Architecture projects

préfabrication béton de chanvre pour une base logistique

Short prefabrication lead times with hempcrete

Two major challenges for building a local authority technical services building: a fast turnaround time and no cost overruns.

Tradical® Hempcrete is now being used for local authority technical services buildings too! The Taffeneaux logistics base, intended for servicing and repairing household waste collection vehicles, is proof of the progress this highly versatile material is making.

BCB’s Tradical® Hempcrete was chosen because it met the two requirements: an extremely fast turnaround time and a tight budget. Concerned to keep the impact of this work to a minimum and wanting an operational building in record time, the contracting authority, Sables d’Olonne district council, called on CAN-ia.

From study to delivery in twelve months

The whole project, from the initial study and project planning to choosing the architects and builders, finalising the building processes, constructing the building and handing over the keys, took twelve months. What a challenge, with an unusually tight building schedule to boot!

The key to success was prefabricating all the timber and Tradical® Hempcrete panels off-site.

An extremely tight schedule was drawn up, streamlining all the building stages and limiting their cost to save time. This led to innovative designs and building methods.

Two inverted sloping roofs for a black and white architectural project

Tradical® Hempcrete fitted right in, naturally. Today this material is increasingly popular for publicly contracted projects.

In the case at hand, it is most probably the first ever technical services building (where waste management is concerned at any rate) to have been built using this material.

The contracting authority wanted a speedy turnaround time, yet also a ‘quality building’, a double requirement met by Tradical® Hempcrete.

The project submitted by CAN-ia offered a beautiful, functional and cost-effective design, and chose a green approach, proposing to use the bio-based material Tradical® Hempcrete, which also meant the project could be finished even faster than a standard building project.

The hempcrete plan

The plan was to have a parking area equipped with a wash station, a fuel station and a workshop for servicing and repairing waste collection trucks, but also offices and changing rooms for employees.

This double requirement inspired CAN-ia to propose a design with two separate buildings, playing with the volumes and visual effects.

Two inverted sloping roofs would enable the office building to counterbalance the much bigger workshop building.

A bio-climatic approach

The office building faces south to make the most of the sun in winter (in summer, the regulating properties of hempcrete means there’s no need for air conditioning), and the workshop faces north. This was a conscious decision for the workshop, which requires non-dazzling natural light.

A large covered walkway links the two buildings, providing users with protection from the sun and rain. Its slanted posts are inspired by rows of trees in a forest.

Timber and hempcrete – the perfect match

The two materials work really well together here. The glue-laminated timber framework of the building was made by local company LCA, who also made the prefabricated panels for the frame structure.

The advantage of timber framing for the builder is its flexibility, which allows for all kinds of shapes. The walls of the envelope for the office building were made out of hempcrete (with a render finish).

The glue-laminated timber framework carries the loads and a standard assembly method was used (beams – sills).

 

→ View the building work project brief

 

PROJECT PROFILE – The Taffeneaux logistics base

Project actors

  • Project owner: Sables d’Olonne district council
  • Main contractor:   CAN-ia – Hangar 20, 20 Quai des Antilles, 44200 Nantes, France. can-ia.fr.
  • LCA – Les Charpentiers de l’Atlantique: Timber framework and Tradical® Hempcrete panels
  • Entreprise Fernandez: Tradical® Hempcrete casting in LCA’s workshop

Contact us for more information 

contact@bcb-tradical.com

Case study produced by Sandrine Wiart, BCB Tradical® Press Officer. Tel: +33 (0)134 947 733

restauration d'un monument historique Luxembourg

Restoration of an iconic historic building in Luxembourg

Hempcrete was placed at the heart of major restoration work on an iconic chateau in Luxembourg. This bio-based material has proved its worth as an ideal solution to meet all the requirements for renovating a historic building.

1638

Construction of one of the most important chateau of the Grand Duchy of Luxembourg.

2018

Renovation and insulation of the chateau with Tradical® Hempcrete

 

In the period intervening these two dates, the Grand-Château d’Ansembourg left lasting impressions, with its extensions, its economic role, its ever-flourishing gardens and park, its different owners and its important place in Luxembourg’s heritage.

Surrounded by world-famous, picturesque botanical gardens, where the delicate and fragrant Jardins d’Ansembourg rose was recently unveiled, the Château d’Ansembourg is experiencing a rebirth thanks to the expert advice of the Service des Sites et Monuments Nationaux or SSMN (Luxembourg’s department for national heritage).

The renovation work made it crystal clear that using a natural, bio-based material, such as Tradical® Hempcrete, is the right and best solution for (insulating and) renovating historic buildings.

The work was also a perfect example of artisan builders working intelligently and communicatively together to organise and complete a large-scale project.

A whole range of tough constraints shaped this renovation and led to specific technical choices and ingenious solutions.

 

From quick renovation to large-scale project

To begin with, the project owner wanted a simple renovation of the first floor. However, preliminary surveys and inspections revealed that there were significant structural problems requiring a more general overhaul: cracks, sagging floors and stairs, etc.

 

A further issue – dry rot

Dry rot was identified in just a few places at first, but unfortunately, it soon became clear that it was more widespread (affecting 700 m²). The initial renovation project had to be completely revised to incorporate an approach closer to archaeology than renovation.

The renovation suddenly went from work on a just few dozen square metres to having to perform work on all the floors of the central building. Work was therefore undertaken on the structure and to treat the dry rot.

  

Finding the right solution

Now a large-scale project, the renovation of this part of the building brought several building specialists together to find a solution to meet all the constraints involved:

  • Ensuring that the layout and ornamental features of the interiors were kept – sculptures, beading, overhangs, intersecting ribs, etc.
  • Preventing the return of dry rot by creating the conditions for maintaining constant temperatures and moisture levels.
  • Ensuring walls can breathe to guarantee longevity.
  • Providing high-performance insulation.
  • Recreating the natural historic look and feel (while also integrating any necessary modern elements).

 

An on-site and decisive test

In 2016, the hempcrete underwent a full-scale test on site in the annex off the Salon Bleu (blue room) on the first floor, a room measuring about 4 by 4 metres.

44 m² of surface area were lined with hempcrete cast on an embedded metal framework. The results confirmed the vapour permeability and acoustic performance of this bio-based material, and proved that this insulating lining could be used without compromising the architecture and the different decorative or ornamental elements.

 

Hempcrete insulation – a compelling approach

The idea of using hempcrete was quickly adopted, as the material provided:

  • The right humidity control characteristics to enable the façade to breathe.
  • Consistent material characteristics to prevent dry rot from reappearing. Dry rot comes from the stonework and spreads if certain humidity and temperature conditions come together. The fact that hempcrete provides a constant surface temperature for interior walls avoids such conditions arising.
  • An indoor temperature of 20°C, as requested by the project owner.

 

Restoration choices governed by architecture and heritage

An inverted metal framework

With cellulose-hungry dry rot in mind, metal had to be used for the secondary framework. Profiles were positioned vertically at 40 cm intervals and a few centimetres away from the substrate.

For a perfect infill and an even coating of profiles, and to meet, for example, the specific thickness required for the correct distance between the flat surface featuring the decorative friezes of the vaults and the flat surface of finished insulated walls (recommended by the SSMN), BCB Tradical®’s Technical Manager, Yannic Santandreu, proposed the ingenious solution of using U-shaped profiles.

Tracks (48 mm) were positioned with the concave part of the profile facing outwards. This solution ensured that the profiles were coated with a sufficient thickness of hempcrete to support the expansion and contraction effects inherent to all materials, and avoid any deterioration through fissuring.

The hempcrete was made in a concrete mixer and poured into the gap between the OSB shuttering panels and the walls, in compliance with the French professional rules for hempcrete. Thanks to this innovative solution, the framework was firmly coated with a thickness of between 7 and 10 cm.

 

Reversible insulation work – a must for renovating historic buildings 

One of the main concerns of the project owner and the SSMN was that the work undertaken should not damage the original building. The insulation had to be removable should the need arise in the future. Hempcrete supported by a metal framework that is separate from the substrate can be easily removed if necessary.

 

Maintaining breathability with air lime finishes

An air lime finish was applied to the hempcrete as a thin coat of render – Tradical® Décor –  whose vapour permeability is in perfect harmony with the moisture transfers inherent to this bio-based insulation. The thin lime render was also used on the mineral-based wall substrates adjacent to the insulated walls. The advantage of this render is that any work delivered is texturally and visually harmonious, regardless of the type of substrate to be finished.

 

A constructive meeting of artisan builders – or the small business’s guide to completing large-scale projects

Atelier Saint-Fiacre France (stone cutter), Entreprise Hennen, Société Millereaux and Atelier Montomble, all won over by hempcrete and trained by BCB in the use of Tradical® Hempcrete, took a methodical approach. They pooled their efforts, shared their experiences and knowledge, tightly scheduled the different work stages and optimised costs. A work and primary material delivery schedule was set out over period of about ten months, at a rate of one week of work per month.

 

Project profile for the restoration of a historic building

  • Work site: Grand-Château d’Ansembourg
  • Location: Ansembourg, Grand-Duchy of Luxembourg
  • Purpose of the building: Tourism, seminars
  • Characteristics of the building: Historic building (dating from 1640)
  • Project owner: Private project owner
  • Main contractor: Agence N. Madoki
  • Restoration supervised by: Service des Sites et Monuments Nationaux
  • Builders & artisans using hempcrete: Atelier Saint-Fiacre France (stone cutter) / Entreprise Hennen / Société Millereaux / Atelier Montomble
  • Expected delivery: 2019
  • Surface area concerned: 1,500 m²
  • Product volume: 130 m of hempcrete

 

Products:

  • Tradical® Hempcrete bio-based insulation: Tradical®PF 70 lime + Chanvribat® hurds
  • Thin air lime-based interior finishing render: Tradical®Décor

 

Tradical® Hempcrete quality hallmarks:

  • Certified aggregate
  • Made in France
  • Compliant with French Professional Rules

 

For further information:

 

Note 1: extract from the press kit produced by Sandrine Wiart, BCB press officer, in June 2018. Document title: AT THE HEART OF MAJOR RESTORATION WORK ON AN ICONIC CHATEAU IN LUXEMBOURG: HEMPCRETE. The kit was finalised after a press visit to the site on 27 June 2018.

Note 2: Photo credits – ©BCB Tradical®

Case study 05 – The advantages of extending upwards using Tradical® Hempcrete

The original house consisted of just a ground floor with a surface area of 50 m². The upward extension consisted of an extra floor and a converted attic, bringing the total surface area up to 90 m², or resulting in 80% extra space.

Why use a timber framework combined with hempcrete?
  • The additional load was reasonable. 320 kg/m3, or 96 kg/ml for a thickness of 30 cm for insulating walls and 48 kg/ml for a thickness of 15 cm for insulating gable walls.
  • The walls and roof were lightweight and insulated, yet they still felt as sturdy as most of traditional buildings in the area.
High-performance insulation with very low heating bills
  • 2 steres of wood
  • That is all it takes to heat the house for a year. And no air conditioning is required for the hotter season either, despite the location.
Tradical® Hempcrete allows for short turnaround times

Mechanical projection meant that

  • The four walls were finished in five days
  • The roof was finished in only two days
A uniform end result

In-situ projection ensured elements were perfectly self-insulated and that there were no thermal bridges where vertical walls joined together and where they joined with floors and the roof.

High-performance from Tradical® Hempcrete
une surélévation chanvre + chaux

les performanes avec Béton Chanvre Tradical

Contact us!

BCB Tradical®: contact@bcb-tradical.com

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