French database of building airtightness, statistical analyses of about 215,000 measurements: impacts of buildings characteristics and seasonal variations

International audienceThe French database of building airtightness has been fed by measurement performed by qualified testers since 2006. In 2015 and 2016, the database was enriched by 63,409 and 65,958 measurements respectively, which is 74% more than in 2014, making the total number of measurements about 215,000. However, residential buildings (multi-family and single dwellings) account for almost all of measurements, only 4% of tests are performed in non-residential buildings. Indeed, since 2013 the French EP-regulation requires a limit for airtightness level for all new dwellings. The justification of the building airtightness level shall be done either by an airtightness test or by the application of a certified quality management approach. In the first part, this paper summarizes the recent results of the database regarding buildings' characteristics (building area, main material, ventilation system, insulation...). The second part proposes first results regarding the evolution of air permeability. In single dwellings, the air permeability at 4 Pa (per unit of envelope area) slightly decreases from year to year with a mean value around 0.41 m 3 .h-1 .m-2 in 2015. In multi-family buildings, the yearly mean air permeability fluctuates between 0.60 and 0.65 m 3 .h-1 .m-2. In non-residential buildings, it fluctuates around 1 m 3 .h-1 .m-2. However non-residential buildings cover a wide variety of buildings. A special focus is made on non-residential buildings depending on the use of the building and its size. The last part of this paper deals with the impact of the seasonal variations on the measured air permeability in single dwellings depending on climatic zones and buildings construction materials (wood, concrete and brick constructions). An impact of seasonal variations on air permeability is only observed in the case of wood constructions, with slightly higher values during summer in the south of France in particular

Assessment of long-term and mid-term building airtightness durability: field study of 61 French low energy single-family dwellings

International audienceThe French ongoing research project "Durabilit'air" (2016-2019) aims at improving our knowledge on the variation of buildings airtightness through onsite measurement and accelerated ageing in laboratory controlled conditions. This paper presents the final results of the second task of the project. This task deals with the quantification and qualification of the durability of building airtightness of single detached houses. It is done through field measurement at mid-term (MT) and long-term (LT) scales. We first present the field measurement protocol. For the MT campaign, a sample of 30 new single-detached houses has been selected nationwide. During the study, the airtightness of each building was measured once per year over a 3-year period. A part of this sample (5 houses) was also measured twice per year during two different seasons in order to investigate the impact of seasonal variation. In addition, the air permeability of a window was measured once per year over the 3-year period in 5 houses. The LT campaign was carried out with a second sample of 31 existing single-detached houses constructed during the last 10 years. The airtightness of each house was measured once. A specific measurement protocol was defined after a detailed literature review. The main challenge is to understand the variations of the airtightness and to identify whether it is related to the products/assembly ageing, the maintenance conditions or other factors such as the occupants' behaviour. The protocol is based on the standard ISO 9972 for the measurement method of building air permeability with additional requirements for the measurement conditions. It also includes a detailed qualitative leakage detection and questionnaire for occupants. Secondly, this paper presents the construction characteristics of both samples. All houses were tested upon completion. The air changes per hour at 50 Pa pressure difference (n50) of both samples show the same mean value of 1.4 h-1 , with larger variations among the LT sample. Finally, we discuss measurement results. Regarding MT sample, the air permeability slightly increases during the first year (mean increase by 18%), and then stabilizes during the second and third year. However, for some houses with exposed timber framing, n50 has increased by more than 100%. Regarding LT campaign, the air permeability (n50) show a similar increase after 3-10 years with a mean value of 20%. Measurements performed during two different seasons did not show a significant impact of seasonal variation. The results show globally an increase in the number of detected leakages for all houses, but this increase is not always correlated with the change in air permeability. For 10 houses of both samples, the building airtightness has improved. For 6 houses, this improvement is maybe due to the building material (wood), the maintenance of windows, or the sealing of leaks by occupants but for 4 houses, we have not been able to explain this improvement

Onsite evaluation of building airtightness durability: Long-term and mid-term field measurement study of 61 French low energy single family dwellings

International audienceThe increasing weight of building leakages energy impact on the overall energy performance of low-energy buildings led to a better understanding of the actual airtightness performance of buildings. However, low expertise is available today on the durability of airtightness products in mid-and long-term scales. The French ongoing research project "Durabilit'air" (2016-2019) aims at improving our knowledge on the variation of buildings airtightness through onsite measurement and accelerated ageing in laboratory controlled conditions. This paper is issued from the second task of the "Durabilit'air" project. This task deals with the quantification and qualification of the durability of building airtightness of single detached houses. It is done through field measurement at mid-term (MT) and long-term (LT) scales. This paper first presents the field measurement protocol. For the MT campaign, a sample of 30 new single-detached dwellings has been selected nationwide. During the study, the airtightness of each building is to be measured once per year over a 3-year period. A part of this sample is to be also measured twice per year in order to investigate the impact of seasonal variations. The LT campaign is to be carried out with a second sample of 31 existing single-detached dwellings constructed during the last 10 years. The airtightness of each dwelling is to be measured once. A specific measurement protocol was defined after a detailed literature review. The protocol is mainly based on the standard ISO 9972 for the measurement method with additional requirements for the measurement conditions (same tester, same calibrated measurement device, same building preparation, same pressure difference sequences, same season…). It also includes a detailed qualitative leakage detection and questionnaire for occupants. The main challenge is to understand the variations of the airtightness and to identify whether it is related to the products/assembly ageing, the maintenance conditions or other factors such as the occupants' behaviour. Secondly, this paper presents the 61 dwelling samples construction characteristics. All dwellings were tested upon completion. The air flow rates at 4 Pa per envelope area excluding lower floor of both samples show the same mean value around 0.3 m 3 .h-1 .m-2 (n50 of 1.4 h-1), with larger variations among the LT sample. Finally, we discuss first measurement results. Regarding MT sample, results after 1-2 years show a slight increase of airflow rate at 50 PA (q50) with a median value of +6%. However, with exposed timber framing, q50 has increased by more than 100%. Regarding LT campaign, measurements results after 3-10 years show a more important increase of q50 with a median value of 28%. The measurement campaigns and data analysis will continue over 2018 to complete the work in order to better understand the in situ variations of the buildings' envelope airtightness. KEYWORDS Airtightness durability, field measurements, building envelope, low-energy dwelling 1 INTRODUCTION The increasing weight of building leakages energy impact on the overall performance of low-energy buildings led to a better understanding and characterization of the actual airtightness performance of buildings. Several European countries have already included in their EP-regulation mandatory requirements regarding the building airtightness. This is the case in France, where the EP-regulation requires a limit airtightness level for residential buildings that must be justified by measurement. However, low expertise is available today on the durability of building airtightness and its evolution in mid-and long-term scales. The French ongoing research project "Durabilit'air" is conducted since 2016 for a 42-month period, in order to improve our knowledge on the variation of buildings airtightness through onsite measurement campaigns and accelerated ageing in laboratory controlled conditions. As part of this project, a comprehensive literature review about building airtightness durability was realized by (Leprince et al., 2017). This review showed an important evolution over time of the air permeability in real buildings, with an increase of more than twice in some cases. The air permeability seems to increase in the 3 first years and then stabilise. This paper is issued from the second task of the "Durabilit'air" project. This task deals with the quantification and qualification of the durability of building airtightness of single detached houses. It is done through field measurement at mid-term (MT) and long-term (LT) scales. This paper presents the first results of both MT and LT measurements

Evaluating assumptions of scales for subjective assessment of thermal environments – Do laypersons perceive them the way, we researchers believe?

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Feedback about a full ventilation system reconditioning in a non-standard sealed building

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Assessing the performance of natural ventilation systems: a review of existing methods

International audienceNatural and Hybrid ventilation systems, by using exclusively or partially natural driving forces, help to reconcile building energy sobriety and good Indoor Air Quality (IAQ). However, in France, Building Regulations restrict the use of natural ventilation by imposing minimum airflows in buildings. Natural ventilation, whose driving forces are atmospheric conditions, has an efficiency depending on the climatic region. Concerning climatic regions where natural ventilation is not likely to provide sufficient airflow, the ventilation system may be featured with a mechanical assistance, which is called Hybrid ventilation systems. Hybrid ventilation systems, taking advantage from natural driving forces when the induced airflow is strong enough, and assisting it otherwise, allow using natural ventilation while verifying airflow requirements. The assessment of mechanical systems performance has already been questioned by the French protocol PROMEVENT. The absence of a similar protocol restricts the development of natural and hybrid ventilation systems. Such a protocol would widen the use of natural ventilation in favourable climatic regions and enable the improvement of the control strategy of hybrid ventilation systems. However, the plurality of openings, variable airflows, and unstable flow patterns make the measurement of the performance of natural and hybrid ventilation systems a challenging task. It represents the objective of the French research project VNAT. This paper is issued from the first task of the VNAT project: the state of the art on the assessment of natural and hybrid ventilation systems. It presents a comprehensive review of existing studies and protocols regarding the measurement of airflow and Air Change Rate (ACR). It appears that direct measurement method of airflow may interfere with the flow pattern, which is troublesome for natural ventilation. Thus, the direct measurement is not likely to be representative. Indirect methods allow measuring Air Change Rate (ACR). They may be conventional tracer gas methods or occupant-generated CO2 methods. Tracer gas methods are numerous and they are based on assumptions which can differ from a method to another. Two of them, called the constant injection and the concentration decay methods, are widely used to characterize the performance of ventilation systems thanks to their ease of implementation. The violation of assumptions leads to important measurement uncertainties. Occupant-generated CO2 methods depend on the occupation rate and on the CO2 emission rate, which induces uncertainties too. These measurement methods as well as tracer gas methods are compared regarding their accuracy and their limits. Modelling methods are also discussed. Results from this paper will help to build a new protocol more suited to the assessment of the performance of hybrid and natural ventilation systems under real conditions

Modélisation dynamique du confort thermique dans les bâtiments naturellement ventilés

Avec les besoins actuels d économie d énergie et de maîtrise des impacts environnementaux du bâtiment, certains doutes se posent sur la définition du confort thermique et la façon de créer et maintenir les conditions de confort. En effet, les normes actuelles considèrent le confort thermique sous une approche analytique, réductrice de la complexité du réel. Les études in situ du confort thermique ont permis de constater une surestimation du niveau de l inconfort perçu en réalité par rapport à celui prévu par ces normes surtout dans les bâtiments naturellement ventilés pendant les périodes chaudes. Ces études ont servi à mettre les bases de l approche adaptative, qui caractérise le confort thermique à travers les interactions adaptatives entre l occupant et son environnement. L utilisation des normes peut conduire à un recours systémique à la climatisation alors que l approche adaptative permet d assurer le confort thermique avec des consommations d énergie plus modestes. Nous nous intéressons dans ce travail à l aspect adaptatif du confort thermique en complément à l aspect analytique dont l ensemble permet d avoir une vision globale du confort thermique dans les bâtiments. En partant d une étude bibliographique sur les approches existantes, nous avons conduit une étude expérimentale in situ dans huit bâtiments pour explorer de plus près le confort adaptatif et caractériser l interaction entre l occupant et le bâtiment. Ensuite en adoptant une démarche systémique, nous avons développé un modèle dynamique sur le confort thermique qui permet d intégrer les différents mécanismes dynamiques identifiés dans la bibliographie et par l expérimentation. Ce modèle, que nous avons appelé AdOCC, permet de déterminer l état thermique de l occupant à partir du modèle dynamique à deux noeuds de Gagge et d en déduire le comportement de l occupant et ses actions adaptatives selon les caractéristiques du bâtiment et la saison. Le modèle a été intégré dans l outil de simulation dynamique TRNSYS. Cela nous a permis d évaluer le modèle AdOCC en confrontant les simulations réalisées avec deux bureaux tirés de l expérimentation vis à vis les résultats de mesures. L application du modèle au cas des bâtiments de bureaux naturellement ventilés nous a permis de déterminer les conditions qui permettent d établir le confort thermique avec des ressources énergétiques limitées, en utilisant un ventilateur local ou la ventilation nocturne, selon l inertie du local, l orientation, les protections solaires, et le climat L utilisation du ventilateur correspond à une consommation de l ordre de 10 Wh/m /jour et la ventilation nocturne 30 Wh/m /jour. Ces valeurs sont négligeables devant les consommations de climatisation qui peuvent être 10 fois plus importantes.n this work we focus on the adaptive approach of thermal comfort by combining features of both the static and adaptive theories. In the first step we have conducted a bibliographical study on the existing theories and approaches and which has led us to carry a field study on thermal comfort in eight office buildings. Afterwards we have adopted the systemic approach to develop a dynamic model on thermal comfort by integrating the dynamic mechanisms identified in the bibliography and the field study. This model, named AdOCC, determines the dynamic thermal state of the occupant from which the model can determine the adaptive behaviour of the occupant. AdOCC has been integrated in the dynamic simulation tool TRNSYS and has been evaluated by comparing the results of the simulations with measurements. By applying this model to the case of a naturally ventilated office building we have found the conditions where thermal comfort can be achieved with limited energy consumptions.VILLEURBANNE-DOC'INSA LYON (692662301) / SudocSudocFranceF

Durability of building airtightness, review and analysis of existing studies

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