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An exemplary renovation.

Key dates Construction : before 1948Design work : october 2010 to april 2011Building work (renovation /extension) : 2011 to 2012Leak testing (Airtightness): 2011 and 2012 (final test)

This project illustrates the transformation of an old bakery into a rural holiday cottage ideal for family and social needs, being accessible to people with reduced mobility. The objective of this renovation and extension was to use materials with low embodied energy and to have a building that was energy neutral.

Introduction

Saint Brieuc

Quimper

Vannes

Rennes

Chauvigné

Maison Neuve

Overview - Photo © Servane Guihaire - Constructys Bretagne

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Convinced of the necessity to develop a social and environmental dimension within their business model, Mr and Mrs Bobon wanted to undertake a program of work split into two parts : the creation of a rural, family holiday cottage designed to accommodate disadvantaged people (5 places) and the implementation of accessibility to existing facilities.Finally to complement these social objectives, they renovated the ancient bakery by experimenting with ecological design and building techniques.The design allowed the character of the existing building and the bakery to be conserved. The architect chose not to create openings or add bay windows to the existing façade in order to preserve the architectural

Contextstyle. For the extension, the project owner and the project supervisor made a conscious decision to use more contemporary materials, such as using sheet metal for roofing, to conserve the feeling of the original bakery. This was a collaborative project, thanks to the introduction of a version of the Integrated Design Process. The Integrated Design Process is a global approach to building design. It enables the grouping together, during the design phase, of all the players involved in the construction project : the architect, the owner, the engineer or engineers, and finally the builders and craftsmen (3 half days). The objective is to optimise the goals and objectives of

Plan © Pierre-Marie Martin

French-British collective Libnam3

the project by bringing together all the players in the project as early as possible.Thermal performance is based on a study conducted with Thermal Dynamics Simulation software «PLEIADES COMFIE». As for the environmental study it is based on the results of «COCON» («COCOON») software.

Building overview The old bakery is built using traditional stone masonry combined with an earth and lime mix. The walls of the ground floor

were partly rendered with a 5cm thick lime-hemp mix used for its good thermal qualities. On the other walls, the joints were redone with lime, using the technique of the «poche» («pocket») to provide an efficient air barrier for the old building. The floor was conserved in its original condition and therefore not insulated.The roofs of the old building and the extension were insulated from the exterior using 30 cm of cellulose fibre (recycled newspaper) and a vapour barrier (or rather «rain screen») of wood fibre 2.2 cm thick.The extension is built on a granular infill of stone, a lime concrete slab over blocks of lime-hemp insulation.

Integrated Design Process - Photo © Pays de Fougères

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The same blocks of lime-hemp insulation «Easy-chanvre» were used in the walls. This construction method combines the lime-hemp blocks with a timber frame.The technical characteristics of the hemp blocks used in this construction project resulted from a research program between laboratories in civil and materials engineering and three Breton businesses.

An effort was also made in water management. Dry toilets were installed along with pressure and flow reduction systems on all the taps.

Technical focus : Cellulose fibre insulation from the exteriorThe roofs of the old building and the extension were insulated from the exterior. The roof of the old building needed replacing. The cellulose fibre was blown in from the outside. In the first instance, the vapour barrier was laid from the inside, then the cellulose fibre was laid on top of it from the outside. Finally a rain barrier of tongue and

Laying the lime/hemp blocks - Photo © études ET chantiers

French-British collective Libnam5

grooved wood fibre was laid to seal the insulating layers.The wooden structure of the roof had to be reinforced to obtain the 30cm depth required for an effective level of thermal insulation. The time of year was favourable to this type of work.

In hindsight the construction businesses involved are not considering using this method in the future. They found it too dependent on weather and it does lead to some unique problems ; the slightest wind could blow the insulation off the roof. The more usual method of blowing in the cellulose fibre from the interior, although slower, is a much «safer» method and will be used in the future.

Barriers and solutionsIt is worth remembering that during this project, the professionals involved had never worked using the techniques or materials employed in this build. According to the project owner and the project supervisor, the obstacles encountered were essentially human ; effectively the people involved should be more prepared to question and apply themselves. In addition, the Integrated Design Process, used for the first time on this project, was too complex for the different people to deal with effectively in the design phase ; it would have been more judicious in the implementation phase of the construction.

The project took longer than originally hoped because a lot of

Laying the vapour barrier - Photo © Pays de Fougères

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time was spent in the design and implementation of the system Easy-chanvre; difficulties with the layout, drying time, and implementation of the «chantier-école 1» (site school).

As for regulations and insurance, the Easy-chanvre blocks lacked certification. Construction using a timber frame is regulated by the DTU standard for timber frames. Futhermore, the site owner did not want to have a ten year guarantee for the work carried out by the «chantier-école» which comes at an extra charge.

Training of the different people involved took various forms : a

«chantier-école» managed by Etudes et Chantiers for the Easy-chanvre system and lime-hemp thermal insulation used on the interior walls, monitoring of companies on site by the Pays de Fougères to help with the implementation of sealing and waterproofing and the two airtightness tests (intermediate and final).

Regarding the professional skills of the craftsmen involved, they discovered new materials and how to successfully implement them. Notably, the carpenter discovered two key problems : the challenge of

Blown cellulose - Photo © Pays de Fougères

French-British collective Libnam7

There has been no measurement or monitoring carried out to date. The occupancy rate is not regular, therefore such measurements would not be accurate. It is planned to install a low energy wood pellet burner to heat the house. The airtightness leak test indicated a renewal rate of air at 3.2 vol/h. (index n50) or 0.73 m3/h.m² (index Q 4Pasurf).

Performancefixing brittle, powdery materials and the greater than normal thickness of the insulation blocks.Adapting the building to accommodate disabled people required specific products: appropriate handles, electrically assisted furniture or drawers, these were solutions that the craftsman had never encountered and in turn has allowed them to offer these products to future customers!

Interior- Photo © Servane Guihaire - Constructys Bretagne

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StakeholdersProject owners : SARL « La Maison Neuve »Marie-Armelle et Luc BOBONProject supervisor : Pierre-Marie MARTIN et Jacques PICARD (35300 Fougères)Consulting firm (Thermal and liquids) : ECIE (35300 Fougères)Site coordinator : Stéphanie GESLOT Pays de fougères (35300 Fougères)Structural work : Alain BAZIN (35460 Coglès)Electrician : Pierrick TROPEE (35133 St Sauveur des Landes)Plumbing, heating, and solar energy : Éric GICQUEL (35490 Chauvigné)Tiler : Sébastien BERTHEL (35490 Chauvigné)Carpenter : Bernard VIEL (35140 St Jean sur Couesnon)Roofer : Didier GOBE (35490 Chauvigné)Insulation, stairs, plasterer, and patio doors : Éric LEROY (35460 Coglès)On-site training : Etudes et Chantiers Bretagne Pays de Loire (35000 Rennes)

Costs Project supervisor : £6,210 all taxes includedConsulting firm (Thermal and liquids) and tests : £2,066 all taxes includedStructural work : £19,251 all taxes includedExterior joinery : £5,019 all taxes includedExterior walls : £4,852 all taxes includedInsulation : £5,327 all taxes includedPlumbing, heating, hot water supply, solar panels : £8,166 all taxes includedElectricity : £3,539 all taxes includedRoofing : £9,074 all taxes includedCarpentry : £4,679 all taxes includedTiling : £3,330 all taxes included

Total : £71,513 all taxes includedSurface area : 81 sq mGiving a cost of £882.57 all taxes included per sq m

Grants obtained :Agence Nationale pour les Chèques-Vacances (ANCV) : £15,074 - from surplus earnings it clears from its management of holiday vouchers, the ANCV supports the modernisation and development of socially oriented tourism facilities favouring those people normally excluded from such facilities.Agence de l’environnement et de la maîtrise de l’énergie (ADEME) : £617 (thermal study).

Elevation view - Photo © Pays de Fougères

ContactPays de Fougèreswww.pays-fougeres.org