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How to sustainably renovate your heritage building - an eco-

housing demonstration.

Key dates Construction : 17th centuryDesign work : 02/2012Building work : 05/2012 – 12/2013

Introduction

Saint Brieuc

Quimper

Vannes

Rennes

Mellé

Mellé

This eco-housing demonstration represents an exemplary renovation of a 17th century house, through the enhancement of rural heritage and sustainable development. This project combines energy performance, natural materials, know-how and local expertise.This project will enable many people to discover how heritage buildings can be restored. It demonstrates the characteristics of the historic building, particularly construction techniques specific to the local region.Overview - Photo © Servane Guihaire - Constructys Bretagne

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ContextLike a number of rural communities, Mellé has seen much of its population leave to move to suburban areas, resulting in a loss of farmland. Its distance from employment catchment areas has been the major factor in this population decline.

To provide practical solutions to these environmental challenges, the borough has been committed for many years to a global sustainable development project. It actually becomes necessary to limit the utilisation of agricultural land, to effectively construct and renovate buildings, but also to promote the development of renewable energy.

The thermal performance obtained through this renovation is based on the skill of the architect and on a study conducted with Thermal Dynamics Simulation software «PLEIADES COMFIE». The technical advice of a consulting firm specializing in airtightness and hygrothermal issues supported the technical choices taken during the project.

Plan © TRICOT Architecture

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French-British collective Libnam3

Building overviewThis 17th century house was constructed using local granite, earth, and lime. It includes a first floor and a gallery in the north façade. Like many buildings of this period, the house is semi-detached and has just three openings in the south façade.As a teaching aid the eco-housing demonstration presents various technical solutions to wall insulation.The north façade was composed of a simple wood panel and an unused door. This was replaced by a timber frame with wood fibre insulation, further insulated from the outside by wood fibre rendered with a lime-

sand mix. The interior was finished with painted plasterboard.The south and west facades were insulated from the inside using lime-hemp brick, whilst the gap between the original wall and the partition wall was filled with loose hemp, permitted by the building regulations. The walls were finished with a lime render. A timber frame filled with flexible «excelsior», or wood wool, was used for the interior of the shared wall to the east. Rigid wood wool with an air gap of 3 cm between the stone wall and frame was used for the exterior. A wooden cladding was used to finish the bedroom and the living room, and plasterboard was used to finish the bathroom.

Laying of geotextile - Photo © Pays de Fougères

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Cellulose fibre (recycled newspaper) 40cm deep makes up the loft insulation. The ground floor is insulated using loose cork between the joists of the local oak parquet floor.A wooden pellet burner was chosen to heat the building. Finally two skylights, one in the stairwell and the other in the bathroom, add natural light to every recess of the house.

Lime /hemp brick - Photo © Pays de Fougères

Technical focus : The ground level floorMellé, like many boroughs in Brittany, has a granite subsurface with a very real risk of radon

pollution. A great deal of attention was paid to the insulation and ventilation of the ground level floor to mitigate this risk.

In addition, the borough has chosen to develop local know-how using a parquet floor on joists and supporting blocks of blue granite from Louvigné. This technique allows space for a network of ventilation pipes within a «hérisson de pierres» or layer of loose stones (stone size of 20/40).

A Geotextile Membrane was then applied to ensure airtightness while

French-British collective Libnam5

Barriers and solutionsDuring this exemplary public project with high environmental demands, the objective was to generate feedback on costs, results and training for businesses. The businesses were hired by means of public tender.The project was long ; the numerous different renovation techniques,

External insulation - Photo © Pays de Fougères

controlling moisture migration. The cork, used for insulation, is not a regional product but was used because its properties are not affected by water; the rotproof nature of cork makes it ideal for underfloor use. Finally the joists and parquet are made of local wood fabricated by a local craftsman.

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Focus on a cross-disciplinary theme : an awareness toolThis eco-housing demonstration was designed as a teaching tool open to all. It is the sixth demonstration of the new «Route of the energies», as

coupled with building layout (long, narrow and on two levels), complicated the sequence of events and therefore the coordination of the various businesses. Furthermore, the airtightness work carried out on the old building was more complex because of the special care necessary for a quality finish.Many unforeseen problems related to the nature of the subsoil (unsound walls because of the unstable sandy soil) lengthened the renovation.The chimney flue no longer met modern building regulations and was condemned.The mason was able to implement an unknown technique - hemp blocks - which did not pose a problem as the mason was accompanied during the work.Throughout the project Stéphanie Geslot of Pays de Fougeres was given the role of demonstrating the value of «green» building airtightness, as well as the installation methods

for high performance technical membranes. The various craftsmen had to adapt to these new technical requirements. This pilot project allowed them to learn new skills opening up new markets.

Finally, a blower-door test was carried out at the end of the project by the company Ty eco² as part of the on-site training. This airtightness leak test indicated a renewal rate of air at 5 vol/h. (index n50) or 0.73 m3/h.m² (index Q 4Pasurf).

Exterior - Photo © Servane Guihaire - Constructys Bretagne

French-British collective Libnam7

The town hall of Mellé rent this renovated house. Since the 1st of March 2014 this new tenant pays a small rent in exchange for «educational» visits by appointment only. There has been no significant monitoring of energy consumption to date. The thermal study carried out using the prescribed ‘Perrenoud’ software estimated the heating system to have an energy use of 33 kWh/m²/year. In real terms 4 x 15kg sacks of wood pellets are used every 2 months. Finally the visual comfort afforded by the skylights, the acoustic benefits despite the adjoining wall, and the thermal comforts from the high performance materials used make a perfect little nest to live in!

Performance

part of the flagship local sustainable development project in the borough from 2008 to 2014. Educational interpretation will be put into place to give an understanding of the project to visitors, with explanations on the choice of techniques and the importance of the associated studies. This signage will be fun and interesting.

Stove - Photo © Servane Guihaire - Constructys Bretagne

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Stakeholders Project owners : Borough of Mellé (Mellé)Project supervisor : TRICOT architecture (Louvigné du Désert)Consulting firm (Thermal and liquids) : THALEM Ingénierie (Bruz)Site coordinator : Pays de FOUGERES (Fougères)Structural work : SARL ROUSSEAU (Louvigné du Désert)Tiling : SARL LAIZE (Romagné)Skylights : SARL MARSOLIER (La Chapelle Janson)Electricity, Heating, Ventilation : SARL RAUT (Javené)Plumbing : SARL DELALONDE (Pontmain)Decoration (painting) : SARL HEUVELINE (Gorron)Insulation, plastering : SARL BREL (Lécousse)Interior and exterior joinery : SARL VIVIER (Mellé)Wood pellet burner : GALLE (Romagné)

Costs Consulting firm : £3,310Project supervisor : £11,946Structural work : £35,246Interior and exterior joinery : £29,408Insulation, plastering : £5,995Decoration (painting) : £3,737Plumbing : £4,925Electricity, Heating, Ventilation : £6,803Skylights : £3,977Tiling : £1,350Wood pellet burner : £4,251

Total : £92,769Total all taxes included : £110,948 Surface area : 68 sq m

Total per sq m : £1,364Total per sq m all taxes included : £1,631

South facade (left) and east gable (right) © TRICOT Architecture

ContactPays de Fougèreshttp://www.pays-fougeres.org/