Jurgis Zemitis

Air pollution remains a major global health concern, contributing to millions of premature deaths annually. Poor indoor air quality (IAQ) is strongly associated with sick building syndrome (SBS), which can lead to various health problems and reduced workplace productivity. This study examines the role of trickle vents as a passive component in natural and hybrid ventilation systems aimed at improving IAQ and occupant comfort. Two types of factory-produced trickle vents were tested in a controlled climatic chamber under systematically varied indoor–outdoor pressure differentials, generated using a blower system. Airflow measurements revealed a strong relationship between pressure difference and vent performance. Differences between the two vent types were largely due to variations in cross-sectional areas, influencing airflow resistance and pressure drop. Although neither vent achieved the required ventilation rates for standard conditions, their integration into hybrid systems, particularly in combination with mechanical exhaust fans, was found to significantly enhance potential airflow. The findings underline both the challenges and opportunities in achieving effective ventilation, especially in upper building floors where natural driving forces are reduced. This work contributes to the understanding of passive ventilation components and their potential to support healthier, more sustainable indoor environments.

As building energy consumption gains ever-increasing attention worldwide, the focus on addressing it through the examination and optimization of efficient heat recovery solutions continues to intensify. With well-insulated and airtight buildings, the proportion of heating needs attributed to ventilation is growing, leading to the widespread integration and optimization of heat recovery solutions in mechanical ventilation systems. Heat recovery in ventilation is a highly efficient strategy for reducing heat losses and conserving energy. This study involves the investigation of a ventilation unit installed in an apartment situated in Riga, Latvia, as a practical examination of heat recovery system efficiency within the Latvian climate conditions, representing a cold climate region. The objective of this study was to examine the heat recovery efficiency of the ventilation system in the Latvian climate with variable outdoor and exhaust air parameters, given that the dry heat recovery efficiency is different from the actual heat recovery efficiency. The ventilation unit was equipped with a plate heat exchanger at an airflow rate of 105 m³/h. To evaluate heat recovery efficiency, extensive measurements of air temperature and relative humidity were conducted. The collected data was analyzed, employing statistical regression analysis to ensure measurement reliability and assess correlations. The findings indicated a strong correlation between variables such as heat content, moisture content, and sensible air parameters. It was observed that the actual heat recovery efficiency was 6% higher than the calculated dry efficiency, emphasizing the importance of considering real-world conditions in heat recovery assessments. Additionally, regression analysis demonstrated a positive linear correlation with a coefficient of 0.77, highlighting the dependency between actual measurements and the theoretical model. These quantitative outcomes provide essential insights for optimizing heat recovery systems and enhancing energy-efficient ventilation practices, especially in cold climate environments. Moreover, this study highlights the strong correlation between variables such as heat content, moisture content, and sensible air parameters. Findings offer essential insights for optimizing heat recovery systems and enhancing energy-efficient ventilation practices, especially in cold climate environments.

This paper is dedicated to research of the impact of the limited heat source capacity on indoor temperature and energy consumption in serial nZEB residential buildings. This is an innovative aspect as it explores the potential design simplification for different locations, allowing for cost optimization and quicker construction timelines. The objective of this paper is to examine the impact of limited heat source capacity by utilizing thermal mass and optimizing the ventilation operation. Numerical results demonstrate that incorporating thermal mass increases heating energy consumption by up to 1%. The study addresses the impact of limited heating capacity on indoor temperatures and the need to manage ventilation’s impact during peak temperatures using simulation software IDA ICE. The study reveals that a limited heating capacity reduces energy consumption up to 2.6%, but may result in lower indoor temperatures. By optimizing ventilation strategies, energy consumption can be reduced from 2.4% to 4.4% compared to the suboptimal solution, and from 2.8% to 6.5% compared to the initial case. Parametric analysis reveals optimal ventilation operation change-over point at an outdoor temperature of −17 °C during winter. The research provides practical recommendations for adjusting heating schedules, selecting appropriate heating capacities and implementing optimal ventilation strategies.

It has been reported that there is a large issue regarding the IEQ in schools and classrooms as they often do not have a mechanical ventilation system or do not operate it to save on electricity bills. However, the measurements and reports from existing research indicate that the indoor air temperatures and CO2 levels are often way outside the recommended values and manual venting by opening windows during brakes is not sufficient. This has become especially alarming during the COVID-19 pandemic, as the virus can spread through the air and under-ventilated classrooms pose a great risk for the pupils located in them. In the scope of this paper, a classroom was simulated concerning IAQ and thermal comfort at various ventilation strategies. The simulation was used to determine the predicted thermal comfort at various locations in the classroom at different window opening areas and orientations. Based on the simulation results potential control strategies for window ventilation were developed. They take into account the changing location of persons and the threshold level of allowed deviation from optimal thermal comfort level to achieve the optimal IAQ as a compromise during the cold winter periods must be made. The results indicated that after 50-second-long natural ventilation at an outside air temperature of -3°C the thermal comfort level will be very low in most of the points of the classroom. None of the various window-opening strategies influences this much. The lowest achieved average PPD was 62.5% and it was in the case when one open window was open at 90° but in the case when two windows were open at 15 cm the average PPD was 98.7%.

As energy consumption for building engineering systems is a major part of the total energy spent, it is necessary to reduce it. This leads to the need for the development of new solutions for the control of heating, ventilation, and conditioning (HVAC) systems that are responsive to humans and their demands. In this review article, the existing research and technology advancements of the modern technologies of computer vision and neural networks for application in HVAC control systems are studied. Objectives such as human detection and location, human activity monitoring, skin temperature detection, and clothing level detection systems are important for the operation of precise, high-tech HVAC systems. This article tries to compile the latest achievements and principal solutions on how this information is acquired. Moreover, it how parameters such as indoor air quality (IAQ), variable air volume ventilation, computer vision, metabolic rate, and human clothing isolation can affect final energy consumption is studied. The research studies discussed in this review article have been tested in real application scenarios and prove the benefits of using a particular technology in ventilation systems. As a result, the modernized control systems have shown advantages over the currently applied typical non-automated systems by providing higher IAQ and reducing unnecessary energy consumption.

The COVID-19 crisis has affected the process of how the study procedures are organized at schools in Latvia. Three different options were available for the school to choose from. However, most schools have opted for option A which states that the classes are organized face-to-face but various safety measures must be ensured. Each class or group is equated to a closed set where there are no distance requirements. In turn, the distance between the classes must be observed. This means that students stay in the same class all day and are accompanied by teachers of the respective classes. This can lead to improper ventilation as for most of the schools in Latvia it is organized through the opening of windows. To test this, measurements of CO₂ concentration were done in a classroom Secondary School in Daugavpils. The results showed that the CO₂ concentration was very high and often reached and exceeded the maximum measuring capacity of the device - 4000 ppm. It indicates that following the special safety procedures cause a negative effect on IAQ as the classrooms are not properly ventilated. This can lead to a drop in the performance of pupils as well as stimulate the transmission of other infectious diseases. Further measurements are necessary to gather data from different schools and best practices must be found.