•Deduces the airtightness influencing factors from references.•Reviews the predictive models and analyzes their ability to be used as design tool.•Emphasizes the need for the standardization for the ...data presentation.•Suggests future research as classification of “infiltration paths”.
In recent decades there has been a growing awareness regarding energy consumption in buildings. Unfortunately, at a time when all building actors should get involved in the challenge to reduce energy consumption, designers cannot rely on effective tools to help them in their decision making process concerning airtightness. This literature review allows the identification of two important issues: new airtightness predictive models are complex to develop and existing airtightness predictive models do not meet the needs of designers and contractors. This paper is divided into three main parts in addition to the introduction and the conclusion. The first part deals with the key concepts of infiltration and airtightness, the second part with influencing factors and the third part with airtightness predictive models. These different chapters highlight a need for standardization regarding the metrics used for data presentation, parameters definition and statistical quantification. The lack of standardization hinders the development of a new airtightness predictive tool for designers and contractors. Along with the problem of standardization, supervision and workmanship are parameters that are difficult to model. Their significant impact can explain why designers and contractors find some existing models unreliable. This paper concludes that none of the existing models can be used in their present form as design tools. Further work should focus on the standardization of data presentation and on the development of a new airtightness predictive model. The first step in the development of such a model is to draw an appropriate classification of “air paths.”
Abstract
Based on the production and detection procedures of a medical infusion connector, the original detection device was innovatively designed, and an airtightness detection device with automatic ...loading/unloading function was developed, in an effort to improve the loading/unloading efficiency and airtightness detection efficiency of the infusion connector and complete the automatic detection task at rate of 20-30 ones per min. The basic device composition of this infusion connector was introduced, and the basic structural features and working principles of each device were analyzed. The importance was attached to the calculation methods for key dimensions that influenced the detection quality and material loading, and in this way, while the batch material loading was realized, the difficulties in the airtightness detection and automatic sorting of finished products were solved. The original manual material loading was converted into automatic material loading and the frequency of simultaneous airtightness detection was increased, which reduced the amount of labor used, improved the overall production efficiency and lowered the production cost.
•The pulse method of airtightness testing produces repeatable and accurate results.•Pulse data from very airtight homes show good agreement with the power law model.•The conversion formula displays ...stronger correlation than the power law equation.
The latest edition of the UK government’s Approved Document L of the Building Regulations, which came into effect on the 15th of June 2022, for the first time included an alternative method of airtightness testing to the traditional fan pressurisation method (DLUHC & MHCLG, 2021). Unlike the fan pressurisation method, the pulse method operates at low pressures that are thought to be representative of natural infiltration. Despite government approval, responses to the Future Homes Standard consultation revealed that respondents did not have confidence in the method, particularly with very airtight properties, and others were concerned with the comparison between testing methods (MHCLG, 2021). In this paper, experimental investigations were performed involving the pulse method to assess its repeatability and accuracy. The results indicated an average repeatability of 4.96% from the mean for consecutive tests, and the pulse results extrapolated up to 50 Pa all fell within the fan pressurisation’s 10% uncertainty range. In addition, two empirical models were applied to the data set to explore the conversion of air permeabilities between high and low pressures. The data showed strong agreement with the power law model and even stronger correlation with the conversion formula suggested in CIBSE TS23:2022 (Godefroy, 2021).
•Changes of building airtightness of 61 houses are evaluated on different time scales.•Airtightness of houses may deteriorate mainly during the first two years.•2-Storey houses with wood frame roofs ...present a higher risk of airtightness deterioration.•The increase in the number of leakages is not correlated with changes in the airtightness.•The airtightness of the houses tested is not affected by seasonal variations.
The main objectives of this paper are to quantify and qualify changes in building airtightness on different time scales, and to identify factors that may explain the variations observed. A special measurement protocol, based on ISO 9972 but with some additional requirements, was defined after a detailed literature review. For the mid-term campaign, 30 new detached houses were measured once per year over a 3-year period. It was observed that air permeability increases slightly during the first year (a mean increase of 18%), and then stabilizes during the second and third years. Five of them were measured twice per year but did not show any significant seasonal variation. For the long-term campaign, 31 detached houses built during the last 10 years were remeasured once. Air permeability shows a similar increase to that of the mid-term campaign after 3–10 years (a mean increase of 20%). The results show an overall increase in the number of leakages detected for all houses, but this increase is not always correlated with the change in air permeability. Results pointed to three factors that could explain the deterioration of airtightness: the number of levels, the type of roof and the type of building material and air-barrier.
As a continued investigation following the previous testing of a house-sized chamber in a sheltered environment, this paper introduces an experimental study of airtightness measurement of an outdoor ...chamber using both the novel Pulse technique and the steady pressurisation method. The chamber has dimensions of approximately half that of a standard 20 ft long shipping container. The chamber's envelope was modified with multiple openings to provide a leakage level similar to that of an average UK house. Two sets of experimental tests were carried out independently at different times to investigate: a) How both methods compare on measuring the airtightness of an outdoor chamber at various leakage levels; and b) How the steady wind at various wind speed may affect the Pulse measurement of the chamber airtightness. Results show that the air permeability at 4 Pa measured by both methods has a percentage difference less than 16% in most testing scenarios, which is a slightly larger discrepancy than that found in the sheltered environment study. In steady wind tests, artificial wind at various speed levels was introduced in the Pulse tests by utilising a multi-gear portable trailer fan. Initial findings have shown that the impact of steady wind on the Pulse test is mostly insignificant when it is under 3.5 m/s. However, high wind speeds (4 m/s-9.5 m/s) decrease the value of air permeability at 4 Pa by 16%–24% in comparison to that measured under the fan-off condition in the steady wind tests.
•This manuscript compares the Pulse and blower door methods on airtightness measurement of an outdoor chamber.•The comparison was made under various leakage levels and steady wind conditions.•Both testing methods have given results of air permeability at 4 Pa (Q4) that fell within ±16% in most testing scenarios.•The wind impact on the Pulse measurement of chamber airtightness is mostly insignificant when it is under 3.5 m/s.•High wind speeds (4 m/s-9.5 m/s) decreased the measured Q4 by 16%–24% compared to the fan-off condition.
Considerable effort has been devoted to the fabrication of electronic skin that can imitate the self‐healing and sensing function of biological skin. Almost all self‐healing electronic skins are ...composed of airtight elastomers or hydrogels, which will cause skin inflammation. Fibrous membranes are ideal materials for preparing highly sensitive breathable electronic skins. However, the development of intrinsically self‐healing fibrous membranes with high stability is still a challenge. Here, a novel interface protective strategy is reported to develop intrinsically self‐healing fibrous membranes with a bionic confined structure for the first time, which were further assembled into an all‐fiber structured electronic skin through interfacial hydrogen bonding. The electronic skin is multifunctional with self‐powering, self‐healing, breathability, stretchability, and thermochromism functionalities, which is highly promising for application in intelligent wearable sensing systems.
A self‐healing fibrous membrane with bionic confined protective structure is constructed through hydrogen bonding and electrostatic interactions. The breathable self‐healing fibrous membrane imitates not only the sensing function, but also the healing process of biological skin, exhibiting great potential for the next‐generation advanced bionic artificial skins.
According to the U. S. Department of Energy (DOE), infiltration accounts for 6% of the energy use and $11 billion in energy cost for U. S. commercial buildings. One strategy to reduce infiltration in ...commercial buildings is to provide more supply airflow than return and exhaust in order to “pressurize the building”. DOE has developed EnergyPlus models of several prototype buildings which assume that pressurization results in system-on infiltration rates that are 75% less than the system-off rates. However, airflow simulations of these buildings using the CONTAM multizone airflow software showed that pressurization reduced infiltration by an average of 44% only. To improve the infiltration rates calculated by the EnergyPlus models of prototype buildings, CONTAM infiltration rates were used to develop coefficients that can be input into EnergyPlus. CONTAM captures the effects of wind, temperature difference, and system operation on infiltration rates. Coefficients were developed for 11 prototype buildings, eight cities, and two levels of building envelope airtightness. Comparisons of the predicted infiltration rates were made between using the DOE prototype model inputs and the NIST infiltration correlations. Using the NIST correlations resulted in an average HVAC-EUI (HVAC-related energy use intensity) savings of 6% or 1.4 kBtu/ft2 due to airtightening. These results indicate that the effects of infiltration on HVAC energy use are important and that infiltration can and should be better accounted for in whole-building energy modeling.
•CONTAM simulations showed infiltration was reduced only 44% when HVAC system was on.•NIST infiltration correlations captured effects of wind, temperature & HVAC operation.•Study predicted annual HVAC energy savings of 6% with airtightening.•Study predicted 1.4 kBtu/ft2 more HVAC savings from airtightening than DOE models.•More accurate infiltration modeling results in greater savings from airtightening.
•We develop an accurate hybrid modeling approach for building infiltration.•It combines machine learning categorization and grey-box sub-modeling.•Accuracy and generalization of grey-box infiltration ...models are improved.•A case study under a standard test environment demonstrates its effectiveness.
Infiltration is responsible for one-third to one-half of the space conditioning load of a typical residential home, but the modeling of infiltration for building energy modeling is either represented by over-simplified equations or dependent on over-generalized rules of thumb. This paper develops a physics-informed data-driven methodology for modeling infiltration using building-specific empirical measurements. The developed hybrid methodology combines machine-learning categorization and grey-box sub-modeling to improve the accuracy and generalization of commonly used grey-box infiltration models. The developed methodology excels at predicting infiltration by improving the ability to predict infiltration under unseen environmental conditions using machine learning algorithms with physical significance. In a case study conducted using the iUnit, a modular studio apartment experimental test facility located at the National Renewable Energy Laboratory, we use empirical airtightness measurements to fit an infiltration model using the developed methodology. We find that the developed methodology can improve the overall model accuracy by 43% and improve extrapolation by 38%, compared with the model based on the common grey-box infiltration equation. We also notice that the selected features can improve the performance of a pure machine-learning model, indicating that our methodology identifies the features with the most physical significance to infiltration modeling.
In this paper, the airtightness problem caused by welding defects in the manufacturing process of composite mold is analyzed. The mechanism analysis of the weld defects of composite mold is ...conducted. According to the mechanism of weld failure, the welding process monitoring, weld metallographic analysis, weld X-ray inspection, panel airtightness detection, and other methods are used to evaluate the welding quality of different welding forms in the welding process of composite mold panels. The measures to optimize the welding quality of composite mold panels are put forward. Finally, through the actual verification, it is proved that the optimized air-tightness welding method is stable and reliable.
The partial space heating/cooling mode and window opening for natural ventilation are significant characteristics of residential buildings' usage patterns in the Hot Summer and Cold Winter (HSCW) ...zone. At present, less attention has been paid to the partial space airtightness performance of residential buildings in this zone. In this study, the airtightness measurements of 4 spaces (whole space–Space 1, living room–Space 2, living room & bedroom–Space 3, living room & study–Space 4) in 11 newly–built and 3 existing high–rise apartments in Chengdu were carried out by the Blower Door Test method (BDT). Under the initial condition, the space with the best airtightness performance is Space 1, and the space with the worst airtightness performance is Space 2. The general disregard for the structural gaps of inner doors during the construction and installation is pointed as the most probable cause for such a significant difference in the airtightness performance under the initial condition of the 4 tested spaces. Although the implementation of stricter building design regulation is advantageous for upgrading whole–suite airtightness performance, the airtightness of the partial space has not been given enough attention, which is quite important in partial heating/cooling apartments. It may be necessary to emphasize the requirements for partial space airtightness in the building performance standards of HSCW zone.
•Airtightness of residential buildings in Hot Summer and Cold Winter zone in China.•Measurement effectively incorporates the building's usage patterns.•Airtightness of the partial space is inferior to that of the whole space.•Disregard for the inner doors' structural gaps causes the worse partial airtightness.
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