Contractor

Name : Commune de Rosny-sous-Bois

Contact : 01 49 35 37 00

Construction Manager

Name : Commune de Rosny-sous-Bois, direction recherche et innovation territoriale

Contact : moerosny93[at]rosnysousbois.fr

Stakeholders

Function : Other consultancy agency

SEMOFI
Geotechnical study office

Function : Environmental consultancy

APAVE SUD EUROPE
Control office

Function : Company

UTB
Charpentier

Function : Company

Menuiserie David et Fils
Carpenter

Function : Company

APIJ BAT
Wood and straw construction, plaster on straw

Function : Manufacturer

Lenoir Bois
Sawmill

Contracting method

Separate batches

Energy consumption

• Primary energy need : 42,00 kWhep/m².an
• Primary energy need for standard building : 50,00 kWhep/m².an

Calculation method : Other

Breakdown for energy consumption : Heating: 24.1 kWhpe/m².year DHW: 7.4 kWhpe/m².year Auxiligo: 0.8 kWhpe/m².year Lighting: 8.9 kWhpe/m².year

Envelope performance

More information :

Straw insulated walls, 47cm thick. Mestizo insulated roofs. Ground floor insulated with foamglass.

R of the walls = 9

Indicator : n50

• Air Tightness Value : 0,60

Systems

Heating system :
• Urban network
• Water radiator
• Radiant ceiling
• Solar thermal
Hot water system :
• Urban network
• Solar Thermal
Cooling system :
• No cooling system
Ventilation system :
• Natural ventilation
• Free-cooling
• Double flow heat exchanger
Renewable systems :
• Solar Thermal
• Other, specify

Natural ventilation with heat recovery.

Solutions enhancing nature free gains :

Ventilation naturelle.
Cloisonnement en plaques d'argiles.
Murs paille, enduits 2 faces.
Végétalisation des toitures.
Cour végétalisée, favorisant l'apport de fraîcheur.

Biodiversity approach

Urban environment :

The Simone Veil primary school is part of a neighborhood in the making. Located in the north of the town of Rosny-sous-Bois, it is on the edge of a suburban district which extends between the Rosny 2 shopping center to the north, the railway lines to the east (RER E), the boulevard Gabriel Péri to the south and the avenue du Charles de Gaulle to the west. This district is currently the subject of a town planning consultation.

• Land plot area : 3 436,00 m²
• Built-up area : 48,00 %
• Green space : 1 137,00

Risks

Hazards to which the building is exposed :
• Urban heat island

Risks measures put in place :

• Building of passive design : this makes it possible to limit heating needs by minimizing losses as well as avoiding overheating in summer while benefiting from free solar contributions in mid-season.
• Straw insulation with an R of 9 : the use of this material limits heating needs in winter and keeps you cool in summer.
• Natural ventilation with heat recovery : no electricity consumption to ventilate the building, maintenance is simple and it is a solution that lasts over time.
• Overventilation at night, ceiling fans : low-tech cooling.
• Kindergarten playground without bitumen and partially green roofs : avoids the heat island effect.
• Massive stove as comfort and emergency heating in the event of a power cut.

Product

Natural ventilation with heat recovery
La solution a été conçue par la direction recherche et innovation, Rosny-Sous-Bois et diffusée en partenariat avec le BET Switch.
Ville de Rosny-sous-Bois, BET Switch

Product category :

We are proposing a project that implements an innovative ventilation system which seems to us to be an appropriate response to the current challenges of controlling energy performance at a controlled technological cost: natural ventilation with heat recovery (VNRC).

The system is based on the use of plate heat exchangers in a natural ventilation network. Properly sized, the exchangers recover approximately 50% of the heat from the extracted air and generate acceptable pressure drops.

The originality of the solution lies in the fact that, unlike most natural ventilation strategies which are based on sweeping between an air intake in the lower part and an outlet in the upper part, we implement ventilation paths supply and extraction so that these flows intersect, thus allowing the implementation of heat recovery.

This diagram works if the network is sized sufficiently generously so that the pressure drops induced by the plate heat exchanger remain acceptable; in this case, the pressure differences due to the temperature differences and the action of the wind make it possible, on average, to achieve the expected air renewal.

The implementation of this system supposes the reversal of several solidly established practices concerning the ventilation of tertiary buildings:
• Consider ventilation as a stakeholder in the architecture, integrated into the building, rather than as an independent technical installation, constituting an added layer of distribution ducts.
• Giving users a hand in simple management of air renewal rather than automating the management of a complex installation.
• Aim for overall energy performance of the system rather than just thermal efficiency – in fact, mechanical ventilation installations with heat recovery have thermal efficiency close to 90% but generate significant electricity consumption. The VNRC developed here shows lower thermal efficiency (~50) but has no power consumption for air movement.
• Design a system on a statistical air quality target, based on CO2 concentration, rather than a flow rate target. Current regulations concerning mechanical ventilation are based on achieving air change rates. Natural ventilation is by nature unstable because it constantly balances itself according to internal and external climatic conditions; the air renewal flow is therefore not guaranteed continuously, it must therefore be resonated statistically and in terms of air quality (on the criterion of CO2 concentration) rather than on flow control.

This system was developed, probably for the first time in France, at the Boutours kindergarten in the municipality of Rosny-sous-Bois, by the City's internal project management unit. The Simone Veil school is the 3rd school project on which the VNRC system has been implemented; the design and implementation have reached a certain maturity. Furthermore, the instrumentation and monitoring of previous projects demonstrated the satisfactory operation of the system.
The Simone Veil school is developing this system on a large scale – it is a school of 11 classes – illustrating the replicability of the system.

Users of school facilities equipped with natural ventilation in Rosny-sous-Bois have integrated this new low-tech technology well, appreciating the thermal comfort of these new buildings compared to the existing aging stock. Simple indicators allow them to know the concentration of CO2 in the classrooms and activity rooms, and the teams are supported by the research and innovation department in handling these buildings.

Construction and exploitation costs

• Renewable energy systems cost : 78 000,00 €
• Total cost of the building : 11 700 000 €
• Subsidies : 1 246 700 €
Additional information on costs :

€50,000 geothermal substation.
28,000€ mass stove.

Sustainable design

Functionality economy, recycled and recyclable materials :

The insulation used is made of recycled cotton, produced by Métisse .

Specificities linked to new materials :

Du bois feuillu francilien a été utilisé pour la structure, de la paille bio pour l'isolant.

Pour les cloisons, ce sont des panneaux en terre sur ossature bois qui ont été choisis.

 

Reproductibility and Innovation

The commune of Rosny-Sous-Bois has the role and ambition of serving the common good. For this, the team ensures that the actions are positive or neutral on the physical, biological and social ecosystems. The innovations implemented with this project fall into three categories.

1. Construction principles and materials :
   • solid oak structure with lattice beams and keyed beams;
   • locally prefabricated facade boxes, wooden frame, straw filling and plastic-free double-sided earth coating;
   • interior partitions in clay plates;
   • solid oak furniture.
2. Water and Energy :
   • natural ventilation with heat recovery;
   • sloping green roof;
   • vegetated and permeable courtyard;
   • mass stove;
   • outside biocontrolled litter toilets;
   • natural water retention basin.
3. Citizen involvement:
   • installation of logs to create outdoor games;
   • educational garden;
   • citizen participatory sites of burnt wood;
   • wood recognition training.

Experience sharing:

• Final report Reflex Wood-Biosourced, 2021 (IDF Region): pdf here .
• Research VNRC 2022 (ADEME): Report to come.

Social economy

Social economy and professional integration :

1 ESS structure was mobilized on this project: APIJBAT

GHG emissions

• Building lifetime : 80,00 an(s)

Water management

A storage tank is set up to recover rainwater. This water is then made drinkable for use in water games for children

Indoor Air quality

Analysis of the CO2 concentration in the building: each classroom is equipped with a sensor that simply displays the CO2 concentration. The probe both controls the activation of natural ventilation and collects information all year round. The first results for the Simone Veil school are good: the concentrations are generally lower than 1000ppm.

Comfort

Health & comfort :

Choice of VOC-free materials.

Acoustic comfort :

Acoustic tests of the facade have been carried out, the results are pending. This will make it possible to know more precisely the acoustic performance of straw facades and the impact of air intakes for natural ventilation.

Life Cycle Analysis

Eco-design material :

By choosing to use local biosourced materials (hardwood from the Ile-de-France region, straw) for the construction of our buildings, we are effectively minimizing the GHG emissions associated with their construction.