Building Ventilation Rate Research Articles

Assessments and application of low-cost sensors to study indoor air quality in layer facilities

Indoor poultry facilities often experience poor air quality due to intensive farming and restricted ventilation. Monitoring the air quality in these barns is crucial considering the health of both the birds and producers. Advancements in sensor technologies have led to the development of low-cost sensors (LCS) that can continuously monitor air pollutants. Even though most poultry facilities in Canada are indoors due to harsh winter weather conditions, there is a lack of indoor air quality (IAQ) studies. This study aimed to evaluate the field performance of the LCS network in a table egg farm in Canada, where the sensors were designed specifically for operating in dusty poultry facilities continuously. The LCS monitored IQA parameters such as particulate matter (PM), carbon dioxide (CO2), relative humidity, and temperature in real-time. By implementing a correction factor, the sensor data resulted in an agreement range of 80 ± 20% with a reference instrument. The study observed that PM concentration exceeded several thousand μg/m3, with PM10 at 5.5 × 104 ± 2.2 × 104 and PM2.5 at 6.3 × 103 ± 2.3 × 103, which was found to be most affected by the chicken activity and light regime. The IAQ parameters also exhibited a complex intercorrelation with each other, as well as the outdoor temperature and the building ventilation rate. Sensors were able to make observations that were found only with research-grade instruments in previous studies. Overall, the study showcases the potential of the LCS network as an affordable solution for environmental monitoring in poultry facilities.

The structure of cross-ventilation flow in an isolated cylindrical building: Numerical study

Cross-ventilation serves as an efficient means to expel pollutants and heat from buildings, requiring no energy consumption due to variations in wind pressure. The structure of the cross-ventilation flow significantly influences ventilation effectiveness. However, limited attention has been given to understanding the impact of a building's cross-section on the structure of cross-ventilation flow. This study aims to fill this gap by numerically investigating the cross-ventilation flow structure in an isolated cylindrical building. The numerical simulation results are validated against reported experimental data, indicating a negligible simulation error of 0.8 % in the volume ventilation rate. This attests to the accuracy of the numerical method in predicting cross-ventilation flow in isolated buildings. As airflow traverses the cylindrical building along the curved side walls, pressure loss diminishes, facilitating increased air inflow. This results in a more horizontal entry of the incoming jet compared to that in a square building. Analysis of Root-Mean-Square streamwise-velocity and turbulence kinetic energy reveals greater airflow fluctuation outdoors for the square building and increased turbulence indoors for the cylindrical building. Notably, the volume ventilation rate of the cylindrical building demonstrates an 8.3 % improvement. Furthermore, the air exchange rate in the cylindrical building surpasses that of the square building by 1.38 times.

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

Radon Gas Estimation from Building Materials

Radon gas originating from building materials is generally thought to cause low concentration. Investigation and estimation of radon levels originating from building materials are important in terms of public health due to the use of dense concrete in tunnel form type houses, which is a building type widely used in Turkey, even though a significant part of Turkey is an earthquake zone. In this article, the effects of different parameters such as 238U concentration in building materials, diffusion constant of building elements, emanation rate, and ventilation rate on radon gas concentration are investigated. As a result, it is concluded that in some cases (such as high diffusion coefficient and insufficient ventilation rate) in houses built with tunnel form concrete structures, the radon level arising from building materials can reach a level that cannot be neglected.

Applying Natural Ventilation for Commercial Buildings With Atrium: Indoor Environment Prediction and Outdoor Pollutant Impact

Abstract The use of natural ventilation for commercial buildings becomes ever attractive due to the potential for economic savings and increased occupant satisfaction. However, it has proven to be particularly challenging to predict the indoor air temperature and airflow distribution from natural ventilation in more complex building geometries such as those with an atrium. This study used the energy-simulation-coupled computational fluid dynamics (CFD) method to predict the indoor temperatures of a typical multi-story, open-floorplan office building with a central atrium. The prediction accuracy using CFD was slightly improved for the periods with extreme outdoor conditions, where large temperature disparities often occur between simulation and experiment. For the tested cases, adjustment of window opening sizes seems to have marginal impacts on the simulation results. This paper further explores the impacts of outdoor gas-phase pollutants on indoor air quality of such a naturally ventilated commercial building with an atrium. A few architectural features such as window blockers and double skin façade (DSF) designs were numerically investigated for their performance to lower the indoor pollution levels while still maintaining adequate building ventilation rates. The results reveal that the features affecting the wind patterns around and above the building have a strong influence on the contamination rates on each floor of the building. DSF can not only reduce indoor pollution levels but also reduce the ventilation rate. When a pollutant source is not close to the building, a conventional central atrium design is preferred for better ventilation rates.

Estimation of Natural Ventilation Rates in an Office Room with 145 mm-Diameter Circular Openings Using the Occupant-Generated Tracer-Gas Method

Natural ventilation in a building is an effective way to achieve acceptable indoor air quality. Ventilation dilutes contaminants such as bioeffluents generated by occupants, substances emitted from building materials, and the water vapor generated by occupants’ activities. In a building that requires heating and cooling, adequate ventilation is crucial to minimize energy consumption while maintaining healthy indoor air quality. However, measuring the actual magnitude of the natural ventilation rate, including infiltration through the building envelope and airflow through the building openings, is not always feasible. Although international and national standards suggested the required ventilation rates to maintain acceptable indoor air quality in buildings, they did not offer action plans to achieve or evaluate those design ventilation rates in buildings in use. In this study, the occupant-generated carbon dioxide (CO2) tracer gas decay method was applied to estimate the ventilation rates in an office room in Seoul, South Korea, from summer to winter. Using the method, real-time ventilation rates can be calculated by monitoring indoor and outdoor CO2 concentrations without injecting a tracer gas. For natural ventilation in the test room, 145 mm-diameter circular openings on the fixed glass were used. As a result, first, the indoor CO2 concentrations were used as an indicator to evaluate how much the indoor air quality deteriorated when all the windows were closed in an occupied office room compared to the international standards for indoor air quality. Moreover, we found out that the estimated ventilation rates varied depending on various environmental conditions, even with the same openings for natural ventilation. Considering the indoor and outdoor temperature differences and outdoor wind speeds as the main factors influencing the ventilation rates, we analyzed how they affected the ventilation rates in the different seasons of South Korea. When the wind speeds were calm, less than 2 m/s, the temperature difference played as a factor that influenced the estimated ventilation rates. On the other hand, when the temperature differences were low, less than 3 °C, the wind speed was the primary factor. This study raises awareness about the risk of poor indoor air quality in office rooms that could lead to health problems or unpleasant working environments. This study presents an example of estimating the ventilation rates in an existing building. By using the presented method, the ventilation rate in an existing building can be simply estimated while using the building as usual, and appropriate ventilation strategies for the building can be determined to maintain the desired indoor air quality.

Urban microclimate and climate change impact on the thermal performance and ventilation of multi-family residential buildings

Urban settings and climate change both impact on energy use and thermal comfort inside buildings. This paper first presents a study of changes in energy demand in residential buildings considering the overlapping effect of climate change and urban heat island intensity in two European locations; Cadiz (Spain) and London (United Kingdom), representing temperate and hot European climates and moderate and dense urban settings. Future-urban weather files were generated and simulations were run considering energy demand and indoor thermal comfort. In hot climate regions such as the one of Cadiz, future climate will increase the cooling demand and the additional impact of the UHI leads to a further increase of up to +28% of total energy demand compared to the current climate without considering urban effects. Future-urban weather conditions will be detrimental also for buildings in London, where the annual energy demand is predicted to increase by up to the 16% if future climate and urban effects are included. This is due to a higher increase in cooling demand compared to the reduction for the heating need. The paper also presents a method to take into account microclimatic conditions in naturally ventilated buildings, especially the effect of wind variations around the building which impacts natural ventilation rates. Air and surface temperature and wind speeds were studied using ENVImet and the resulting microclimatic conditions were used as inputs to the EnergyPlus Airflow Network model for the calculation of the building ventilation rates. It was found that ventilation rates are reduced (in comparison to meteorological weather files) and this reduction impacts negatively on internal operative temperatures. A thermal comfort analysis was carried out indicating that the selection of a suitable weather file and microclimatic conditions is essential for more accurate predictions of internal thermal comfort and will assist in the sizing of passive and active systems to avoid overheating.

Theoretical and experimental investigation of ventilation rates and their relation with IAQ and thermal comfort in university classrooms during SARS-COV-2 pandemic

During the pandemic of Covid-19, ventilation rate of buildings and especially in spaces with high occupancy like classrooms, presents high research interest. The ventilation strategies, combined with the use of masks, contribute to the decrease of the infection risk of Covid-19. Also, ventilation improves Indoor Air Quality (IAQ), contributing to the good health of the users and potentially influences their thermal comfort. In the proposed work, the experimental investigation of the ventilation’s adequacy in naturally ventilated classrooms located at the University of Western Macedonia, in Kozani, Greece, took place. Measurements include thermal comfort parameters, as well as IAQ ones, namely carbon dioxide (CO2), volatile organic compounds (VOCs), aldehydes and ozone (O3). The air exchange rates were determined according to the tracer gas decay and equilibrium analysis methods, using CO2 as tracer gas, while simulations analysis using appropriate computational approaches was applied. The results between tracer gas method and simulation analysis were compared, allowing the validation of the adopted models. Given that for both approaches natural ventilation proved to be inadequate, different simulated scenarios of ventilation, including natural and mechanical configuration, were investigated; the relation of ventilation rates to IAQ and thermal comfort was investigated. Moreover, the infection risk, given the determined or simulated IAQ, was assessed, according to relevant approaches.

Investigating the impact of urban microclimate on building thermal performance: A case study of dense urban areas in Hong Kong

Urban microclimate conditions could be an important factor influencing building thermal performance. However, most studies on urban building energy modeling (UBEM) use the typical meteorological year (TMY), often developed from observations of exposed/ rural sites, as input weather data. This study aims to assess the impacts of urban heat on building thermal performance by coupling a high-resolution urban climate simulation with UBEM. The simulated building thermal performance was compared with and without urban microclimate considerations, using weather data from the TMY, weather observations from an urban oasis, and outputs from the urban climate model. The physical parameters of typical building archetypes used in the UBEM were calibrated against indoor-measured data during summer days. Without considering urban microclimate, there was an underestimation of up to 140% of the average overheating risks of urban buildings. Furthermore, neighboring urban contexts and building ventilation rates considerably affected the thermal performance of individual buildings within high-density urban areas. The study reveals that neglecting the influence of the urban microclimate can result in a notable error in the building thermal performance assessment even at the urban level.

Controlled air exchange rate method to evaluate reduction of volatile organic compounds by indoor air cleaners

Air cleaning technologies are needed to reduce indoor concentrations and exposure to volatile organic compounds (VOCs). Currently, air cleaning technologies lack an accepted test standard to evaluate their VOC removal performance. A protocol to evaluate the VOC removal performance of air cleaning devices was developed and piloted with two devices. This method injects a VOC mixture and carbon dioxide into a test chamber, supplies outdoor air at a standard building ventilation rate, periodically measures the VOC concentrations in the chamber using solid phase microextraction-gas chromatography-mass spectrometry over a 3-h decay period, and compares the decay rate of VOCs to carbon dioxide to measure the VOC removal air cleaning performance. The method was demonstrated with both a hydroxyl radical generator and an activated carbon air cleaner. It was shown that the activated carbon air cleaner device tested had a clean air delivery rate an order of magnitude greater than the hydroxyl radical generator device (72.10 vs 6.32 m3/h).

Evaluating machine learning models to classify occupants’ perceptions of their indoor environment and sleep quality from indoor air quality

ABSTRACT A variety of factors can affect a person’s perception of their environment and health, but one factor that is often overlooked in indoor settings is the air quality. To address this gap, we develop and evaluate four Machine Learning (ML) models on two disparate datasets using Indoor Air Quality (IAQ) parameters as primary features and components of self-reported IAQ satisfaction and sleep quality as target variables. In each case, we compare models to each other as well as to a simple model that always predicts the majority outcome. In the first analysis, we use open-source data collected from 93 California residences to predict occupant’s satisfaction with their indoor environment. Results indicate building ventilation rate, Relative Humidity (RH), and formaldehyde are most influential when predicting IAQ perception and do so with an accuracy greater than the simplified model. The second analysis uses IAQ data gathered from a field study we conducted with 20 participants over 11 weeks to train similar models. We obtain accuracy and F1 scores similar to the simplified model where PM2.5 and TVOCs represent the most important predictors. Our results underscore the ability of IAQ to affect a person’s perception of their built environment and health and highlight the utility of ML models to explore the strength of these relationships. Implications: The results from this study show that two outcome variables – occupant’s indoor air quality (IAQ) satisfaction and perceived sleep quality – are related to the measured IAQ parameters but not heavily influenced by typical values measured in apartments and homes. This study highlights the ability of machine learning models as exploratory analysis tools to determine underlying relationships within and across datasets in addition to understanding the importance of certain features on the outcome variable. We compare four different models and find that the random forest classifier has the best performance in both analysis on IAQ satisfaction and perceived sleep quality. It is a suitable model for predicting IAQ-related subjective metrics and also provides value insight into the feature importance of the IAQ parameters. The accuracy of any of these machine learning models in predicting occupants’ comfort or sleep quality is limited by the dataset size, how data is collected, and range of data. This study identifies the factors that are important to IAQ perception: ventilation rate, relative humidity, and concentrations of formaldehyde, NO2, and particulate matter. It indicates that sensors that can measure these variables are necessary for future, related studies that model occupants’ IAQ satisfaction. However, this study does not find strong relationships between any of the IAQ parameters measured in this study and perceived sleep quality despite the logical pathway between these many pollutants and respiratory issues. A prediction model of IAQ perception or sleep quality can be integrated into home management systems to automatically adjust building operations such as ventilation rates in smart buildings. Once buildings are equipped with a network of low-cost sensors that measure concentrations of pollutants and operating conditions of the ventilation system, the prediction model can be used to predict the occupants’ comfort and facilitate the control of the ventilation system.

THE IMPACT OF VENTILATION RATE ON RADON CONCENTRATION INSIDE HIGH-RISE APARTMENT BUILDINGS.

Radon is the main pollutant of indoor air, being considered a primary cause of lung cancer, especially in non-smokers. In 2013, European legislation required the standardization of regulations on radon exposure in member states using EC Directive 59/2013 EURATOM. The directive establishes basic safety rules for protection against the dangers represented by the exposure to ionizing radiation. Directive 59/2013 mandates each European country to establish a national action plan to reduce the risks of lung cancer attributed to radon in the general population and exposed workers. Romania is a European country with almost 20 million citizens, with over half of population living in urban locations. Most urban buildings in Romania are high-rise structures (4-10 floors), having many residential units. In this paper, we present results of season-dependent measurements of radon concentration and ventilation rates in high-rise apartment buildings and show the influence of ventilation on indoor radon levels. Indoor radon concentrations varied between 70 and 168Bqm-3 in winter and 17-30Bqm-3 in summer, being higher than the respective outdoor concentrations by 2-5 times in winter and 1-4 times in summer. Ventilation rates varied with season and were influenced by meteorological conditions at the time of measurements. Findings indicate that levels of indoor radon concentration depend on ventilation rates of the unit, but also on building materials, wind speed around building, time of day (higher around noon) and season of the year (higher in the cold season when ventilation rate is lower).

A new PM2.5-based PM-up method to measure non-mechanical ventilation rate in buildings

Air exchange rate (AER) is related with sustainable development of human society. Its convenient measurement in realistic environments remains a challenge due to disturbance for occupants' normal activities. This study developed a new PM-up method to overcome this challenge. This method uses PM2.5 as tracer and determines non-mechanicntal ventilation rate by fitting a model to indoor PM2.5 concentration in an initial bouncing period. Compared to results by mostly used CO2 decay methods, PM-up method has a normalized mean error (NME) of 0.27 and correlation coefficient (r) of 0.69 for AER smaller than 1 h−1 (n = 39). For all the tests (n = 73), NME is 0.35 and r is 0.76. This indicates satisfactory performance of the PM-up method for engineering application. The method's performance seems not impacted by fitting coefficient, AER level, or indoor PM2.5 concentration. We applied the method to continuously measure hourly non-mechanical AER in 6 days, indicating its feasibility in practice. This PM-up method offers new option to measure non-mechanical AER with little disturbance to occupants' normal activities.

Vapor-selective active membrane energy exchanger with mechanical ventilation and indoor air recirculation

It is widely known that increasing outdoor air ventilation rates in buildings can help improve indoor air quality and mitigate the spread of diseases. However, cooling and dehumidifying outdoor air requires significantly more energy than treating indoor recirculated air. Recent developments in water vapor-selective membranes, which use a vapor partial pressure gradient to remove water vapor from air, offer a unique opportunity to provide highly efficient dehumidification in HVAC systems that can justify high outdoor air ventilation rates without drastic increases in energy consumption. This work presents an analysis of a novel membrane HVAC system referred to as the Active Membrane Energy Exchanger (AMX), which couples a refrigeration cycle with selective membranes to simultaneously cool and dehumidify air. While past selective membrane dehumidification systems have been isothermal, the AMX is the first to deliberately target non-isothermal operation by combining membrane dehumidification and active heat exchange. A thermodynamic model is developed for the AMX in a system that uses both outdoor air ventilation and indoor air recirculation (AMX-R) to elucidate the limitations around increasing ventilation rates. This study is among the first to consider recirculation for selective membrane processes, rather than only 100% outdoor air. The AMX-R can achieve up to 50% cooling and dehumidification electricity savings in warm and humid climates under current ventilation standards. Furthermore, ventilation rates can be nearly tripled with the AMX-R while consuming similar amounts of energy as conventional HVAC systems. Lastly, the incorporation of EnergyPlus building simulations for 114 US cities shows that the AMX-R has the greatest potential in the southern regions of the US.

Potted plants can remove the pollutant nitrogen dioxide indoors

Nitrogen dioxide (NO2) is a significant pollutant in both outdoor and indoor environments with exposure linked to serious respiratory illnesses, decreased lung function and airway inflammation. Here, we investigate whether potted plants can contribute as a simple and cost-effective indoor air pollution mitigation technique. Our study investigates the ability of the combination of the three plant species Spathiphyllum wallisii ‘Verdi’, Dracaena fragrans ‘Golden Coast’ and Zamioculcas zamiifolia with two different growing media to remove in situ concentrations (100 ppb) of NO2 in real-time at two typical indoor light levels (0 and 500 lx) and in ‘wet’ and ‘dry’ growing media conditions. All studied ‘growing medium–plant systems’ were able to reduce NO2 concentrations representative of a polluted urban environment, but to varying degrees. The greatest NO2 removal measured inside a 150 L chamber over 1-h period in ‘wet’ growing media at ~ 500 lx was achieved by D. fragrans. When accounting for dilution, this would correspond to a removal of up to 3 ppb NO2 per m2 of leaf area over the 1-h test period and 0.62 ppb per potted plant over the same period when modelled for a small office (15 m3) in a highly polluted environment. Depending on building ventilation rates and NO2 concentration gradients at the indoor-outdoor interface that will vary massively between polluted urban and rural locations, potted plants offer clear potential to improve indoor air quality—in particular in confined indoor spaces that are poorly ventilated and/or located in highly polluted areas.

Assessment of ventilation rates inside educational buildings in Southwestern Europe: Analysis of implemented strategic measures

The pandemic caused by COVID-19 has highlighted the need to ensure good indoor air quality. Public buildings (educational buildings in particular) have come under the spotlight because students, teachers and staff spend long periods of the day indoors. This study presents a measurement campaign for the assessment of ventilation rate (VR) and ventilation strategies in educational buildings in Southwestern Europe, Portugal and Spain. A representative sample of the teaching spaces of the Azurém Campus (Guimarães, Portugal) and the Fuentenueva Campus (Granada, Spain) have been analyzed. Natural ventilation is the predominant ventilation strategy in these spaces, being the most common strategy in educational buildings in Europe. VR was estimated under different configurations, using the CO2 decay method. Subsequently, the CO2 concentration was estimated according to occupancy and the probability of infection risk was calculated using the Wells-Riley equation. The obtained VR varied between 2.9 and 20.1 air change per hour (ACH) for natural cross ventilation, 2.0 to 5.1 ACH for single-sided ventilation and 1.8 to 3.5 for mechanically ventilated classrooms. Large differences in CO2 concentrations were verified, depending on the analyzed ventilation strategy, ranging from 475 to 3903 ppm for the different scenarios. However, the probability of risk was less than 1% in almost all of the classrooms analyzed. The results obtained from the measurement campaign showed that the selection of an appropriate ventilation strategy can provide sufficient air renewal and maintain a low risk of infection. Ventilation strategies need to be reconsidered as a consequence of the health emergency arising from the COVID-19 pandemic.

The Role of Ab-Anbars in the Vernacular Architecture of Iran with Emphasis on the Performance of Wind-Catchers in Hot and Dry Climates

Vernacular and traditional Iranian architecture has always acted rationally, harmoniously, and climate-friendly to meet the needs of the people in dealing with the environment. In addition, without harming the environment, they have achieved the best initiatives with the least facilities. For example, we can mention that the Ab-Anbars in arid and desert areas of Iran, which are used to store water in seasons with precipitation for use in the rest of the year, has been an optimal way to use natural resources and provide climate comfort. The Ab-Anbars are realized with ventilated cisterns through openings on their roof or wind-catchers to keep the water cool and provide comfortable conditions for the occupants. In order to study the essential role of natural ventilation and cooling in the Ab-Anbars, thermal analysis with CFD software was carried out to assess the effectiveness of a typical wind-catcher according to different wind directions in Yazd city. The results showed that Ab-Anbars have played an important role in reducing cooling loads and supply the necessary ventilation rate of buildings and can be used in the future for application in contemporary architecture and urban planning.

Field study to characterize customer flow and ventilation rates in retail buildings in Shenzhen, China

Reduction of the customers’ exposure risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the retail buildings, i.e., supermarkets and small shops where residents purchase daily necessities is of prime importance during pandemic. In this study, the main influencing factors of the exposure risk of SARS-CoV-2, namely the occupant density, dwell time, and fresh air volume per person, were on-sited measured in 5 supermarkets and 21 small shops in Shenzhen, China. The small shops with an occupant area per person of 4.7 m2/per presented a more crowded environment than the supermarkets with an occupant area per person of 18.8 m2/per. The average dwell time of customers in the supermarkets linearly increased with the floor area and its probability distribution was fitted well by the Gamma distribution with a shape parameter of 3.0. The average dwell time of customers in the supermarkets was relatively longer than the combination of five types of small shops. In addition, the measured average outdoor air change rate of the small shops by natural ventilation was 10.7 h−1, while that of the supermarkets by mechanical ventilation was only 0.7 h−1. Correspondingly, the CO2 concentration in the small shops was 100–150 ppm lower than the supermarkets. The small shops provided an average fresh air volume per person of 216 m3/(h·per), far exceeding the supermarkets with a value of 95 m3/(h·per).

Proposing Alternative Solutions to Enhance Natural Ventilation Rates in Residential Buildings in the Cfa Climate Zone of Rasht

Today, renewable resources and the crucial role of passive strategies in energy efficiency in the building sector toward the sustainable development goals are more indispensable than ever. Natural ventilation has traditionally been considered as one of the most fundamental techniques to decrease energy usage by building dwellers and designers. The main purpose of the present study is to enhance the natural ventilation rates in an existing six-story residential building situated in the humid climate of Rasht during the summertime. On this basis, two types of ventilation systems, the Double-Skin Facade Twin Face System (DSF-TFS) and Single-Sided Wind Tower (SSWT), were simulated through DesignBuilder version 4.5. Then, two types of additional ventilation systems were proposed in order to accelerate the airflow, including four-sided as well as multi-opening wind towers. The wind foldable directions were at about 45 degrees (northwest to southeast). The simulation results show that SSWT could have a better performance than the aforementioned systems by about 38%. Therefore, the multi-opening system was able to enhance the ventilation rate by approximately 10% during the summertime.

Real-time ventilation control based on a Bayesian estimation of occupancy

Demand-controlled ventilation (DCV) is commonly implemented to provide variable amounts of outdoor air according to an internal ventilation demand. The objective of the present study is to investigate the applicability and the performance of occupancy-based DCV schemes in comparison with time-based and CO2-based DCV schemes. To do this, we apply the occupancy estimation method by the Bayes theorem to control the ventilation rate of an office building in real-time. We investigated six cases in total (two cases for each control scheme). Experiments were conducted in a small office room with controllable ventilation equipment and relevant sensors. The observed results indicated that the occupancy-based schemes relying on Bayes theorem could be applied successfully to perform continuous control of ventilation rates without causing recursive problems. Additionally, we discussed the time delays associated with the control procedure, including dispersion time, sensor-response time, and data processing time. Finally, we compared the performance of the proposed approach in six DCV cases in terms of a resultant indoor CO2 level and the total ventilation-air volume. We concluded that DCV control based on both occupancy and floor area provided the best conformity to the ASHRAE standard among the analyzed schemes.