Search Results (58)

Accurate forecasting of energy consumption in buildings is essential for achieving energy efficiency and reducing carbon emissions. However, many existing models rely on limited input variables and overlook the complex influence of indoor environmental quality (IEQ). In this study, we assess the performance of hybrid machine learning ensembles for predicting hourly energy demand in a smart office environment using high-frequency IEQ sensor data. Environmental variables including carbon dioxide concentration (CO₂), particulate matter (PM_2.5), total volatile organic compounds (TVOCs), noise levels, humidity, and temperature were recorded over a four-month period. We evaluated two ensemble configurations combining support vector regression (SVR) with either Random Forest or LightGBM as base learners and Ridge regression as a meta-learner, alongside single-model baselines such as SVR and artificial neural networks (ANN). The SVR combined with Random Forest and Ridge regression demonstrated the highest predictive performance, achieving a mean absolute error (MAE) of 1.20, a mean absolute percentage error (MAPE) of 8.92%, and a coefficient of determination (R²) of 0.82. Feature importance analysis using SHAP values, together with non-parametric statistical testing, identified TVOCs, humidity, and PM_2.5 as the most influential predictors of energy use. These findings highlight the value of integrating high-resolution IEQ data into predictive frameworks and demonstrate that such data can significantly improve forecasting accuracy. This effect is attributed to the direct link between these IEQ variables and the activation of energy-intensive systems; fluctuations in humidity drive HVAC energy use for dehumidification, while elevated pollutant levels (TVOCs, PM_2.5) trigger increased ventilation to maintain indoor air quality, thus raising the total energy load. Full article

Infectious diseases can spread through virus-laden respiratory droplets exhaled into the air. Ventilation systems are crucial in indoor settings as they can dilute or eliminate these droplets, underscoring the importance of understanding their efficacy in the management of indoor infections. Within the field of fluid dynamics methods, the dispersed droplets may be approached through either a Lagrangian framework or an Eulerian framework. In this study, various Eulerian methodologies are systematically compared against the Eulerian–Lagrangian (E-L) approach across three different scenarios: the pseudo-single-phase model (PSPM) for assessing the transport of gaseous pollutants in an office with displacement ventilation (DV), stratum ventilation (SV), and mixing ventilation (MV); the two-fluid model (TFM) for evaluating the transport of non-evaporating particles within an office with DV and MV; and the two-fluid model-population balance equation (TFM-PBE) approach for analyzing the transport of evaporating droplets in a ward with MV. The Eulerian and Lagrangian approaches present similar agreement with the experimental data, indicating that the two approaches are comparable in accuracy. The computational cost of the E-L approach is closely related to the number of tracked droplets; therefore, the Eulerian approach is recommended when the number of droplets required by the simulation is large. Finally, the performances of DV, SV, and MV are presented and discussed. DV creates a stratified environment due to buoyant flows, which transport respiratory droplets upward. MV provides a well-mixed environment, resulting in a uniform dispersion of droplets. SV supplies fresh air directly to the breathing zone, thereby effectively reducing infection risk. Consequently, DV and SV are preferred to reduce indoor infection. Full article

Chinese local governments mandate public buildings to maintain a cooling set point temperature (SPT ≥ 26 °C). To explore how thermal history and air conditioner use behavior under different cooling SPT modes influence health, an experimental study and field investigation was carried out in split air-conditioned office buildings in China’s cold climate regions. Two categories were established based on energy policy: the H group (SPT ≥ 26 °C) and the L group (SPT < 26 °C). The results showed that L group subjects experienced longer, colder, and higher CO₂/formaldehyde exceedance rate exposures in air-conditioned environments, demonstrating greater reliance on air conditioners, although indoor air quality satisfaction showed no significant difference between groups. Air quality perception demonstrates long-term adaptation to indoor air temperature and CO₂. Compared with the high SPT mode, the adverse influences and mechanisms of the low SPT mode on health are as follows: making people adapt to cold environments due to colder thermal history and inducing pathological adaptation cycles, thus promoting strong reliance on the air-conditioned environment. This leads to a substantial increase in air conditioner use time, thereby increasing the severity of sick building syndrome (SBS), indoor pollutants, formaldehyde carcinogenic risk, and desensitized air quality perception. China’s government should systematically enhance the enforcement of SPT-related policies. Full article

This study investigates the performance of different demand-controlled ventilation strategies for improving indoor air quality while optimizing energy efficiency. The experimental research was conducted at the Indoor Live Lab at the University of Coimbra using a smart window equipped with mechanical ventilation boxes, occupancy sensors, and a real-time CO₂ monitoring system. Several occupancy-based and CO2-based ventilation control strategies were implemented and tested to dynamically adjust ventilation rates according to real-time indoor conditions, including (1) occupancy period-based control, (2) occupancy level-based control, (3) ON-OFF CO₂-based control, (4) multi-level CO₂-based control, and (5) modulating CO₂-based control. The results indicate that intelligent control strategies can significantly reduce energy consumption while maintaining indoor air quality within acceptable limits. Among the CO₂-based controls, strategy 5 achieved optimal performance, reducing energy consumption by 60% compared to the simple ON-OFF strategy, while maintaining satisfactory indoor air quality. Regarding occupancy-based strategies, strategy 2 showed 58% energy savings compared to the simple occupancy period-based control, but with greater CO₂ concentration fluctuation. The results demonstrate that intelligent DCV systems can simultaneously reduce ventilation energy use by 60% and maintain compliant indoor air quality levels, with modulating CO₂-based control proving most effective. The findings highlight the potential of integrating sensor-based ventilation controls in office spaces to achieve energy savings, enhance occupant comfort, and contribute to the development of smarter, more sustainable buildings. Future research should explore the integration of predictive analytics and multi-pollutant sensing to further optimize demand-controlled ventilation performance. Full article

Prefabricated timber buildings offer a low-carbon approach that can help reduce the environmental impact of the building and construction sectors. However, construction materials such as manufactured timber products can emit a range volatile organic compounds (VOCs) that are potentially hazardous to human health. We evaluated 24 years (2000–2024) of peer-reviewed publications of VOCs within prefabricated timber buildings. Studies detected hazardous air pollutants such as formaldehyde, benzene, toluene, and acetaldehyde (indoor concentration ranges of 3.4–94.9 µg/m³, 1.2–19 µg/m³, 0.97–28 µg/m³, and 0.75–352 µg/m³, respectively), with benzene concentrations potentially exceeding World Health Organization indoor air quality guidelines for long/short term exposure. Most studies also detected terpenes (range of 1.8–232 µg/m³). The highest concentrations of formaldehyde and terpenes were in a prefabricated house, and the highest of benzene and toluene were in a prefabricated office building. Paradoxically, the features of prefabricated buildings that make them attractive for sustainability, such as incorporation of manufactured timber products, increased building air tightness, and rapid construction times, make them more prone to indoor air quality problems. Source reduction strategies, such as the use of low-VOC materials and emission barriers, were found to substantially reduce levels of certain indoor pollutants, including formaldehyde. Increasing building ventilation rate during occupancy is also an effective strategy for reducing indoor VOC concentrations, although with the repercussion of increased energy use. Overall, the review revealed a wide range of indoor VOC concentrations, with formaldehyde levels approaching and benzene concentrations potentially exceeding WHO indoor air quality guidelines. The paucity of evidence on indoor air quality in prefabricated timber buildings is notable given the growth in the sector, and points to the need for further evaluation to assess potential health impacts. Full article

Office workers spend a considerable part of their day at the workplace, making it vital to ensure proper indoor environmental quality (IEQ) conditions in office buildings. This work aimed to identify significant factors influencing IEQ and assess the effectiveness of an environmental intervention program, which included the introduction of indoor plants, carbon dioxide (CO₂) sensors, ventilation, and printer relocation (source control), in six modern office buildings in improving IEQ. Thirty office spaces in Porto, Portugal, were randomly divided into intervention and control groups. Indoor air quality, thermal comfort, illuminance, and noise were monitored before and after a 14-day intervention implementation. Occupancy, natural ventilation, floor type, and cleaning time significantly influenced IEQ levels. Biophilic interventions appeared to decrease volatile organic compound concentrations by 30%. Installing CO₂ sensors and optimizing ventilation strategies in an office that mainly relies on natural ventilation effectively improved air renewal and resulted in a 28% decrease in CO₂ levels. The implementation of a source control intervention led to a decrease in ultrafine particle and ozone concentrations by 14% and 85%, respectively. However, an unexpected increase in airborne particle levels was detected. Overall, for a sample of offices that presented acceptable IEQ levels, the intervention program had only minor or inconsistent impacts. Offices with declared IEQ problems are prime candidates for further research to fully understand the potential of environmental interventions. Full article

The air quality in educational campuses affects the health and work efficiency of teachers and students. Studies into this matter are of great significance for optimizing the management of campus living environments. Low-cost online sensors to monitor PM_2.5 and CO₂ levels were used in typical functional areas of a university campus in Beijing, China, including offices, dormitories, leisure spaces, canteens, and laboratories. By comparing the findings with data from nearby national monitoring stations, the seasonal and spatial variations in PM_2.5 and CO₂ concentrations were analyzed. Findings indicate PM_2.5 levels within the campus were notably lower compared to the surrounding urban environment. There was variation in PM_2.5 and CO₂ concentrations across different functional areas. Typically, indoor PM_2.5 levels were lower than outdoor ones, while CO₂ concentrations in enclosed indoor spaces with human activities progressively escalated. The main internal emission sources affecting the PM_2.5 level on campus included traffic emissions, dust generated by human activities, and emissions from catering. In contrast, in areas with better green coverage or where a lake system participates in the atmospheric circulation, the PM_2.5 level and CO₂/PM_2.5 were lower. This indicates that the cleansing impact of plants and aquatic systems is instrumental in lowering PM_2.5 concentrations, offering healthier leisure spaces. Seasonal variations also impact PM_2.5 levels. During the non-heating period, less pollution source emissions led to decreased outdoor PM_2.5 concentrations. The campus monitoring sites experienced an approximate 5 µg/m³ and 29 µg/m³ reduction in the average PM_2.5 levels as compared to the PM_2.5 of the surrounding urban environment, respectively, during the non-heating and heating period. During indoor activities or sleep, CO₂ levels can build up to as high as 2303 ppm due to breathing. It is advisable to stay indoors on days when pollution levels are high, whereas on days with clean air, it is healthier to be outdoors or to air out indoor areas by opening windows. Our research provides clearer scientific evidence for incorporating behavioral strategies for improving air quality into both daily work and life. Moreover, the findings are quite meaningful for the widespread adoption of low-cost sensor monitoring in various environments, with applications beyond just the campus settings. Full article

The incidence of respiratory and cutaneous allergic disorders may be variable if we consider work activity. These disorders are reported in the current literature to have a relevant psychosomatic involvement. The aim of the study was to submit a survey on the self-reported occurrence of allergic respiratory and cutaneous diseases in outdoor and indoor workers to verify the onset or exacerbations of such pathologies, encourage surveillance, and suggest the need for further studies. Two groups of workers were compared when exposed and not exposed to air pollutants. An outdoor population of motorway toll collectors (153 workers; M: 58.03 years old, SD: 6.1; and female prevalence of 66.01%) and an indoor group of office employees (59 workers; mean age 54.44 years, SD: 8.50; and male prevalence of 61.02%) entered the study. The results of three multivariate analyses of the obtained data, investigating contributions of external factors, including age, sex, smoking habits, working type, and seniority, on allergic conditions were significant in both workers’ groups. The findings highlighted that age and smoking habits were significant contributors to allergic conditions, both independently and in combination with other factors, such as sex and working type. The data suggest the presence of phenomena related to different etiological domains, as already reported in the literature. Through the collection of these data, it was possible to highlight the need to analyze clinical signs from different perspectives. Full article

Ventilation may lead to a deterioration in indoor air quality in urban environments located close to roads. Understanding the differences in the chemical compositions of size-resolved particulate matter (PM) in indoor air and outdoor air could aid in assessing the health impacts of air in these settings and establishing relevant regulation policies. In this study, indoor and outdoor size-resolved PM was collected from an office in Beijing in summer (between 5 and 25 July 2020) and winter (between 5 and 31 January 2021). Its chemical components, including sulfate, nitrate, ammonium, chlorine, organic matter (OM), elemental carbon (EC), crustal materials (CM), and heavy metals (HM), were analyzed. The mean levels of indoor and outdoor PM_2.1 and PM₉ were found to be much higher than those in the guidelines for PM_2.5 and PM₁₀ outlined by the National Ambient Air Quality Standard. Moreover, the levels of PM_2.1 and PM_2.1–9 mass were higher outdoors than they were indoors. The size distributions of mass concentrations were shown to be bimodal, peaking at 0.43–0.65 μm and 4.7–5.8 μm, respectively. The most abundant chemicals were OM, nitrate, and sulfate for PM_2.1 and OM, CM, and nitrate for PM_2.1–9. We found higher percentages of sulfate, nitrate, ammonium, EC, and HM in smaller-size fractions of PM. Additionally, positive matrix factorization showed that biomass burning, secondary inorganic aerosol, coal combustion, dust, traffic, and industrial pollution were the main sources of PM during the study period. The greatest non-carcinogenic and carcinogenic hazards were found at 0.43–0.65 μm in summer and 2.1–3.3 μm in winter. Our results indicate that size-resolved PM of ambient origin may infiltrate buildings near roads to varying degrees, resulting in negative health effects. Full article

Combustion processes are the primary source of fine particulate matter in indoor air. Since the 1970s, plants have been extensively studied for their potential to reduce indoor air pollution. Leaves can retain particles on their surfaces, influenced by factors such as wax content and the presence of hairs. This study introduces an innovative experimental approach using metal oxide particles in an office-like environment to evaluate the depolluting effect of plant walls. Two plant walls were installed in a controlled room, housing three plant species: Aglaonema commutatum ‘Silver Bay’, Dracaena fragrans, and Epipremnum aureum. Metal oxide particles were introduced via a compressed air blower positioned between the two walls. The concentration of these particles was monitored using PM_2.5 sensors, and the deposition of iron (Fe) on the leaves was quantified through Inductively Coupled Plasma Mass Spectrometry (ICP-MS). This novel methodology effectively demonstrated the utility of both real-time sensors and ICP-MS in quantifying airborne particle concentrations and leaf deposition, respectively. The results revealed that Dracaena fragrans had a 44% higher Fe particle retention rate compared to the control (wallpaper). However, further validation through methodological replication is necessary to confirm the reproducibility of these findings. Full article

Waste-Sorting Plant (WSP) workers are exposed to bioaerosols containing a large variety of bacterial and fungal species, posing a critical health risk that needs to be assessed and mitigated. The present study aimed to evaluate the indoor air quality in a Portuguese WSP and the air decontamination efficiency with UV-C. The concentrations of bacteria and fungi and particulate matter (PM_2.5 and PM₁₀), CO₂, relative humidity, and temperature were determined at different hours in manual sorting areas (cabin and ramp) in autumn and winter in 2022 and in administrative offices and canteen in the autumn of 2023. The PM_2.5 and PM₁₀ concentrations in the air increased with the daily waste-sorting activities, especially inside the cabin, averaging 22 and 42 μg/m³, respectively, while the CO₂ concentration was in the range of 343–578 ppm in both sampling sites. The bacterial species were mainly environmental (mesophilic bacteria) rather than human sources. In the waste-sorting areas, the concentration of bacteria was often found to exceed outdoor values by more than 1000 CFU/m³ on average. Additionally, the concentration of fungi indoors was consistently higher than outdoor values, in many cases exceeding 500 CFU/m³. These findings suggest that workers in these areas are frequently exposed to high levels of microbes. The indoor-to-outdoor (I/O) contamination ratios revealed that the air quality inside the administrative offices and the canteen had high pollutant concentrations during some time periods. The worst scenarios were observed in the canteen and offices with high occupancy in the afternoon. UV-C lamps at 253.7 nm and with 5.0 W irradiation power were used in the sorting cabin to test the indoor air and surface decontamination, and the results showed a high bacterial removal efficacy of over 87.6% after one hour of exposure to UV-C. The present study raises the question of whether 37 °C is the optimal incubation temperature for WSP samples since the microorganisms’ habitat before the sampling had a much lower temperature. As the waste-sorting industry expands, these findings show that the air quality of WSPs remains concerning and requires a holistic approach, integrating the working conditions of all personnel and the implementation and monitoring of mitigation measures. Full article

In urban areas like Chicago, daily life extends above ground level due to the prevalence of high-rise buildings where residents and commuters live and work. This study examines the variation in fine particulate matter (PM_2.5) concentrations across building stories. PM_2.5 levels were measured using PurpleAir sensors, installed between 8 April and 7 May 2023, on floors one, four, six, and nine of an office building in Chicago. Additionally, data were collected from a public outdoor PurpleAir sensor on the fourteenth floor of a condominium located 800 m away. The results show that outdoor PM_2.5 concentrations peak at 14 m height, and then decline by 0.11 μg/m³ per meter elevation, especially noticeable from midnight to 8 a.m. under stable atmospheric conditions. Indoor PM_2.5 concentrations increase steadily by 0.02 μg/m³ per meter elevation, particularly during peak work hours, likely caused by greater infiltration rates at higher floors. Both outdoor and indoor concentrations peak around noon. We find that indoor and outdoor PM_2.5 are positively correlated, with indoor levels consistently remaining lower than outside levels. These findings align with previous research suggesting decreasing outdoor air pollution concentrations with increasing height. The study informs decision-making by community members and policymakers regarding air pollution exposure in urban settings. Full article

In indoor spaces without mechanical ventilation systems, a common approach involves using a ceiling-mounted 4-way fan coil unit (4WFCU) to regulate indoor temperature and placing floor-level air purifiers (APs) to remove indoor pollutants. This study introduces a differentiated displacement ventilation system (DVS) that connects multiple APs to the 4WFCU using ductwork. The age of air was compared between the case where the newly designed DVS was implemented and the reference case where 4WFCU and APs operated independently. When there were no obstacles in the office central area, the reference system exhibited a lower age of air. Conversely, when obstacles such as desks and partitions were present in the central area, the proposed DVS was found to improve indoor air quality. The DVS resulted in minimal interference among pathlines of the air discharged from multiple floor-level APs and their efficient suction through the ceiling-mounted 4WFCU and diffusers, significantly reducing stagnant air zones, while pathlines of the air discharged from the 4WFCU and APs interfered significantly when they operated independently, leading to larger stagnant areas in the air distribution. Therefore, modifying office spaces with ceiling-mounted 4WFCUs using the proposed DVS is anticipated to substantially enhance indoor air quality through a straightforward installation process. Full article

Global energy resources are becoming increasingly scarce, and environmental problems are becoming more serious. The construction industry significantly contributes to energy consumption, and building energy efficiency has become a global concern. A critical aspect of building energy efficiency is exterior shading, which controls sunlight exposure and heat input to the interior. By effectively reducing indoor temperature and light intensity, exterior shading provides a more comfortable learning and working environment. In particular, west-facing exterior shading is essential for building shading and heat protection. This study aims to analyze school office buildings’ light and thermal comfort performance in various climatic zones. These buildings are equipped with west-facing external shading. Numerical analyses were performed using Ladybug Tools 1.6.0 software to evaluate the light and thermal comfort performance of the building. The primary objective of this study is to enhance the light performance and thermal comfort within buildings facing west. The main focus of this research is to examine the effectiveness of four different shading devices in improving light performance and thermal comfort in school office buildings located in severe cold (SC) and cold (C) regions. By studying these specific buildings, valuable insights and recommendations can be provided for selecting suitable shading devices for typical urban buildings in similar regions. The study results demonstrate that in typical cities in SC and C regions, light and thermal comfort are significantly improved with appropriate shading devices by a factor of about 1.5 to 2.5 compared to the no-shading condition (NSC). Beijing shows the most significant improvement among the cities studied, with energy efficiency and comfort improved to 2.6 times that of NSC. At the same time, Urumqi has a relatively lower effect, with an improvement of 1.59 times that of NSC. This study provides an essential reference for selecting suitable west-facing shading devices in typical cities in SC and C regions. It is expected that this will contribute to the construction industry’s efforts to achieve more significant results in energy conservation, emission reduction, and green buildings, ultimately helping to address the energy crisis and environmental pollution problems. Full article

Human beings experience a large fraction of their exposure to air pollutants in indoor environments. Air pollution is a large environmental health risk, and exposure to ambient air pollution and indoor air pollution contribute equally to the total number of fatalities worldwide. Although legislative authorities have established limit values for ambient outdoor air and stack emissions, there are inconsistent and variable national and regional limit values for gaseous substances and airborne particulate matter in the built environment (schools, homes, healthcare facilities, offices, and other public spaces). This lack of regulation is unsurprising, because indoor spaces are characterized by complex air chemistry, and their construction materials and types of activities vary significantly. The current understanding of indoor pollutants, including short-lived oxidants, degradation of VOCs, particle formation, and particle composition, is incomplete. It is necessary to identify and assess emerging pollutants and their toxicity, and to consider new consumer products and green construction materials and their impact on indoor air quality (IAQ). Learning from IAQ surveys and audit protocols, research methodologies should be regularized for cross-research comparisons. Some indoor air quality guidance and standards have been written, and several more are in development, with the international ISO 16000 series of indoor standards leading the way for improving indoor air data quality. The WHO has established some ambient air limit values which can mostly be translated into indoor limit values. The built environment needs to harmonize energy efficiency, thermal comfort and air quality standards and guidance. In this review, we discuss the next steps for improving international, regional and national standards and guidance, leading to better and more complete indoor air quality regulations. Full article