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A passive house made of local wood for a retired farming

couple.

Key dates Project planning : since 2004. Design phase : 2010/2011. Build : February 2012 to 1st half of 2014.

Once they had retired, Bernard and Viviane wanted a new house. They wanted it to be comfortable but also self-sufficient in energy (without the need for heating) to avoid dependency on fossil fuels, as they were convinced that prices would go up.They therefore used trees from their garden for the build and insulated it with recycled newspapers (cellulose fibre insulation). The whole build was contracted to local craftsmen.

Introduction

Saint Brieuc

Quimper

Vannes

RennesRostrenen

Coatleven

South facade - Photo © Servane Guihaire - Constructys Bretagne

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ContextAs well as living in a « no heating » home, the owners were determined to use wood from the site for the frame and to use the skills of local tradesmen. They also wanted their house to be future-proof, in case of reduced mobility in their older years.Architect Christophe Gauffeny, supported by the Thermal Office, imagined a modular building with a passive core of 120 sq m (for 211 sq m of total area) South / South West facing. This is surrounded by annexes : with either low consumption or non-insulated rooms in buffer zones (utility room, garage, indoor garden etc.).In the passive part of the building,

no heating system was installed apart from the heat exchanger.Wood from the farm was used in the bungalow structure, on a 2000 sq m plot on the outskirts of a town of 3400 inhabitants.

Building overviewThe timber frame rests on concrete blocks and a concrete foundation, on a 60 cm crawlspace with an anti-radon membrane.The I-beams (German brand Steico), thanks to a potential length of 13 m, enable continuity between the attic and the crawlspace, thus eliminating

Plan © Christophe Gauffeny

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thermal bridges between the walls and the floor.The outer shell is insulated with blown cellulose fibre by Isocell (22 cm in the walls, 32 cm in the floor and 36 cm in the roof) and wool insulation (for partition walls) and is clad with fibre boards permeable to water vapour (35 mm Pavatex).Many timber posts have been made from local timber. The outer windows (made by Menuiserie André), certified by the Passive House Institute in Darmstadt, are triple glazed. Jambs and frames

are kept to a minimum to reduce thermal loss (only the glazing is visible from the outside).Heating is provided naturally, by the sun and human activity. A heat exchanger (by Danish company Nilan) optimises the recycling of the exiting air (80% return) in order to heat the air inside as well as heating the hot water. Its position on the first floor enables an optimal layout of cables from the underfloor to the roof.Floor structure : concrete blocks and slab – protection membrane – I-beams with cellulose fibre – 16 mm bracing – vapour barrier – joists

Timber frame - Photo © Christophe de Quelen - Menuiserie de Quelen

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Technical focus : Farm woodIn this building, the use of wood is predominant as it covers 20 to 25 m3 of the space. The use of metal was reduced as much as possible, even the partition wall structure is made of wood.

– local oak floorboard.Outside wall structure : Douglas fir cladding or plaster board (BA13) – 5cm gap (for ducts) – bracing panels – 35 mm Pavatex (glued wood fibre boards) – 27 mm battens – Douglas fir cladding.Roof structure : BA13 plasterboards – battens – 5 cm gap – vapour Barrier – 8 mm bracing – I beams and cellulose fibre – 12 mm OSB boards – rain barrier – 6x4 rafters – poplar battens – hessian – zinc.

The wood from the contractors’ farm, comes from oak, cypress and Sitka spruce. The timber was cut to be used for beams, panelling, bracing, battens and floorboards.The wood was cut on site using a mobile sawmill. It was then dried in a warehouse and stored onsite before being engineered in the Menuiserie de Quelen workshop. The owner followed the work on his wood in the workshop to observe the different steps of fabrication.The finish is immaculate as the timber was knotty – therefore no two floorboards are identical.In West central Brittany, a short chain of construction timber supply is currently developing in order to optimise the use of local wood. Buying-in-bulk schemes are being set up.

Wood sawing - Photo © Christophe de Quelen - Menuiserie de Quelen

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Barriers and solutionsPlanning regulations required the building to face the road rather than south. It was necessary to raise the energy performance objective with the planning department to overcome this obstacle.During groundwork, workers were faced with the problem of bedrock close to the surface. The crawlspace was therefore limited to a 60 cm gap and the idea of a well had to be abandoned.During the building phase, the frame manager facilitated communication between trades thanks to his experience and his position as Chairman of the ECOB association, which coordinates 25 members interested in Eco construction, 15

of whom are craftsmen. Several companies involved in the building process were also members.The building process benefited from the input of Conseil d’Architecture, d’Urbanisme et de l’Environnement des Côtes d’Armor, a local architecture advising bureau (CAUE 22 - www.caue22.fr). Also, a huge temporary “Eco-Dome”, a sort of hot air balloon tunnel, inflated with huge fans, was installed on site. This enabled builders to continue working regardless of the bad weather (http://domedebretagne.com/ ).On the technical side, passive joinery was a particular focus. Because of really thin jambs and window frames, it was preferable to fit the windows from the outside.At the time, it proved difficult

Wooden floor - Photo © Servane Guihaire - Constructys Bretagne

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to source passive doors without doorsteps which constrain the mobility of wheelchair users.Nilan was the obvious choice for heat exchangers as it is the only 4 in 1 device (heat exchanger, air and water heating and cooling system all in 1), endorsed in France (Certification number V RT2012) and by the PassivHaus Institute.From a financial point of view, focusing on the “passive” side of the core of the house, whilst providing continuity for the roof between the passive side and the annexes proved to be good value for money. The architectural design is therefore simplified, while the annexes soften the «cuboid shape» impression.The use of local timber, crafted in a

traditional manner, didn’t add to the final cost.From a regulation point of view, it is compulsory to install a heating source, even in a passive house, despite the lack of use.Also, regulations do not systematically take into account the imperative of enabling water vapour movement along the walls. For example, OSB boards are compulsory in the outer shell whilst their water vapour resistance is relatively high (bringing a risk of condensation).The insurer agreed to provide insurance cover to the carpenter-joiner if he provided order receipts

Installation of windows - Photo © Christophe de Quelen - Menuiserie de Quelen

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and a building material list during their annual meeting.This build was however his first passive house. He had to undertake several training courses, joinery by the menuiserie André, training at the Energy-Saving building methods Institute (Formations aux Economies d’Energies dans le BATiment FEE BAT), resistance material, air tightness (www.averti-expertises.com), cellulose fibre insulation (Cellaouate - www.cellaouate.com and Soprema) and bioclimatic design.It proved difficult to identify a competent installer for the heat exchanger for this build.

The passive core of the house relies essentially on the heat from the sun and human activity to keep it warm. Eventually, in the middle of winter, depending on the occupation of the house, a slight heating of the habitat can be proved useful (a towel drier would be enough).Thanks to the heat exchanger, the heating consumption does not exceed 14 kWh/year/sq mThe main contractors were not aiming for an official certification, but the PHPP (Passive House Planning Package), awarded in France by «La Maison Passive Service», provided guidance on the design throughout the build.

Performance

Eco-dôme - Photo © Christophe de Quelen - Dôme de Bretagne

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Stakeholders Main contractors : Bernard and Viviane Coatleven Project manager : Christophe Gauffeny (Design, planning, planning permit application)Thermal survey : Passiflore Conseil (Lannion)Masonry : CKB (Rostrenen)Carpentry, joinery, insulation : Menuiserie de Quelen (Locarn)Roofing : Ets Glou (Rostrenen)Plumbing - electricity : Entreprise Goaziou (Rostrenen)Heat exchanger : ATS (La Méaugon)Finishing touches : done by the owners with traders’ helpMobile sawmill : Letur (Sizun) Advise bureau : CAUE 22 (Saint-Brieuc)Eco-dome : Dôme de Bretagne (Locarn)

Costs Plot : £30,595 Project managing : £10,786 Thermal survey : £742 Ground survey : £235 Groundwork : £3,133 Masonry : £12,504 Carpentry, joinery, insulation : £134,089Plumbing - electricity : £10,191 Heat exchanger : £18,000 Wood cutting and drying : £4,119Plastering : £1,275 Roofing : £13,499Miscellaneous : £5,534 Total build cost : £214,107 after taxTotal per sq m : £1,014

Integration © Christophe Gauffeny

ContactConstructys Bretagnewww.constructys-bretagne.fr