- Building Type : Office building < 28m
- Construction Year : 2021
- Delivery year : 2021
- Address 1 - street : 7 Avenue d'Ecolys 5020 NAMUR, Belgique
- Climate zone : [Cfb] Marine Mild Winter, warm summer, no dry season.
- Net Floor Area : 400 m2
- Construction/refurbishment cost : 694 000 €
- Cost/m2 : 1735 €/m2
Primary energy need :
(Calculation method : RT 2012 )
Our project is the result of the Eco-construction Cluster's desire to promote eco-construction and, in this case, to highlight straw construction. By creating this exemplary building, we want to show the evolution of straw techniques, deconstruct clichés and allow for the dissemination of construction possibilities to the various target audiences, not only through the promotion of this building, the location of the Cluster's offices and the possibility of coworking, but also through the numerous events that will be organised there. It is an integral part of the Cluster's theme to highlight bio and geo-sourced materials, companies (and the people in them) and techniques linked to eco-construction in all its aspects.
In this respect, this project is exemplary in more ways than one.
From the outset, team-building was favoured and is, in the Walloon context, a first element of innovation.
The innovative technique used, which makes little use of raw wood, as well as the straw insulation, make this a European, if not world, first.
Its ecological footprint is an additional asset.
The small footprint (construction on piles) and the choice of innovative materials (in addition to straw - insulation with grass) in short circuits and in circular economy make it a building that can be easily deconstructed.
Finally, the architecture is also in line with the philosophy of straw construction, having as a concept the idea of the straw bale inscribed in the contemporary world.
DesignerHellium 3 Caroline Broux Lead architect
DesignerHAVRESAC Denis Delpire Co-contracting architect, straw construction expertise
Thermal consultancy agencyHOMECO Elie Delvigne BET Thermal and fluids
Construction companyMOBIC Jean-Philippe Moutschen Timber builder, General contractor
Owner approach of sustainability
The Cluster, as a representative of the professionals in the eco-construction sector, wanted a building that would represent the expertise of the eco-construction sector. As this project is financed under the INTERREG UP STRAW programme, it should obviously be made of straw. The specifications were drawn up in terms of performance requirements (thermal, acoustic, watertightness, daylighting, water saving, etc.) while aiming for the lowest possible building technology.
The procedure chosen for the contract is 'Design & Build' so that the expertise on straw construction can be shared with the whole of the project management team from the very first stages of the sketch.
The Eco-construction Cluster needed an innovative, inspiring building that reflected the values it stands for, to house its offices and training areas.
This Design and Build project was part of the Interreg UPSTRAW project, which aims to promote the use of straw in construction.
Inexpensive, from a renewable and local source, available in abundance, without conflict with agricultural needs, easily recyclable, straw can effectively store CO2. Moreover, the analysis of its life cycle reveals a much more advantageous balance than that of conventional building materials. However, it requires a lot of manpower on site and a composition adapted to the size of the bale, which can be an obstacle. To overcome this, an innovative method based on the prefabrication of 3D modules was developed in Wallonia for this project.
The construction principle is simple: a wooden supporting structure integrates the straw insulation. The innovation lies in the composition of the walls: the local wood logs were sawn in half and installed vertically. When joined together and split, they contain the loose straw, also local, inside the wall. The sawn side of the log thus acts as a cladding, both inside and outside the building, while the core of the log plays a structural role.
These 3D modules, which are entirely prefabricated in the workshop, are then assembled and placed on screwed piles on site. This construction method is economical, ecological and practical. It reduces the duration of the building site (and therefore the nuisance), production costs, journeys to the site and the consumption and transformation of raw materials (and therefore waste). The installation of the modules on piles makes it possible to do away with concrete and to preserve the soil as much as possible by reducing excavation/embankment and by limiting waterproofing.
Architecturally, a bale of straw was placed on a forest of wooden columns. A symbol, a signal, a claim. The various functions housed in the 3D modules are articulated on two levels around an open, generously glazed space. This central space, conducive to exchanges and meetings, echoes the very essence of the Cluster.
In addition to its exterior walls, the project integrates other aspects and materials of eco-construction. The photovoltaic solar panels installed on the roof and the overhang of the modules on the first floor over the glazed hall on the ground floor act as a fixed protection to limit overheating. The partition wall of the meeting room and the technical floors have been designed to offer greater flexibility in the use of the building over time. Finally, the partitions and floors are insulated with a grass-based insulation and the half-logs are used as stair treads.
Innovation, optimisation of resources and reduction of needs are the key words that guided the design choices.
The building is intended to be inspiring, didactic and welcoming, a showcase of the advantages and possibilities of eco-construction.
If you had to do it again?
We are dealing here with innovation, and the development of a new construction technique can in some cases increase the time needed for implementation. From the idea at the start of the project to its implementation, a long process of fine-tuning and trial and error was required.
Moreover, team-building is an interesting tool, but it requires perfect collaboration between all the players and a clear understanding of the roles and obligations of each. It takes time to adapt.
Building users opinion
The building will be occupied from April / May 2021
- 71,00 kWhep/m2.an
- 170,00 kWhep/m2.an
- 28,50 kWhef/m2.an
- 0,38 W.m-2.K-1
- Heat pump
- Individual electric boiler
- Reversible heat pump
- No cooling system
- Double flow heat exchanger
- Solar photovoltaic
- 14,50 % Les panneaux solaires sont aussi utilises comme protections solaires des vitrages
- 15,60 KgCO2/m2/an
- 60,00 an(s)
- 949,00 KgCO2 /m2
Life Cycle Analysis
Indoor Air quality
The building is located in the Ecolys business park dedicated to eco-construction, sustainable development, promotion of renewable energies, etc. Ecolys is located 7 km north of Namur.
The land is an old field located on the top of a plateau with unobstructed views of the surroundings.
Access is mainly by road: the site is located at the intersection of the E42 motorway and the RN4. Access by bus is possible via Line 32 Namur - Gembloux.
1 public house and a supermarket are located near the building.
All information on Ecolys: https://www.bep-entreprises.be/parcs/40/
Land plot area
1 disabled parking space on the plot. The building has a collective car park on the plot adjacent to the building.
Reasons for participating in the competition(s)
The timber construction company wanted to develop a more economical construction system than the traditional timber frame by using ground and assembled logs to form panels between which the straw is compressed. The volume of wood per m² of wall used by this construction system is equivalent to a conventional timber frame.
The company processes the wood itself. By using unprocessed logs directly, it also significantly reduces the cost of the wood. The quantities of wood used are ultimately of the same order of magnitude as a conventional framework and the wood used for this project comes from forests within a radius of less than 100 km from the sawmill.
Building candidate in the category
Other case studies
- sophie boone