Saint-Exupéry - two buildings in modular wooden construction

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Last modified by the author on 04/09/2023 - 09:44

New Construction

  • Building Type : Collective housing < 50m
  • Construction Year :
  • Delivery year : 2021
  • Address 1 - street : 1-12 impasse Antoine de Saint-Exupéry 38550 SAINT-MAURICE-L'EXIL, France
  • Climate zone : [Cfb] Marine Mild Winter, warm summer, no dry season.

  • Net Floor Area : 718 m2
  • Construction/refurbishment cost : 1 046 341 €
  • Number of Dwelling : 12 Dwelling
  • Cost/m2 : 1457.3 €/m2

Proposed by :

  • Primary energy need
    74 kWhep/m2.an
    (Calculation method : RT 2020 )
Energy consumption
Economical buildingBuilding
< 50A
A
51 à 90B
B
91 à 150C
C
151 à 230D
D
231 à 330E
E
331 à 450F
F
> 450G
G
Energy-intensive building

 

Since 2021, the town of Saint-Maurice-l'Exil, in Isère, France, hosts a social, innovative and ecological residence comprising two buildings of six rental housing units each. Reflecting the wishes of the social landlord Alpes Isère Habitat, this project combines local wooden modular construction with low-consumption energy systems. This is a first for the lessor, who aims to reproduce this construction system on other residences in order to reduce its environmental impact while offering quality services to tenants.

Local modular constructions in wooden frame

For the Saint-Exupéry residence, the project owner chose a modular construction approach using a wooden frame. The concept is based on the workshop manufacturing of structural elements and finishes in 3D modules. The macro-elements are manufactured, assembled and equipped off-site, in a dedicated workshop. They are then transported by road and assembled on site. This method makes it possible to obtain an excellent quality of finish, thanks to the industrialization of the construction process. The accommodations are delivered and assembled in just a few days. The mission was entrusted to a company located in Villefontaine, less than an hour away from the construction site.

The advantages of this approach are multiple. Off-site construction offers optimal construction conditions, protected from bad weather, which increases the reliability and quality of housing. In addition, overall costs are reduced thanks to the limitation of travel, bad weather and hazards. The construction time is shorter than following a traditional construction method, because the modular elements arrive on site with an advanced level of finish. On this project, the housing was completed in 16 months instead of 18 months! Finally, this approach helps to reduce the environmental impact, because the nuisance linked to the construction site and the emissions due to the transport of materials are also optimized.

Beyond the advantages, choosing this construction system required adaptation efforts on the part of the project owner. The lessor had to adapt to a new way of thinking about building design, framed by the aesthetic and practical constraints of off-site. Collaboration and exchanges were key elements in carrying out this adaptation, in particular with the town hall of Saint-Maurice-l'Exil which was able to ensure that local elected officials and residents would accept these original buildings.

Anticipate regulatory thermal requirements

This residence also stands out for its energy performance. With a primary energy consumption of 74 kWhep/m².year, the objective of the project was to respect, and even anticipate, the environmental regulations governing the performance of new constructions, while controlling rental charges. Thus, the housing has been designed to achieve energy consumption at least 20% lower than the RT2012 thresholds. In the occupancy phase, the housing complies with the 2022 thresholds of the RE2020 environmental regulation.

Heating and domestic hot water are provided by efficient individual gas boilers, which can receive green gas, further reducing the impact of the two buildings. These systems are coupled with significant wood wool or cellulose wadding insulation of the structural elements, in order to correct the low inertia of the wooden walls and reduce losses.

Building users opinion

Tenants appreciate the apparent originality of their wooden housing, a mark of a commitment to a more sober and respectful future. In addition, the need for interventions is reduced and simple (small leaks, electrical or carpentry problems).

If you had to do it again?

  • The size of the modules is limited to road dimensions (max 4m), which requires strict organization of transport and additional efforts on the design of the interior of the housing.
  • As a large part of the work was carried out in the factory, it was necessary to adapt the control to validate progress and refine the payment terms.

Photo credit

Alpes Isère Habitat
A. Messabhia

Contractor

Construction Manager

Stakeholders

Type of market

Not applicable

Other type of market

Design-Production

Allocation of works contracts

Build and sell construction

Energy consumption

  • 74,00 kWhep/m2.an
  • RT 2020

    (Values expressed in kWh/m²(Sref).year)

    Building A:

    • Heating: 32.9 (final energy) / 33.3 (primary energy)
    • Cooling: 2.2 (final energy) / 5.1 (primary energy)
    • ECS: 21.1 (final energy) / 21.4 (primary energy)
    • Lighting: 2.2 (final energy) / 5.1 (primary energy)
    • Aux. distribution: 0.3 (final energy) / 0.7 (primary energy)
    • Aux. ventilation: 1.4 (final energy) / 3.2 (primary energy)
    • Elevator/parking: 2.0 (final energy) / 4.6 (primary energy)

    Building B:

    • Heating: 31.6 (final energy) / 32 (primary energy)
    • Cooling: 3.2 (final energy) / 7.4 (primary energy)
    • ECS: 21.4 (final energy) / 21.7 (primary energy)
    • Lighting: 2.2 (final energy) / 5.1 (primary energy)
    • Aux. distribution: 0.3 (final energy) / 0.7 (primary energy)
    • Aux. ventilation: 1.5 (final energy) / 3.5 (primary energy)
    • Elevator/parking: 2.0 (final energy) / 4.6 (primary energy)


    (Sref): The reference surface area of RE2020 corresponds to the useful surface area (SU) for tertiary buildings and the habitable surface area for housing (SHAB).

Real final energy consumption

    61,60 kWhef/m2.an

Envelope performance

    U of the walls (in W/m².°C):
    - Exterior wall: 0.187
    - Floor over crawl space: 0.197
    - Wooden terrace roof: 0.128
    - Common wall of accommodation: 0.115

Systems

    • Individual gas boiler
    • Individual gas boiler
    • No cooling system
    • Humidity sensitive Air Handling Unit (Hygro B
    • No renewable energy systems

Urban environment

    Saint-Maurice-l'Exil is a town of 6 413 inhabitants (2020), in the heart of the Rhône valley. Historically, cultivated land is predominant. Cultural, sporting and leisure facilities also sit alongside some preserved green spaces.

Product

    Modular wooden construction

    VIEO Habitat Innovant

    Gros œuvre / Structure, maçonnerie, façade

    The manufacturing and assembly of the structure, as well as 90% of the finishing touches to the housing, are carried out in the workshop. The elements are then transported by road and assembled on site.

    The advantages of off-site construction are multiple: weather-proof construction increases reliability and quality, the overall cost is reduced and delivery times are shorter. Associated with wood, this constructive principle allows the creation of efficient buildings, anticipating regulations!

Construction and exploitation costs

  • 1 046 341

Comfort

    The results obtained and measured, in relation to airborne noise and impact sound insulation, are superior to regulatory requirements.

    Shock sound insulation (the lower the measured value, the better the result):

    • Regulation: L’nTw = 58 dB
       

    Project :

    • Stacked premises: L’nTw 51 to 52 dB
    • Juxtaposed premises: L’nTw 39dB
       

    Insulation from airborne noise: speech noise, television noise, etc. (the higher the measured value, the better the result):

    • Regulation: DnTA = 53 dB
       

    Project:

    • Stacked premises: DnTA 60 to 63 dB
    • Adjoining premises: DnTA 67 to 68 dB

Quality of life and services

  • Thanks to the insulation and efficient systems of the housing, rental charges are lower than for other social housing.
  • Each accommodation has an outdoor space: garden or balcony.
  • Tenants have access to covered parking lots with storerooms (carports), parking spaces for visitors and a household waste area along the road.

Ic Energy

499,52 KgCO2 /m2

Ic Construction

589,15 KgCO2 /m2

Initiatives promoting low-carbon mobility

Residents have a collective covered bicycle room.

GHG emissions

  • 12,00 KgCO2/m2/an
  • RE2020

Reasons for participating in the competition(s)

The choice of off-site for this operation made it possible to optimize deadlines and maximize the share of wood material in the constructions. Added to this are strong energy and carbon requirements. Performance is at least 20% lower than the RT2012 thresholds and RE2020 compatible, in particular thanks to low-consumption energy systems. Results: comfortable accommodation with controlled costs.

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Ludovic GUTIERREZ

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