Life cycle assessment of a positive energy house in France

Disponible à l'adresse : http://leso.epfl.ch/files/content/sites/leso/files/download/publications/cisbat_proceedings_final_download.pdfInternational audienceThe « positive energy house » concept combines energy saving, e.g. applying the passive house approach, and electricity production using a renewable resource, leading to a positive primary energy balance on a yearly basis. Compared to a standard house, more materials and components are used (thicker insulation, triple glazing windows, renewable energy systems...), this is why the environmental relevance of this concept is often questioned. In order to contribute to answer this question, a life cycle assessment (LCA) has been used to evaluate the environmental impacts of such buildings, including the fabrication of components, construction, operation, maintenance, dismantling and waste treatment. This paper presents results in the case of a positive energy building, showing also the influence of the choice of the heating system on various environmental impacts considered in this assessment (e.g. global warming potential, radioactive waste production, photochemical oxidant formation potential, cumulative energy demand, abiotic depletion potential). The case study concerns two attached passive houses built in Picardy, France, in which renewable energy systems are studied theoretically: the real houses include solar water heating but no renewable electricity production. The envelope has a high insulation, high airtightness and very low thermal bridges. The technical equipment includes a heat recovery ventilation and an earth-to-air heat exchanger. In this study, PV solar panels mounted on the roof have been added so as to obtain a positive primary energy assessment. For these houses, three different heating solutions have been studied: an electric heat-pump, a wood pellet condensing boiler and a wood pellet micro-cogeneration unit. The three alternatives have been modeled using the building thermal simulation tool COMFIE, in order to evaluate their heating load, possibly cooling load and thermal comfort level. Environmental impact indicators have been evaluated for these alternatives applying the LCA tool EQUER, linked to the building simulation tool COMFIE and using life cycle inventories from the Swiss Ecoinvent data base

Studying innovative concepts by coupling simplified: Simulation and multizone airflow model

Disponible à l'adresse : http://leso.epfl.ch/files/content/sites/leso/files/download/publications/cisbat_proceedings_final_download.pdfInternational audienceIn order to respond to global warming and natural resources depletion challenges, industrials from the building sector need to propose an adequate offer. Energy simulation tools can support this process. In order to reach high performance level, e.g. primary energy consumption below 50 kWh.m-2 per year (including heating, cooling, domestic hot water, lighting and ventilation), various studies and real cases show that, appropriate architecture, high insulation, free cooling and the use of a heat recovery exchanger for ventilation are needed. This last technology will be particularly affected by airflows across the building envelope caused by a low airtightness. Moreover, free cooling ventilation rate will highly depend on temperature difference between outside and inside. Thermal modelling tools need therefore to deal with those two issues precisely. A multizone model has been developed to compute building airflows in order to evaluate them with a higher degree of precision in the frame of a simplified simulation tool that can be used in early phases of a project. This model is based on well-mixed zones and mass conservation principles. The air flow rate between two zones is expressed as a function of the pressure drop between those two zones. Wind pressure and buoyancy effects are the causes of pressure drops. Several types of connection are implemented: cracks, ventilation inlets, large openings. More types of connection will be added. This model has been implemented in the thermal building simulation tool COMFIE [1]. The airflow model uses the temperatures of the zones as an entry and the thermal model uses the airflows as an entry as well. Both thermal and airflow model run at each time step until convergence is reached using a synchronous coupling method. An algorithm has been developed to ensure the convergence for each time step (from 1/10 to 1 hour). Two case studies are presented. First, the case of a residential building, project of Vinci Construction France where the influence of air tightness on heating loads is being studied. Then the case of a concept building, Effibat, being developed by Vinci Construction France and MINES ParisTech. This building is an urban dwelling building including an atrium. Natural ventilation is used to cool the building at night in summer and the model aims at evaluating the resulting comfort level

Performance evaluation of an air-to-air heat pump coupled with temperate air-sources integrated into a dwelling

ISBN : 978-0-947649-40-1 Disponible à l'adresse : http://www.ibpsa.org/proceedings/BS2009/BS09_2266_2273.pdfInternational audienceAn inverter-driven air-to-air heat pump model has been developped and implemented in the thermal simulation tool COMFIE, in order to compare the seasonal performance of a variable capacity air-to-air heat pump coupled with temperate air sources (crawlspace, attic, sunspace, heat recovery ventilation, earth-to-air heat exchanger) with the performance of a conventionally installed heat pump. The empirical model of the heat pump is presented in this paper, including full-load and part-load model at rating and non rating conditions, and also frosting conditions. Several coupling configurations are studied and applied on a case study: a French typical residential house. The influence of the climatic region is evaluated, giving indications on energy saving using such systems

Eco-design of buildings and comparison of materials

International audienceSustainable building integrates many issues, for instance: reducing energy consumption while keeping a high level of thermal comfort (in winter as well as in summer conditions), global environmental problems such as global warming or ozone depletion, indoor air quality issues, relevant material resource and waste management. Such issues are highly related to the choice of building materials. Eco-design requires therefore a relevant integrated assessment for the building materials not only at the process stage but over the whole life cycle of the buildings including the dominant use phase. Life Cycle Assessment (LCA) applied to buildings is enlarging the scope of material assessment. An innovative approach, EQUER (Evaluation of environmental quality of buildings), has been developed at Ecole des Mines for architects and consultants by linking a life cycle simulation tool with a building thermal simulation. The life cycle inventory database Ecoinvent is used to evaluate the environmental impacts of material fabrication and other processes (energy, transport,...). There are still many uncertainties and limits to the present state of the art of LCA. The uncertainties concern both the data (inventories) and impact indicators. For instance, the global warming potential (GWP) of other gases than CO2 is known with a high rate of uncertainty. Global indicators related to human or eco-toxicity are doubtful because the location of the emissions is not considered: in fact air pollution inside buildings do have a much larger effect than diluted external emissions and no indoor indicator has yet been elaborated. Also, the processes occurring at the end of the building life cycle are difficult to foresee, particularly because buildings are generally long lasting (though it may be assumed that mixing materials -concrete with polystyrene or wood for instance- will make the future waste management more difficult). Despite these limits, an attempt to convert these inventories data into a meaningful environmental profile is proposed in order to perform sensitivity studies for different building materials and derive environmental material performance according to a specific building use. We propose here a contribution concerning the evaluation of quantifiable environmental impacts of buildings for different material choices and end of life scenarios. The output of the software is an eco-profile including the different CML indicators (global warming, acidification, eutrophication potentials, smog, etc.), IMPACT2002+ indicators (human toxicity and ecosystem quality) plus some aggregated values like primary energy and water consumption, generation of radioactive and other waste. These indicators are given either for the different phases or for different alternatives or projects. The methodology is presented and illustrated by a comparative study on a single family house, concerning the comparison of three structural materials: concrete blocks, bricks, and timber. The results of this exercise are presented and its limits are discussed

Des éco-techniques à l'éco-conception des bâtiments

Disponible sur internet : http://perso.univ-lr.fr/fcherqui/IBPSAmars2006/02_BPeuportier.pdfNational audienceLes recherches menées à l'École des Mines de Paris depuis la fin des années 70 ont porté sur diverses techniques d'économie d'énergie et d'intégration des énergies renouvelables dans les bâtiments (solaire passif, solaire actif, solaire photovoltaïque). Plus récemment, des travaux ont été initiés sur les échangeurs air/sol (appelés parfois " puits canadiens "). Des modèles de bâtiments ont été développés pour évaluer les besoins de chauffage, de climatisation et d'éclairage, puis ils ont été étendus à l'évaluation des impacts environnementaux par l'analyse de cycle de vie. La programmation orientée objets a permis de capitaliser les connaissances, en facilitant le chaînage de ces différents modèles. Cet ensemble logiciel comporte un certain nombre de limites, en particulier sur la prise en compte des mouvements d'air, de l'humidité et de certains équipements. Des activités complémentaires de validation seraient utiles, en particulier dans le cas de bâtiments à très faibles besoins. L'utilisation de ces outils comme aide à la conception est facilitée par une interface conviviale, qui pourrait encore être améliorée de manière à progresser vers l'écoconception des bâtiments. Enfin, une extension à l'échelle d'un quartier est en cours de développement. Research activities have been performed at Ecole des Mines de Paris since the seventies, regarding energy efficient techniques and the integration of renewable energy systems in buildings (passive and active solar, photovoltaic systems). More recently, earth/air heat exchangers have been studied. Building models have been developed to evaluate heating, cooling and lighting loads. Thesenmodels have been complemented with life cycle assessment in order to estimate environmental impacts. Object oriented programming allowed the modelling contributions on each technique to be integrated in a whole software package. The limits of this model concern air movements, humidity transfer, and some types of equipment. Complementary validation work would be useful, particularly for low energy buildings. The use of these tools as design aid benefits from a user friendly interface, but further improvement would still be useful in order to progress towards eco-design. Finally, an extension of the models at a settlement level is in progress

Towards the development of a simplified LCA-based model for buildings: recycling aspects

Disponible à l'adresse : http://leso.epfl.ch/files/content/sites/leso/files/download/publications/cisbat_proceedings_final_download.pdfInternational audienceThe building sector identified as a main contributor of energy and resources consumption contributes to many environmental impacts such as resources depletion or climate change. The identification, quantification and analysis of the main flows of matter, energy and pollution through the building system by means of appropriate methods can help to provide knowledge and tools for decision making. The Life Cycle Assessment (LCA) is, in this context, a method which can be applied to study the environmental impacts of buildings. Several LCA-based environmental analysis tools have been developed over the past few years. However, the relevance of such tools is often questioned. The methodological choices seriously influence the results of the analysis particularly in terms of data quality, type and number of environmental indicators, recycling take-account, modelling of the end of life (EOL) and more widely the chosen system boundaries. As a result of all of these shortcomings, the LCA studies are often seen as being too complex for application in the design process. In this article, we present the current LCA models characteristics for buildings. Then, we focus the analysis on the recycling and EOL of products by presenting the current practices. It has been found that current LCA models do account for material, recycling and end of life aspects but in a way so that it is not an easy task to evaluate the design choices for these aspects. Through the adopted methodology, main recycling criteria of LCA models were identified and consequences of defining a proper boundary system for a LCA model are discussed. We conclude by discussing the challenges of improving the LCA methodology for buildings

Vers un habitat à énergie positive : éclairage sur notre futur commun

Disponible à l'adresse : http://www.r2ds-ile-de-france.com/IMG/pdf/Eclairages_numero_2VF.pd

COMFIE: a software for passive solar design

International audienceThe "object oriented programming" and model reduction techniques give some new possibilities to develop computer tools. It is now possible to design a building on the computer, using computer objects corresponding to architectural concepts (materials, walls, windows,...). Representing the building as a structure of objects is an approach which is particularly adapted to a thermal analysis and a comparison of designs, possibly with the help of an expert interface. On the other hand, a fast and accurate thermal evaluation of a project is now possible by simulation, thanks to mathematical models of reduced order. The simulation offers a sensitivity to the numerous design parameters, and provides both an estimation of the heating load and of the summer comfort. Such a design tool, COMFIE, has been developed on these bases at the Ecole des Mines in Paris, on an IBM compatible microcomputer (AT type). A version also exists on a macintosh. These machines are accessible to all professionnals, and not only to large consultant offices

Couplage d'un modèle thermique issu de COMFIE avec un chauffage régulé électriquement pour une simulation temporelle hybride à pas variable

National audienceLe but de cet article est de présenter le couplage réalisé entre un modèle thermique de bâtiment construit à partir du logiciel COMFIE et un modèle de chauffage dans MATLAB/Simulink. Il s'agit d'une interopérabilité entre deux domaines régis par des phénomènes de natures différentes : continus pour la thermique et événementiel pour la régulation du chauffage, le tout interagissant de manière fortement couplée. La simulation par pas variable assure une bonne gestion de cette hybridation et permet de simuler rapidement les températures en tenant compte d'une manière précise de l'occurrence des évènements dus au système de contrôle. Cette étude se fait dans le cadre de la nécessité de coupler des modèles thermiques (COMFIE) et électriques (cf. régulation chauffage) dans la perspective de simulation des bâtiments BBC et à énergie positive : ceci nécessitant de gérer des problèmes d'interopérabilité entre environnements