Elementary School in Mulhouse, France

21 Bis rue des Franciscains

68100

Mulhouse, Frankreich

Architekt

Pierre Lynde, Formats Urbains Architectes Associés
39 rue de Victor Schoelcher 68200 Mulhouse
contact@formats-urbains.fr
33 (0)3 89 33 27 90

Besitzer

Ville de Mulhouse - Pôle Education et Enfance
11 avenue du Président Kennedy 68200 Mulhouse
education-enfance@mulhouse-alsace.fr
(+33)3 89 32 58 72

Ansprechpartner

Elodie HEBERLE
Cerema
elodie.heberle@cerema.fr
+33388777931

Other Information

Visits
Please contact Ville de Mulhouse to visit the school outside of class hours.

Related publications
The school is one of the case studies of the CREBA (French knowledge center for responsible retrofit of heritage building) website.
General picture of the building (author : CREBA)
This hard-stone elementary school is located in Mulhouse in the Alsace region (north-eastern France), near the border with Germany. It is a listed building, as it witnesses the history of the city of Mulhouse : it first was a spinning factory at a time which Mulhouse was well-known for its textile industry and became a school after the annexation of Alsace and Moselle by Germany in 1870. It has recently been retrofitted. The project reaches a balance between low energy consumption and heritage preservation, despite a constraint budget. The school is one of the case studies of the CREBA (French knowledge center for responsible retrofit of heritage building) website.
Energieeffizienz
69 kWh/m2.y

Klimazone Cfb

Höhe über dem Meer 301 m ü.d.M.

Heizgradtage 1961

Kühlgradtage 719

Unterschutzstellung denkmalgeschützt

Ensembleschutz:
Nein

Stufe der Unterschutzstellung:
The street-facing façade, the roof and two inner staircases are classified on the French supplementary historic monument list.

Baualter 1700-1800

Letzte Sanierung:
2015

Vorhergehende Sanierungen:
1980

Gebäudenutzung Educational/Research

zusätzliche Nutzung:
NA

Gebäudebelegung:
Discontinuous occupancy (i.e. holiday home)

Anzahl der Bewohner/Nutzer:
300

Gebäudefläche Nettogeschossfläche [m²]: 1925,0

Gebäudetyp:
Detached house

Anzahl der Stockwerke:
2

Keller ja/nein:
Ja

Anzahl der beheizten Stockwerke:
2

Bruttogeschossfläche [m²]:
1925,0

Thermische Gebäudehülle [m²]:
5775,0

Volumen [m³]:
5775,0

NGF Berechnungsmethode:
SHON (fr)

Bauart
Stone masonry wall

Außen:
Rendered

Innen:
Lime coating

Dach:
Pitched roof

+ MEHR - WENIGER
General picture of the building (author : CREBA)
General picture of the building (author : CREBA)
3d-view of the building (author : Pierre Lynde)
3d-view of the building (author : Pierre Lynde)
City map from 1642 (author : Wikipédia)
City map from 1642 (author : Wikipédia)
Sandstone and limestone (author : Pierre Lynde))
Sandstone and limestone (author : Pierre Lynde))
Mass lay-out (author : CREBA)
Mass lay-out (author : CREBA)
Main facade (author : CREBA)
Main facade (author : CREBA)
Mercury's head (author : CREBA)
Mercury's head (author : CREBA)
Listed staircase during the works (author : Pierre Lynde)
Listed staircase during the works (author : Pierre Lynde)
Rococo style lounge (author : CREBA)
Rococo style lounge (author : CREBA)
Cement coating and cracks (author : Pierre Lynde)
Cement coating and cracks (author : Pierre Lynde)
Wall tilting inwards (author : Pierre Lynde)
Wall tilting inwards (author : Pierre Lynde)

RENOVIERUNGS-PROZESS

Architektur

BESCHREIBUNG

The school is located in Mulhouse, the third city of the Alsace region after Strasbourg and Colmar. The parcel is known since 1726 as the "Cour de Lorraine" (backyard of Lorraine), due to the origin of its first owner, coming from the neighbouring Lorraine region. The building was probably bought in the mid-18th century by the famous Mulhousian industrialist Jean-Henri Dollfus, to install a cotton priting factory (called "indiennes"). In the beginning of 1800, an imposing spinning factory was built in the backyard, in front of the building today sheltering the school (see mass lay-out : to the left, the parcel in 1825, to the right, the parcel today). This building was then dedicated to housing for the manager and his family and workshops. In 1870, the factory and the northern part of the building burned down. This part is still today ended by a blind gable wall. In 1871, Alsace-Moselle becomes German. Unlike in France, education is compulsory in Germany and raises a huge needs for schools. The "Cour de Lorraine" building is requisitioned and shelters since then an elementary school. Before retrofitting, the school welcomed over 300 pupils, split into 13 classes. The ground floor was occupied by the canteen, an official housing and a technical room. The building is built in Mulhouse intra-muros, which was long surrounded by canals (see the 1642 city plan). It has no real basement, the attic is inoccupied and the building as a shape of a "L" : the exterior façades are giving to the streets and the interior façades to the backyard. They are 60 cm thick and are made of rubbles of yellow sandstone and limestone. The lower sections, the horizontal string courses and the window frames are in pink Vosges sandstone. The building has a heated area of 1925 m² on three storeys. A gymnasium, that was built in 1891 in the backyard had been demolished in 2010.
Städtebaulicher Kontext
The building is located in the city-center of Mulhouse. At the time of its construction, it was in Mulhouse intra-muros, which was long surrounded by canals.

DENKMALWERT

ERHALTENSWERTE ELEMENTE
The street-facing façade is remarkable : it is symetric with yellow sandstone decorations. One of these represents the head of the god of commerce Mercury and a lion's head. A triangular pediment, pierced by an oculus, and a carriage entrance were preserved. The entire façade is listed since 1981. A rococo style lounge, located in the second floor, is a rare remaining of the interior design, with the staircases and the ironwork. Some cast irons columns from the 19th century, which were meant to strengthen the structure, were reused as decorations. A complete survey of all the elements worthy of preservation was made by the regional commissioner for historic monumentsnd archived. The Survey revealed some original construction techniques, as solid wood and plaster partition walls from the 17th century, when the initial building was built on the parcel. Archeological excavations were conducted before the works. In the backyard, Gallo-Roman coins, a medieval enclosure and civilans protection galleries from World War I were found. In the inside of the building, a medieval basement was also discovered, surveyed and filled in with soil.
Denkmalwert und wie er bestimmt wurde
The street-facing façade, the roof and two inner staircases (see picture) are classified on the French supplementary historic monument list : http://bit.ly/30YVwNO As a listed building, the validation of the works and the main façades, the roof and the two inner staircases by the Regional commissioner for historic monuments was required by regulation.
Dateien zur Bewertung
Engraving of the spinning factory (author : Engelmann, 1823)
Engraving of the spinning factory (author : Engelmann, 1823)

Erhaltungszustand

Erhaltungszustand der Gebäudehülle
The presence of the canals, not deep enough foundations and the progressive replacement of the exterior lime coating with cement coating in the eighties (see picture) led to disorders : - insufficient stability of the structure : the foundations subsided from several centimeters, and so did the partition walls and the floors. The internal angle of the building showed cracks and tilted clearly inward (see picture). - moisture accumulation : Almost all the joists were mouldered and had already been repared in the past, possibly during the German annexation. Efflorescence were visible on the lower sections. Dry rot, developing in moist and dark areas, was also discovered at the foot of one of the listed staircases and immediatly treated, as it spreads very quickly and feeds on wood. The backyard of the school was depolluted after mercury was discovered while digging. Asbestos, coming from works carried out in the eighties, was also removed. Ventilation, which was provided by opening the windows, was also insufficient. The framework, which was replaced in the 19th century, was in good state. Double-glazing windows were installed progressively, from the nineties to more recently.
Haustechnische Anlagen vor Sanierung
The school was never insulated before. A fuel boiler was installed in a technical room in the ground floor. The heat is distributed throughout the building by water circulating through pipes. Domestic hot water was provided by instant electric heaters, installed in sanitations.

Ziel der Sanierung

Renovation + Extension
The retrofitting project lasted from 2015 to 2017. This project is part of a wider program, aiming to retrofit all the Mulhousian schools and create the best conditions possible for pupils. The project in particular consists in two differents ones : - the retrofitting of the existing building - the construction of a new building in the backyard, sheltering the canteen, sanitations, rooms for after-school activities and a sports hall. Because of the presence of a listed building near the new construction, the validation of the works by the Alsatian architectural review board was required by regulation. For the retrofitting, the project owner had several objectives : - strengthening of the structure ; - adressing regulatory obligations, like the risk of fire and the seismic risk, as Mulhouse obtains the rating of 3 on the French seismic risk scale, going from 0 to 5, but also ensuring accessibility for disabled people ; - improving the indoor air quality, even above the French regulatory standards, but also the acoustic comfort ; - conserving the listed parts of the building but also the rare remaining of the interior design ; - keeping the costs under control, because of a restraint budget ; - and, of course, reducing the energy consumption. In the first version of the project, achieving the French low energy building ("Bâtiment basse consommation") label was not an objective. But thermal simulations showed that it was technically possible. Thanks to a grant from the Alsace Region and the French environment and energy management agency, the label was also financially achievable. The project management team was composed of an architect as the project supervisor and several engineering consultants specialised in building physics, structure, electricity, acoustics and building services. The craftspeople were coming from the near region and were medium-sized companies.
Gewonnen Erkenntnisse / besondere Erfahrungen
The project management team used building information modeling (BIM) for the construction of the new building but also for the retrofitting of the existing one. This has prevented conflits between technical and architectural decisions. It was also a powerful tool to communicate with every stakeholders, including the project owner. This project was difficult in many ways : - first, it was a double project, with both a new construction and a retroffiting ; - then, mercury pollution in the backyard had not been anticipated, resulting in extra costs. - the retrofitting building was in a very bad state, because of structural issues, but also previous works that engendered moisture accumulation. - finally, a real effort of communication has been necessary to find compromises between low energy consumption, heritage preservation and the constraint budget. The school was inaugurated in 2017 and was the subject of several articles in the regional press. A visit was also organised on the occasion of the Heruitage Days in the same year.
Beteiligte Akteure
Öffentliche Hand
Ville de Mulhouse - Pôle Education et Enfance
11 avenue du Président Kennedy 68200 Mulhouse
education-enfance@mulhouse-alsace.fr
Tel.( 33)3 89 32 58 72
Architekt
Pierre Lynde, Formats Urbains Architectes Associés
39 rue de Victor Schoelcher 68200 Mulhouse
contact@formats-urbains.fr
Tel. 33 (0)3 89 33 27 90
Energieberater
IBEO
39 rue de Victor Schoelcher 68200 Mulhouse
contact@ibeo.fr
Tel. 33 (0)3 89 33 27 98
Eingesetzte Software/Berechnungstools
Folgte die Sanierung einer spezifischen Methode? Nein
Energiebilanz The consumption for heat, domestic hot water, ventilation, lighting and pumps was calculated, before and after retrofitting, with a State approved calculation software. The software doesn't provide a dynamic simulation.
Hygrothermische Bewertung A dew point analysis was performed for walls.
Life Cycle Analysis (LCA) No life cycle analysis has been conducted.
Anderes BIM

SANIERUNGS-LÖSUNGEN

Außenwände

Yellow sandstone and limestone rubbles

Yellow sandstone and limestone rubbles

The original exterior lime coating was progressively replaced with of cement coating in the eighties. To put things back the way they were before and prevent more moisture-related damages, cement coating was removed and replaced with lime coating. In the interior, plaster coating was also removed and 8 cm of mineral wool and a humidity-variable vapour-retarder were installed and recovered with plasterboards. A technical space between the vapour-retarder and plasterboards was designed in order to pass the electrical network but also to prevent the piercing of the vapour-retarder. Biobased insulation was first chosen, but mineral wool was finally used because it was cheaper. A dew point analysis (see picture) was performed for walls to validate this choice.

The original exterior lime coating and some exterior decorations, like the lion's head, were restored. The colour of the lime coating is given by the local sand and close to the yellow limestone used to build the building. In the interior, there was no painting on walls or other elements to preserve. So there is no real issue about conservation compatibility

U-Wert (vor Sanierung) [W/m2K]: 3,0 W/m²K U-Wert (nach Sanierung) [W/m2K]: 0,34 W/m²K
Mehr Details
Aufbau Bestandswand
Render - Ciment coating:
30 mm
Stone - Limestone and sandstone rubbles:
500 mm
Plaster - Plaster coating:
30 mm
Aufbau sanierte Wand
Render - Lime coating:
25mm
Stone - Limestone and sandstone rubbles:
500 mm
Insulation - Mineral wool:
80 mm
Other - Humidity-variable vapour-retarder:
1 mm
Air gap - Technical space:
48 mm
Dry-lining - Plasterboard:
18 mm


Fenster

Double-glazed wooden windows

Double-glazed wooden windows

For cost reasons, only half of the windows was changed. There were already all double-glazed and some of them were replaced in 2010. The windows in bad state were replaced by wooden double-glazed windows with glazing bars. The others were repaired and adjusted and their seals were changed. The walls around the windows were not insulated because it was technical too difficult. So there are assumed thermal bridges between the walls and the windows.

The original single-glazed windows were replaced long ago. As there was no regulatory requirement on them, they were not replaced with identical ones. However, the windows are still in wood and with glazing bars.

Bestandsfenster U-Wert Glas [W/m2K]: 2,8 Neues Fenster U-Wert Glas [W/m2K]: 1,4 Bestandsfenster U-Wert Rahmen [W/m2K]: 2,8 Neues Fenster U-Wert Rahmen [W/m2K]: 1,4
Mehr Details
Fenstertyp Bestand Casement window
Verglasungsart Bestand Double
Verschattung Bestand NA
Ungefähres Einbaujahr 1980
Neuer Fenstertyp Casement window
Verglasungsart des neuen Fensters Double
Verschattung des neuen Fensters Inner curtains
Neuer Energiedurchlassgrad g [-] 0,5

Weitere Maßnahmen

DACH

ERDGESCHOSS

SONSTIGES

MASSNAHMEN UM DIE LUFTDICHTIGKEIT ZU VERBESSERN

DACH

The attic floor was insulated by the interior with 26 cm of mineral wool. A vapour-retarder was installed between the insulation and the ceiling cladding. The attic floor is suspended to the roof with iron fittings. This is the traditional technique, dating from the 18th century. But it does not comply with fire safety and every iron fitting had to be shuttered with plaster and wood. To even more security, a fire detector was installed in the attic. The tiles dated from the thirties. Only the ones in bad state were replaced.

Original tiles were replaced long ago. Dormers, that had been removed, were rebuilt in a more contemporary style. They today hide the exhaust and air intake stacks of the two dual-flow air handling units of the building. All these works were validated by the Regional commissioner for historic monuments, as the roof is a listed part of the school. Therefore, there is no issue about conservation compatibility.

U-Wert (vor Sanierung) [W/m2K] 0.95 U-Wert (nach Sanierung) [W/m2K] 0.12
Mehr Details
Aufbau Bestandsdach
Other - Original wooden floor of the attic:
20 mm
Other - Wooden joist:
200 mm
Other - Old ceiling cladding:
20 mm
Aufbau saniertes Dach
Other - Original wooden floor of the attic:
20 mm
Other - Wooden joist:
200 mm
Other - Mineral wool:
260 mm
Other - New ceiling cladding:
20 mm
ERDGESCHOSS

The ground floor sits on a concrete slab. It was insulated with 8 cm of polyurethane and an underfloor heating was installed above.

Original ground floor were replaced long ago. Therefore, there is no real issue about conservation compatibility. Regarding the high ceilings, adding insulation on the ground floor did not have a noticeable impact on floor level.

U-Wert (vor Sanierung) [W/m2K] 1.7 U-Wert (nach Sanierung) [W/m2K] 0.35
Mehr Details
Aufbau Boden/Kellerdecke im Bestand
Concrete slab - Concrete slab:
200 mm
Finish - Old finish:
1 mm
Aufbau Boden/Kellerdecke nach Sanierung
Concrete slab - Concrete slab:
200 mm
Insulation - Polyurethane:
80 mm
Other - Underfloor heating:
50 mm
Finish - New finish:
1 mm
SONSTIGES

To prevent moisture accumulation in the lower sections of the buildings, a paved strip of 1 m 40 was managed between the walls and the bituminous surfacing of the backyard (see picture). Almost all the joists ends of the intermediate floors were mouldered. It was decided to completely replaced these floors (see picture). The new floors, consisting in hollow-care slabs, have several advantages : they have a better fire resistance, provide a better acoustic comfort and strengthen more effectively the structure than wooden floors. Because of the foundations that had subsided from several centimeters, concrete screeds were poured on the new intermediate floors in order to have a right horizontal surface. The peripherical edges of the new floors were not insulated so there are assumed thermal bridges between the walls and the intermediate floors. Thanks to the construction of the new building in the backyard, the canteen and the technical room were removed from the ground floor of the existing building. This resulted in a space saving and the school can now welcome 18 classes instead of 13 before. The interior design was also rearranged, in order to comply with the accessibility requirements. An elevator and new staircases were installed.

In the second floor, the ceiling of the rococo style lounge was preserved and reinforced from above with steel beams. A derogation was delivered for the two listed staircases, as they could not be brought up to regulatory accessibility standards. There is no issue about conservation compatibility.

MASSNAHMEN UM DIE LUFTDICHTIGKEIT ZU VERBESSERN

The carriage entrance was very leaky. On the other hand, it was not used any more as an entrance for pupils. So the solution was to install in the inside a glazed door, more airtight, in front of the carriage entrance (see picture). An airtightness test was conducted, even if it is not required for French low energy building label for existing non-residential buildings, and lead to a good value, even lower than what is required for new non-residential buildings. To improve this value, some adjustments on windows and on the door giving in the attic were done. NB : the only available value was the French airtightness indicator Q4Pa,surf, which can not be converted in n50 without some other values, that are unfortunately missing.

Airtightness (pre-intervention) [ach@50Pa] 0 Airtightness (post-intervention) [ach@50Pa] 0

HVAC

HEIZUNG

LÜFTUNG

HEIZUNG

The technical room was shifted from the existing building to the new one. It shelters two condensing gas boilers of 224 kW each, that cover 200 % of the heating demand. This is a specific requirement of the city of Mulhouse, in case of failure of one of the boilers. A underfloor heating was installed in the entire ground floor. The intermediate floors are heated with new radiators. The cost of the reuse (checkup, cleaning, painting and storage) of the existing ones was judged too expensive. Temperature is being controled in each classroom by the city's technical services, to the nearest 0,1 degrees Celsius, thanks to a building management system (BMS). This BMS was also installed in the new building and energy consumptions of both buildings are monitored. The BMS needed several months to be fully operational.

There are few remainings of the interior design and the existing radiators were installed in the 20th century. Therefore, there is no issue about conservation compatibility.

Mehr Details
Heizungssystem nach Sanierung zusätzliches Heizungssystem nach Sanierung
Art der Heizung Boiler Condensing
Brennstoff Gas Gas
Wärmeverteilung Radiators Radiating floor
Nennleistung 0 kW 244 kW
LÜFTUNG

There was no mechanical ventilation. Improving indoor air quality, even above the French regulatory standards, was one of the objective of the retrofitting. As natural ventilation hardly meet the regulation, a mechanical system was installed. Two dual-flow air handling units were installed in the attic (see picture) and the exhaust and air intake stacks were hidden in the new dormers. They are only functioning during the class hours, in order to save energy. In winter, the fresh air is filtered to eliminate fine particles, then preheated by the heat exchanger and a hot water battery and finally distributed all over the classrooms at a temperature of 21 °C. The air flow is calculated from the number of pupils in the classroom and the exhaust and air intake vents are located on both sides of the classroom to ensure an effective ventilation. In mid-seasons, the heat exchanger by-pass is activated and the fresh air is not preheated anymore.

The two dual-flow air handling units are installed in the attic. The integration of the exhaust and air intake stacks in the new dormers was validated by the Regional commissioner for historic monuments. In the interior, the ducting needed for the air handling system resulted in lowered ceiling. But as there was no painting on walls or other elements to preserve, there is no real issue about conservation compatibility.

Mehr Details
Aufbau Bestandsdach Neues Lüftungssystem
Lüftungstyp Centralized
Type flow regime Cascade
Wärmerückgewinnung Ja
Feuchterückgewinnung Nein
Nennleistung Unknown kW
Elektrische Leistung 0,0 kW
Regelung Yes

Energieeffizienz

Energieeffizienz
Energieausweis The retrofitted school reaches the class B of the French energy performance certificate.
Freiwillige Zertifikate The retrofitted school obtained the French low energy building ("Bâtiment basse consommation") label. To obtain this label, the consumption for heat, domestic hot water, ventilation, lighting and pumps must be calculated with a State approved calculation software and be lower than 40% compared to a calculated reference. The energy consumption detail can be find in the energy use section. It shows that heating is the largest energy user in the building, followed by ventilation.
Energievrabrauch
Heizung
Primärenergie 69 kWh/m2.y
Documents:
GE_T_P_3.jpg
Energy consumption of the building (author : Pierre Lynde)

Energieverbrauch vor Sanierung 214 kWh/m2.y
Energieverbrauch nach Sanierung 69 kWh/m2.y

Primärenergie
Berechnungsmethode Steady state simulation (e.g. EPC, PHPP)
Energieverbrauch vor Sanierung 214 kWh/m2.y
Energieverbrauch nach Sanierung 69 kWh/m2.y
Gemessene Parameter
Raumklima
Type_of_monitoring: Continuous
Description: The classrooms temperature and air flow are constantly monitored by the building management system and adjusted.

Raumklima

Temperatur

The classrooms temperature is constantly monitored by the building management system and adjusted. Overheating was reported at the end of the school year in 2017. The dual-flow air handling units were programed to provide a constant indoor temperature. This probably means that the windows were opened although they were supposed to remain closed for the good functioning of the units.

Indoor Air Quality

Improving indoor air quality, even above the French regulatory standards, was one of the objective of the retrofitting. Two dual-flow air handling units include fine particles filters and the classrooms air flow is constantly monitored by the building management system and adjusted.

Daylight

Visual comfort was also studied. Indirect lighting and white-coloured paints were favored in the classrooms. LEDs and presence detectors were also installed, as lighting is a major energy consumer in non-residential buildings.

akustischer Komfort

Acoustic comfort is very important in a school. Acoustic suspended ceiling were installed both in the classrooms and in the circulations.

Kosten

Finanzielle Aspekte

In the first version of the project, achieving the French low energy building ("Bâtiment basse consommation") label was not an objective. But thermal simulations showed that it was technically possible. Thanks to a grant from the Alsace Region and the French environment and energy management agency, the label was also financially achievable.

Betriebskosten
Lifecycle cost
Nein

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