Search

Digital twins represent a promising approach for sustainable building operations and management in the context of the carbon neutrality goals of the European Union (EU). Using OpenStudio, an opensource platform for building energy modeling, we demonstrated the creation and editing of building digital twins. OpenStudio provides a user-friendly interface and extensive simulation capabilities, allowing detailed and accurate modeling of building components and systems. Using OpenStudio Measures, users can automate tasks and customize simulation models to optimize the building performance. The process of creating a building digital twin involves collecting historical data and accurately representing the building geometry; materials; schedules; and heating, ventilation, and air conditioning (HVAC) systems. Challenges such as data availability and model accuracy highlight the importance of modeling practices. Editing the digital twin involves modifying the OpenStudio model files and EnergyPlus weather files to simulate different building operation scenarios. Python programming language opportunities were considered for digital twin file modification. The potential of digital twins lies in their ability to simulate future building conditions and optimize building system settings. By integrating digital twins with machine learning algorithms and connecting them directly to building management systems, optimal building control strategies can be automated, thereby reducing energy consumption and improving occupant comfort levels. [ABSTRACT FROM AUTHOR]

During the pandemic and periods of martial law, educational institutions in Ukraine implemented various forms of organising the educational process, combining in-person and remote classes. As a result, there has been a decrease in the level of use of building premises. The analysis of the characteristics of energy consumption in these conditions requires additional attention. In this study, a dynamic energy model of the building was created using the educational building of Igor Sikorsky Kyiv Polytechnic Institute as an example. Energy consumption for heating needs was determined for normal operating conditions and quarantine conditions in Ukraine (only a specific part of the premises is being operated, ensuring that the standard temperature value is maintained while people are present). Based on the results of the study, the features of the energy consumption of the building during quarantine/martial law restrictions, subject to the partial use of the building, were analysed, and the main disadvantages of such a mode were identified. For the educational building of the university, the total energy consumption for heating needs depends on the number of rooms that are actively used, and the modes of regulation of heating and ventilation; the consumption can decrease depending on the chosen scenario by 61 %, 56 %, and 34 % in quarantine mode. The findings indicate that the efficiency of regulation modes can decrease by more than four times when compared to normal mode due to internal heat exchange with unoccupied rooms. [ABSTRACT FROM AUTHOR]

Buildings consume about 40 % of all energy. Ventilation plays a significant role in both the energy consumption of buildings and the comfort of occupants. To achieve energy efficiency and comfort, smarter ventilation control algorithms can be employed, such as those with feedback based on CO2 levels. Furthermore, by knowing the current number of people in a space, ventilation can theoretically be adjusted to maintain a constant CO2 level without wasting energy when people are not present. An additional benefit of such control could arise due to occupants' habits. For example, if a person senses elevated CO2 levels, even if the ventilation system has started operating more intense, they might choose to open a window, potentially compromising energy efficiency. Therefore, if the control algorithm were to maintain a constant CO2 level, occupants may be less likely to open windows. In our work, we explore a model in combination with a custom monitoring system based on computer vision to implement such control. The monitoring system combines outside and inside CO2 sensors with precise people counting based on computer vision to provide data to the model. The model relies on the mass balance equation for CO2 and considers the historical data of the number of occupants and their activities to estimate the overall CO2 generation in indoor spaces. The results suggest that the model can effectively forecast CO2 dynamics with an absolute deviation of 40 ppm. However, it was observed that the analysis of the actual air exchange level could be compromised by several factors. [ABSTRACT FROM AUTHOR]

Digital twins represent a promising approach for sustainable building operations and management in the context of the carbon neutrality goals of the European Union (EU). Using OpenStudio, an opensource platform for building energy modeling, we demonstrated the creation and editing of building digital twins. OpenStudio provides a user-friendly interface and extensive simulation capabilities, allowing detailed and accurate modeling of building components and systems. Using OpenStudio Measures, users can automate tasks and customize simulation models to optimize the building performance. The process of creating a building digital twin involves collecting historical data and accurately representing the building geometry; materials; schedules; and heating, ventilation, and air conditioning (HVAC) systems. Challenges such as data availability and model accuracy highlight the importance of modeling practices. Editing the digital twin involves modifying the OpenStudio model files and EnergyPlus weather files to simulate different building operation scenarios. Python programming language opportunities were considered for digital twin file modification. The potential of digital twins lies in their ability to simulate future building conditions and optimize building system settings. By integrating digital twins with machine learning algorithms and connecting them directly to building management systems, optimal building control strategies can be automated, thereby reducing energy consumption and improving occupant comfort levels.

Introduction. Overflow air heating is a rarely used, but possessing a significant economic effect technology, the research of which is given insufficient attention. The subject of the research is the parameters of the thermal and humidity state of the air. The purpose of the research is to develop an algorithm describing the change of air state during the work of overflow air heating. Research objectives: to develop a model of air state change for overflow air heating; to apply the developed model and to formulate the recommendations on the organization of the overflow air heating for the warehouse building.Materials and methods. The research methodology is based on the traditional laws and equations of heat and mass transfer, aerodynamics and continuum mechanics; application of I–d diagram and the rules of construction of heat and humidity air treatment; principles of operation and design of ventilation equipment; sanitary and hygienic bases of ventilation design. Selection of climatic data, properties of materials, as well as the development of design solutions were carried out in accordance with the current regulatory documentation.Results. An algorithm including methods and models and describing the change in the state of the air for overflow air heating was developed. A model of air cooling in an unheated room was developed. It was tested on the example of a warehouse building with an unheated part. It confirmed the relevance of the developed model. Additionally, recommendations on the organization of optimal air distribution and selection of equipment were designed.Conclusions. The application of overflow air heating, calculated according to the proposed algorithm, will make it possible to increase the energy efficiency solutions in the field of ventilation of industrial buildings. The use of the algorithm implies that the organization of overflow air heating does not violate the technological process and requirements for fire and sanitary-hygienic safety of the building.

In this study, the sensitivity of a novel dehumidification requirement model (DehumReq) is analyzed to evaluate the effect of the predominant factors on the dehumidification needs of the greenhouses. The hourly dehumidification demand and sensitivity coefficient (SC) are estimated for three different seasons: warm (July), mild (May), and cold (November), by using the local sensitivity analysis method. Based on SC values, the solar radiation, air exchange, leaf area index (LAI), and indoor setpoints (temperature, relative humidity (RH), and water vapor partial pressure (WVPP)) have significant impact on the dehumidification needs, and the impact varies from season to season. Most parameters have a higher SC in summer, whereas solar radiation and LAI have a higher SC in mild season. The dehumidification load increases 4 times of its base value with increasing solar radiation by 200 W/m2, and the highest LAI (10) caused 5 times increment of the load. The changing of WVPP from its base value (1.5 kPa) to maximum (2.9 kPa) reduces the load 70% in summer. Air exchange was found to be the most crucial parameter because it is the main dehumidification approach that has a large range and is easily adjustable for any greenhouses. Sufficient air exchange by ventilation or infiltration will reduce the dehumidification load to zero in May and November and minimizes it to only nighttime load in July. For the other parameters, higher ambient air RH and indoor air speed will result in higher the dehumidification load; whereas higher inner surface condensation will result in lower dehumidification load. The result of this study will assist in the selection of the most efficient moisture control strategies and techniques for greenhouse humidity control.

An increase in warming in the Arctic relative to the rest of the Northern Hemisphere or the globe continues attracting attention, despite the large amount of research being conducted. Possible causes of the Arctic amplification have been considered and continue to be discussed in many articles and reviews. In this article, for the first time, a quantitative assessment of the role of atmospheric transports in the formation of variability and trends in the mean near-surface air temperature (SAT) in the Arctic and at adjacent latitudes of the Northern Hemisphere is carried out and an analytical description of amplification in high latitudes is proposed. For the study, data from NCEP and ERA5 reanalyses for 1989–2020 and a representation of the set of events of air exchange between latitudes in a simple hemispheric atmospheric model under constant conditions at the boundaries, on the basis of which analytical expressions are obtained for the standard deviation ratios (SDRs) and temperature trends in neighboring areas. The degree of closeness between the empirical and model ratios of SDR and trends is taken as a contribution measure of air exchange to the increase in SDR and trends during warming. It has been found that the exchange between the polar and adjacent regions reaches lower latitudes as the polar region expands from 70° N up to 60° N. The latitude to which the polar air propagates on average decreases with the trend taken into account in the SDR, which confirms the effect of warming on the increase in air mass exchange. The model value of the increase in the average air temperature trend in the polar region of an isolated homogeneous atmosphere above the hemisphere relative to the trend in the adjacent region is determined by the ratio of their areas multiplied by the ratio of the trend determination coefficients. An increase in the temperature trend in the polar region of the real atmosphere, according to the NCEP and ERA5 reanalyses for 1989–2020, was compared with the model value, thereby assessing the contribution of air mass exchange to the increase in the temperature trend in the polar region. It was found that the exchange explains 54% of the increase in the air temperature trend (Arctic amplification) in the region of 90–60° N on average per year and 66% in the cold year part relative to the rest of the Northern Hemisphere. If we take into account the established southern boundary of air mass exchange between the polar and adjacent regions, then the amplification of an air temperature trend in the area of 90–60° N relative to the trend in the adjacent area, with which the exchange of air masses occurs, will almost completely (by 93% on average per year) be the result of exchange and, in the area of 90°–70° N, it will mostly be the result of exchange (by 74% on average per year). [ABSTRACT FROM AUTHOR]

Featured Application: Revealing the airflow exchange mechanism between different floors generated by the up and down movements of elevator cars is significant guidance for building airflow environment design and preventing infectious disease transmission. An elevator shaft provides passage for air exchange across floors and thus imposes infectious disease transmission risk. The moving elevator car generates positive air pressure in the shaft section to which the car approaches, while negative air pressure is generated in the section where the car leaves away. This investigation adopted computational fluid dynamics (CFD) to model the exchange airflow between the lobbies of each floor and the shaft accompanying the car movement. Dynamic distributions of the air pressure, velocity, and airborne pollutant concentration inside both the shaft and the lobbies were solved. The modeling results were verified with some experimental test data. The results revealed that the alternatively changed air pressures inside the shaft while the car was moving caused significant airflow exchange via the clearances of the protecting doors and, thus, the transmission of airborne pollutants across floors. The sudden changes in the airflow rates could be due to the elevator car passing by the protecting door's opening on the concerned floor or the generated water hammer when the car was parked. To minimize the transmission of airborne pollutants across floors, the pressures inside the shaft must be better controlled, and the clearance of the elevator's protecting doors shall be further minimized. [ABSTRACT FROM AUTHOR]

Freestanding high tunnels are cost-effective, plastic film-covered growing structures that use very little to no modern environmental control technology. Natural ventilation is used to control temperature and humidity. Typically, ventilation openings are created along the sides by manually rolling up a section of the plastic film cover. While common on greenhouses, roof vents are not typically part of high tunnel designs used in the United States. This paper focuses on high tunnel ventilation during the summer, when maximizing the air exchange rate results in a low differential between inside and outside air temperatures. Computational fluid dynamics (CFD) simulations were used to evaluate the effects of several roof vent designs on the air flow rate through the high tunnel and the inside air temperature. The CFD models were developed and validated using environmental data collected at the Pennsylvania State University High Tunnel Research and Education Facility (Rock Springs, PA, USA). Five ventilation designs were simulated using a commercial CFD software package that was augmented with a radiation and crop architecture model. A root mean square error of 0.87 °C was found between the measured and simulated high tunnel temperatures (n = 144). The designs with roof vents were found to increase mass-based ventilation rates through the high tunnel by 20% to 78%. However, they did not lower inside air temperature more than 0.1 °C compared to the traditional design with roll-up side vents only. Additional research is needed to evaluate whether the control of other environmental parameters and weather conditions warrants the use of high tunnel roof vents, especially for humidity control and the combination of high temperature with low wind speed conditions.

Introduction.It is necessary to learn the wind speed distribution and its impact on facades to study the aeration characteristics of a built-up area. An important task is to assess an increase in the heat loss from a building. In addition, the building itself, its shape and location have a significant impact on the nature of the air flow. The wind speed and direction change near a building; there is strong eddying around it, depending on the shape in plan and the volumetric-spatial solution. A built-up area, accommodating different layouts of buildings, also affects the nature of the air flow.Materials and methods. Methods of theoretical, field studies of the aeration of buildings were adopted to identify the influence of different terrains on the nature of air flows. Domestic and foreign methods of scientific research have been analyzed. The methodology that allows predicting the aeration pattern in curtilages has been developed.Results. Approaches to the problem of improving the environment in terms of studying methods of aerodynamic calculations, used in structural aerodynamics, are considered. The purposeful statement of theoretical and experimental researches, focused on developing an effective method for the calculation of natural aeration of buildings is outlined. The intensity of air exchange between indoor and outdoor environments under the wind pressure, wind loads on buildings, aeration of premises, heat losses from infiltration, or air leakage through enclosing structures were identified. The designed model, simulating the formation of a circulation zone for various dimensions of buildings, wind flow velocities, and slope steepness values allows projecting the aeration in curtilages.Conclusions. The proposed calculation method can be used to project the aeration in curtilages and identify windless regions on the windward side of a building; it is also possible to identify the amount of air flowing in and out through the opposite windward and windward openings in the walls of buildings when they are located in the windward side of a mountain, the aeration of rooms, wind loads on buildings, and heat losses from infiltration.

Freestanding high tunnels are cost-effective, plastic film-covered growing structures that use very little to no modern environmental control technology. Natural ventilation is used to control temperature and humidity. Typically, ventilation openings are created along the sides by manually rolling up a section of the plastic film cover. While common on greenhouses, roof vents are not typically part of high tunnel designs used in the United States. This paper focuses on high tunnel ventilation during the summer, when maximizing the air exchange rate results in a low differential between inside and outside air temperatures. Computational fluid dynamics (CFD) simulations were used to evaluate the effects of several roof vent designs on the air flow rate through the high tunnel and the inside air temperature. The CFD models were developed and validated using environmental data collected at the Pennsylvania State University High Tunnel Research and Education Facility (Rock Springs, PA, USA). Five ventilation designs were simulated using a commercial CFD software package that was augmented with a radiation and crop architecture model. A root mean square error of 0.87 °C was found between the measured and simulated high tunnel temperatures (n = 144). The designs with roof vents were found to increase mass-based ventilation rates through the high tunnel by 20% to 78%. However, they did not lower inside air temperature more than 0.1 °C compared to the traditional design with roll-up side vents only. Additional research is needed to evaluate whether the control of other environmental parameters and weather conditions warrants the use of high tunnel roof vents, especially for humidity control and the combination of high temperature with low wind speed conditions. [ABSTRACT FROM AUTHOR]

An elevator shaft provides passage for air exchange across floors and thus imposes infectious disease transmission risk. The moving elevator car generates positive air pressure in the shaft section to which the car approaches, while negative air pressure is generated in the section where the car leaves away. This investigation adopted computational fluid dynamics (CFD) to model the exchange airflow between the lobbies of each floor and the shaft accompanying the car movement. Dynamic distributions of the air pressure, velocity, and airborne pollutant concentration inside both the shaft and the lobbies were solved. The modeling results were verified with some experimental test data. The results revealed that the alternatively changed air pressures inside the shaft while the car was moving caused significant airflow exchange via the clearances of the protecting doors and, thus, the transmission of airborne pollutants across floors. The sudden changes in the airflow rates could be due to the elevator car passing by the protecting door’s opening on the concerned floor or the generated water hammer when the car was parked. To minimize the transmission of airborne pollutants across floors, the pressures inside the shaft must be better controlled, and the clearance of the elevator’s protecting doors shall be further minimized.

A field test was carried out in Koralmtunnel in order to enhance process understanding and to optimize the drainage system in a tunnel section that is complex in terms of hydrochemistry, water inflow and mineral (calcareous scale, iron ochre) and biological (microbial mats) deposits. The field test comprised three test fields with different system components and flow characteristics. The development of critical waters and deposits was recorded by continuous measurements of relevant water and air parameters by means of autonomous sensors/data loggers. Furthermore, the components were "forensically" examined with respect to scale formation. The experiments show the crucial importance of gas exchange (CO2, oxygen ingress), filling level (flow geometry/regime), residence time of waters and water‐air interaction in the drainage system. The type, material consistency, and amount of scale and biofilms depend significantly on specific gradients. Floating scale crusts formed in stagnant sections, biofilms and iron ochre deposits of soft consistency formed at higher flow rates. Seepage packs and siphons turned out to be potential sediment traps with decreasing flow‐through with no access. Drainage hoses and dimpled membranes tend to be beneficial because they can prevent air exchange at relatively high flow rates. High CO2 partial pressure within these components (measured and modeled) inhibits carbonate precipitation. The drainage system is locally designed as a series of direct cross‐drains with simple flow paths, restricted air exchange, precautionary cleaning access, and optional water hardness stabilization (liquid conditioning). [ABSTRACT FROM AUTHOR]

The aim of the article was to elaborate a single system of hygienic evaluation of welding materials in accordance with the standards of DSTU ISO 15011 series and justify the appropriateness of its application. The essence of the problem of a correct comparative hygienic evaluation of domestic and foreign welding materials is explained. The methods of improvement of the procedure of studying indices of levels of emissions and chemical composition of welding fumes due to the application of DSTU ISO 15011 standards are presented. The scope of the requirements of each of the standards of the specified series is characterized. The main procedures of hygienic evaluation of welding materials, their specifics and sequence, as well as the main indices, based on which it is carried out, are highlighted. [ABSTRACT FROM AUTHOR]

The main issue highlighted in the given paper is deviation of microclimate parameters from regulatory values due to improper distribution of air flows in living rooms of blocks of flats. The present work is aimed at obtaining a working mathematical model of natural ventilation system operation, and its further studying for optimization or modernization. The analysis of regulatory documents, research works of national and foreign scientists, developments in the field of natural ventilation and ventilation of residential buildings in general, as well as specific field experiments describing or mentioning similar problems has been carried out. The author’s mathematical model of air exchange in the living room has been presented and analyzed. The boundary conditions in the mathematical model were set as air flow rate and air temperature, and the temperature on the surface of the heater. The features and patterns of air flow distribution inside the room were determined, obtained as a result of mathematical modeling. The distributions of air velocity in the volume of the room were given. Similar problems were indicated for premises of residential buildings of a different functional purpose. Amendments to the existing standards, as well as technical solutions were proposed.

The aim of the study was to present the scale of greenhouse gas emissions from animal production, and to provide test results from different housing systems. In three free stall buildings, two with slurry in deep channels and one with cattle in cubicles staying on shallow litter concentration of ammonia and carbon dioxide were measured in summer season by using dedicated equipment from Industrial Scientific Research. Air exchange was calculated on the base of balance carbon dioxide method. This method was used in order to estimate the air flow rate. Concentrations of ammonia and CO2 were measured as the base for air exchange and ammonia emission rates. Ammonia emissions were product of ammonia concentration and air exchange rate. Temperature and relative humidity were measured to establish microclimate conditions in buildings tested to show the overall microclimatic situation in buildings. Differences between ammonia emission rates were observed in both housing systems. The highest ammonia emission rate was equal to 2.75 g·h−1·LU−1 in well-ventilated cattle barn with the largest herd size. [ABSTRACT FROM AUTHOR]

Introduction. The purpose of the article is to assess the quality of indoor air in university by measuring the concentration of suspended particles. In the Russian Federation, the rationing of maximum permissible concentrations of undifferentiated dust in atmospheric air depends on particle size.Materials and methods. The research carries out measurements of suspended particles concentrations in the air of six audiences in the Moscow State National Research University of Civil Engineering (NRU MGSU).Results. The obtained results of concentration measurements (particle/m3) are recalculates in mg/m3, and compared with threshold values of maximum one-time concentrations of suspended particles.Discussion and conclusions. In calm weather, air pollution by suspended particles in the surface layer practically does not affect the quality of internal microclimate, which is associated with significant decrease of dust concentration in height and insufficient air exchange in natural ventilation systems.

Energy saving policy conducted all over the world and in Belarus, particularly, leads to revision of technical standard and legal acts on thermal protection of buildings. Gradual increase of resistance to heat transfer of enclosing structures reduces transmission heat losses however expenses on infiltration air heating remain unchangeable. Due to this their portion in overall heat balance of residential buildings is gradually increasing: up to thermal rehabilitation of a building the portion constitutes 30 %, after this process the portion is equal to 53 %. In order to find methods for reduction of heat losses the paper considers an origin of the current standard for inlet air which is equal to 3 m³/h per 1 m² of residential area. It has been shown that the given value has been determined on the assumption of air exchange which is required for assimilation of carbon dioxide and residential area standard per one person. The required air exchange can be reduced up to 1.5 m³/(h×m²) due to improvement of population living conditions and increase in provision of residential area. Calculations have also shown that the given reduction makes it possible to enhance energy efficiency class of a building and decrease portion of heat losses on heating inlet air in overall heat balance. The paper has also revealed that rational light location on both sides permits to reduce a specific index of heat energy consumption for heating and ventilation of a residential building. Determination of outlet air consumption for kitchens has been considered simultaneously with determination of inlet air consumption. It has been ascertained that in order to support combustion process and removal of combustion products consumption of outlet air must constitute 10–20 m³/h according to type of gas stove. Due to the fact that windows can not support the proposed and existing air exchanges they must be completed with plenum valves.

Purpose. Apply integrated approaches for the air exchange rate determination based on CO2 concentration in educational and residential buildings of Ukraine. Methods. Taking into account variability of building's visitors and occupants operational and behavioral features experimental and calculated determination of the air exchange rate are considered. Results. Recommendations for providing comfort conditions in terms of air quality in the considered objects premises, recommendations on the premises operating conditions, ventilation schedule. Scientific novelty. The comprehensive approach to in-depth analysis of energy consumption has been developed, procedures for assessing the air quality and the level of air exchange in buildings have been improved taking into account the variability of operating conditions. The practical significance. Experimental studies of changes in CO2 concentration were conducted in three schools, in higher education institution and in residential building. The research results allowed to establish the actual level of CO2 concentration and air change rate under different operational and behavioral conditions in buildings during working hours, subject to comfortable conditions, and during non-use hours. The research results also help to determine the dynamics of changes in the studied factor over time under the building performance indicators influence. The obtained results allow to provide recommendations on ensuring the quality of indoor air exchange and on providing comfort working, studying and living conditions. The use of experimental and calculated air exchange rate values for various premises would allow to avoid in mathematical modeling the overestimation of the level of buildings energy consumption, which arises when standard air change rate values is using. So the obtained results allow to approximate more accurately the mathematical modeling results of buildings energy efficiency to the actual conditions and help to choose the optimal schedule for the building engineering networks managing considering comfort conditions with intermittent operation. [ABSTRACT FROM AUTHOR]

Copyright of Architectus is the property of Oficyna Wydawnicza Politechniki Wroclawskiej and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Many old public buildings in Central and Eastern Europe are characterized by low energy efficiency and often lack of mechanical ventilation. The general trends are aimed to improve the energy efficiency of the building sector and to provide comfort conditions. The indoor air quality can be determined based on the CO2 concentrations. In the article, a complex approach to the definition and analysis of data on the indoor CO2 concentration and the air exchange rate in educational institutions at natural air exchange and in the absence of mechanical air circulation was implemented. Educational institutions in Kyiv have been considered. The study of the CO2 concentration of indoor and outdoor air of three typical schools of mass development in the 80 s, as well as the training building of Igor Sikorsky KPI, was carried out. Experimental determination of the background CO2 concentration during the day next to the considered objects showed that the background concentration of CO2 is in the range of 400-420 ppm. Measurements of the CO2 concentration distribution were carried out after classes throughout the classroom area, according to which the difference between the values at the level of the working area was 30...180 ppm. It was found that the concentration of CO2 varies during classes between 700-1100 ppm. During the break, the CO2 concentration decreases to 500-1000 ppm, depending on the type of ventilation. Experimental data on the dynamics of changes in the indoor CO2 concentration are used to determine the air exchange rate based on balances of air flows and CO2. It is shown that the number of present persons influences the indoor CO2 concentration more significantly than the air exchange rate. On the example of an experimental study of the CO2 concentration in the classrooms for high school students it was found that the air exchange rate during the classes is in the range of 0.4...0.75 h-1. During breaks the air exchange rate increases to 2.9-3.5 h-1. For the range considered, the weighted average air exchange rate is 0.8 h-1, and even with forced airing, the air exchange rate is insufficient to ensure acceptable CO2 concentration. For the training building of Igor Sikorsky KPI a field experiment was carried out to determine the dynamics of changes in CO2 concentration in time and on the basis of it the air exchange rates for representative classrooms were determined. The concentration of CO2 ranged from 500 to 2000 ppm and increases by 350-850 ppm depending on the use and location of classrooms. Based on experimental data, the air exchange rate for the training building of the education institution is in the range of 0.35-0.7 h-1. During the periods of airing the air exchange may increase by 0.45 h-1, but this does not allow reaching the standard value. When analyzing the obtained results, simulation models of natural air exchange of the examined classrooms were used on the basis of the improved ASHRAE method. The natural air exchange rate based on simulations is in the -0.8...0.5 h-1 range. Negative values are explained by exfiltration, which is typical for the upper floors. Not only the comfort and condition of the building envelope, but also the total energy consumption of the building depend on the actual level of air exchange rate. In the total energy balance the ventilation component is 30-60%. Further use of the obtained results can be connected with monitoring of the actual level of air exchange rate and its consideration during complex modernization or implementation of the ventilation systems with heat recovery in the premises of educational institutions. [ABSTRACT FROM AUTHOR]

The most common ventilation system in residential buildings in Ukraine is natural ventilation. In recent years, due to increased tightness of structures, an increase in the content of synthetic finishing materials in them, the quality of microclimate parameters deteriorated. One of the measures to improve the parameters of indoor air in residential buildings is the use of mechanical inflow and exhaust ventilation system. In this article the regulatory documents concerning the design of ventilation systems in Ukraine and Estonia and the requirements for air exchange in residential buildings are considered. It is established that the existing normative documents in Ukraine are analogous to European norms, which allow design the system of ventilation of residential buildings according to European standards. However, the basis for the design of ventilation systems in Ukraine is the national standards, in which mechanical ventilation, unfortunately, is provided only for the design of high-rise buildings. To maintain acceptable microclimate parameters in residential buildings, it is advisable for designers to apply the requirements for designing ventilation systems in accordance with European standards.

Objectives. The aim of the study is to analyse the effect of the design and methods for heating the ventilation duct of a buoyancy- driven system on the formation of free convective air currents in it.Methods. The study of free convection under the conditions of interior problem was carried out using the CFD software, based on the finite volume method with unstructured grid. Ansys Fluent software was used as a calculation tool in the study, due to its having a high convergence of numerical solutions offering full-scale measurements of convective currents.To evaluate the reliability of the results obtained, a validation procedure was carried out, allowing us to determine how accurately the selected conceptual model describes the investigated flow through a comparison of experimental and numerical data.Results. The results of numerical modelling of free convective currents occurring in the heated channel of the ventilation system of the top floor of a multi-storey residential building are presented in the article. In the course of the study, the air velocity at the entrance to the ventilation duct was found to depend on the calculated temperature difference θ ˚C for various heating methods. A gradual increase in the discrepancy between the numerical simulation and experimental results is observed if the calculated temperature difference > 20 ° C. This phenomenon is due to the fact that with increased duct temperature, it is quite difficult to achieve even heating under actual conditions; this is especially noticeable when considering the variant when the vertical part of the vent duct and the take-off are both heated. The maximum deviation of the results is 4.4%. The obtained velocity profiles in the calculated sections indicate the impact of the ventilation take-off on the nature of the air flow motion.Conclusion. One of the drawbacks of the existing systems of natural ventilation of residential buildings is the low efficiency of work in the warm and transitional periods of the year, especially in bathrooms. The use of buoyancy-driven ventilation with vertical heating of the vent duct combined with the take-off allows a stable air exchange in the rooms to be provided.

The worldwide trend toward the construction of high-rise buildings with high energy efficiency highlights the role of building materials as a source of indoor radon in the modern urban environment. The aim of the study is to analyze the relationship between the Ra-226 activity concentration in building materials and indoor radon concentration using the example of multi-story buildings in Ekaterinburg. Measurements of the activity concentration of natural radionuclides in building materials were carried out using a new non-destructive method. A radon survey conducted early provided the data on indoor radon concentrations in the same apartments. The obtained Ra-226 activity concentrations in building materials in high-rise buildings were found to be relatively low, ranging from 9.1 to 51 Bq/kg. The typical radon entry rate by diffusion from building materials for modern Russian multi-story buildings can be accepted as equal to 0.5 Bq/(m3∙h) per 1 Bq/kg of Ra-226 activity concentration. Ra-226 in building materials has been shown to be a primary source of indoor radon in modern high-rise buildings, where this factor can cause indoor radon concentrations above the reference level of 100 Bq/m3 at low air exchange rates. The activity concentration of Ra-226 in building materials should be considered a separate parameter for regulation within the national radiation protection systems. [Display omitted] • Indoor Rn versus Ra-226 in building materials are investigated in high-rise buildings. • Rn diffusion entry rate is 0.5 Bq/m3/h per 1 Bq/kg Ra-226 in energy efficient buildings. • Ra–Rn diagram is created for various air exchange rates in multi-stores buildings. [ABSTRACT FROM AUTHOR]

Recently, there has been a great increase in the importance of issues related to energy efficiency [...]

The paper considers reasons of internal air parameter mismatch in warm season of the year for public building premises having large area of translucent structures. The main reason of uncomfortable air environment is an underestimated value of air supply volume due to air exchange calculation according to multiplicity factor or air exchange rate per one person which are determinative values only for cold period and transient conditions. In other words multiplicity factor and air exchange rate do not take into account equipment abundance in modern offices and heat input of the office equipment is rather significant value. The paper contains an analysis and comparison of the existing air exchange rates for the Republic of Belarus, Russian Federation, European countries and USA. Calculation of heat input and air exchange for public building premises during warm season of the year for assimilation of evident heat excess has been made at various orientations of curtain walls. The paper provides structure of heat input into premises. The required rate of air supply volume per one person has been determined on the basis of air exchange and it has been compared with the existing air exchange rate. The required rate averagely exceeds the standard one by 12-fold. But this does not mean that there is necessity to increase the rate in such a way because it entails an increase in capital and operational costs. In this connection the paper reviews variants for improvement of micro-climate in the building premises with large area of translucent structures: automatic regulation of heat transfer in heating appliances during cold period of the year; usage of air conditioning and increase in temperature difference of input and output air during warm period.

Nowadays energy resources saving problem is extremely important, especially for heating in buildings. The aim of the paper is to simulate indoor air temperature depending on heating rate, solar heat gains, infiltration rate and outdoor air temperature. In order to get the desired result dynamic model of the room was created in EnergyPlus program, which is a widely used building energy simulation program. Based on the developed model and modified IWEC weather data the series of simulations were performed for inside air temperature calculation depending on internal and external factors changes. The analysis of individual and aggregate factors influence on inside air temperature change is performed. The multiple linear regression model structure is analysed and background of factors change over the past three days is chosen. Regression models for daily average inside air temperature dependence on each of the factors and all of them are created. Results verification is performed for prognosis values of temperature in comparison with simulation for December weather data from IWEC. Regression models can be used for complex analysis of problems connected with selecting heating rate, influence assessment of climatic conditions on indoor air temperature, qualitative and quantitative heating system regulation.

The relevance of the research is caused by the necessity to maintain the effective heat insulation of engineering lines at their underground laying in a zone of permafrost soils. The aim of the research is to predict temperature fields in building envelopes using the developed program complex, and in ground under a building and near it in the climatic conditions of Yakutsk; work out recommendations for effective warming of the engineering networks laid underground. Methods. The authors propose physical-mathematical model of the thermal state of underground taking into account the air exchange and design features of construction in permafrost conditions Numerical solution of the problem using the developed software package is made. Results. The authors developed the computational scheme of predicting temperature fields in building envelopes, in the ground under a building and near it in climatic conditions of Yakutsk. Numerical simulation of temperature fields' change of the basic building envelopes and the soil during a year was carried out. The comparative analysis of the obtained results with the empirical ones shown their satisfactory coordination. The authors selected the effective thickness of a warming layer of engineering lines at their underground laying in a zone of permafrost. Two-dimensional non-stationary symmetric problem of heat conductivity in semi-limited mass with a set of boundary conditions was considered. The authors proposed physical-mathematical model of heat exchange in a technical underground of a building taking into account the influence of air exchange and snow cover outside of a building and carried out a series of field experiments in Yakutsk to define the types of soil in a zone of construction. The results of numerical simulation showed that the warmth coming through the ceiling over technical underground and through the walls, does not actually influence the temperature of soils both under the building, and at distance from it. According to the carried out researches, temperatures in soil mass outside the construction zone are equal to their natural values. Comparison of results of the numerical solution with the solution obtained from other computer programs (for example, Temper-3D) showed their satisfactory coordination. Nevertheless, the program Temper-3D does not consider air exchange in a technical underground, which plays an essential role in formation of temperature fields in building envelopes and soil.

The relevance of the research is caused by the necessity to ensure the efficiency of attic floor thermal shield when repairing long life buildings with nonstandard roofing. The aim of the research is to solve the problem of occurrence of "dew point temperature" conditions on to enclosure envelope surface when repairing residential building with non typical roofing system; to design the considerations relating to removal of moisture condensation cause from building envelope by placing the effective thickness mineral wool boards in front of attic ventilation drain. Methods: the proposed physic-mathematical model of attic floor space thermal state considering air interchange and design features of nonstandard roofing. Numerical solution of stated problem with the use of the developed software. Results: The author has developed the computational scheme of influence of heat engineering factors and attic air exchanges in non-ty-pical roofing on temperature pattern in its enclosing structures. The effective underlining thickness of attic ventilation drain was selected. It allows excluding the perspiration water conditions on building envelope surface inside accommodations without any additional actions.

This work concerns the performance analysis of the sensors contained in a victim detection system. The system is a mobile platform with gas sensors utilized for real time victim localization in urban environments after a disaster has caused the entrapment of people in partially collapsed building structures. The operating principle of the platform is the sampling of air from potential survival spaces (voids) and the measurement of the sampled air’s temperature and concentration of CO2 and O2. Humans in a survival space are modelled as sources of CO2 and heat and sinks of O2. The physical openings of a survival space are modelled as sources of fresh air and sinks of the internal air. These sources and sinks dynamically affect the monitored properties of the air inside a survival space. In this paper, the effects of fresh air sources and internal air sinks are first examined in relation to local weather conditions. Then, the effect of human sources of CO2 and sinks of O2 in the space are examined. A model is formulated in order to reliably estimate the concentration of CO2 and O2 as a function of time for given reasonable entrapment scenarios. The input parameters are the local weather conditions, the openings of the survival space, and the number and type of entrapped humans. Three different tests successfully verified the presented theoretical estimations. A detection system with gas sensors of specified or measured capabilities, by utilizing this model and based on the expected concentrations, may inform the operator of the minimum required presence of humans in a survival space that can be detected after “some time”.

Currently, the rapid development of large-scale high-rise buildings using various project principles and building materials is developing. Depending on the purpose of these buildings, different rooms have different technological processes and use different types of products and appliances. Therefore, when designing a building's ventilation systems, it is important to take into account the uneven distribution of air in separate rooms. In order to accurately determine the air circulation in the premises, it is necessary to create a heat and humidity balance for each room and to keep the microclimate parameters in each room. Excess heat exits in public and residential buildings is key indicator of air regulation. The following aspects should be taken into account when arranging the air exchange: the air being absorbed by the room air must be perfectly mixed; the thrust air is evenly distributed in the room; there should be no local suction during airflow. According to the sanitary and hygienic standards, the air exchange, which is directly exposed to the working area and absorbed under the ceiling, is considered to be the best. The article analyzes the main ventilation methods and shows the method of reporting air exchange rates. [ABSTRACT FROM AUTHOR]

An improved understanding of particle movement in ventilated rooms would help reduce airborne disease transmission in healthcare facilities. More empirical data are needed on the movement of small particles in rooms to investigate effects of air relative humidity (RH) and air exchange rates. In this study, small particles were injected into a reduced-scale room, and the particulate mass (PM) concentrations were measured at 12 interior locations in the room as well as at the ventilation air exhaust. The particulates were certified 'plain surface' melamine (polymethylenemelamine) microspheres (1.51 g cm−3 density; 1.98 µm diameter) with hydrophilic surfaces. Experiments were conducted using three conditions of ventilation rate (4, 6 and 8 air changes h−1 (ACH)) and two RH levels (35% and 70%). Increasing the ventilation rate did not significantly decrease PM concentrations in the interior room area, but significantly decreased exhaust air PM concentrations. RH did not affect room PM concentrations for any of the ventilation rates. RH did not affect exhaust air PM concentrations for the 4 ACH or 8 ACH ventilation rates, but the exhaust air PM concentrations were higher at low RH than at high RH for 6 ACH. Regardless of ventilation rate and RH, PM concentrations were uniform throughout the room interior (potentially occupied) zone. [ABSTRACT FROM AUTHOR]

Naturally ventilated cold attics are traditional in many Danish single-family homes. The moisture balance of these attics is dependent on sufficient ventilation for removal of excess moisture. Moisture is generated in the dwelling below, and transported to attic spaces through convection and diffusion. Therefore, airtight ceilings are vital for reduction of excess moisture, which may yield mould growth in the attic. If mould spores migrate to the dwelling it can cause risk of health concerns for occupants. The presents study includes analysis of tracer gas and temperature/relative humidity measurements, in 30 dwellings/attics. The measurements yielded results of both air change rates in attics and dwellings, as well as air exchange between the two zones. Four of 30 houses, met the recommended air change rate of 0.5 h−1, and only in summer. The air change rate in the attics was found to be higher, and with larger variation compared to the dwelling. Visible mould growth was found in three attics, which all exhibited low air change rates. Air exchange between zones occurred in houses both with and without vapour barriers. The downward air exchange in summer, was however slightly larger in cases without vapour barriers. These results highlight the importance of airtight ceilings for both dwelling and attic performance.

The article contains the analysis of experimental ventilation measurement in selected classrooms of the Elementary School Štrba. Mathematical model of selected classroom was prepared according to in-situ measurements and air exchange was calculated. Interior air temperature and quality influences the students ´ comfort. Evaluated data were compared to requirements of standard (STN EN 15251,2008) applicable to classroom indoor environment during lectures, highlighting the difference between required ambiance quality and actually measured values. CO2 concentration refers to one of the parameters indicating indoor environment quality.

The direct measurement of emissions from naturally ventilated dairy barns is challenging due to their large openings and the turbulent and unsteady airflow at the inlets and outlets. The aim of this study was to quantify the impacts of the number and positions of sensors on the estimation of volume flow rate and emissions. High resolution measurements of a naturally ventilated scaled building model in an atmospheric boundary layer wind tunnel were done. Tracer gas was released inside the model and measured at the outlet area, using a fast flame ionization detector (FFID). Additionally, the normal velocity on the area was measured using laser Doppler anemometry (LDA). In total, for a matrix of 65 × 4 sensor positions, the mean normal velocities and the mean concentrations were measured and used to calculate the volume flow rate and the emissions. This dataset was used as a reference to assess the accuracy while systematically reducing the number of sensors and varying the positions of them. The results showed systematic errors in the emission estimation up to +97%, when measurements of concentration and velocity were done at one constant height. This error could be lowered under 5%, when the concentrations were measured as a vertical composite sample.

Residential inter-zonal (e.g., between rooms) ventilation is comprised of fresh air infiltration in and exfiltration out of the whole house plus the “fresh” air that is entering (and exiting) the room of interest from other rooms or areas within the house. Clearly, the inter-zone ventilation rate in any room of interest will be greater than the infiltration/exfiltration ventilation rate of outdoor air for the whole house. The purpose of this study is to determine how much greater the inter-zonal ventilation rate is in typical U.S. residences compared to the whole house ventilation rate from outdoor air. The data for this statistical analysis came from HouseDB, a 1995 EPA database of residential ventilation rates. Analytical results indicate that a lognormal distribution provides the best fit to the data. Lognormal probability distribution functions (PDFs) are provided for various inter-zonal ventilation rates for comparison to the PDF for the whole house ventilation rates. All ventilation rates are expressed as air change rates per hour (ACH). These PDFs can be used as inputs to exposure models. This analysis suggests that if one were performing a deterministic analysis for unknown housing stocks in the U.S., a default mean and median ACH values of 0.4/hr and 0.3/hr, respectively, for whole house ventilation would be appropriate; and 0.7/hr and 0.6/hr, respectively, for inter-zonal ventilation. [ABSTRACT FROM AUTHOR]