These buildings are distinguished from those of the 1949-1973 period, being in general less energy consuming and presenting a very different hygrothermal operation.
The study-council of the State is free download.
The renovation of the existing building stock is a major challenge to achieve the objectives of lower energy consumption and greenhouse gas emissions:
- In 2012, nearly 45% of the final energy consumed in France came from residential and tertiary energy, a figure reduced to 38% in Alsace, of which 25% came from housing alone.
As part of the Plan for the energy renovation of housing, the Regional Directorate for the Environment, Planning and Housing of Alsace (DREAL) and the Regional Directorate for Cultural Affairs of Alsace (DRAC) have launched a study "Old housing in Alsace: energy and heritage".
This study is freely available via sheets and reports to download at the bottom of this page or on the DREAL site :
- eight sheets (general method and one sheet by type of frame studied);
- technical reports;
- a state of the art of renovation practices.
Published in two phases, "Comprendre" (September 2014) and "Agir" (September 2015), the study "Ancient housing in Alsace: energy and heritage" was conducted by CEREMA-Est and the architectural firm Oziol-De Micheli, in association with all the local partners involved in the energy renovation of buildings.
A thermal typology of pre-1948 buildings was first defined, for the first time in Alsace. Seven representative dwellings were selected, instrumented and studied (physical parameters, hygrothermia) for seven months:
- the apartment in a building adjoining the suburbs
- the apartment in a semi-detached building
- the mansion built of bricks
- the independent masonry house
- the masonry dwelling house in a farmhouse
- housing in a half-timbered farmhouse
- the half-timbered house with schlupf
These observations allowed to model seven housing-types thanks to a thermodynamic software, on which a wide range of energy renovation gestures were tested and compared.
Different insulation materials were compared (benefits, risks, costs). Three renovation scenarios were proposed for each type, and evaluated according to five criteria: energy savings, summer comfort, reduced cold wall effect in winter, no risk related to moisture in the walls, respect for the heritage and architectural aspect. The construction costs were estimated, both in terms of profitability and sustainability, and were compared to the cost of inaction in euros and tonnes of CO² not emitted.
The study reveals the qualities of the old Alsatian building before renovation:
- energy label close to or above the national average, which represents rather good thermal performance given the harsh local climate;
- very good summer comfort, linked to its good inertia, almost no thermal bridges, hygrothermal balance;
- buffer spaces (cellars, lean-to, etc.) and "Schlupf" (empty spaces about 80 cm wide between houses) with a beneficial thermal role.
The study demonstrates the good results in terms of energy savings obtained through the work:
- a significant energy improvement (BBC-renovation) can be achieved while respecting the main characteristics of facades, roofs and carpentry.
- Other approaches are also possible to gain one to two classes of energy label, favoring other criteria: limit costs, act in stages or favor a more complete preservation of the heritage and architectural quality of the building.
- The study also shows that proper maintenance of the frame and limiting air leakage is in itself an effective action.
The study highlights points of vigilance:
- Energy renovation actions impact summer comfort, more or less significantly depending on the scenarios;
- the installation of an external thermal insulation has a significant impact on the architectural aspect of the old building (in the study, this solution was tested only in a particular case); the installation of an insulating external coating is sometimes possible;
- the conservation and/or improvement of existing windows and doors is almost equivalent to their replacement from an energy point of view when the walls are insulated, making it possible to reconcile performance and complete preservation of the architectural value of the facades;
- The choice of insulation and the quality of its implementation are essential to preserve the initial hygrothermic balance of the old walls;
In conclusion, the study highlights that the approach to energy renovation of old buildings must be multi-criteria.
This work was carried out in partnership with many local stakeholders:
Regional Council of Alsace, Departmental Councils of Bas-Rhin and Haut-Rhin, Eurométropole of Strasbourg, Communauté d'agglomération de Mulhouse, CAUE 67 and 68, ADEME, Info Service Renovation Points, Regional Natural Parks of the Vosges du Nord and Ballon des Vosges, Pôle de compétitivité Énergivie-Fibres, Caisse des Dépôts, FNAIM, Lessors, FFB, EDF, CAPEB, ASMA/MPF, Regional Order of Architects, AART-A.
1Source: ASPA 14040401-ID, version 19.05.2014
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