Air Tightness Research Articles

Full scale experimental performance assessment of a prefabricated timber panel for the energy retrofitting of multi-rise buildings

A prefabricated timber façade system is presented for the energy retrofitting of buildings. Large panel dimensions facilitate the installation of this system, with reduced disturbance to building users and increased overall quality in terms of thermal bridge mitigation and air tightness of architectural junctions. A full scale proof of concept test is performed, where several prefabricated timber panels were installed over a pre-existing brick façade, their junctions tested, and the differential thermal performance of the system is evaluated.It is concluded that the overall thermal performance of the system is satisfactory in terms of overall U-value, thermal bridge coefficient and, temperature factor. Furthermore, and based on experimentally obtained data, a dynamic characterization of the harmonic thermal response of the system is performed.

B-1 建物の気密性を用いた換気量の簡易計算法

B-1 建物の気密性を用いた換気量の簡易計算法

덧유리 및 방풍재 적용을 통한 슬라이딩 창의 단열 및 기밀성능 개선효과 분석

Purpose: Thermal performance and air tightness of window are improved for the building energy efficiency. As the deteriorated houses are increased, the improve measures with low cost and easy installation are developed in the energy performance of window. Attached glazing and windbreak can be easily applied to the window with low cost. In this paper, the effect of the attached glazing and windbreak on the thermal performance and air tightness of window is analyzed as the measure to improve performance of window. Method: Thermal transmittance of glazing is evaluated through WINDOW simulation according to thickness of attached glazing and air cavity. Based on the simulation results, thermal transmittance, air tightness and condensation resistance performance of four cases are tested according to Korea standards. One type of PVC sliding double window is chosen as the specimen. For the analysis on low performance of window, the outside of window is excluded in the PVC sliding double window. Result: This study shows that thermal performance of glazing can be increased by the application of attached glazing. Furthermore, lower thermal performance of glazing can obtain the higher effect of attached glazing. The application of attached glazing and windbreak can effect on increasing thermal performance and air tightness of window.

A new chamber design for measuring nitrous oxide emissions in maize crops

AbstractNitrous oxide (N2O) emissions from agricultural land are often estimated by measuring changes in N2O concentrations over a given period in the headspace of a gas‐sampling chamber covering a specific soil area. This technique is particularly challenging in tall growing row crops such as maize (Zea mays L.), to which farmers regularly apply fertilizer banded below the seeds to ensure good crop development. Placing chambers in the inter‐row space leads to bias in flux measurements, due to exclusion of fertilized and rhizosphere soil. Chambers for N2O flux measurements should therefore be placed centered over the row. A new split chamber for gas sampling was developed in this study from a closed, rectangular chamber (original chamber: 78 cm × 78 cm, 51 cm height). The new chamber is applicable for use for the complete maize growing cycle until harvest. For each flux measurement, the two parts of the chambers are placed in a gas‐tight seal on a collar previously inserted into soil covering a representative area of land. In a later growth stage, when plant height exceeds chamber height, stalks of developed maize plants can be fixed between the two chamber parts through a rubber‐tightening opening on the top of the chamber. Air tightness of the split chamber was tested in the laboratory and the split chamber was compared with the original chamber in a field experiment with slurry injection under maize seeds. The laboratory test demonstrated similar air tightness of both chamber types. The field test yielded almost identical N2O fluxes for the original chamber (244 µg N2O‐N m−1 h−1) and the split‐chamber (254 µg N2O‐N m−1 h−1). It can be concluded that the split chamber is an adequate gas‐sampling unit, with particular advantages when flux measurements are conducted in tall growing row crops.

Influence of architectural style on indoor radon concentration in a radon prone area: A case study

Indoor radon is a major health concern as it is a known carcinogenic. Nowadays there is a trend towards a greater energy conservation in buildings, which is reflected in an increasing number of regulations. But, can this trend increase the indoor radon concentration? In this paper, we selected a radon prone area in Spain and focused on single-family dwellings constructed in a variety of architectural styles. These styles ranged from 1729 up to 2014, with varying construction techniques (from local resources to almost universally standard building materials) and regulations in force (from none to the Spanish regulation in force). The 226Ra concentrations in soil and surface radon exhalation rates were rather similar in this area, mean values ranging 70–126Bq/kg and 49–100mBq/m2·s, respectively. Indoor radon concentration was generally greater than the contribution from soil exhalation (surface exhalation rates), especially in New dwellings (1980–2014). Its concentration in dwellings built in the Traditional style (1729–1940) was significantly lower than in the new houses. This can be consequence of the air tightness of the dwellings as a consequence of the different regulations in force. In the period covered by the Traditional style, there was no regulation in force, and dwelling had loose air tight. Whereas in recent times, there are mandatory regulations assuring a better air tightness of the buildings. Refurbishment of Traditional dwellings also seems to increase the indoor radon concentration, as they must also comply with the regulations in force.

Office buildings with electrochromic windows: A sensitivity analysis of design parameters on energy performance, and thermal and visual comfort

In this paper, a representative office building zone with an electrochromic (EC) glazed façade was simulated in TRNSYS and Radiance/Daysim for a large number of different combinations of design parameters (i.e. location, façade orientation, window control, window-to-wall ratio, internal gains, thermal mass and envelope air tightness). Results of energy consumption, peak energy demand, useful daylight index (UDI) and predicted percentage of persons dissatisfied (PPD) for a total of 7680 scenarios were obtained and used in a sensitivity analysis considering the Main effect of the building parameters. The relative influence of the parameters is presented and the different designs improving the outputs are determined. Results have shown that the greatest total energy savings considering EC windows are for warmer climates with higher solar radiation exposures. The presence of an EC window mostly influences the cooling peak load and acts as an alternative solution to thermal mass from the perspective of peak reductions. While the choice of the specific window control strategy is having a limited impact on the energy savings and peak load reductions, the analysis revealed that this parameter has a larger impact on the visual comfort (UDI). The use of smart window does not appear to greatly influence the thermal comfort within the zone (small impact on the PPD).

High temperature EXAFS experiments in molten actinide fluorides: The challenge of a triple containment cell for radioactive and aggressive liquids

An airtight double barrier cell with simple geometry has been developed for X-rays absorption measurements at high temperature in solid and molten actinide fluorides. The aim was both to improve the air tightness, to avoid any possible leakage and to maintain the high quality of the signal. The dimensions of the heating chamber were also constrained and minimized to be compatible with the limited space available usually on synchrotron beam lines and with a geometry suitable for absorption/diffraction measurements at high temperature. The design of the double barrier cell was also driven by the safety requirements in every experiment involving radioactive materials. The furnace itself was designed to ensure easy operating modes and disassembly, the aim being to consider the furnace as the ultimate containment.The cell has been tested with different molten fluorides up to more than 1000 °C, starting from non-radioactive LiF-ZrF4 mixtures in order to prove that the cell is absolutely airtight and that not any contamination of the environment occurs. Then it has been successfully applied to thorium fluoride- and uranium fluoride-alkali fluorides mixtures.

Investigation of Indoor Air Quality and the Identification of Influential Factors at Primary Schools in the North of China

Over 70% of a pupil’s school life is spent inside a classroom, and indoor air quality has a significant impact on students’ attendance and learning potential. Therefore, the indoor air quality in primary school buildings is highly important. This empirical study investigates the indoor air quality in four naturally ventilated schools in China, with a focus on four parameters: PM2.5, PM10, CO2, and temperature. The correlations between the indoor air quality and the ambient air pollution, building defects, and occupants’ activities have been identified and discussed. The results indicate that building defects and occupants’ activities have a significant impact on indoor air quality. Buildings with better air tightness have a relatively smaller ratio of indoor particulate matter (PM) concentrations to outdoor PM concentrations when unoccupied. During occupied periods, the indoor/outdoor (I/O) ratio could be larger than 1 due to internal students’ activities. The indoor air temperature in winter is mainly determined by occupants’ activities and the adiabatic ability of a building’s fabrics. CO2 can easily exceed 1000 ppm on average due to the closing of windows and doors to keep the inside air warmer in winter. It is concluded that improving air tightness might be a way of reducing outdoor air pollutants’ penetration in naturally ventilated school buildings. Mechanical ventilation with air purification could be also an option on severely polluted days.

Improved the quality of the glass/glass laser bonding through the optimization of glass powder size in planetary ball mill

ABSTRACTGlass paste for laser bonding is composed of low melting point glass powder, organic carrier and additives. As the particle size of glass powder is increasing, the crack defects of glass frit film growing and it is not conducive to the encapsulation air tightness. This work has succeeded in optimizing processing parameters of ball milling and investigating the effect of different parameters on powder particle size through orthogonal test. The result show that ball-to-powder ratio (weight ratios) has the primary influence on the particle size. An optimized ball-to-powder ratio of 3:1 exhibits the best performance. The best performance of glass powder which milled by optimization parameters can be attributed to the quality of glass/glass laser bonding. The grinding glass frit film has not appeared cracks after laser bonding, and the shear strength values is higher than the not grinded.

Influence of the conditions of casting and heat treatment on the structure and mechanical properties of the AlMg10 alloy

Purpose: Assessment of the possibilities of shaping the structure and improvement of mechanical properties of casting from AlMg10 alloy through a selection of casting technology and precipitation hardening. Design/methodology/approach: the work evaluated the impact of casting and heat treatment technology on the mechanical properties and structure of AlMg10 alloy castings. The tests were performed on 200 mm × 100 mm × 25 mm plate castings produced by gravity casting methods for sand and metal moulds and by a liquid state press moulding technology. Castings made with these technologies solidify in substantially different heat- evaporation conditions and exhibit varying degrees of primary structure fragmentation. Metallographic and strength tests were performed on raw castings and after heat treatment. Findings: The changes in the morphology and size of primary crystals and the dispersion of the reinforcing phase according to the casting solidification rate and the precipitation hardening treatment were analyzed. Solidifying castings in the form of sand show a globular structure, whereas in die and press castings, a typically dendritic structure occurs, with the dendritic crystals in pressed castings being much smaller in size than the die castings. In castings which were not heat-treated, the reinforcing phase of Al3Mg2 occurs in interdendritic spaces, and its dispersion increases with the rate of cooling. After supersaturation and ageing treatments, the phase α has a grain structure in all samples. The largest dispersion of reinforcing molecules is characterized by press castings. In a raw state, the highest mechanical properties are shown by castings made in the form of sand and the method of pressing in a liquid state. Heat treatment of AlMg10 alloy castings significantly influences the increase of mechanical indexes in all castings investigated. The highest features of Rm are approx. 330 MPa and A5 above 10% is obtained in castings made by the press method. Research limitations/implications: Particular attention should be paid to the avoidance of the effects of slag inclusion, shrinkage and magnesium oxidation during casting of AlMg10 alloys. In die castings of a plate type, due to own stresses, a significant decrease in mechanical properties occurs. Practical implications: The most advantageous mechanical properties of AlMg10 alloy castings are obtained by using liquid-state pressing technology. In addition, this technology makes it possible to produce thin-walled castings of high dimensional accuracy, high air- tightness, fine grain structure, lack of surface defects and low roughness. Originality/value: The paper presents the possibility of improving the mechanical properties of AlMg10 castings by applying heat treatment. It has been proven that the casting method has a significant effect on the mechanical properties of the castings.

Retrofitting strategy for building envelopes to achieve energy efficiency

With the excessive energy consumption worldwide, the demand for saving strategies increases. Energy consumption in public buildings increased drastically over the last decade. Significant policy actions towards the promotion of energy-efficiency in the building sector have been developed with different intensity and structure. This study aims at proposing a retrofit strategy in an attempt to improve energy efficiency in a sample of higher educational buildings located in a hot arid climate (Egypt). Retrofitting some of the building’s envelope features can provide comfort without compromising functional needs. Comfort needs, which include thermal, visual and acoustical, can reduce energy consumption. Emphasis is placed on thermal comfort in terms of energy efficiency. Some of the important measures used in the retrofitting process of the building envelope include: external walls’ insulation, windows’ glazing type, air tightness (infiltration) and solar shading. The study results show that simple retrofit strategies such as solar shading, window glazing, air tightness then insulation can reduce energy consumption of an average of 33%. From the feasible envelope features’ used in this study, the research provides a suggestion for design codes that maintains thermal comfort, propose a feasible strategy for retrofitting and a baseline reference specifically devised for local energy efficiency.

Evaluation of Real-World Implementation of Partitioning and Negative Pressurization for Preventing the Dispersion of Dust From Renovation Sites.

The aim of this study was to assess the implementation of partitioning and the negative pressure method in limiting the dispersion of dust to areas adjacent to renovation sites. The pressure difference between the worksites and adjacent areas and PM10 concentrations in the both zones were measured in 12 renovation sites, and the factors affecting the prevention of dispersion of dust were assessed. Poor implementation of partitioning and negative pressurization found in half of the renovation sites lead difficulties in achieving a proper negative pressure, causing dispersion of dust into adjacent areas. Main problems related to flimsy partitioning walls and poor air tightness of the enclosure. Dust concentrations in adjacent areas were substantially lower when natural ventilation in the renovation site was rejected and partitioning walls and their junctions to existing structures were sealed. In case of leaky enclosures, despite the high air exchange rates, a definite negative pressure could not be maintained. Instead, negative pressure minimum of -5 Pa was found to be sufficient for limiting the dispersion of dust from renovation sites. Improvement on implementation of dust controls is required through revising the guidance documents, education, and efficient supervision. This study revealed that the current Finnish practice to implement the negative pressurization based on the air exchange rate achieved with the portable exhaust fans alone is not reasonable to assure adequate dust containment. Continuous negative pressure minimum of -5 Pa is suggested, and it should be monitored with alarm devices throughout the renovation processes.

A pre and post evaluation of indoor air quality, ventilation, and thermal comfort in retrofitted co-operative social housing

In comparison to building energy performance, assessment of the impact of energy upgrades on indoor air quality and occupant comfort has received little attention.Concentrations of indoor air pollutants in fifteen, three bed semi-detached co-operative social dwellings were monitored before and after an energy upgrade during the winter periods of 2015 and 2016. The fifteen dwellings consisted of seven cavity wall (CW) dwellings and eight hollow block (HB) wall dwellings. Concentrations of indoor air pollutants including CO, PM2.5, CO2, TVOCs, formaldehyde, BTEX, NO2 and thermal parameters including temperature and relative humidity, were measured in the main living area and main bedroom before and after the energy upgrade.Building air tightness decreased from pre retrofit values of 9.26–10.00m3/(h.m2) @ 50 Pato an average of 5.53 m3/(h.m2) @ 50 Pa and 8.61m3/(h.m2) @ 50 Pa post retrofit (CW group and HB group, respectively). Concentrations of CO2, TVOC, and PM2.5 significantly changed post-retrofit, increasing post retrofit in both dwelling groups (CW; p = 0.014; p = 0.009; p = 0.005) (HB; p = 0.003; p = 0.032; p = 0.008). Increases in pollutant concentrations were correlated with lower building air exchange rates post retrofit. This study suggests that the energy retrofit had a positive impact on occupant comfort and building temperature; however, concentrations of some pollutants were found to increase following the retrofit.The study highlights the importance of characterising indoor air quality post energy retrofits within the overall building energy performance to ensure improved health outcomes for building occupants post retrofit.

Probabilistic modeling of the indoor climates of residential buildings using EnergyPlus

The indoor air temperature and relative humidity in residential buildings significantly affect material moisture durability, heating, ventilation, and air-conditioning system performance, and occupant comfort. Therefore, indoor climate data are generally required to define boundary conditions in numerical models that evaluate envelope durability and equipment performance. However, indoor climate data obtained from field studies are influenced by weather, occupant behavior, and internal loads and are generally unrepresentative of the residential building stock. Likewise, whole-building simulation models typically neglect stochastic variables and yield deterministic results that are applicable to only a single home in a specific climate. The purpose of this study was to probabilistically model homes with the simulation engine EnergyPlus to generate indoor climate data that are widely applicable to residential buildings. Monte Carlo methods were used to perform 840,000 simulations on the Oak Ridge National Laboratory supercomputer (Titan) that accounted for stochastic variation in internal loads, air tightness, home size, and thermostat set points. The Effective Moisture Penetration Depth model was used to consider the effects of moisture buffering. The effects of location and building type on indoor climate were analyzed by evaluating six building types and 14 locations across the United States. The average monthly net indoor moisture supply values were calculated for each climate zone, and the distributions of indoor air temperature and relative humidity conditions were compared with ASHRAE 160 and EN 15026 design conditions. The indoor climate data will be incorporated into an online database tool to aid the building community in designing effective heating, ventilation, and air-conditioning systems and moisture durable building envelopes.

Field study of the building physics properties of common building types in the Inner Himalayan valleys of Bhutan

Traditionally, buildings in the Inner Himalayan valleys of Bhutan were constructed from rammed earth in the western regions and quarry stone in the central and eastern regions. Whilst basic architectural design elements have been retained, the construction methods have however changed over recent decades alongside expectations for indoor thermal comfort. Nevertheless, despite the need for space heating, thermal building performance remains largely unknown. Furthermore, no dedicated climate data is available for building performance assessments. This paper establishes such climatological information for the capital Thimphu and presents an investigation of building physics properties of traditional and contemporary building types. In a one month field study 10 buildings were surveyed, looking at building air tightness, indoor climate, wall U-values and water absorption of typical wall construction materials. The findings highlight comparably high wall U-values of 1.0 to 1.5W/m²K for both current and historic constructions. Furthermore, air tightness tests show that, due to poorly sealed joints between construction elements, windows and doors, many buildings have high infiltration rates, reaching up to 5 air changes per hour. However, the results also indicate an indoor climate moderating effect of more traditional earth construction techniques. Based on these survey findings basic improvements are being suggested.

Study of a sealed high gas pressure THGEM detector and response of alpha particle spectra**Supported by National Natural Science Foundation of China (11575193, 11205240, 11265003, U1431109)

A sealed high gas pressure detector working in pure argon is assembled. It consists of a 5 cm × 5 cm PCB THGEM (THick Gaseous Electron Multiplier). The detector structure and experimental setup are described. The performance under high pressure (2 atm) is examined, selecting optimal voltages for the ionization region and induction region. The dependence of the shape of alpha particle spectra measured with relative gas gain on gas pressure (1.3–2.0 atm) has been studied. Eight data sets of relative gas gain versus working voltage of THGEM, expressed by weighting field E/P, are normalized, consistent with theory. The results show that the air tightness of the chamber is good, measured by a sensitive barometer and checked with gas gain. The experimental results are compared with Monte Carlo simulation of energy deposition without gas gain involved.

Annual Performance of Sensible and Total Heat Recovery in Ventilation Systems: Humidity Control Constraints for European Climates

Ensuring a comfortable indoor air quality requires a minimum fresh air supply by ventilation. Moreover, the improvement of the air tightness in new and refurbished high performance buildings enhances the role of mechanical ventilation and its importance in further increasing the energy efficiency. Indeed, a reduction of the ventilation load can be achieved by installing air-to-air heat recovery devices, whose potential energy savings can be easily assessed by means of their nominal effectiveness. However, this estimation does not consider the impact on the overall performance of the system, in particular when humidity control is needed. Proper control strategies can be defined on the basis of the indoor latent load to prevent preheating or avoid moisture recovery when dehumidification by cooling is then required. In this work, the energy saving potential of heat recovery systems has been analyzed, considering the impact of different control strategies on both energy and cost savings. The calculations have been generalized using the specific latent load, which allows for the analysis of strategies and savings based on typical utilization categories, without considering in detail all the building characteristics. Representative hourly weather data for 66 European cities have been used to evaluate sensible and total heat recovery devices. The energy and the cost saving results have been mapped per each European Köppen-Geiger climate class and each country, respectively. The proposed strategies based on humidity control can strongly reduce the attractiveness of total heat recovery with respect to sensible heat recovery in terms of energy and cost savings, especially when high specific latent loads are considered.

Design of Airtight Test for Aircraft Air-conditioning System

This paper put forward a new design scheme of air tightness testing equipment mainly for the air conditioning system of a certain aircraft, with the introduction of pressure transmitter, temperature transmitter and single chip microcomputer. the system in the original basis, aimed at some problems in the optimization, the manipulation of the measuring equipment to improve automation, increasing the automatic data acquisition, recording and judgment, adopting touch screen technology, and improves the human-computer interaction.

Air leakage levels in timber frame building envelope joints

Air leakage levels from eight joints that use different tightening solutions for a prefabricated timber frame building envelope were measured under laboratory conditions. Air tightness levels in field conditions were also studied by using houses that have already been built.Joints in the external wall with an inserted floor and separating walls, as well as in the external corner of walls, all showed the largest levels of air leakage. The lowest air leakage levels were recorded in the joint between the external wall and the window.Tightening up the external weather barrier significantly improved the air tightness levels of the joints. Using self-adhesive tape in tightening up the air-vapour barrier and the weathering barrier seems to be the most promising solution when it comes to guaranteeing the air tightness of wooden-framed structures.The difference between air leakage levels as measured in field conditions and those which were calculated based on laboratory measurements was noticeably large. This was caused mainly by workmanship quality levels on the construction site sealing the building envelope's joints and the fact that there were other leakage places in addition to the typical joints that were studied. Improved research, development, design, construction, and supervision are needed to fulfil airtightness requirements in future construction when it comes to producing nearly Zero Energy Buildings (nZEB).In order to be able to estimate the airtightness levels of a building in the design phase a larger database is needed, with different combinations made available in terms of joints, materials, and workmanship.

Energy Consumption Analysis for Concrete Residences—A Baseline Study in Taiwan

Estimating building energy consumption is difficult because it deals with complex interactions among uncertain weather conditions, occupant behaviors, and building characteristics. To facilitate estimation, this study employs a benchmarking methodology to obtain energy baseline for sample buildings. Utilizing a scientific simulation tool, this study attempts to develop energy consumption baselines of two typical concrete residences in Taiwan, and subsequently allows a simplified energy consumption prediction process at an early design stage of building development. Using weather data of three metropolitan cities as testbeds, annual energy consumption of two types of modern residences are determined through a series of simulation sessions with different building settings. The impacts of key building characteristics, including building insulation, air tightness, orientation, location, and residence type, are carefully investigated. Sample utility bills are then collected to validate the simulated results, resulting in three adjustment parameters for normalization, including ‘number of residents’, ‘total floor area’, and ‘air conditioning comfort level’, for justification of occupant behaviors in different living conditions. Study results not only provide valuable benchmarking data serving as references for performance evaluation of different energy-saving strategies, but also show how effective extended building insulation, enhanced air tightness, and prudent selection of residence location and orientation can be for successful implementation of building sustainability in tropical and subtropical regions.