17 research outputs found

    Reliability of quantitative and qualitative assessment of air leakage paths through reductive sealing

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    A full characterization of a building air leakage is labour intensive. As results of laboratory and mock-up experimentation rarely portray in situ conditions, the assessment of real case studies bring added value. Still, the results of experimentation of the latter face more challenges than the former. In this work a full quantitative and qualitative assessment of air leakage paths is performed, using a light steel framing (LSP) modular building with structural insulated panels (Sips) as case study. Blower-door measurements undergo for a sealing campaign of eleven steps, a technique often described as reductive sealing. Additionally, smoke tracer measurements were carried out to visually identify the air leakage locations. The application of three regression methods resulted in different uncertainty estimates. Less than 7% of the total air leakage was not attributed to one of the considered types of air leakage paths. Assessing less impacting leakage paths first and placing similar types of air leakage paths in a consecutive sealing order seems to be the most correct strategy when using the reductive sealing technique. On average, at a reference pressure difference of 4 Pa, the sealing step uncertainty averaged, 9.9%, 18.8%, and 27.5%, depending on the method used for regression of the blower door test results. Despite the highest calculated uncertainty, literature shows that the application of the method leading to it, Weighted Line of Organic Correlation (WLOC), provides the results in closer agreement with the observed uncertainty of measurements.- This work was financially supported by: Base Funding - UIDB/04708/2020 and Programmatic Funding - UIDP/04708/2020 of the CONSTRUCT-Instituto de 1&0 em Estruturas e Construcoes - funded by national funds through the FCT/MCTES (PIDDAC). The author would like to acknowledge the support of FCT - Fundacao para a Ciencia e a Tecnologia, the funding of the Doctoral Grant PD/BDIl35162/2017, through the Doctoral Programme EcoCoRe

    Improved FTIR retrieval strategy for HCFC-22 (CHClFâ‚‚), comparisons with in situ and satellite datasets with the support of models, and determination of its long-term trend above Jungfraujoch

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    Hydrochlorofluorocarbons (HCFCs) are the first, but temporary, substitution products for the strong ozone-depleting chlorofluorocarbons (CFCs). HCFC consumption and production are currently regulated under the Montreal Protocol on Substances that Deplete the Ozone Layer and their emissions have started to stabilize or even decrease. As HCFC-22 (CHClF2) is by far the most abundant HCFC in today\u27s atmosphere, it is crucial to continue to monitor the evolution of its atmospheric concentration. In this study, we describe an improved HCFC-22 retrieval strategy from ground-based high-resolution Fourier transform infrared (FTIR) solar spectra recorded at the high-altitude scientific station of Jungfraujoch, the Swiss Alps, 3580 m a.m.s.l. (above mean sea level). This new strategy distinguishes tropospheric and lower-stratospheric partial columns. Comparisons with independent datasets, such as the Advanced Global Atmospheric Gases Experiment (AGAGE) and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), supported by models, such as the Belgian Assimilation System for Chemical ObErvation (BASCOE) and the Whole Atmosphere Community Climate Model (WACCM), demonstrate the validity of our tropospheric and lower-stratospheric long-term time series. A trend analysis on the datasets used here, now spanning 30 years, confirms the last decade\u27s decline in the HCFC-22 growth rate. This updated retrieval strategy can be adapted for other ozone-depleting substances (ODSs), such as CFC-12. Measuring or retrieving ODS atmospheric concentrations is essential for scrutinizing the fulfilment of the globally ratified Montreal Protocol

    Révision des méthodes de mesure de l'étanchéité à l'air de composants du bâtiment

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    L’étude des déplacements d’air au niveau des airpaths est particulièrement compliquée, autant au niveau théorique que pratique. Ce rapport a pour objectif de proposer une nouvelle méthode pour mesurer in-situ l’étanchéité à l’air d’un airpath. Ce rapport se divise en quatre parties. Dans un premier temps, nous développons le concept d’incertitudes de mesure et de loi de propagation. Ce concept est primordial dans la description d’une méthode de mesure puisqu’il informe sur sa fiabilité. Pour illustrer ce concept, nous développons brièvement le cas de la « fan pressurization method ». Dans un second temps, nous faisons une review des méthodes de mesure développées dans d’autres articles. Cette review reprend autant des méthodes de mesure in-situ que des méthodes de mesure de laboratoire. Dans un troisième temps, nous décrivons en détail la méthode de mesure proposée et le calcul d’incertitude qui lui est lié. Dans un quatrième temps, ce rapport conclut sur les prochaines étapes pour la validation de la méthode de mesure proposée

    RAPPORT DE MESURE – ÉVALUATION DES INCERTITUDES DU TEST DE PRESSURISATION

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    La mesure d’étanchéité à l’air est devenue indispensable dans le monde de la construction aujourd’hui. Tout d’abord dans un souci d’exactitude. Il a été montré récemment que les calculs de performances énergétiques n’étaient fiables qu’après vérification de l’étanchéité à l’air du bâtiment. Ensuite, les cahiers des charges contiennent de plus en plus souvent une contrainte d’étanchéité à l’air (souvent en 50 ou 50). Quand ce n’est pas le cas, on se réfère à une performances énergétiques calculée selon la PEB. En Belgique la PEB impose une valeur forfaitaire par défaut dissuasive (50=12 m³/(h.m²)) si aucun test n’a été effectué. Dans cette session, nous avons effectué une succession de tests en conditions de répétabilité. Cette démarche permet de développer une petite base de données pour compléter ou vérifier les développements théoriques autour des incertitudes

    Assessment of the direct component testing for in-situ measurement of building component airtightness

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    Air infiltration strongly impacts heating and cooling demands in buildings. However, limiting its impact to energy consumption would be prejudicial considering the many ways by which infiltration impacts indoor spaces. Air infiltration may impact the building durability by inducing excessive moisture migration and by reducing the hygrothermal performances of the insulation; the comfort of the occupants by transporting smells or causing draughts; and the health of the occupants by introducing particles from the outside. In addition, air infiltration may facilitate the spread of smoke and fire throughout rooms. Consequently, airtightness, which is the fundamental building property impacting air infiltration, is of considerable importance for the building sector. The last decade has seen important developments, generating a tremendous increase in building airtightness testing and in the number of countries implementing qualification schemes for testers. However, the fan pressurisation test, the method used to measure building airtightness, assumes a uniform leakage distribution along the building envelope. Spending all available resources in the building-performance approach reveals a paradox in the current practice: airtightness is measured at a building scale while air infiltration occurs at a crack scale. In other words, measurement of building component airtightness assumes the leakage uniformly distributed along the building envelope while the consequences of air infiltration depend on the location of different leaks. This results in a poor understanding of pressure and airflow distributions along the envelope, which is crucial to grasp the challenges facing air infiltration and airtightness. In this context, it is hypothesised that improving the methods for quantification of building component airtightness is a massive step towards a better assessment of air infiltration and its consequences. The most promising method in this context is the direct component testing that measures airtightness of building components in-situ. Other methods are not expected to be as relevant because of the large impact of supervision and workmanship on airtightness and of the lack of crack data. In this thesis, we thoroughly described the direct component testing and conducted multiple experiments to assess its effectiveness. These experiments consist of: evaluating the capability of the method to report the airflow exponent alongside the air leakage rate; quantifying the biases in airflow due to the background leakage and in pressure differences due to the pressure losses in the duct; quantifying the direct component testing uncertainty; and identifying the issues when using this method to measure building component airtightness in-situ and to determine building airtightness. These experiments demonstrate that the direct component testing can measure in-situ the leakage characteristics of an opening with high reliability (between 3% and 10% of their value). Experiments also show that the reliability of the method depends on the design of the pressure chamber and may be affected by the human errors. Moreover, this thesis provides evidence that the direct component testing is appropriate to respond to the demand of the field for the update or the development of appropriate databases. The aim of these databases is to improve air infiltration models and prediction of building airtightness. In conclusion, this thesis is a step forward in a better description of complex airflow and pressure distributions along the building envelope; and of the numerous consequences of air infiltration on buildings and on the comfort and the health of their occupants. Research efforts in the field should focus on generalising these results to other types of building components and on broadening the range of measurable air leakage rate and airflow exponent. Finally, future studies should also investigate the changes that improved databases of building component airtightness could introduce in the current practice. More specifically, how it affects the use and the reliability of air infiltration models and prediction of building airtightness.(BAUR - Art de bâtir et urbanisme) -- UCL, 202

    Factors Influencing Airtightness and Airtightness Predictive Models: A Literature Review

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    Ces dernières années, une prise de conscience collective s'est fait ressentir par rapport à la consommation énergétique dans le bâtiment. Malheureusement, alors que tous les acteurs du milieu de la construction devraient être impliqués dans les challenges de réduction de consommation, les designers ne peuvent compter sur des outils efficace pour les aider à traiter la question de l'étanchéité à l'air. Cette synthèse de la littérature permet l'identification de deux problèmes : les modèles de prédiction d'étanchéité à l'air sont difficile à mettre en place et les modèles de prédiction existant ne conviennent pas du tout aux aux besoins des entrepreneurs et des designers. Cet article est divisé en trois grandes parties en plus de l'introduction et de la conclusion. La première présente les concepts-clés de l'étanchéité à l'air et de l'infiltration, la seconde partie traite des facteurs influençant de l'étanchéité à l'air et la troisième partie traite des modèles prédictifs d'étanchéité à l'air. A travers ces différents chapitres, les auteurs mettent en avant le besoin de standardisation que ce soit au niveau du métré utilisé pour la présentation des données, de la définition des paramètres ainsi que de la quantification statistique. Le manque de standardisation freine le développement de nouveaux outils de prédiction pour les designers et les entrepreneurs. A côté de ce manque de standardisation, les paramètres de supervision et de mise en oeuvre sont particulièrement compliqué à modéliser. Leur important impact peut expliquer pourquoi les designers et entrepreneurs trouvent parfois les modèles existant peu fiables. Pour conclure, les auteurs de cet article considèrent qu'aucun des modèles existant ne peut être utilisé, dans sa forme actuelle, comme un outil d'aide au designer. Les travaux futurs devraient se concentrer sur la standardisation de la présentation des données et sur le développement de nouveaux modèles de prédiction d'étanchéité à l'air. La première étape dans le développement de tels modèles est de créer une classification appropriée des "chemins de fuite".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.

    A Method to Quantify Uncertainties in Airtightness Measurements Zero-Flow and Envelope Pressure

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    In airtightness measurements using the fan pressurization method, the calculation of uncertainties does not take into account the zero-flow pressure approximation. It was recently suggested that neglecting the uncertainties related to zero-flow pressure approximation could be an unrealistic hypothesis. In this study, a method for quantifying this source of uncertainty is proposed, illustrated and discussed. The method is applied to a series of 31 zero-flow pressure tests performed on a newly-constructed apartment within a period of 15 days in Brussels, Belgium. For each test, 32 different zero-flow pressure approximations were compared. Since the data had a nested structure, multiple multi-level models were used for their analysis. The results show that, for the tested building, the zero-flow pressure approximation uncertainty is 0.45, 0.91 and 1.52 Pa respectively under low-, medium- and large-wind conditions. These uncertainties can be reduced to 0.42, 0.80 and 1.39 Pa when using longer zero-flow pressure measurement periods. As a comparison, uncertainty in pressure measurement at 50 Pa due to the equipment is 0.25 Pa. The uncertainty of zero-flow approximation makes the envelope pressure uncertainty non-negligible, therefore having an impact on the regression technique used to determine the building airtightness

    In-situ measurement of building component using direct component testing

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    Nowadays, the indirect method is the most common method for measuring airtightness of building components. This method is easy to setup in practice, but it can lead to substantial uncertainties. In laboratory, many authors use the direct component testing. However, it can be difficult to perform in-situ and, to our knowledge, no recent studies used it to quantify airtightness of building component in real buildings. This research aims at evaluating the practicability of the direct component testing. The method is applied to measure airtightness of installed windows in three different configurations. These tests highlight specific point of attention and possible limitations of the method. Direct component testing is then compared to indirect method. This paper concludes on the potential of the direct component testing method and mentions important limitations related to its setup. Further work should focus on repeatability studies for direct component testing and its practicability when measuring other building components than windows

    On the applicability of meta-analysis to evaluate airtightness performance of building components

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    The scientific literature lacks comprehensive and updated information regarding the airtightness of building components, this hindering the development and improvement of models for a robust prediction of their performance. To fill this gap, this paper presents a meta-analysis conducted on literature studies reporting laboratory and in-situ measurements of airtightness for various building components. Meta-analysis is a powerful methodological tool to compare and combine data from previous research, even when they have inherent differences. The results of the meta-analysis allowed to attain three outcomes: a classification of building components related to their airtightness performance; the update and improvement of existing databases of building component airtightness; and, the identification of factors specifically influencing airtightness performances of windows. In addition, the critical appraisal of the findings led to the definition of the requirements for future studies reporting measurements of airtightness of building components. This study offers a step ahead from existing knowledge by improving existing databases and by proposing a methodological framework of analysis that can be extended to several other domains of the built environment

    On the impact of regression technique to airtightness measurements uncertainties

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    The Ordinary Least Square (OLS) method is often used in the estimation of buildings’ airtightness. However, recent research demonstrated that this regression technique neglects a significant part of uncertainty. This paper investigates two alternative methods: Weighted Line of Organic Correlation (WLOC) and Iterative Weighted Least Square (IWLS). A series of 30 repeated tests were performed on a newly-constructed apartment in Brussels (Belgium). Real uncertainty and its estimation were compared for the three regression methods. In-situ observations showed that the statistical significance of differences between regression techniques depends on the considered pressure difference. Theoretical calculations showed that uncertainties estimated with IWLS and WLOC were higher than OLS. Lastly, comparing calculations and in-situ observations confirmed that IWLS and WLOC provide a better uncertainty estimation than OLS. Therefore, WLOC or IWLS should be preferred to OLS, especially in the presence of wind. WLOC is expected to be more robust than IWLS since it does not imply an iterative procedure. Along with ongoing work investigating other sources of errors, these findings contribute to a deeper understanding of uncertainty in fan pressurization tests
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