Air Tightness Research Articles

Analysis of airtightness performance of residential areas in Mediterranean climate: Balıkesir houses

Airtightness is one of the crucial physical characteristics of building envelope that affect the building thermal performance and energy consumption. The airtightness of the building is influenced by the quality of workmanship and various design parameters such as window/wall ratio, type of joinery, size of the usage area, wall material, and thermal insulation on the external wall. In this study aiming to determine the airtightness performance of buildings in the Mediterranean climate of Balıkesir houses, airtightness conditions of 43 different houses were determined by blower door test measurement. The air exchange rate (n50) values of 43 houses/residences were obtained between 1.94 and 49.02 h−1 and compared with the current various standards. The effect level of the design parameters on the air tightness of the building envelope was obtained as a result of the analysis performed with analysis of variance and post hoc methods. According to the analysis, joinery type was the most effective design parameter in terms of airtightness, followed by usage area and transparency of facades. The result will help in deciding on the design parameters affecting the airtightness of the building envelope for energy efficiency in the Mediterranean climate.

Study on the Influence of Walnut Shell Coarse Particles on the Slurry Permeation and the Air Tightness of Filter Cake.

Slurry shields rely on the formation of a compact filter cake to maintain excavation face stability and ensure construction safety. In strata with high permeability, significant slurry loss occurs, making filter cake formation and air tightness maintenance challenging. In this study, light organic walnut shell was selected as an additive coarse particle material for slurry. Slurries incorporating two types of coarse particles, sand and walnut shell, were prepared, and tests on slurry permeation and air tightness of the filter cake were conducted in three different strata. The results indicate that the addition of coarse particles effectively improves filter cake formation and air tightness in high-permeability strata. It is essential to use graded particles in highly permeable strata, with controlled maximum and minimum particle sizes. As the content of coarse particles increases, the air tightness of the filter cake initially increases and then decreases. Notably, the air tightness of filter cakes containing walnut shell is superior to those containing sand. Replacing sand with walnut shell as a slurry plugging material enhances filter cake quality in high-permeability strata. For highly permeable strata with a permeability coefficient greater than 1.0 × 10-3 m/s, an addition of 30 g/L to 40 g/L is recommended.

A Review of Three-Dimensional RGB Images and Drone Thermal Camera Images Merged for Building Information Modeling for Energy Audit

The site visit is the core of the energy audit, where you inspect, measure, and document the building's energy performance and efficiency. Various tools and techniques may be used for this purpose, such as a walk-through survey to observe the building's condition, a blower door test to measure air tightness and infiltration, a thermographic scan to detect heat loss and gain, a lighting audit to assess lighting quality, quantity, and controls, a plug load audit to quantify appliance and equipment energy consumption, a submetering or data logging system to monitor specific systems or zones, and a power quality analyzer to measure electrical parameters and harmonics. Additionally, it is important to interview the building's owner, manager, and occupants in order to gain their feedback and suggestions on energy performance and issues. This paper review of how a drone can help in the energy audit of a building using thermal images and RGB images from thermal camera which will be use in Building Information Modelling (BIM). There are a variety of relevant literatures that serve as sources of inspiration for the conduct of this study. One example is the utilization of teleoperated helicopters that are equipped with an infrared thermal camera. These helicopters are intended to be investigated for energy audits in order to readily assess the conditions of the structure. More improvements will be made to the collected photographs, such as merging them with three-dimensional RGB images. This will allow for an exact determination of which area of the building need upgrading in order to reduce the amount of energy that is emitted; this notion is similar to that of finite element analysis.

Airtightness evaluation of lined caverns for compressed air energy storage under thermo-hydro-mechanical (THM) coupling

Large-scale compressed air energy storage (CAES) technology can effectively facilitate the integration of renewable energy sources into the power grid. The airtightness of caverns is crucial for the economic viability and efficiency of CAES systems. This paper presents a new thermo-hydro-mechanical (THM) model for investigating the effects of complex thermodynamic changes on air leakage in concrete-lined rock caverns. The model is validated using field measurement data, numerical simulations, and analytical solutions. Subsequent simulations were conducted to analyze air leakage, pore pressure, and leakage range under various operating conditions. Finally, the impacts of different parameters on air tightness were assessed. The results indicate that the daily air leakage mass percentage (TDALMP) in the concrete-lined CAES cavern is 0.60 % under the operating pressure of 4.5–10 MPa, which meets the tightness requirement. The permeability of the lining is a key parameter for airtightness, in this case, the permeability of the concrete lining cannot exceed 1 × 10−19 m2. The daily air leakage rate can be reduced by modestly increasing the cavern radius, lowering the temperature of the injected air, and decreasing the maximum operating pressure. These results can provide a reference for the study and construction of CAES caverns in similar projects.

Zirconia and Crofer Joint Made by Reactive Air Brazing Using the Silver Base Paste and Cu-Ti Coating Layer.

This study proposes a method to enhance the airtightness of the joint between the ZrO2 and Crofer alloy using coating technology. With the aid of vacuum sputtering technology, a titanium-copper alloy layer with a thickness between 1.5 μm and 6 μm was first deposited on the surface of ZrO2 and Crofer, respectively. The chemical composition of the deposited reaction layer was 70.2 Cu and 29.8 Ti in at%. Then, using silver as the base material in the reactive air brazing (RAB) process, we explore the use of this material design to improve the microstructure and reaction mechanism of the joint surface between ceramics and metal, compare the effects of different pretreatment thicknesses on the microstructure, and evaluate its effectiveness through air tightness tests. The results show that a coating of Cu-Ti alloy on the ZrO2 substrate can significantly improve bonding between the Ag filler and ZrO2. The Cu-Ti metallization layer on the ZrO2 substrate is beneficial to the RAB. After the brazing process, the coated Cu-Ti layers form suitable reaction interfaces between the filler, the metal, the filler, and the ceramic. In terms of coating layer thickness, the optimized 3 μm coated Cu-Ti alloy layer is achieved from the experiment. Melting and dissolving the Cu-Ti coated layer into the ZrO2 substrate results in a defect-free interface between the Ag-rich braze and the ZrO2. The air tightness test result shows no leakage under 2 psig at room temperature for 28 h. The pressure condition can still be maintained even under high-temperature conditions of 600 °C for 24 h.

Effect of brazing process on microstructure evolution and mechanical properties of Ti6Al4V/ZrO2 joints after laser surface treatment

Ti6Al4V alloy and ZrO2 ceramic have similar application fields and complementary properties. Brazing connections can broaden the application range. When using sealing glass with good air tightness, good electrical insulation, and low connection temperature to connect, the solder is difficult to wet on the metal surface. The traditional method is to oxidize the surface of the alloy at a high temperature, but the film is not uniform and the treatment time is long. In this study, nanosecond laser surface treatment was used as a prewelding pretreatment method to form a micro-nano structure on the surface and perform oxidation treatment. It is particularly important to select the brazing process. After the laser parameters and processing times were determined, the effects of different welding temperatures and holding times on the properties of the joints were compared, and it was found that there were regular changes. Finally, it is concluded that the maximum shear strength is 46 MPa when the welding temperature is 650 °C and the holding time is 30 min. Under this process, the performance of the joint significantly improved under the dual effects of mechanical bonding and metallurgical bonding. This study provides a new idea for the connection of metal and ceramic and has reference value for the selection of the brazing process.

Energy Losses or Savings Due to Air Infiltration and Envelope Sealing Costs in the Passivhaus Standard: A Review on the Mediterranean Coast

To obtain the Passivhaus Certificate or Passivhaus Standard (PHS), requirements regarding building envelope air tightness must be met: according to the n50 parameter, at a pressure of 50 Pa, air leakage must be below 0.6 air changes per hour (ACH). This condition is verified by following the blower door test protocol and is regulated by the ISO 9972 standard, or UNE-EN-13829. Some construction techniques make it easier to comply with these regulations, and in most cases, construction joints and material joints must be sealed in a complex way, both on façades and roofs and at ground contact points. Performing rigorous quality control of these processes during the construction phase allows achieving a value below 0.6 ACH and obtaining the PHS certification. Yet, the value can increase substantially with the passage of time: as windows and doors are used, opened, or closed; as envelope materials expand; with humidity; etc. This could result in significant energy consumption increases and losing the PHS when selling the house at a later point in time. It is therefore important to carefully supervise the quality of the construction and its execution. In this study, we focused on a house located in Sitges (Barcelona). The envelope air tightness quality was measured during four construction phases, together with the sealing of the joints and service ducts. The blower door test was performed in each phase, and the n50 value obtained decreased each time. The execution costs of each phase were also determined, as were the investment amortisation rates based on the consequent annual energy demand reductions. Air infiltration dropped by 43.81%, with the final n50 value resulting in 0.59 ACH. However, the execution costs—EUR 3827—were high compared to the energy savings made, and the investment amortisation period rose to a 15- to 30-year range. To conclude, these airtightness improvements are necessary in cold continental climates but are not applicable on the Spanish Mediterranean coast.

Airflow and Pressure Design Review of Modular Negative Pressure Wards

In the aftermath of the COVID-19 pandemic, the urgent need for the rapid deployment of healthcare facilities propelled the rise of modular construction using an infill approach. In these modular, negative-pressure wards, the design of indoor airflow and pressure plays a crucial role in meeting the ventilation strategies required for isolation facilities. Accordingly, this paper focuses on modular negative-pressure wards employing an infill construction method and proposes an appropriate spatial pressure distribution to address the problem of air tightness degradation due to leakage. This study analyzed the indoor airflow and pressure distribution of a unit module corresponding to an infill. It aimed to examine whether the pressure difference with the adjacent room is maintained and to assess its effectiveness in isolating contaminated air. First, the airflow rate of the heating, ventilation, and air conditioning system in the unit module was calculated to ensure that it would meet the performance criteria of the negative-pressure ward. Afterward, based on the calculated rate, the study assessed the airflow and room-specific pressure within a typical floor, encompassing both the unit module and associated nursing support facilities. Here, the airflow in the external corridor of the typical floor was divided into two cases according to the pressure distribution: negative pressure and atmospheric pressure. The calculation results were compared using a computational fluid dynamics tool. The analysis results confirm that the air isolation performance is adequate as the pressure difference between adjacent rooms in the unit module and the typical floor was maintained at 2.5 Pa. Additionally, the indoor airflow in the negative-pressure isolation room formed a stable flow at a slow speed of 0.1–0.2 m/s, minimizing the possibility of air contamination from outside the isolation room. In particular, Case B of the typical floor design proposes a method to optimize the pressure distribution in the modular negative-pressure ward by designing the ventilation flow rate at atmospheric pressure level. Thus, this study emphasizes that atmospheric pressure design is appropriate when designing pressure in areas where negative-pressure control is difficult and can contribute to the design and improvement of similar medical facilities in the future.

Encapsulation of SiC/SiC cladding tubes with excellent mechanical performance and air tightness using a CaO-modified Y2O3–Al2O3–SiO2 glass

Currently, the encapsulation of SiC/SiC has been a key technical challenge limiting further application, and YAS-based glass offered a possible solution. In this paper, different CaO-doped Y2O3–Al2O3–SiO2 (YAS) glass solders were prepared and employed to join SiC/SiC. The joints were all structurally dense with the room temperature shear strengths higher than or equal to ∼51.7 MPa. Notably, joints containing 3.0 wt% CaO exhibited increased shear strength of ∼57.1 MPa, and the shear strength at 1200 °C was about 15.8 MPa in an air environment, meeting the requirements of the LOCA conditions. Optimal performance was achieved by using 3.0 % CaO-doped YAS glass to encapsulate SiC/SiC cladding, yielding a continuous, dense encapsulation region with predominantly small closed pores (≤1.0 mm3). Glass infiltration was found in both the end plug and cladding wall. The joints did not leak after 72h of holding pressure at 15 MPa, indicating their excellent air tightness.

Air tightness detection method in parallel for aerospace: mechanical design, system modeling and optimum control

To address the problems of high cost, complex operation, and low efficiency of existing equipment for aerospace, a simple but efficient multichannel air tightness detection device is designed. A physical system model is constructed for the process of inflation, deflation, and inflation with leakage. The expression between the inflation/deflation rate and the valve area is obtained. Through modeling the intersection and rotation of spatial curves, the relationship between the valve area and the valve core angle is derived, and the optimal valve core angle calculation method is proposed to achieve precise rate control of inflation and deflation. Simulation experiments and numerical analysis demonstrate the superiority of the proposed system scheme, the effectiveness of the control method, as well as the accuracy of the mathematical model. For the tested object of 0.3 L, the target pressure of 400 KPa, and the inflation and deflation rate of 75 Kpa/min, by using four channels with a 10 s interval for sequential operation and adjusting valves every 60 s, the efficiency of inflation and deflation is more than 3.5 times that of a single device with a single circuit. Its performance is not much different from real-time automatic control equipment, but the economy is greatly improved.

Evaluation of energy-saving potential and indoor thermal environment of passive solar houses in various heating climate regions of China

ABSTRACT Passive solar houses comprise crucial strategies of reducing heating and cooling energy for buildings, which have been extensively used in plenty of nations. This study develops a study on indoor thermal environment, the energy-saving performance and natural lighting in different heating climate regions (represented by Lhasa, Xining and Urumqi). An attached-sunspace solar house integrated with phase change material floors is also proposed to ameliorate indoor thermal comfort and simultaneously diminish the heating energy consumption. In addition, the dominant factors analysis of building envelope affecting building energy consumption are sensitively studied. Moreover, the influence of the depth of sunspace and the intensities of internal heat gain on indoor thermal conditions and heating energy consumption are further analyzed. The results indicate that among the three types of solar houses, the passive solar sunspace offers the most stable indoor temperature and Trombe-wall solar houses and attached-sunspace solar houses have striking energy-saving advantages compared with the traditional houses. And the annual power consumption of 695.1 kWh, 427.4 kWh and 688.8 kWh in Lhasa, Xining and Urumqi can be saved in view of natural lighting respectively. Additionally, the whole natural temperature of attached-sunspace solar house is on the rise apparently when the PCM floors are embedded in the house and the energy saving fraction of these three regions is 81.9% for Lhasa, 68.8% for Xining, 55.7% for Urumqi respectively with the integration of phase change floors. The sensitivity analysis of key parameters impacting building energy consumption from high to low are the heat transfer coefficient of external wall, the ratio of window to wall, air tightness, the heat transfer coefficient of external window, and the heat transfer coefficient of roof. The depth of 1.2 m for sunspace is recommended as the optimal choice. Indoor natural temperature is on the rise as intensities of internal heat gain increase. The same downward trend for the main bedroom and the whole building is displayed with the increasing interior heat sources in terms of annual heating load.

Reducing inter-unit pollutant transfer through multifamily unit compartmentalization

Compartmentalization, which refers to air sealing each unit within a building from the exterior and other interior spaces, has been proposed as a strategy to improve indoor air quality and energy efficiency in multifamily buildings. This study collected field data on air tightness and pollutant transfer in three new-construction multifamily buildings in California, which was used to develop a model in CONTAM that simulated the impact of leakage levels, ventilation strategies, and climate zones on inter-unit pollutant transfer in multifamily buildings. Air leakage testing found an average total unit leakage of 0.8 L/s50/m2, almost twice as tight as California’s current compartmentalization requirement (1.5 L/s50/m2). Two buildings designed with balanced ventilation systems were measured to have imbalanced continuous unit ventilation flows, which were further imbalanced by intermittent exhaust fan operation. Tracer gas testing in two buildings indicated that only about 1–3% of the total air entering a unit came from each neighbouring unit. Furthermore, all particles were apparently removed along the way, as there was no observable particle matter transfer at the tested air tightness levels (0.6–0.9 L/s50/m2). Modelling results indicated that leakier units led to greater dilution of pollutants generated within the unit but increased gaseous pollutant transfer from neighbouring units. The average concentration of benzene, a proxy gas for cigarette smoke, transferred into non-smoking units from neighbours who did smoke almost doubled, surpassing acceptable exposure levels, in the leaky simulation (2.3 L/s50/m2) compared to the tight simulation (0.8 L/s50/m2). Overall, this study suggests that stricter compartmentalization requirements should be adopted in multifamily building code updates, as tighter requirements appear to be manageable for builders and beneficial for indoor air quality when combined with mechanical ventilation.

Mechanical Behavior and Air Tightness of Roadway Surrounding Rock Under High Internal Pressure

Mechanical Behavior and Air Tightness of Roadway Surrounding Rock Under High Internal Pressure

Study on air tightness and thermal comfort of high-rise Glulam structure buildings

ABSTRACT Building air tightness, indoor temperature, and humidity moment affect the building indoor personnel’s subjective comfort. Therefore, this article takes a six-story Glulam post and beam with shear wall construction as the main test object, with a light wood frame construction house and a log house in the same area as comparison objects. The research conclusion shows that the air change frequency of the tested building is 4.64 h−1, which is consistent with the normal situation; the air tightness is good. There are thermal bridges at the building nodes of each structure type. The joints of the enclosure structure members have a certain influence on the generation of thermal bridges. Compared with the comparison objects, the building has the best thermal insulation performance, the most stable indoor temperature and humidity, and the best way to keep the indoor environment at a more comfortable stage for the human body.

Fine dust inflow paths and heating load variation based on field measurement of air tightness in two Korean schools

This study aimed to determine the effects of fine dust reduction, as well as the energy load reduction in association with the improvement plans by measuring the airtightness and indoor and outdoor fine dust concentrations in middle and high school classrooms and by identifying the fine dust inflow paths. The air tightness and indoor and outdoor fine dust concentrations were measured at two schools, and the paths of outdoor fine dust inflow were identified for an extensive analysis of the effects of fine dust reduction and the energy load reduction in association with improvement plans. Air tightness in the classroom at school A and B was improved by 32.26% and 38.58% with sealing, respectively. Analyzing the outdoor air inflow paths at school B according to the variation in air tightness, the probability of outdoor air inflow increased in the following order from the highest to the lowest: corridor windows, corridor doors, exterior windows, supply and exhaust units. For the rate of reduction in heating load, the highest rate was shown to be 27% at school A with improved air tightness at the exterior windows and 32% at school B with improved air tightness at the interior doors. This is expected to be reflected in the selection of equipment such as heat pumps and show cost-saving effects such as capacity reduction.

Strength characteristics and carbonation depth evolution of modified magnesium slag based solid waste storage backfill materials

CO2 storage is one of the effective ways to achieve China's 30·60 dual carbon goal. The study of the interaction between CO2 and storage backfill material lays a foundation for the long-term stability and gas tightness of CO2 storage. Based on the modified magnesium slag-based solid waste backfill material constructed by the storage, in order to explore the strength characteristics and carbonation depth evolution of the CO2 storage backfill material, the interaction between CO2 and the storage backfill material was analyzed from the perspectives of uniaxial compressive strength, carbonation depth test, pore structure distribution, microstructure and phase composition. The results show that carbonation can significantly improve the compressive strength of the storage backfill material, and the carbonation depth increases with the increase of carbonation time, and increases slowly after complete carbonation. The later the initial carbonation age, the faster the growth rate of compressive strength and carbonation depth, and the greater the growth rate. After high concentration CO2 curing, the diffusion rate and carbonation degree of the storage backfill material gradually decreased from the outside to the inside, and the calcium carbonate content also gradually decreased. The carbonation can significantly reduce the porosity of the sample, gradually transform from large pores to small pores, and the pore size distribution and pore structure are significantly improved. Therefore, the later the initial carbonation age is, the more beneficial the carbonation effect is for the long-term stability and air tightness development of the backfill material of the CO2 storage, which provides important theoretical guidance for the construction and storage method of the CO2 storage.

Application of gas chromatography-stable isotope mass spectrometry to determine the oxygen isotope ratio of water in concentrated fruit juice

In this study, we developed a method to determine the authenticity of concentrated fruit juice using the δ18O ratio of water. We utilized the gas chromatography-isotope ratio mass spectrometry (GC-IRMS) technique along with the offline isotope exchange equilibrium method to pretreat and measure the oxygen isotopes in water in concentrated apple juice. This innovative approach uses anhydrous ethanol as a solvent to dissolve concentrated juices, thereby facilitating a more comprehensive reaction between the water in the sample and the CO2 standard gas. Additionally, the reaction vessel exhibits excellent air tightness, ensuring rapid equilibrium time and enabling accurate determination of δ18O in the water content of concentrated juice. The reaction vessel had excellent air tightness and rapid equilibration time, enabling accurate measurement of δ18O of water in concentrated fruit juice. The reaction vessel used had excellent air tightness and rapid equilibration time, ensuring accurate measurement of the δ18O of water in concentrated fruit juice. We analyzed 40 samples of concentrated apple juice and found that the range of δ18O values in the water of concentrated apple juice was between 1.29 ‰ and 7.59 ‰. Additionally, we used prepared sucrose syrup as a simulated sample and found that the δ18O distribution range was between −10.43 ‰ and −10.53 ‰. Furthermore, we conducted adulteration simulation experiments on randomly selected real samples and discovered a linear negative correlation between the adulteration ratio and the δ18O value of water in the samples.

Low-pressure plasma sprayed dense scandia-stabilized zirconia electrolyte and its effect on SOFC performance

The plasma spraying process has been proven capable of fabricating high-performance metal-supported solid oxide fuel cells (MS-SOFCs), and the critical technology is to prepare dense MS-SOFC electrolytes. Usually, very low-pressure plasma spraying (<1000 Pa) is adopted as it can significantly improve the electrolyte density and air tightness. However, at the same time, it also has the disadvantages of low deposition efficiency and high cost. This paper explores whether it is possible to prepare dense MS-SOFC electrolytes under low-pressure conditions (1000–10000 Pa) with ideal deposition efficiency and cost. Specifically, 4000 Pa and 7000 Pa were chosen to prepare scandia-stabilized zirconia (ScSZ) electrolytes. The effects of spraying pressure and distance on the electrolyte microstructure and cell electrochemical performance were investigated. It was found that the electrolyte prepared at a pressure of 4000 Pa and a spraying distance of 325 mm had the lowest porosity of 3.28%. Meanwhile, the cell exhibited the best electrochemical performance with an open circuit voltage of 1.008 V and a maximum power density of 970 mW/cm2 at 800 °C.

Energy Efficient Design for a Conventional Building using BIM Tools

Nowadays, energy has become a key player in the AEC industry because of the increase in global warming and energy crisis. Due to global warming the consumption of energy has increased enormously in buildings. The no. of buildings have grown in tandem with rise in levels of urbanization in developing & developed countries, which in return rises the bar for energy consumption. The improved energy performance of the building is significantly influenced by both interior and exterior building factors. It is preferred to perform energy analysis in the design stage of the building. The current paper is the talks about the energy model by improving the design of a conventional buildings, an energy – efficient model is been created which uses less energy and reduces its carbon footprint. Energy analysis using BIM can be used to optimize the building’s design and identify opportunities for improvement, such as implementing energy-saving technologies, improving insulation and air tightness, and reducing energy loss through window frames, it’s glazing type and also redesigning the other parameters including HVAC types, Window shades, change in orientation etc. In the earlier, the conventional model to produce energy through renewable sources like solar and wind, and incorporate them into the building’s design. Thus, obtained results after analysis can be used to take design decisions and ensure the building meets energy efficiency standards and sustainability goals. The use of BIM in the design and analysis of energy-efficient buildings can help support the transition to a low-carbon, sustainable future.

Rain resistance of windows – Lessons learned from two decades of laboratory testing

Windows are important in buildings intended for human activities as they let in daylight and provide views. However, they may also be vulnerable in terms of heat loss, air leaks, rain tightness, and durability. In Nordic climates featuring severe driving rain exposure, water tightness is of outmost importance. SINTEF has for many decades been testing windows as part of the Norwegian yearly product control. Air permeability and water tightness are tested according to NS-EN 1026 and NS-EN 1027, respectively. The windows are then classified as described in NS-EN 12207 and NS-EN 12208. This paper summarises experiences from the last two decades of testing, presenting the results of 1130 tests of windows’ air permeability and rain tightness. The overall trend is that air and rain tightness performance of the windows have improved over time. Certain hinge configurations are clearly better than others, with tilt and turn windows performing the best and top hung casement windows the poorest. There is a clear trend that highly rainproof windows also exhibit lower air permeability. Multiple-window screens fail the test more often since they feature longer perimeters of opening. The contribution of weather sweep seals to the water tightness is significant as it makes an extra rain barrier to the joint between casement and frame. In general, leakage between the frames of double windows and in the joints of the frame occurs at lower air pressures than leakages between casement and frame. The lessons learned from the survey may guide future development of weatherproof windows.