Rehabilitation of a barn in a Third Place

Heritage renovation

  • Building Type : Other building
  • Construction Year : 1880
  • Delivery year : 2021
  • Address 1 - street : 20 Boulevard Lyautey 91490 MILLY-LA-FORET, France
  • Climate zone : [Cfb] Marine Mild Winter, warm summer, no dry season.

  • Net Floor Area : 185 m2
  • Construction/refurbishment cost : 525 000 €
  • Cost/m2 : 2837.84 €/m2
  • Primary energy need :
    80 kWhep/
    (Calculation method : RT existant )
Energy consumption
Economical buildingBuilding
< 50A
51 à 90B
91 à 150C
151 à 230D
231 à 330E
331 à 450F
> 450G
Energy-intensive building

The project is located in the heart of Milly-la-Forêt, on the plot of an old farm transformed into the Maison du Parc naturel régional du Gâtinais francais. The barn is positioned in a constraining situation: adjacent to the separating limits, mainly oriented to the north and surrounded by different levels of base.

The project proposes a rehabilitation and an extension of the barn by preserving the characteristics of the rural architecture of the French Gâtinais. The construction favors the use of bio-sourced materials and the extension is treated in a contemporary way by taking inspiration from the characteristic elements of the vernacular architecture, in particular the beehives and dryers. The project is presented as follows:

  1. Three levels are organized in the barn for its activities with a low first floor in half level and an interior structure in wood. The north facade is modified: the barn's carriage door is replaced by a wooden glazed frame and a large horizontal bay is created under the eaves of the roof. The existing roof is preserved, only pierced by flush roof windows on the southern slope.
  2. An extension is created on the west façade to accommodate a meeting room. This cantilevered extension signals the commitment of the French Gâtinais Regional Nature Park to sustainable and biosourced architecture. It presents a volume with a double slope roof at the R+2 level, suspended from the existing gable. It consists of a wood frame, a roof of wood shingles, wood cladding, interior insulation in plant fibers and wood joinery high performance protected by external blinds. A horizontal bay is created under the extension to light individual offices; it accompanies and emphasizes the extension of the cantilevered structure.

The project combines modern techniques with traditional know-how :

  • The stone masonry and lime renderings are preserved. The interior wall finishes are also made of lime plaster.
  • The use of hemp concrete on old masonry ensures a very good thermal comfort while promoting local know-how and short channels.
  • The existing framework is preserved and the new frame is designed around the existing trusses. Entirely modeled in 3D, the framework was digitally shaped and assembled in one month.
  • A flexible rainwater collection tank is integrated into the lower level for sanitary purposes.
  • Electric vehicle charging stations are located under the extension.
  • The Cep energy performance objective is set at 80 kWhep/m².year. The summer/winter comfort levels are optimized (inertia, cold wall sensation, phase shift...).
  • The furniture is made from reused wood by an integration company.

All of these recommendations contribute to limiting the ecological footprint of the construction, to thermal comfort and to the qualitative atmosphere of the project.

Photo credit

abdpa / Daniele Rocco


    Parc Naturel Régional du Gâtinais français

    Cathy Bos - Chargée de mission Architecture et Paysage - 01 64 98 23 38 - c.bos[a]

Construction Manager


    Antoine Brochard - Architecte, Associé - 0175501481


    Thermal consultancy agency

    LM Ingenieurs

    Other consultancy agency



    Seve mobilier

    Matthieu Renard - Directeur - 07 87 03 14 22

    Reuse and integration furniture

Contracting method

Separate batches

Energy consumption

  • 80,00 kWhep/
  • 98,00 kWhep/
  • RT existant

Envelope performance

    Hemp concrete insulation on existing masonry.
    Wood fiber, and hemp flax on the roof slopes.


    • Wood boiler
    • Individual electric boiler
    • No cooling system
    • Free-cooling
    • humidity sensitive Air Handling Unit (hygro A
    • Canadian well
    • Wood boiler

Biodiversity approach

    The project is located in the center of Milly-la-Forêt, close to the town's facilities and shops. The plot of an old farm was divided during the creation of the house of the PNR of the French Gâtinais, realized by Joly and Loiret in 2009-2013. The barn remained unoccupied, without destination during the development of the site. It is located at the bottom of the plot, adjoining on two sides and with a variable level, which has complicated its use and rehabilitation.


    SEVE Mobilier

    +33 3 23 53 27 23

    Second œuvre / Équipements intérieurs

Construction and exploitation costs

  • 525 000

Reuse : same function or different function

    • Structural works
    • Structural framework
    • Roofing
    • Facades
    • Indoor joineries

    The rehabilitation preserves the characteristics of the rural architecture of the barn: sandstone and limestone masonry, existing frameworks, flat tile roofs, zinc work... These elements are kept in place, reused in fact (132 m3 of masonry, 5.3 m3 of timber, 140 m² of tiles, 32 ml of zinc, 1 carriage porch...). Other elements are reworked, reorganized (flat tiles for the creation of roof windows, external doors condemned...).

    The reuse also concerns the furniture resulting from the upcycling of wood of frame or joinery (oaks, fir, beech). From these materials, 6 individual desks, 4 double desks, 2 meeting tables and 8 storage boxes were made.

    The integration company Seve Mobilier, based near Soissons, has collected, machined and assembled framework wood, floor elements or interior joinery, workshop scraps from the region.

Sustainable design

    In our opinion, the project is a manifesto of biosourced architecture. It favors the use of wood (solid spruce, glued laminated spruce, spruce cladding, chestnut for shingles, plywood spruce, OSB, glued laminated beech staircase, solid exterior joinery ...) but also other ecological materials (hemp concrete, hemp wool in crawls, linoleum...).

    Our will to limit the elements of second work in the project decreases the quantity of reusable materials: no false ceilings, furniture acoustic panels, cable trays and apparent cvc... As described below, the aluminum-glass partitioning of the offices is adaptable or recoverable in case of change of destination or evolution of the project partition.

    The project also includes a grey water system (collector, flexible tank, pump) to reuse rainwater in the sanitary facilities.

    Great attention was paid to the selection of materials that are compatible with each other (primary structure, envelope and finishing work) and that correspond to the specific characteristics of an old building (interior lime coatings, hygrothermal compatibility of insulation materials, etc.). The choice of hemp concrete is particularly indicated for the insulation of old buildings, especially since hemp is cultivated on the territory of the "PNR du Gatinais" and that a processing industry is being installed near Malesherbes.

    The interior partitions of the offices and glass doors were made of aluminum profiles and glass panels. Adapted to the height of the levels, they could be moved to change the configuration of the equipment.

    Oui, en grandes proportions, voirs points précédents.

    Le mobilier du tiers lieu a fait l'objet de trois lots : l'un de mobilier issu du réemploi, l'autre d'achats public via la plateforme ugap, garantissant des critères sociaux ainsi que le made in france, enfin la vaisselle a été fournie par une ressourcerie.

Environmental assessment

    Little demolition in the barn, but adaptation of the existing. Much less impact than a demolition/reconstruction operation.

    Categories Avoided CO2 (kg)  Avoided water consumption (m3) Avoided waste (kg)
    Outdoor facilities 0 0 0
    Exterior fittings / Locksmithing - Metalwork 0 0 0
    Carpentry 302,8666667 4,8433 262,8357626
    Partitions 0 0 0
    Coverage 2216,76 11,6536 1223,181589
    Roofing / Exterior fittings 0 0 0
    Lighting 0 0 0
    Safety lights 0 0 0
    Climatic engineering equipment 0 0 0
    Electrical equipment 0 0 0
    Facades 0 0 0
    False ceilings 0 0 0
    False floors 0 0 0
    False ceilings 0 0 0
    Structural work 269406,6052 1818,211568 351022,252
    Sanitary installations 0 0 0
    Insulation 0 0 0
    Exterior carpentry 0 0 0
    Interior carpentry 173,326208 3,49438386 225,0903078
    Furniture 1329,122753 12,36986045 901,8513461
    Paint 0 0 0
    Plumbing 0 0 0
    Floor coverings 0 0 0
    Floor and wall coverings 0 0 0
    Wall coverings 0 0 0
    Building security 0 0 0
    Locksmithing - metalwork 0 0 0
    VRD 0 0 0
    TOTAL Avoided CO2 (kg)  Avoided water consumption (m3) Avoided waste (kg)
      273428,6808 1850,572712 353635,211
      Km in a small car Nb of rectangular bathtubs nb of years of household waste of a French person
    Equivalent 2187429 12337 707
    Equivalent trip Paris- Nice 2486,0    

    The reuse operation has saved the equivalent of 2187429 kilometers traveled by a small car, or 2486 Paris-Nice trips, 12337 rectangular bathtubs filled with water and 707 years of household waste of a French person.

Reproductibility and Innovation

    The rehabilitation of barns is a theme shared by all rural areas, or rural that have become peri-urban. Our project, created in a particularly complex situation (jointness, interlocking....) can testify of the feasibility of this type of ambitious operations on the environmental plan.

    Carried out by the GO lot.

    Storage of the elements on pallets (tiles, doors...), transport to the companies' premises before re-use.

Social economy

    SEVE MOBILIER is a social integration structure with 6 employees and 25 employees on a professional integration path. Since its creation in 2015, more than 150 people have been trained and accompanied in the workshop.

Water management

    Recovery of rainwater for sanitary grey water, flexible tank of 8 m3.

 heritage renovation
 circular economy
 Circular Buildings 2022 Awards
 tertiary building
 materials and solutions

Author of the page

  • Other case studies



    Green Solutions Awards 2022-2023 / France