Stale Air Research Articles

Performance of Windcatchers in Improving Indoor Air Quality, Thermal Comfort, and Energy Efficiency: A Review

The growing concerns over climate change and energy scarcity have highlighted the need for building energy conservation. Windcatchers, renowned for their effective ventilation capabilities, have emerged as a pivotal solution for saving energy and improving indoor thermal comfort. Serving as rooftop installations, windcatchers harness high-altitude airflow to provide fresh indoor air while expelling stale air. This comprehensive review encompasses over 96 studies published between 2000 and 2024, examining the performance of various types of windcatchers. The review reviews previous articles and concludes that using different types of wind catchers in hot and arid areas can increase indoor air velocity by about 10–50%, reduce building energy consumption by about 20–50%, and increase thermal comfort duration by about 25–50%. The article combines the perspectives of multiple disciplines such as architecture, environmental engineering, and sustainable design, providing a new perspective for the study of windcatchers. The article not only summarizes the design and performance of existing wind catchers, but also provides 13 suggestions for the design of wind capture towers, while also identifying areas for future research, such as combining wind capture machines with other passive cooling technologies and evaluating their performance under different climate and urban conditions.

A numerical framework for the analysis of indoor air quality in a classroom

This paper presents a framework for applying Computational Fluid Dynamics (CFD) to study indoor air quality in a classroom environment by analysing the transport and extent of human-generated aerosol and carbon dioxide (CO2) accumulation. A methodology is outlined for identifying the appropriate amounts of exhaled aerosol and CO2 needed as boundary conditions for human breathing in CFD simulations, which is validated with in situ measurements obtained within a stale air classroom environment at matched conditions. This is crucial for quantifying the exhaled CO2 and aerosols from occupants, which is essential for designing ventilation settings that promote a healthy indoor environment. Good agreement is observed between the CFD and experiments for CO2 and aerosol concentration within the size range of 0.7-1μm. Further, we explore the impact of individual heat sources and breathing momentum flux on air stratification and aerosol dispersion. The analysis reveals that the thermal plume generated by each occupant and the momentum created from breathing are the characteristics of airflow in a stale air environment. This paper demonstrates the ability of the developed numerical model to reproduce realistic exhaled aerosol and CO2 in indoor ventilation settings, serving as a benchmark for investigating indoor air quality in the built environment.

Comparing In Silico Fungi Toxicity Prediction with In Vitro Cytotoxicity Assay for Indoor Airborne Fungi

Technological advancements have shifted human living and working environments from outdoor to indoor. Although indoor spaces offer protection from unfavorable weather conditions, they also present new health challenges. Stale, humid, and warm indoor air creates an ideal breeding ground for bacteria and fungi, leading to health issues such as asthma and bacterial infections. Although proper ventilation is crucial, a comprehensive inspection of local indoor air quality is necessary to prevent widespread diseases. In vitro experiments involving bacteria and fungi collected from indoor air yield accurate results but are time- and cost-intensive. In silico methods offer faster results and provide valuable insights for guiding further in vitro experiments. In this study, we conduct an in vitro cytotoxicity assay on 32 fungi species and compare its results with a memory-efficient in silico modeling method using parameter-efficient fine-tuning (PEFT) and ProtBERT. This study suggests a potential methodology for predicting the toxicity of indoor airborne fungi when their identities are known.

Review of peculiarities of using wind catchers in energy-saving ventilation systems

Natural ventilation plays an important role in ensuring comfortable living conditions. Wind catchers are part of this process and can provide the required ventilation rate for buildings. The performance of wind catchers depends on the relevant parameters, such as height, configuration, cross-sectional shape, number of inlets, speed of movement and variability of air movement direction. HVAC equipment is not only responsible for the largest portion of the total energy consumption within a building, but also for most indoor air quality problems. Vents, air ducts, and dirty filters are a suitable place for the growth of fungi and molds produced by organic dust, which contaminate the circulating air and cause significant pollution problems. This could be more critical given that we spend almost 90% of our time indoors during our lives and work. Improvements in ventilation and air conditioning systems therefore play an important role in increasing energy efficiency in buildings, providing a better indoor climate for occupants and, as a result, reducing the likelihood of health problems. The cooling process plays an important role in creating comfortable conditions for humans. One of the most well-known elements of a passive cooling system for buildings with no or minimal energy consumption is a wind catcher. The effective-ness of wind catchers is influenced by wind force and buoyancy, and knowledge of the size, shape, and position of the outlet will help to understand new ideas and technologies for their application in modern architecture. A well-known example of natural ventilation that improves indoor quality by reducing pollution and humidity by replacing stale air with fresh outside air is a wind catcher (or wind tower). Nowadays, wind catchers are widely used in the world, having advantages in densely populated urban areas and in areas with low wind speeds, significantly affecting the reduction of cooling loads and providing the required ventilation rate of buildings. At present, there are many types of wind traps that can be classified according to the number of inlets, cross-sectional shape, and number of levels. The number of internal partitions, as well as the size and location of the openings of the wind collector, significantly affect its ventilation characteristics, efficiency, air flow velocity and turbulence, and also divide the cross-section of the wind collector into smaller channels, increasing the strength of its structure and reducing sensitivity to different wind directions

Enhancing respiratory comfort with fan respirators: Computational analysis of carbon dioxide reduction, temperature regulation, and humidity control

Respirators provide protection from inhalation exposure to dangerous substances, such as chemicals and infectious particles, including SARS-COVID-laden droplets and aerosols. However, they are prone to exposure to stale air as masks create a microclimate influenced by the exhaled air. As a result, exhaled air from lungs accumulating in the mask produces a warm and humid environment that has a high concentration of carbon dioxide (CO2), unsuitable for re-inhalation. Fans are a favorable option for respirators to ventilate the mask and remove the stale air. This study utilized computational fluid dynamics simulation consisting of a hybrid Reynolds-averaged Navier–Stokes-large eddy simulation turbulence method to compare the inhalation flow properties for different fan locations (bottom, top, and side) with regular respirator breathing. Three mask positions, top, side, and bottom, were evaluated under two breathing cycles (approximately 9.65 s of breathing time). The results demonstrated that adding a fan respirator significantly decreased internal mask temperature, humidity, and CO2 concentration. The average CO2 concentration decreased by 87%, 67%, and 73% for locations bottom, top, and side, respectively. While the top and side fan locations enhanced the removal of the exhaled gas mixture, the bottom-fan respirator was more efficient in removing the nostril jet gas mixture and therefore provided the least barrier to respiratory function. The results provide valuable insight into the benefits of fan respirators for long-term use for reducing CO2 concentration, mask temperature, and humidity, improving wearer safety and comfort in hazardous environments, especially during the COVID-19 pandemic.

Experimental and numerical evaluation of a novel dual-channel windcatcher with a rotary scoop for energy-saving technology integration

With the increasing requirements for fresh air supply in buildings after the COVID-19 pandemic and the rising energy demand from buildings, there has been an increased emphasis on passive cooling techniques such as natural ventilation. While natural ventilation devices such as windcatchers can be a sustainable and low-cost solution to remove indoor pollutants and improve indoor air quality, it is not as reliable as mechanical systems. Integration with low-energy cooling, heating or heat recovery technologies is necessary for operation in unfavourable outdoor conditions. In this research, a novel dual-channel windcatcher design consisting of a rotary wind scoop and a chimney was proposed to provide a fresh air supply irrespective of the wind direction. The dual-channel design allows for passive cooling, dehumidification and heat recovery technology integration to enhance its thermal performance. In this design, the positions of the supply and return duct are “fixed” or would not change under changing wind directions. An open wind tunnel and test room were employed to experimentally evaluate the ventilation performance of the proposed windcatcher prototype. A Computational Fluid Dynamic (CFD) model was developed and validated to further evaluate the system's ventilation performance. The results confirmed that the system could supply sufficient fresh air and exhaust stale air under changing wind directions. The ventilation rate of the rotary scoop windcatcher was higher than that of a conventional 8-sided multidirectional windcatcher of the same size.

User’s Perception of Indoor Air Quality (IAQ) in Tall Office Buildings as the Cause of Symptoms of Sick Building Syndrome

The user’s assessment or perception of indoor air quality (IAQ) refers to an individual’s subjective assessment or perception of the quality of the air they breathe inside a particular building or space. This assessment or perception is very individual and can vary from one individual to another. This study aims to determine the IAQ felt by users of the Rectorate Building, State University of Malang, and its effect on Sick Building Syndrome (SBS) symptoms. This research is included in the quantitative research with the study population being all employees at the building, which has 215 people. The data collection technique in this study used the MM040NA questionnaire and the data analysis technique used was binary logistic regression analysis with the help of the IBM SPSS Statistics with crosstabs test. The results of this study indicate that all independent variables have no significant relationship with SBS symptoms experienced by respondents and all independent variables have a very weak correlation. In addition, from 80 respondents, 27 people (33.75%) experienced SBS and 53 people (66.25%) did not experience SBS. This shows that there is a SBS phenomenon in the building. The significance value for all independent variables is greater than the significance level value (>0.05). Furthermore, based on the test criteria, it is concluded that the variable airflow, high temperature, temperature change, low temperature, stale air, dry air, odor, air electrostatics, cigarette smoke, sound level, lighting, and air pollution have approximate significance values greater than 0.05 (null hypothesis was failed to be rejected). It is concluded that those variables have no significant relationship to the dependent variable (the SBS symptoms) experienced by the respondents.

Performance of a CO2-based demand controlled dual core energy recovery ventilation system for northern housing experiencing varying occupancy

Indoor air quality and health are major areas of concern in northern and remote communities where homes experience varying occupancy, often overcrowding and are influenced by ventilation. Heat/energy recovery ventilators installed in the north are selected to provide required minimum ventilation rate set by ventilation standards (ASHRAE 62.2, etc.). Northern overcrowded homes become under-ventilated, leading to deteriorated IAQ, mold and health-related problems. This paper present results from a side-by-side testing of a CO2-based demand-controlled ERV versus a constant air flows ERV, using twin houses with simulated occupancies. The control strategy was based on the difference in CO2-concentration between exhaust/return air from the house and outdoor air. The implemented strategy based on a CO2 sensor network connected with an ERV continuously exhausting stale air from kitchen and bathrooms was simple and efficient in adjusting ventilation rate based on occupancy rate. The CO2-based demand-controlled ERV provided a much better control of indoor CO2 concentrations in the main floor and master bedroom, and with lower CO2 concentrations in bedrooms during night time, compared to the reference house with concentrations exceeding 2000 ppm. However, the CO2-based demand-controlled ERV had higher power consumption than conventional ERV with constant air flows.

Numerical investigations on roof ventilator turbine performance characteristics using ANSYS

Rooftop wind turbine ventilators are natural air circulation systems that employ a rotating blade to remove stale air from a building, improving the indoor air quality and saving money in the process. The effectiveness of a roof ventilator turbine depends heavily on its construction. By varying the diameter of the turbine blades (500, 670, and 690 mm), this CFD study modeled and examined three distinct designs for wind-driven ventilation devices. This numerical analysis was further developed to compute the presentation of a rotating ventilator by analyzing the pressure, turbulence kinetic energy, and velocity of the airflow related with the ventilator at variant designs. To investigate the viability of a numerical approach to modeling the many aspects of a ventilator flow, a computational fluid dynamics (CFD) analysis was conducted utilizing the conventional k- turbulence model with the multiple reference frame meshing method. The proposed design of a 690 mm ventilator blade for a rooftop turbine was found to perform better than two alternative designs using computational fluid dynamics (500 and 670 mm turbine blade diameter). The trend lines appear to be in virtuous contract with formerly available data, signifying that mathematical modelling could be a useful and cost-efficient tool for the design, growth, and performance evaluation of a wind-driven rotational ventilation system in the future.

Achieving reduced emission and enhanced air quality by designing a solar-driven indoor CO2 capture system

Green buildings desire low CO2 emission and high indoor air quality (IAQ), which, however, are inherently conflicted on energy consumption and cannot be achieved simultaneously in air conditioning-based ventilation methods. One alternative can be combining building-integrated renewable energy and CO2 capture technology to remove CO2 from stale indoor air and return CO2-depleted air to save air conditioning's (AC) energy demands. Despite the great potential, developing such a system remains challenging owing to the complex mass-energy exchange between the two subsystems, which has been oversimplified in previous research. This study for the first time developed an integrated solar-driven indoor air CO2 capture system and unveiled the dynamic mass-energy balance while considering selective air recirculation. Specifically, multi-variate analyses are conducted to evaluate the proposed system's overall performance, characterized by CO2 capture capacity, air quality enhancement and energy-saving potential. A scenario analysis covering different crowdedness and room areas is also conducted to obtain optimal design configurations for practical implementations. Results show that for one example case of a 40 m2 room with 39 occupants, the proposed system with optimal configuration captures 40.655 kg CO2 per day, controls the indoor CO2 concentration below 800 ppm and saves 24.082 kWh (38.18%) cooling energy by selectively recirculating clean post-captured air. This study sheds light on the rational design of a renewable hybrid system for enhanced indoor air quality, CO2 emission reduction, and energy saving, all of which are preferred in establishing a smart, sustainable and comfortable city.

The Lost Heritage of Koryoin: Citizen or Outcast?

The icy winds of the Baltic bite deep into the bones of barely-clothed prisoners of an unnamed war camp. The cold is unbearable in the frigid Prussian hinterlands, the chatter minimal, and everyone is huddling to survive. Amidst the stale air of death and starvation, small clouds of melodic choir powerfully pierce through the hushed chill: “Ari-rang, ar-ri-rang, ara-ri-yo...”1 From the bellies of a group of Koryo Saram, the Korean folk anthem wistfully winds its way through the barbed wires, straining to reach back home. In a curious, seeming oddity, ethnic Koreans, Koryoin, found themselves conscripted from the Far Eastern regions to fight for the Russian Empire thousands of miles away on the Eastern Front of World War I. During a particularly brutal beatdown at the Battle of Tannenberg, a lethal saber thrust into the heart of Russian Northwest forces, 4,000 ethnic Koreans2 were among the 90,000 Russian soldiers taken as prisoners of war. A small minority of these Koryo Saram, or Koryoin, would soon be afforded some warmth at Humboldt University, where German linguist Dr. Wilhelm Albert Döggen studied their language and music.

USER PERCEPTION OF NATURAL VENTILATION STRATEGY AT INPATIENT WARD, KUALA KANGSAR HOSPITAL

Hospitals and healthcare facilities are known to be among the most energyintensive buildings. This concern has resulted in a resurgence of sustainability awareness in the built environment. Nowadays, many have adopted environmental strategies such as natural ventilation. It offers a low-cost alternative to remove stale air and replace fresh air efficiently through cross ventilation. Studies have shown that natural ventilation is one of the most energyefficient solutions to improve thermal comfort and hospitals and healthcare facilities will greatly benefit from this initiative. Passive Design has been valued as a key strategy in controlling airborne infection, especially in hospital wards with limited resources. Comparatively, the installation of ceiling-mounted mechanical fans will create a negative ventilation pressure difference. This paper explores the potential of the passive design method based on the experience of inpatient ward users. The study utilised questionnaires based on the end user's experience in a naturally ventilated inpatient ward area. The survey administration method ensures the 51 respondents’ anonymity is preserved especially in a healthcare setting. This investigation shows that natural ventilation provides a higher ventilation rate and is more energy-efficient than mechanical ventilation. Therefore, natural ventilation is a suitable solution in public buildings such as hospitals' inpatient wards. The outcome of this study will be paramount for designers to meet passive design objectives. Consequently, these will be the guidelines and outline information for hospital design in the future.

The Private Investigator

The Private Investigator

Evaluation of the main sensitivity drivers in relation to indoor comfort for individuals with autism spectrum disorder. Part 2: Influence of age, co-morbidities, gender and type of respondent on the stress caused by specific environmental stimuli

Variations of environmental parameters, like thermo-hygrometric, acoustic, visual and indoor air quality can influence the sensitivities of individuals on the spectrum. This paper presents research on this issue, studied by means of questionnaires administered to parents and professional caregivers taking care of people with Autism Spectrum Disorder (ASD).The study highlights that there are clear differences if the indirect evaluations are performed by parents or professional caregivers, in relation to the specific identification of stress sources. Additionally, acoustic domain is identified as the one causing the major stress, especially caused by strong noises and particular sounds such as voices, animal sounds and impacts, and its dependence on the severity of autism is evidenced. Furthermore, a lower impact of thermal, visual and IAQ factors is determined, with the exception of some specific stimuli like light contrast (glare), high illumination, particular light sources or stale air. Finally, this paper provides evidence of the influence of age, severity of autism and co-morbidities on perceived stress.

The problem of indoor environmental quality at a general Slovenian hospital and its contribution to sick building syndrome

The hospital setting is among the more complex and challenging indoor environments with its different users and risk factors. The sick building syndrome (SBS) in association with environmental risk factors and measurements of environmental parameters remains underresearched. The aim of our study was to combine the results of i) self-perceived indoor environmental quality in the observed hospital wards, ii) SBS symptoms and iii) identified deviations of the measured environmental parameters from the legally required and/or recommended values for the hospital environment. Based on that, we aimed to identify measures for improving indoor environmental quality. A cross-sectional study was conducted at a Slovenian hospital in 2019 on a sample of 258 healthcare workers and 78 allied health professionals/other employees. Data were gathered using the standardized questionnaires MM NA Hospital and MM NA Office. Measurements of environmental parameters were conducted at ten measurement locations at different hospital wards/units. The most frequently self-reported SBS symptoms over the previous three months included fatigue (healthcare workers: 42.6%; allied health professionals/other employees: 30.8%) and a heavy head (healthcare workers: 29.8%; allied health professionals/other employees: 20.5%). The most frequent environmental risk parameters were unpleasant odor (39.1%) and stale air (34.6%). A significant difference in the measurements of environmental parameters (air temperature, relative humidity, horizontal illumination, carbon dioxide (CO2) concentration, and noise level) was identified at measurement locations of hospital wards/units compared to the legally required and/or recommended values (p = <0.001). Our study underlines the importance of raising awareness among healthcare workers and allied health professionals/other employees about ensuring appropriate environmental factors in the hospital setting.

Nature as a Healer against Anthropocentric Disposition in Anita Desai's Fire on the Mountain

In her novel Fire on the Mountain, Anita Desai, by making her characters burn the images related to the ill and superstitious law of the anthropocentric world, intends to revere the natural world, which for her possesses healing capacity to revive the dying identity. Nanda Kaul, the protagonist and her great-granddaughter, finds pleasure with nothing else but with the barrenness, stillness, calmness and voice of silent breeze and music of nature itself. The fresh air of the quiet breeze in the naturally painted house wins the heart of the protagonist over the stale air of the electric fan in the artificially painted house. By utilizing theoretical ideas of ecofeminism in communication with deep ecology, the article concludes that the proper tribute to nature is possible when hierarchies between human and non-human blur and biocentric world view exists.

Effect of Supply and Exhaust Air Velocity on the Enthalpy and Temperature Exchange Efficiency of a Paper Heat Exchanger

Heat Recovery Ventilators (HRV) are gradually becoming more popular in urban cities and buildings as it is able to effectively maintain the indoor air quality while also using minimal amounts of energy. The key component in the HRV is the Paper Heat Exchanger, which allows the heat exchange of indoor and outdoor air through a crossflow, while also filtering out stale air and dust particles. This article investigates the effect of manipulating the supply and exhaust air velocity on the enthalpy and temperature exchange efficiency of a paper heat exchanger. Data is obtained from experimental results, where the experiments are conducted in a test lab using heat recovery ventilators (HRV) installed with paper heat exchangers. Two paper heat exchangers from different suppliers were tested inside a HRV installed in an air conditioned room. The HRV fan speed was varied at a fixed interval of 0.5 m/s, and the air velocity was measured by using a wind speed meter. At the same time, a USB data logger was used to collect relative humidity and temperature of the air at the supply inlet, indoor air inlet, and return air outlet to determine temperature exchange efficiency and the enthalpy of air. The results of the testing shows that the HRV was able to achieve a temperature exchange efficiency of 47 to 63% and enthalpy exchange efficiency of 63 to 94% for PHEX-A, and a temperature exchange efficiency of 28 to 48% and enthalpy exchange efficiency of 57 to 85% for PHEX-B. The data shows that PHEX-A has higher efficiency than PHEX-B.

Welcome back to Junkspace! Performing infinity while confined in lockdown

For months we have been locked out of Junkspace. So, who’s complaining? Confined to domestic spaces, #stayhome has given many of us a forced opportunity to rethink the type of spaces that are not only functional and useful, but that make us feel comfortable. Our own residential arena may have felt restrictive and even – for some – oppressive at times, but who would say that they truly missed their daily passage through the endlessly stale air of check-in desks, departure gates, and duty frees at the airport; the epic journeys through low ceiling corridors and passageways of railway terminals and subway stations; and the blinding hallucinatory proliferation of brands and franchises in malls…?

CFD simulations to improve air distribution inside cold climate broiler houses involving heat exchangers

While chicken meat production is less polluting than other meats, it remains a problem, given a target of 1 ton CO2-eq per capita in 2050. Most of the emissions are associated with feed production, but cold climate requires an additional energy input for space heating. This input is usually provided by propane gas. Since 2014, energy efficiency has sparked in the world of broiler production. Heat recuperation through heat exchanger can reduce significantly the heating requirement, by preheating fresh air inlet with stale air outlet. While there have been many studies on the improvement of direct ventilation in both hot and cold climate, little attention has been given to heat exchangers in broiler houses. It is therefore unknown how best to integrate this equipment in a broiler house to provide homogenous housing conditions (air temperature, humidity, contaminants). This thesis studies the integration of heat exchangers (HX) in a commercial broiler house located in a cold climate (Sainte-Melanie, Canada). The goal is to improve the housing conditions of a rectangular 1760 m3 broiler house equipped with two ductless air-to-air heat exchangers (0.38 m3s-1). Computational fluid dynamics (CFD) software OpenFOAM was used to create a 3D steady-state buoyant simulation with RNG k-e turbulence model. CFD model was validated with experimental data collected at the participating broiler house. In the original configuration (C0), the two heat exchangers are parallel, on the same longitudinal wall. Three alternative configurations (C1, C2, and C3) were studied to improve housing conditions at chick height (0.1 m): C1 consists of increasing the distance between the HX, C1 consists of a 30° rotation of the HX, and C3 consists of positioning one HX on each end wall. Air velocity, air temperature and age of air were used as performance criteria. All configurations behaved and performed differently. The configuration with the best overall performance was C2. It showed a 45% improvement in age of air distribution and 24% in velocity distribution. Temperature distribution also improved, but it was not reflected in the coefficient of variation.

Design of a Passive Downdraught Evaporative Cooling Windcatcher (PDEC-WC) System for Greenhouses in Hot Climates

A windcatcher is a wind-driven natural ventilation system that catches the prevailing wind to bring fresh airflow into the building and remove existing stale air. This technology recently regained attention and is increasingly being employed in buildings for passive ventilation and cooling. The combination of windcatchers and evaporative cooling has the potential to reduce the amount of energy required to ventilate and cool a greenhouse in warm and hot climates. This study examined a greenhouse incorporated with a passive downdraught evaporative cooling windcatcher (PDEC-WC) system using Computational Fluid Dynamics (CFD), validated with experimental data. Different hot ambient conditions of temperature (30–45 °C) and relative humidity (15–45%) were considered. The study explored the influence of different spray heights, layouts, cone angles and mass flow rates on indoor temperature and humidity. The average error between measurements and simulated results was 5.4% for the greenhouse model and 4.6% for the evaporative spray model. Based on the results and set conditions, the system was able to reduce the air temperature by up to 13.3 °C and to increase relative humidity by 54%. The study also assessed the influence of neighbouring structures or other greenhouses that influence the flow distribution at the ventilation openings. The study showed that the windcatcher ventilation system provided higher airflow rates as compared to cross-flow ventilation when other structures surrounded the greenhouse.