Indoor Air Relative Humidity Research Articles

Appraisal of thermal comfort in rural household kitchens of Punjab, India and adaptation strategies for better health

There is increasing evidence of adverse health impact of solid biomass fuel, and its use may hinder thermal comfort, which may lead to lower quality of life. Hence, current study aims to assess the thermal comfort at a rural location of Punjab, India. The indoor air temperature and relative humidity in rural households during winter varied from 11.9–25.2 °C and 63.4–90.5% respectively, during pre-summer it ranged between 21.3 and 27.4 °C and 48.4–78.4% while during summer it ranged between 28.4 and 37.8 °C and 13.7–63.8% respectively. The PMV of the households ranged between −0.85 to 0.69 (winter), −0.32 to 0.4 (pre-summer) and 0.53 to 1.25 (summer) for American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 55-2017 and −0.56 to 1.11 (winter), 0.04 to 0.99 (pre-summer) and 1.21–2.36 (summer) for European Committee for Standardization (CEN) European standard EN15251 while the Predicted Percentage of Dissatisfied ranged between 5 and 20% (winter), 5–8% (pre-summer) and 11–38% (summer) for ASHRAE 55-2017 and 5–31% (winter), 5–26% (pre-summer) and 36–90% (summer) for EN15251 guidelines. On the other hand, Adaptive thermal comfort (ATC) during winter and pre-summer was comfortable for 80 and 90% acceptable limits (ASHRAE-2017) and ranged between too cool to comfortable for EN15251 (Class I, II and III) while during summer thermal comfort for occupants was comfortable for ASHRAE 2017 and EN15251 (Class I, II, III) but did not comply with EN guidelines in some households using either clean fuel or chullah. Thermal comfort sensation was observed to be slightly cool to neutral during winter, neutral during pre-summer and slightly warm during summer according to Predicted Mean Vote method. The results were also compared using a thermal comfort and household survey and found to be similar with the model results. Climate change is leading to changes in temperature which may have an impact on the built environment. Hence, the current study suggests formulating policies on the uses of household fuel and design of kitchen with proper ventilation to increase thermal comfort which in turn will also reduce air pollutants.

Instantaneous field measurements of thermal bridge parameters in ground floor residential room

The “thermal bridges” are defined as an isolated building’s areas, where the construction elements have higher thermal conductivity, compared with the rest of the building envelope. Thus, at cold winter conditions, a significant temperature difference may occur between neighbouring solid and air volumes within the construction. Moreover, it has been documented, that the heating energy demand of a building may be increased with more than 30%, due to the existence of thermal bridges and the increased heat losses from the indoors. Consequently, in the recent years, norms and standards have been developed, for avoiding thermal bridges during the building design process. But still, thermal bridges exist in the indoor environment, especially in older buildings, where no energy efficient measures have been applied. That is why, the presented study focuses on instantaneous field measurements of thermal bridge parameters in real existing ground floor residential room. The thermal bridge propagation is analysed relative to the indoor and outdoor air temperature and relative humidity, as well as with infrared thermal images of the affected external walls. The achieved results give valuable information about the generic conditions for thermal bridge existence, without considering the building envelope properties.

EMI-Free Bidirectional Real-Time Indoor Environment Monitoring System

Indoor air quality, temperature, and relative humidity affect the thermal comfort and health of the inhabitants. Therefore, monitoring these parameters is essential to prevent indoor air pollution and to improve labor productivity. Most recently, the research conducted has used radio frequency wireless communications to monitor the indoor environment. However, long-term exposure to electromagnetic interference (EMI) causes a detrimental impact on the human body, especially on the elderly, patients, and infants, while it concurrently affects the operation of electronic devices. Thus, we propose a unique indoor environment monitoring system using an EMI-free bidirectional visible light communication technology. The sensing data from the smart sensor tag and the command data used to request the environmental sensing data are transferred bidirectionally between the base station and the smart sensor tag by being modulated into the light-emitting diode (LED) light beam. The proposed smart sensor tags are designed to measure five important parameters of indoor environments, such as CO2 concentration, volatile organic compound level, O2 concentration, temperature, and relative humidity, at multiple positions in real time. In addition, a proposed average-voltage tracking algorithm is adopted to allow the LED illumination to be used as a lighting system and as a long-range wireless communication system. As a result, the proposed system is demonstrated to be error-free when the distance between the base station and the smart sensor tags is 6 m. The measured live data are aggregated and visualized in a cloud platform by a graphical user interface. A web-based application and a mobile application are also developed to display the real-time data.

Impact of occupant behavior on energy use of HVAC system in offices

The current methods for simulating building energy consumption are often inaccurate, and the error could be as large as 150%. Various types of occupant behavior may explain this inaccuracy. Therefore, it is important to identify an approach to estimate the impact of the behaviors on the energy consumption. The present study used EnergyPlus program to simulate the energy consumption of the HVAC system in an office building by implementing a behavioral artificial neural network (ANN) model. The behavioral ANN model calculates the probability of behavior occurrence according to indoor air temperature, relative humidity, clothing level and metabolic rate. The probability was used to predict energy use in 20 offices for one month in winter, spring and summer in 2018, respectively. Measured energy data from the offices were used to validate the simulated results. When a behavioral artificial neural network (ANN) model was implemented in the energy simulation, the difference between the simulated results and the measured data was less than 13%. Energy simulation using constant thermostat set point without considering occupant behavior was not accurate. Our further simulations found that adjustment of thermostat set point and clothing level by occupants could lead to 25% and 15% energy use variation in interior offices and exterior offices, respectively.

Dew point temperature analyses in ground floor residential room with existing thermal bridge

The presented study reveals a dew point temperature analyses in ground floor residential room with existing thermal bridge. The dew point temperature is analysed, based on field measurements of indoor air temperature and relative humidity in the residential room, without organized occupants’ behaviour. Furthermore, the dew point temperature is cross-analysed with existing thermal bridge propagation in one of the outer walls of the room, via infrared thermal images. The results represent a valuable indicator for moisture accumulation over the thermal bridge zone, as well as an indicator for future mold growth and other humidity related problems. In the building design practice, the “thermal bridge” is defined as a distant zone, where construction elements have higher thermal conductivity, compared with the rest of the building envelope. These thermal bridges mostly affect the energy performance of the buildings, because of the higher heat losses from inside towards outside. But even more important, moisture build-up and considerable humidity related problems in the occupied areas are probable, due to the decreased surface temperature over the affected thermal zones.

Indoor Air Quality and Sustainability Management—Case Study in Three Portuguese Healthcare Units

Adequate management of indoor air quality (IAQ) in healthcare units has relevant impacts on sustainability performance due to its effects on patient safety, occupational health and safety, and energy consumptions. This study sought to identify improvement opportunities on IAQ management by collecting and analyzing experimental data of selected parameters in three healthcare units in Portugal: Two general hospitals and one primary healthcare center. Indoor air temperature, relative humidity, CO2, bacteria, and fungi concentrations were measured in summer and winter campaigns in June/July 2017 and in January/March 2018. Results show that the exclusive use of natural ventilation is not adequate when the affluence of users is high, but the analyzed parameters revealed acceptable results under low occupation intensity conditions. Results also show that keeping low indoor air relative humidity has a significant impact in reducing fungi concentration and that there is a significant correlation at the 0.05 level between indoor air CO2 concentration and bacterial loads. Therefore, as opportunities to improve sustainability, IAQ management in healthcare facilities should consider natural ventilation as a complement to mechanical ventilation systems and should focus on adequate control of indoor air relative humidity and CO2 concentration to reduce the risk of airborne infections.

Monitoring of indoor air quality in Macedonian homes during summer season

Abstract Measurements of indoor air quality (IAQ) factors in Macedonian homes were aimed at the determination of indoor air temperature, relative humidity, sound pressure level, particulate matters (PMs) and total volatile organic compounds (TVOC). IAQ monitoring were performed in 25 houses during summer period. Results pointed out that sound pressure level were high in most of the houses with mean values of 66.60 dB (A) - 55.30 dB (A). Limit value of 40 dB (A) was exceeded in 72% of houses. Mean values of indoor air temperature and relative humidity ranged from 21.6°C to 28.6°C and from 35.8% to 60.2%, respectively. Mean concentrations of particulate matter concentrations ranged between 9.75 μg/m3 - 71.73 μg/m3 and 23.63 μg/m3 - 145.10 μg/m3 for PM2.5 and PM10, respectively. Level of PM10 were high in 30% of the monitored houses. 56% of houses achieved higher concentration of PM2.5 than permissible value of 25 μg/m3. Excessive presence of TVOC was recorded in monitored homes with mean values from 260 ppm to 791 ppm. Results show that high exposure by noise, concentrations of TVOC and PMs in indoor air can affect family house users. Therefore, the indoor air quality needs to be investigated and people need to be informed about possible health consequences.

Indoor Environmental Quality performance of mixed-mode ventilated shopping malls in hot-humid climatic region

Studies have revealed important roles quality indoor environment plays on human health and productivity; consequently, its influence on certain shopping behavior has also been well spelt out. In other to keep up with the demand for quality indoor environment, new trend has been evolving in the design of Malaysian shopping malls. From fully air-conditioned to newly designed ones that integrate passive ventilation strategies; and as such operating under mixed-mode ventilation system. These passive ventilation strategies are implemented to reduce energy consumption and also to improve the indoor environment within the mall’s indoor space. However, the potentials of these designs in terms of their indoor environmental quality (IEQ) performance have not been studied nor have their advantages been revealed. In this study, occupants’ thermal perception and IEQ performance was investigated in two mixed-mode ventilated malls selected based on their design concept (‘open’ and ‘enclosed’). Both subjective and objective measurements were carried out in accordance with the ASHRAE performance measurement protocol for commercial buildings. Five IEQ factors (indoor air temperature, operative temperature, relative humidity, air speed, and carbon dioxide concentration level) were evaluated in the two malls. The results revealed that both malls fell below the ASHRAE comfort requirement but majority of the occupants still found the indoor thermal performance acceptable despite the high indoor air temperature recorded. For both malls, high air speed and low humidity level were recorded. However, higher air movement was still preferred by the occupants while the recorded mean carbon dioxide (CO2) concentration was within the recommended level. The ‘open’ concept mixed-mode ventilated mall proved superior compared to the ‘enclosed’ concept by providing a more thermally tolerance indoor environment for its occupants. Generally, results from this study contribute to the knowledge on the advantages of adopting sustainable designs in commercial buildings for improving the indoor environment as well as the health and general well-being of the occupants. The study will open more opportunities for future IEQ studies to be carried out in hot-humid climatic regions.

Indoor air quality of newly built low-energy preschools – Are chemical emissions reduced in houses with eco-labelled building materials?

The use of an airtight frame in low-energy buildings could increase the risk of health-related problems, such as allergies and sick building syndromes (SBS), associated with chemical emissions from building materials, especially if the ventilation system is not functioning properly. In this study, the indoor air quality (IAQ) was investigated in newly built low-energy and conventional preschools by monitoring the indoor air temperature, relative humidity, particle-size distribution and levels of carbon dioxide (CO2), nitrogen dioxide (NO2), formaldehyde and total volatile organic compounds (TVOC). The thermal comfort was satisfactory in all preschools, with average indoor air temperature and a relative humidity at 21.4°C and 36%, respectively. The highest levels of TVOC (range: 130–1650 µg/m3 toluene equivalents) and formaldehyde (range: 1.9–28.8 µg/m3) occurred during the first sampling period associated with strong emissions from building materials. However, those preschools constructed with environmental friendly building materials (such as Swan Eco-label) had lower initial TVOC levels compared to those preschools constructed with conventional building materials. The IAQ and indoor chemical emissions were also strongly dependent on the functioning of the ventilation system. Preliminary risk assessment indicated that exposure to acrolein and crotonaldehyde might lead to respiratory-tract irritation among occupants.

Investigation of CO2 production depending on physical activity of students

ABSTRACTThis paper aims to carry out measurements of indoor air temperature, relative humidity and carbon dioxide (CO2) concentrations as well as to determine CO2 production by students and teacher during various physical activities. Two classrooms of Technical University of Kosice were selected for the research. Results of objective measurements confirmed strong correlation between CO2 concentration occupancy for all measurements. Recommended value for indoor CO2 level according to Pettenkofer (1,000 ppm) was exceeding in 60.9%. Results of this study showed the insufficient ventilation intensity in classrooms as well as obvious rise of CO2 concentration during the exams. The highest increase of CO2 was recorded during harder physical activity (run on the spot, squats, right and left side lunges, and rotating of the hips). Regarding CO2 production by respondents it can be see that it is visibly increased with increasing physical activity.

Heatstroke at home: Prediction by thermoregulation modeling

BackgroundAs global warming continues, the incidence of heatstroke due to exposure to high temperature will become more prevalent. Although most heatstroke deaths occur at home, the effect of home environment on the development of heatstroke has not yet been addressed. ObjectivesTo investigate the influences of home environmental parameters on the development of heatstroke using thermoregulation modeling. MethodsA classical multi-segment multi-node human thermoregulatory model was extended to consider the role of dehydration in the sweating and cutaneous vasodilation during exposure to heat stress. The model was then used to systematically examine the effects of indoor critical environmental parameters on the time course of body core temperature (Tcore) in the development of heatstroke, and to estimate the survival time (τs). ResultsOur extended thermoregulatory model predicted that Tcore course during heat stress consists of three stages: an initial linear increase due to uncompensated heat load, an equilibrium plateau due to sweating, and a final rapid progression due to dehydration. Heatstroke occurred either early at the first stage due to the lack of thermoregulation in hot and humid environment or late at the third stage due to thermoregulatory breakdown caused by dehydration in warm and dry environment. Increasing air velocity delayed occurrence time of heatstroke in warm and dry environment but advanced the occurrence time in hot and humid environment. We obtained the survival time τs=exp(50−ISI) where ISI=44.2+0.02Ta+0.209RH−6.55RH/Ta is the indoor stress index, indicating that the time that heatstroke occurs was exponentially increased with the indoor air temperature (Ta) and relative humidity (RH). ConclusionsWe suggested a new thermoregulation model by considering the role of dehydration in the development of body core temperature during heat stress, which can be used to predict heatstroke at home. Easy-to-use indoor stress index and survival time table were obtained to early recognize and alert the risk of heatstroke.

Lighted-weighted model predictive control for hybrid ventilation operation based on clusters of neural network models

Abstract As one of the most significant factors to determine the success of a hybrid ventilation building, the control strategy for the hybrid ventilation operation attracts increasing attentions from both building designers and researchers these years. Recent advancements of the building control strategy have shown the potential to improve the hybrid ventilation operation. In this paper, we demonstrate the development of an advanced data-driven model predictive control (MPC) algorithm, i.e. a light-weighted three phase NN (neural network) model, for controlling the operation of hybrid ventilation buildings. To develop a robust model predictive control algorithm, firstly, different levels of uncertainties that commonly exist in the real world and building simulation are quantified to efficiently train the central model of the MPC and thoroughly test it in the future. In addition, in the model predictive control establishment process, four candidate mathematical models and ten prediction variables were analyzed during the MPC development to investigate its performance on the prediction as well. The results show that the neural network (NN) achieves the best performance considering both prediction performance and computation time. Six variables including the indoor and outdoor air temperature, relative humidity, office and season index and wind speed were finally chosen. At last, we conduct the validation of the algorithm for hybrid ventilation across four cities in different US climates under uncertainties presented in real practice. The comparison between the MPC and the rule-based control clearly presents that the developed MPC could be better at maintaining the thermal comfort of hybrid ventilation buildings while achieving a comparable amount of energy savings.

Method to control an air conditioner by directly measuring the relative humidity of indoor air to improve the comfort and energy efficiency

In modern society, air conditioning systems are widely used in places where people tend to congregate, such as in homes, companies, schools and work sites. Both the dry-bulb temperature and relative humidity should be measured and controlled to achieve better comfort and to improve the energy efficiency of air conditioning systems. However, the current evaporation pressure control technique based on evaporator outlet pressure reading (EPCP) method only uses the dry-bulb temperature to control the evaporation pressure, making this method insufficient with regard to improving comfort. An evaporation pressure control approach based on the evaporator pressure and the relative humidity reading (EPCR) method is developed here. The EPCR method changes the evaporation pressure based on the dry-bulb temperature and the relative humidity of the air. The performance of an identical air conditioner is measured experimentally while switching the control method between the conventional EPCP method and the newly proposed EPCR method. The results demonstrate that the new EPCR method improves both the thermal comfort of indoor air and the energy efficiency.

Study on indoor thermal environment in winter for rural residences in Yulin region

Yulin region is located in the northern part of Shaanxi Province, China. The winter here is very cold and it has a long duration. In this paper, a rural residence which was located in Yulin region was taken as a study object. Indoor thermal environment of the rural residence were tested, including indoor air temperature and air relative humidity. Then, test data were analyzed. It was summarized that indoor thermal environment of test room can not fully meet human thermal comfort needs, and some tactics of regulation building thermal environment were proposed. This research contributes to improvement of indoor thermal environment for local rural residences and it provides reference for rural residences in other cold regions.

Prediction of Indoor Temperature and Relative Humidity Based on Cloud Database by Using an Improved BP Neural Network in Chongqing

For continuous improvement of productivity, accurate, stable, and reliable control of temperature and humidity is important in industrial production. Accurate prediction of air temperature and humidity can improve the predictability and stability of air conditioning control systems. In this paper, based on the cloud database of industry settings, an improved prediction model based on backpropagation (BP) neural networks was established to forecast indoor air temperature (IT) and relative humidity (IH) every 10 min and 6–72 h in advance. The experimental building was in Chongqing, a typical humid, hot-summer, and cold-winter area in China. The test data were used to determine the optimal parameters of the neural network model. The experimental results showed that the IT and IH predictions by our model have strong correlations with the actual data, with the coefficients of determination being 0.9897 and 0.9778, respectively. Compared with other literature, our model was more effective in temperature prediction. The presented method can be used for the prediction and control of the indoor temperature and relative humidity in industrial production.

Influence of Courtyard Ventilation on Thermal Performance of Office Building in Hot-Humid Climate: A Case Study

The influence of courtyard on the thermal performance of Development Department office building in University Malaysia Perlis (UniMAP, Pauh Putra campus) is investigated through simulation study for the effect of ventilation on indoor air temperature and relative humidity of the building. The study is carried out using EnergyPlus simulator interface within OpenStudio and SketchUp plug in software to measure both of air temperature and relative humidity hourly on 21 April 2017 as a design day. The results show that the ventilation through the windows facing the courtyard has sufficient effect on reducing the air temperature compared to the ventilation through external windows since natural ventilation is highly effective on driving the indoor warm air out to courtyard. In addition, the relative humidity is reduced due to ventilation since the courtyard has high ability to remove or dilute indoor airborne pollutants coming from indoor sources. This indicates that the presence of courtyard is highly influential on thermal performance of the building.

Seasonal variation of window opening behaviors in two naturally ventilated hospital wards

Natural ventilation enables personal control, and occupant behaviors in window opening play a decisive role on natural ventilation performance, indoor air quality (IAQ), and/or airborne infection risk in a hospital setting. The occupant behaviors differ significantly from different building types with different functions and living habits. Based on a one-year field measurement in two general hospital wards in Nanjing, China, the effects of air quality (i.e. indoor CO2 concentration and outdoor PM2.5 concentration) and the climatic parameters (i.e. indoor/outdoor temperature, relative humidity, and outdoor wind speed, wind direction and rainfall) on window opening/closing behaviors are analyzed. Indoor air temperature or relative humidity is found to be a dominant factor for window opening behaviors. Seasonal differences are observed for the different influences of physical factors. The outdoor temperature is found to be associated with the window opening probability negatively during the cooling season, but positively during the transition and heating seasons. The indoor relative humidity positively affects the window opening probability during the transition season while a negative impact appears during the cooling and heating seasons. Based on the seasonal variation of window opening behaviors, Logistic regression models in different seasons (cooling, transition and heating seasons) are developed to predict the window opening/closing state and are verified to be promisingly adaptable with results of accuracy bigger than 70%.

Determination of optimal plaster thickness for moisture buffering of indoor air

The relative humidity of indoor air influences the health and wellbeing of building occupants and the integrity of the building fabric. One potential solution for regulating relative humidity is provided by the plaster used for finishing internal spaces if it has the ability to passively buffer moisture through adsorption and desorption of vapour. During the adsorption and desorption, the water vapour will only penetrate to a certain depth of the plaster. Therefore, it is important to know the minimum thickness of plaster required for the maximum buffering effect. Uniquely, this paper presents a method for determining the optimal thickness from experimental measurements on specimens of varying thickness. In this paper it is demonstrated through a novel method, that there is a thickness of material beyond which there is no increase in moisture buffering capacity. Below the optimal thickness moisture sorption increases linearly as a product of the density and specific moisture capacity. Significantly, existing numerical methods were found to overestimate the performance when compared to empirical measurements. The expected impact of this work is the increased knowledge of surrounding material performance and use, that will ultimately improve the indoor environment quality of buildings and occupant health.

Reliance of building energy in various climatic regions using multi criteria

Selecting a ventilation system for a certain building has always been considered as one of the critical problems for designers. Kingdom of Saudi Arabia (KSA) is characterized by a large area of significant climatic changes. In this research, five criteria are identified to compare and select one of the most popular ventilation systems, mechanical or natural. The identified criteria include Energy efficiency in buildings, Building function, Thermal comfort, the Maintenance cost of building, and Microclimatic conditions. The use of a mechanical system may be useful for achieving the building function and thermal comfort, while it seems to be more expensive. On the other hand, the natural ventilation system saves energy in the long run but it may not meet a comfort level for many users. Three regions which cover most of the climatic variations in the country are selected as a case study. A Ventilation Decision Making Model (VDMM), depends on the Analytic Hierarchy Process (AHP) as a multi-criteria analysis technique, is proposed and developed. For feeding data to the VDMM, field measures for indoor air temperature and relative humidity are conducted as well as applying an energy simulation model to predict indoor energy performance in the selected regions. Based on the results of VDMM application on the investigated case study, a decision to KSA construction market is introduced. The results absolutely support using the mechanical system in both Riyadh and Jeddah regions while utilizing the natural system in Abha region is more preferable. The VDMM is characterized by its flexibility, accepting more alternatives or criteria and its validity to be applied to other regions inside or outside KSA.

Switching Control Strategy for Greenhouse Temperature-Humidity System Based on Prediction Modeling: A Simulation Study

It is difficult to achieve coordination control of multiple facilities that are driven by on-off actuators in a greenhouse, especially when there is more than one indoor environmental factor to consider at the same time. With the consideration of indoor air temperature and relative humidity, we propose a switching control strategy based on prediction modeling. The operation of the greenhouse system was divided into several modes according to the on-off control characteristics of the available facilities. Then, a switching diagram was designed according to the relationship between the indoor air temperature and humidity and their setting ranges. When the two indoor environmental factors reach their upper or lower limits, IARX models are used to predict them over a specified horizon for each optional mode respectively. Mode switching is carried out based on prediction results. The switching control strategy was simulated based on a mechanistic model of the greenhouse microclimate. The results show that the facilities can be coordinated very well by the proposed control strategy and it is easy to implement. The control strategy is still applicative when more facilities or more indoor environmental factors need to be taken into account.