Very low energy buildings: analyse of two case studies in France

Due to the exhaustion of fossil resources and greenhouse warming, the control of energy has become a key subject for the 21st century. To control energy demand, each countryhas to conceive low and very low energy buildings.In this context, we first inquire what characterize low and very low energy building so as to agree on a definitionof those buildings. Then, the paper introduces the seven guidelines of design of low energy buildings and describes techniques to set them up. Those guidelines are of two kinds, structural ones dealing with envelope and bioclimatic conception, and functional ones dealing with equipments and energy transformation.The paper then reviews two case studies located in the west part of France in the oceanic climate, a single house and a collective building, both low consumption. They comply with the seven guidelines in different ways, the collective building preferring structural guidelines, and the house promoting functional ones. The comparison goes through their conception and their results. First, it presents the two different approaches in their conception and introduces low energy techniques used in the building.Then, questionnaire and measurement give the distributionof their consumptions, indoor air temperature and comfort. Last, the results analyse leads us to inquire into the appropriate way to build low consumption buildingsin our climate and to ask how relevant the package mechanical ventilation with heat recovery and superior thermal insulation is for the French oceanic climate.