and it is also easily computationally detectable that in winter period the indoor relative humidity level often drops below 30% RH. Low and high relative humidity levels have negative effects on the comfort feeling and health of the occupants of the dwelling and should therefore be avoided. However, it is expensive to increase or decrease the humidity in houses mechanically. Therefore, the existing room moisture should be used sensibly in buildings with a ventilation system. In buildings with a high indoor humidity it is necessary to adjust the ventilation depended on moisture production. This paper focuses on low indoor humidity and presents some different methods by which the indoor relative humidity can be regulated. The effects of adapting parameters such as ventilation rate and buffering material in the dwelling were clearly reflected in the measured temperature and relative humidity. “BuildOpt_VIE” software developed at the Vienna University of Technology was used for the dynamic building simulation in this study.     

Correlating indoor and outdoor temperature and humidity in a sample of buildings in tropical climates

The incidence of several respiratory viral infections has been shown to be related to climate. Because humans spend most of their time indoors, measures of indoor climate, rather than outdoor climate, may be better predictors of disease incidence and transmission. Therefore, understanding the relationship between indoor and outdoor climate will help illuminate their influence on the seasonality of diseases caused by respiratory viruses. Indoor-outdoor relationships between temperature and humidity have been documented in temperate regions, but little information is available for tropical regions, where seasonal patterns of respiratory viral diseases differ. We have examined indoor-outdoor correlations of temperature, relative humidity (RH), and absolute humidity (AH) over a 1-year period in each of seven tropical cities. Across all cities, the average monthly indoor temperature was 25 ± 3°C (mean ± standard deviation) with a range of 20–30°C. The average monthly indoor RH was 66 ± 9% with a range of 50–78%, and the average monthly indoor AH was 15 ± 3 g/m³ with a range of 10–23 g/m³. Indoor AH and RH were linearly correlated with outdoor AH when the air conditioning (AC) was off, suggesting that outdoor AH may be a good proxy of indoor humidity in the absence of AC. All indoor measurements were more strongly correlated with outdoor measurements as distance from the equator increased. Such correlations were weaker during the wet season, especially when AC was in operation. These correlations will provide insight for assessing the seasonality of respiratory viral infections using outdoor climate data, which is more widely available than indoor data, even though transmission of these diseases mainly occurs indoors.     

The Effects Of Air Temperature And Relative Humidity On Thermal Comfort In The Office Environment

The objective of this study was to assess the effect of air humidification and temperature on thermal comfort in sedentary office work. A blinded twelve-period cross-over trial was carried out in two similar wings of an office building, contrasting 28–39% steam humidification with no humidification, corresponding to 12–28% relative humidity. The length of each period was one working week. The study population was 169 workers who judged their thermal sensations in a weekly questionnaire. The percentage of dissatisfied was lowest when the air temperature was 22 °C. At 22 °C an increase in relative humidity raised the mean thermal sensation only slightly. At 20 °C when the air was humidified there were fewer workers who judged their air temperature as being too low. On the other hand, at 24 °C humidification increased the percentage of workers who judged their air temperature to be too high. The percentage of dissatisfied increased rapidly when the air temperature was outside of its optimum value, 22 °C. The percentage of workers complaining about draft increased when the air temperature was lower than 22 °C. Thus we consider that the temperature range from 20 to 24 °C during wintertime may be too wide without individual temperature control from the point vzew of thermal comfort. We recommend that the air temperature should be kept between 21 and 23 °C if no individual control is available. The best solution would be individual temperature control permitting adjustment of the temperature at 22 ± 2 °C.     

The effects of building‐related factors on classroom relative humidity among North Carolina schools participating in the ‘Free to Breathe,Free to Teach’ study

Both high and low indoor relative humidity (RH) directly impact Indoor Air Quality (IAQ), an important school health concern. Prior school studies reported a high prevalence of mold, roaches, and water damage; however, few examined associations between modifiable classroom factors and RH, a quantitative indicator of dampness. We recorded RH longitudinally in 134 North Carolina classrooms (n = 9066 classroom‐days) to quantify the relationships between modifiable classroom factors and average daily RH below, within, or above levels recommended to improve school IAQ (30–50% or 30–60% RH). The odds of having high RH (>60%) were 5.8 [95% Confidence Interval (CI): 2.9, 11.3] times higher in classrooms with annual compared to quarterly heating, ventilating, and air‐conditioning (HVAC) system maintenance and 2.5 (95% CI: 1.5, 4.2) times higher in classrooms with HVAC economizers compared to those without economizers. Classrooms with direct‐expansion split systems compared to chilled water systems had 2.7 (95% CI: 1.7, 4.4) times higher odds of low RH (<30%). When unoccupied, classrooms with thermostat setbacks had 3.7 (95% CI: 1.7, 8.3) times the odds of high RH (>60%) of those without setbacks. This research suggests actionable decision points for school design and maintenance to prevent high or low classroom RH.     

Biodeterioration of sandstone under the influence of different humidity levels in laboratory conditions

Excessive moisture in building materials supports microbial growth. It has been referred that relative humidity more than 55% promotes the microbial growth. To test the effect of different relative humidity tropical chamber test was set up at 52%, 76%, 85% and 96% RH and maximum diversity of fungi was found at 85% and 96% RH. Two fungi Aspergillus sydowi and Aspergillus flavipes were present throughout the course of study from moderate to highly abundant form. It was observed that Fusarium moniliforme, Cephalosporium acremonium, Papulospora sp. proliferated at higher relative humidity (i.e. at 85% and 96.6% RH) and Fusarium roseum, Fusarium oxysporum only at 96% RH level. The relative humidity level lower than 62%, i.e. at 52% level exhibited no fungal growth on sandstone surface during two-year observations. During the study pattern it was noticed that diversity decreased gradually and dominance of particular species increased with the time factor. Analysis of sandstone after fungal colonization by X-ray diffraction and SEM showed the formation of newly formed biomineral.     

Comparison of risk factor profiles concerning self-reported skin complaints and objectively determined skin symptoms in German office workers

The correspondence between impact factor profiles of self-reported skin sensation and of objectively determined skin symptoms was examined using data from the ProKlimA project (1994-1999). A sub-sample of 925 office workers participated in measurements of skin hydration and sebum content and responded to a questionnaire assessing sensory perception. The calculation of multiple logistic regression models revealed a significant increased risk for female sex [Odds ratio (OR): 2.3; confidence interval (CI): 1.4-3.6], poor software (OR: 2.2; CI: 1.3-4.0), unfavorable job characteristics (OR: 1.8; CI: 1.1-2.8), allergic illness (OR: 1.5; CI: 1.1-2.2) and the use of skin cream (OR:2.6; CI: 1.6-4.4) on the subjective perception of skin sensation. Regarding the objective medical examination of the skin humidity a significant increased risk was detected for a high concentration of Total Volatile Organic Compounds (OR: 2.5; CI: 1.3-4.8) and a low relative humidity (OR:1.9; CI: 1.1-3.4). The likewise objectively measured low sebum content is not associated with environmental variables. The impact profiles on subjective vs. objective outcome variables differ in a clear and typical way. Skin related sensory perception is mainly influenced by job-related and personal impacts. Indoor environmental characteristics affect skin hydration. We conclude the need to develop, to adapt and to use objective clinical methods applicable for field monitoring parallel to questioning.     

Study on the lower limit of indoor humidity subject experiments on psychological responses

As a basis for determining the lower limit of acceptable humidity in an indoor environment, experiments were conducted for 25 subjects to assess the maximum expected sensations of dryness, discomfort based on humidity, and intolerance based on humidity, under conditions of 26°C and 10% RH. As results, distinct negative evaluations (dry, uncomfortable, or intolerable) were not obtained as the majority response; however, a small number of subjects declared distinct negative responses. In addition to the whole-body evaluation, the sensations for individual body parts were collected and found to be more intense for the eyes, nose, throat, and lips than for the other body parts. Significant differences between the genders were not found. For 8 of the subjects, similar experiments under a condition of 30% RH were conducted, and the difference between two humidity conditions was clearer for discomfort and intolerance than for dryness. The results suggest that the evaluation of the specific individuals who respond intensely, the consideration of intense responses for a specific part of the body, and the careful selection of an evaluation word for a psychological response might be effective to link this study to the determination of the lower limit of indoor humidity.     

Thermal and health outcomes of energy efficiency retrofits of homes of older adults

Mitigation of thermal stress and adverse indoor climatic conditions is important to older low‐income populations whose age, health, and economic circumstances make them vulnerable to indoor environmental conditions. This research examines whether energy retrofits in affordable housing for older adults can also improve indoor climatic (i.e., temperature, humidity, air infiltration) conditions and whether such improvements correspond with improved health and comfort of residents. An apartment complex for low‐income older adults in Phoenix was the study site. In 2010, renovations were undertaken to make it more energy efficient and to replace interior cabinetry, flooring, and paint with materials that had low or no volatile organic compounds (VOCs). Fifty‐seven residents from 53 apartment units participated in both baseline (pre‐renovation) and 1 year post‐renovation data collection trials. Environmental measures included temperature, relative humidity, and air infiltration. Health measures included general health, emotional distress, and sleep. Four questions addressed residents' perceptions of temperature quality. Results demonstrated a 19% reduction in energy consumption following the retrofit. In addition, fixed effects statistical models of the panel data showed significant stabilization of unit temperature from pre‐retrofit to 1 year post‐retrofit. Reductions in an apartment's temperature extremes of 27.2°C (81°F) and above also corresponded with improvement in occupant's reported health over the same time period, although not with occupant's perceptions of thermal comfort.     

Wall relative humidity: a simple and reliable index for predicting Stachybotrys chartarum infestation in dwellings

Because the indoor mold Stachybotrys chartarum has been considered as potentially responsible for serious health effects, its identification in dwellings with water damages is of utmost importance. As such dwellings are many, it would be of great value to have a simple and reliable index for predicting its presence. The aim of the study was to compare measurements of wall relative humidity (RH) to mold identification in 458 samples from 100 dwellings. Mold identification was performed by direct microscopic examination of a sample collected on the wall by the gummed paper technique. Mean (+/- s.d.) wall RH (%) was much higher (97.0 +/- 6.1) on the 30 samples where S. chartarum was identified compared with the 291 samples where other molds were identified (41.8 +/- 36.9) and to the 137 samples where no molds were identified (38.9 +/- 34.8). There was no straightforward relationship between wall and room RH. In conclusion, this study clearly demonstrate that the simple measurement of wall RH can be used as a reliable index for discarding and suspecting S. chartarum infestation in dwellings. PRACTICAL IMPLICATIONS: This paper suggests that very high relative humidity (RH) within walls is a strong risk factor for their infestation with the 'toxic mold' Stachybotrys chartarum. Besides, data from the literature demonstrate that other molds are able to produce mycotoxins when RH is very high. Thus, measurement of wall RH, which is easy to perform and very cheap, could be used as a screening tool to select those dwellings where mold identification should be performed and remediation should be promptly carried out.     

Non-Specific Symptoms In Office Workers: A Review And Summary Of The Epidemiologic Literature

Epidemiologic research into the causes of non-specific symptoms among office workers has produced a variety of conflicting findings which are difficult to synthesize. This paper first discusses methodologic issues important in the interpretation of epidemiologic studies, and then reviews the findings of 32 studies of 37 factors potentially related to office worker symptoms. Among environmental factors assessed, there were generally consistent findings associating increased symptoms with air-conditioning, carpets, more workers in a space, VDT use, and ventilation rates at or below 10 liters/second/person. Studies with particularly strong designs found decreased symptoms associated with low ventilation rate, short-term humidification, negative ionization, and improved office cleaning, although studies reviewed showed little consistency of findings for humidification and ionization. Relatively strong studies associated high temperature and low relative humidity with increased symptoms, whereas less strong studies were not consistent. Among personal factors assessed, there were generally consistent findings associating increased symptoms with female gender, job stress/dissatisfaction, and allergies/asthma. For other environmental or personal factors assessed, findings were too inconsistent or sparse for current interpretation, and there were no findings from strong studies. Overall evidence suggested that work related symptoms among office workers were relatively common, and that some of these symptoms represented preventable physiologic effects of environmental exposures or conditions. Future research on this problem should include blind experimental and case-control studies, using improved measurements of both environmental exposures and health outcomes     

Preparation and performances of a novel intelligent humidity control composite material

A novel intelligent humidity control composite material with excellent humidity control performances has been prepared, comprising a natural polymer derivative (carboxymethyl cellulose (CMC)), a porous natural mineral (sepiolite), and an acrylic acid (AA)/acrylamide (AM) copolymer. It features high moisture adsorption capacity, fast response to humidity changes, small equilibrium humidity control range and good acid gas absorbability. It is suitable for maintaining a proper micro-environment for places such as museums or galleries. The appearance and structural properties of the resultant material have been investigated by scanning electronic microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The humidity control performances of the material at certain relative humidity (RH) and changed absolute humidity (AH) have been measured. The adsorption capabilities of the material for sulphur dioxide and nitrogen dioxide have also been investigated in this study. The results reveal that the material maintains a relative humidity in the 57–60.5% range at 25 °C, and reaches the equilibrium levels within 3.5 h. It is worth noting that the composite material shows an excellent humidity buffering effect at changed AH and temperatures. The equilibrium moisture adsorption amount is 78.6% of its own weight. The adsorption capacities for nitrogen dioxide and sulphur dioxide are 227 mg g^?1 and 288 mg g^?1, respectively.     

Measurement Of Indoor Relative Humidity Using A Passive Sampler For Water Vapour

As part of the energy and indoor climate survey recently carried out in Sweden (the ELIB study) a simple, inexpensive but reliable passive sampler for estimating monthly averages of relative humidity has been developed. The diffusion sampler consists of a 5 ml plastic tube prepared with lithium chloride monohydrate (LiCl. H₂O) as trapping medium. After necessary calibration of this particular design of sampler the relative humidity can be calculated from the weight change of the sampler, the time of sampling and the average temperature during this period. The estimated accuracy of the method is better than k 2% RH up to65% RH.     

Space conditioning using evaporative cooling for summers in Delhi

The article examines the possibility of space conditioning the interiors of a multistorey office building in Delhi using evaporative cooling in the summer months of April, May and June. The temperature and humidity conditions obtained in a room of the building with direct evaporative cooling are studied by simulation. In this case study, the room is assumed to have a south-facing wall with a window and all other walls, ceiling and floor are interior partitions. The effect of number of air-changes per hour (ACH) from 1 to 40 and fresh-air bypass factor (BPF) 0% to 100% on performance is studied by simulation. The aim is to find whether some combination of ACH and BPF succeeds in keeping room conditions below 80% RH and temperatures between 27 and 31°C, depending on RH. It is found that the desired results are achieved by keeping the ACH and the BPF within certain limits depending on weather conditions. If the temperature and relative humidity of the ambient air are too high then a direct evaporative cooler cannot achieve comfort in the room. Appropriate combinations of ACH and BPF have to be selected to obtain the best results.     

Associations between indoor environment in residential buildings in wet and dry seasons and health of students in upper northern Thailand

We performed a repeated questionnaire study on home environment and health (six medical symptoms) in 1159 junior high school students (age 12.8 ± 0.7 years) in upper northern Thailand in wet and dry seasons. Data on outdoor temperature, relative humidity (RH), and air pollution were collected from nearest monitoring station. Odds ratios (OR) were calculated by multi-level logistic regression. Most common symptoms were rhinitis (62.5%), headache (49.8%), throat (42.8%), and ocular symptoms (42.5%). Ocular symptoms were more common at lower RH and rhinitis more common in dry season. Water leakage (28.2%), indoor mold (7.1%), mold odor (4.1%), and windowpane condensation (13.6%) were associated with all six symptoms (ORs: 1.3–3.5). Other risk factors included cat keeping, environmental tobacco smoke (ETS), other odor than mold odor, gas cooking, and cooking with biomass fire. Biomass burning inside and outside the home for other reasons than cooking was associated with all six symptoms (ORs: 1.5–2.6). Associations between home environment exposure and rhinitis were stronger in wet season. In conclusion, dampness-related exposure, windowpane condensation, cat keeping, ETS, gas cooking, and biomass burning can impair adolescent health in upper northern Thailand. In subtropical areas, environmental health effects should be investigated in wet and dry seasons.     

Effects of 6‐h exposure to low relative humidity and low air pressure on body fluid loss and blood viscosity

The purpose of this study was to investigate the effects of 6‐h exposure to low relative humidity (RH) and low air pressure in a simulated air cabin environment on body fluid loss (BFL) and blood viscosity. Fourteen young healthy male subjects were exposed to four conditions, which combined RH (10% RH or 60% RH) and air pressure (NP: sea level or LP: equivalent to an altitude of 2000 m). Subjects remained seated on a chair in the chamber for 6 h. Their diet and water intake were restricted before and during the experiment. Insensible water loss (IWL) in LP10% condition was significantly greater than in NP60% condition; thus, combined 10%RH and LP conditions promoted a greater amount of IWL. The BFL under the LP condition was significantly greater than that under the NP condition. Blood viscosity significantly increased under LP conditions. Increases in red blood cell counts (RBCs) and BFL likely contributed to the increased blood viscosity. These findings suggest that hypobaric‐induced hypoxia, similar to the conditions in the air cabin environment, may cause increased blood viscosity and that the combined low humidity and hypobaric hypoxia conditions increase IWL.