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The restoration of an old rectory into a public elementary school.

Key dates Original Construction : before 1948Design : 2012 (01/2012 – 01/2013)Renovation, extension : 01/2013 – 02/2014

The project owner wished to renovate the ancient rectory whilst keeping its architectural identity. The architect was given the objective of designing an efficient project using breathable materials for the renovation.

Introduction

Saint Brieuc

Quimper

Vannes

Rennes

Saint Marc le Blanc

«Le Picaou»

Overview - Photo © Pays de Fougères

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ContextFrom the architectural point of view : a courtyard with its own garden surrounded the old rectory. The architect chose to stay within these limits when designing the extension to the rectory. Granite was chosen for the façade to maintain the character of the place. The wooden cladding and the glass roof give a contemporary touch to the building as a whole.According to the project owner, ‘the buildings within the town-centre have a harmonious architectural style, which also applies to the rectory’. The heritage development,

together with an architectural extension consistent with the history of the area ensures the link to the town-centre. In addition, pedestrian paths allowed all municipal services to be linked. This project allows the regrouping of the school, school restaurant, library, and sports hall. It was given the label of Eco-FAUR*

* Eco-FAUR is recognition and funding from the Regional Council of Brittany for boroughs who opt for sustainable development objectives in their projects.

Plan © Pays de Fougères

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French-British collective Libnam3

Building overviewThe project can be split into two parts: firstly, the renovation of the stone masonry and earth section of the original building, and secondly the new construction using less eco materials - concrete blocks and stone. We will focus mainly on the renovation.

The project owner wanted a high performance, low environmental impact project. The architectural project maximised the use of local materials (stone and wood), eco-sourced materials (lime-hemp blocks, lime-hemp render, earth, lime and sand), as well as recycled material; using the granite stones of the demolished surrounding wall, and reusing wood from the old wooden frame.

A workshop was created for the building using lime-hemp blocks, and the interior wall was finished using lime, sand and earth render. This also involved the repairs of exterior joints using a lime mortar made by Weber. This project was supervised by Etudes ET Chantiers.

The heating system chosen was a 36 kW vertical ground to water geothermal heat pump.

A twin / dual network for ventilation was put in place with a single flow controlled mechanical ventilation system managed by a CO2 sensor and a movement sensor in the toilets, and a dual flow controlled mechanical ventilation system for the rest of the areas. Particular attention was given to the quality of the finishing materials to ensure good air quality (“Ecolabel” paint, earth render).

Structure - Photo © Pays de Fougères

Earth plaster - Photo © études ET chantiers

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Technical Focus : « chanvribloc »For this project, the owner opted to use hemp blocks from the supplier CHANVRIBLOC. It is an eco-sourced material made of hemp «straw» and hydraulic lime. The blocks are made in Isère (La Mure region) and sourced in the Haute-Saône and l’Aube regions. This focus will concentrate on two elements: firstly, the building constraints related to seismic regulations, and secondly the different renders (earth, lime-sand, and lime-hemp).

Two types of blocks were used on site : 10 cm blocks for the south wall and 20 cm blocks for the north wall. The supervising officer, a Chartered

building surveyor, imposed an open void of at least 5 cm between the wall of the original stone and the concrete structure built inside the building, concrete slab included (see picture). The insulation of loose hemp, originally specified, could not be used because of the seismic regulations mentioned earlier. However, the thermal performance is not affected by this change in materials. The project owner opted to screw the blocks onto a smooth wooden base, following the manufacturers’ recommendations.

In an effort to maximise the characteristics of the hemp blocks, natural renders were used : earth, lime-sand, and lime-hemp. These were an industrially produced render with an earth finish (Argilus), handcrafted lime-sand and lime-hemp renders. In fact the sub-soil of the region of Saint Marc le Blanc does not have earth easily usable for producing handcrafted earth renders.

Lime/hemp block - Photo © Chanvribloc

Interior plaster - Photo © Servane Guihaire - Constructys Bretagne

French-British collective Libnam5

Barriers and solutionsAs for the organizational and relational side of things the site ran rather smoothly, thanks to the omnipresence of the project owner. He was able to be very reactive and make himself available whenever needed.

The establishment of the insertion workshop / integration project, of Etudes ET Chantiers, allowed the world of integration to confront the world of business, both working under different regulations. This required the project owner, the companies present, and the «integration teams» to deal with the constraints of each person and organization.

The supervising officer (Chartered building surveyor) was uncompromising on the application of seismic regulations, which made the building of the hemp blocks and work on air tightness much more complex.

The Pays de Fougères offered work support to ensure the smooth running of the site, notably concerning the air tightness work. This collective involvement was very positive and allowed the site to run fluidly.

The application of the lime-hemp

and renders was entrusted to Etudes ET Chantiers (integration project management and vocational training agency). Two groups of between eight and ten people were trained via work experience and their instructor and given theoretical and practical training by the use of modules on «insulating and finishing with render» (earth, lime-sand, lime-hemp).

Yard - Photo © Pays de Fougères

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PerformanceThe building opened its doors for the start of the school term in April 2014. Therefore, there is no feedback on the actual performance of the building at this time.The final blower door test indicated a renewal rate of air of 7.67 vol/h. (index n50) or 1.86 m3/h.m² (index Q 4Pasurf).

The air tightness obtained did not correspond to the objective of 1.7 m3/h.m² at 4Pa (obtained from the thermal study) for this type of building. During the intermediate test the building was within this threshold, but the need to respect the law concerning access for persons with reduced mobility necessitated the installation of a lift: this was placed in the heated area of the building (probably through a lack of familiarity associated with these new constraints and / or difficulty

in meeting the architectural style with the lift positioned outdoors). Openings were made in the shell of the building, the breathable waterproof membrane was therefore pierced to allow the lift to go up and down without suffering from a vacuum and suction effect. This in turn allowed a significant amount of air into the building.

The initial state of the building showed a theoretical consumption of 509 kWhEP/m² per year. The thermal study gave 426 kWhEP/m² (this drop is almost certainly due to the higher than expected amount of air entering the building).As for CO2 emissions they dropped from 140 kg eq.CO2/m².an with the old method of heating to just 3 with the use of the vertical geothermal solution.

Entrance- Photo © Servane Guihaire - Constructys Bretagne

French-British collective Libnam7

Stakeholders Project owner : Borough of Saint Marc le BlancProject supervisor : Laurent et associés (Fougères)Thermal consulting firm : ECIE (Fougères)Supervising office (Chartered building surveyor) : Veritas (Rennes)Structural work : CF Constructions (St Aubin du Cormier)Suspended ceilings : MORAND-BERREE (St Jacques de la Lande)Aluminium joinery : RETE Serge (Louvigné du Désert)Paint : FC Peinture (La Chapelle Janson)Plumbing : GOUPIL Alain (Bazouges la Pérouse)Electricity : KALEO (St Germain en Coglès)Wood joinery : HUMBERT Pascal (St Marc le

Blanc)Tiling / screed : Sarl HUARD Jacky (Romagne)Roofing : Sarl GOBE Didier (St Marc le Blanc)Timber frame : ROBIDEL Sarl (Le Ferre)Heating / ventilation : DELALONDE Sébastien (Pontmain)Dry walling / insulation : Sarl BARON-MILLE (St Martin des Champs)Hemp blocs / interior render / exterior pointing (old building) : Etudes ET chantiers (Rennes)Lift : ABH

3D projection of the completed building - Photo © Pays de Fougères

ContactPays de Fougèreswww.pays-fougeres.org

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Costs Supervising office: £4,075Project supervisor: £48,687Structural work: £283,897Suspended ceilings: £26,181Aluminium joinery: £69,929Paint: £28,450Plumbing: £9,117Electricity: £25,931Wood joinery: £28,836Lift: £14,827Tiling / screed: £19,576Dry walling / insulation: £29,790Roofing: £40,503Timber frame: £47,602Heating: £52,354Ventilation: £22,725Hemp blocs / interior render: £35,145

Surface area Total: 776.45 sq mSurface area Existing: 508.45 sq mSurface area Extension: 268 sq m

Total (land excluded): £787,634 (£938,131 charges included)Total existing: £490,197 (£583,667 charges

included)Total extension: £297,436 (£354,464 charges included)

Existing: £964 /sq m (£1,147 charges included)Extension: £1,110 /sq m (£1,322 charges included)Global: £971 /sq m (£1208 charges included)

The calculation of price per sq m was done as a ratio proportional to the surface (65/35) except for specific costs that were easily identifiable by their function or directly noted on the estimate.

The insertion workshop / integration project is not subject to VAT.

Grants obtained : Eco-FAUR – £78,450 (case-file developed with the help of Fréderic MARCHAND of the Pays de Fougères).

Courtyard - Photo © Servane Guihaire - Constructys Bretagne