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chaux aérienne pour une décoration créative

Creative decoration with air lime

Air lime has long been used for decorative purposes, trompe l’oeil architectural features, ersatz materials, etc. Here, Christine Biard-Feltre applies traditional techniques to deliver an original and high-impact contemporary creation. Be inspired (by materials)!

Interview with Christine Biard-Feltre on 8 May 2019: Weber Tradical®

Context: We met up with Christine in a two-storey 1930s house in the Haut-Doubs department in France. The interview took place in a cosy ground-floor room.


Weber: What was your source of inspiration?

Christine Biard-Feltre: The project owner wanted to base this creation on a painting by a local artist, which was to be adapted to the area to be decorated.


Weber: Could you explain the concept behind this air lime decoration?

CBF: It’s a decoration based on the idea of layers, using the wooden panelling as a visual starting point. The colour of the panelling is dark, and is also used on the window and door frames, making the openings part of the creation too.


Weber: Would it be right to say that each individual layer seems quite complex?

CBF: Yes, in the sense that each one is made up of several hues. But on another level, there’s also an interplay between transparency and opacity. This gives an additional opaque-to-transparent effect, running from the first stratum just above the wooden panelling to the lightest part of the decoration at the top.

At the bottom, the waxed stucco gives a bold colour, whereas towards the top, a lighter effect is produced using limewash, patina, glazes, etc.


‘This decoration showcases all the lime-based techniques’


Weber: What was your method for the actual decoration work?

CBF: I worked wall by wall. First I prepared all the colours, with enough of each for the whole surface area to be decorated. This was to ensure overall coherence for each phase.

There were at least ten different colours over the initial primer coat, not to mention the altering effects of materials and density.

And for the third and lightest surface area, from 1.5 metres high, I also created an arrangement of very blurred layers, ranging from brown to beige and textured using sands. I then covered the whole work with a patina, varying slightly in transparency, to allow alternating hues of colour to come through.

After that, I applied a polychrome separation between the three decorative areas to highlight the character of each one


Weber: How can you keep preparations simple for this type of creation?

CBF: All the colours were made using air lime (Tradical® H98) as a base product to which I then added sands, pigments, casein, etc. This provided me with a single medium to ensure consistency in terms of materials and in terms of drying time (overnight drying between each phase). In the end, despite the aesthetic scope and thus the need for several applications, the decor work only took five days. The whole job, including painting the woodwork, took ten days.

chaux aérienne pour enduit, badigeon et patine

air lime for rendering, limewash and patina

Weber: The final effect is that the walls take on the look of a painting!

CBF: Yes, it provides all the decor you need. We are in the lounge and very few additional furnishings are necessary, just a screen and two or three objets d’art. The overall composition is perfect for the project owner who, as an organ and harpsichord maker, embraces art and creation every day.


Note: Christine Biard-Feltre has a diploma from the Ecole d’Avignon and is officially qualified as a Peintre en Décor du Patrimoine (heritage painter-decorator). The nine-month course she took enabled her to gain the technical and artistic knowledge required for restoration work. The aim of the course is to familiarize students with traditional materials and their uses. Equipped with this knowledge, Christine Biard-Feltre carries out restoration and creative work on all types of substrate and adapts her skills to all pictorial styles.


Air lime project profile:


Air lime product solution

Limewash and lime patina: Tradical® H 98, which is a hydrated air lime in powder form graded as CL 90 S as per European building lime standard NF EN 459

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chaux aérienne pour une décoration exclusive

exclusive decoration with air lime

Weber Tradical, your expert in hempcrete and air lime

extension béton de chanvre st malo

Craft and design for a hempcrete extension

With hempcrete you can build and restore. Here, the project was an extension, a meeting of old and new. The idea was to create an additional room using state-of-the-art eco-friendly materials and an eco-friendly approach.

Entreprise Durand Bâtiment 1/3
Interview with Fabien Pautrel on 17 May 2018: Weber Tradical®


Weber: The timber framework is the first thing that strikes you!

Fabien Pautrel: Yes, on this project, the framework stands out with its unusual thick timber sections playfully arranged in a contrasting chevron and cross design between closely spaced load-bearing posts.


Weber: What’s the configuration for this extension?

FP: It covers a floor area of 30 to 40 m², with a gable wall on one side belonging to a house made of granite near St Malo. Hempcrete was used for the floor slab.

The plinth is made of local stone retrieved from a demolition. It was laid using Tradical® formulated lime and the interior was lined with pumice stone masonry. The whole plinth was topped with a levelling course on which the timber structure rests.


Weber: And what about the insulation?

FP: The owner assigned the design to a main contractor specialised in thermally insulating eco-friendly materials. So naturally, Tradical® hempcrete became a part of the project. We manually cast the hempcrete between shuttering panels, wall by wall. We cast in 50-cm-high layers, from the ground floor to under the eaves.

The framework design is visible from the inside. The hempcrete was flush to begin with, but a 10 mm layer was scraped off after removal of the shuttering formwork while the hempcrete was still fresh. A lime and sand finish was then applied, flush with the timber work.

Woodwool was placed over the wood and hempcrete wall on the outside, and was cladded with timber.


Weber: How did you handle the conduit and pipework?

FP: The conduits run through the draining layer and are embedded in the hempcrete.


Weber: Can this extension be rated as high-end?

FP: No, in terms of size, but yes when it comes to the technical choices made. One thing’s for sure, all the different materials used for this project made progress more complicated, with extensive phasing.

It was a project spearheaded by high-quality materials and expert knowledge. The timber sections were fastened together using traditional mortise and tenon joints, and the pegs were made of wood too.


Project profile

  • Project owner: Private individual
  • Location: St Malo
  • General contractor: Durand Bâtiment – La Ville Joie, 35540 Le Tronchet, France |
  • Products: Tradical® Hempcrete
  • Wall application: Tradical®PF 70 + Chanvribat®.
    Tradical® PF 70 is a building lime complying with standard NF EN 459


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Architecture and learning to think green

Alexis Monjauze, a registered architect (DPLG) specialising in green construction, has many a journey under his belt. He offers us a tour of responsible materials such as hempcrete. And what’s the end goal? Architecture that meets the French high environmental quality standard (HQE) for green building. Let’s jump on board now!

Weber Tradical® interview with Alexis Monjauze on 13 June 2018 during the 6th edition of the Tradical® Regional Conference held in Sayat, France.


Weber: What training and career path have you followed?

Alexis Monjauze: After my baccalaureate and a diploma in civil engineering, I went to an architecture school, where I took three years out to work on building sites and travel around Europe (Eastern Europe, Spain, Italy, etc.). These trips broadened my architectural culture. I then worked with various associations (environmental awareness-raising) in Lyon. After that, I worked for six years with contracting authorities in the public sector in Puy-en-Velay.

I opened my own agency there in 2005. Today, we’re a team of five!


Weber: What made you choose green construction?

AM: My parents! They were entrepreneurs. They passed on the idea of respect for the environment, along with a sense of individual responsibility (being aware of the impact of our actions).


Weber: Architecture, why did you choose this path ?

AM: I’ve always been fascinated by architecture; it was my thing. But not at any price! It was plain to me that the building industry as it stands today is bad for the environment. I didn’t want to contribute to this generalised collective madness. That’s why I did quite a few different jobs before setting up my own company. I can only see myself working towards HQE-standard green construction, even if this market only accounts for 10% of the whole construction sector.

‘People don’t realise the impact of their decisions when they buy, build, etc. They are inevitably contributing to one type of economic system or another (wastage or recycling). We don’t speak enough about the impact of eco-friendly materials on the health system’.


Weber: How did you discover hempcrete?

AM: One day, a builder offered to cast a hempcrete screed. I dug out some old architecture school documents that had interested me a lot at the time and looked into the subject. I had a first try at hempcrete in 2007. I then worked with a company experienced in hempcrete to offer it as a solution for one of my clients in 2009.


Weber: What benefits of hempcrete caught your attention?

AM: Simplicity! You only use one material for the whole wall. And I loved its truly natural feel too. Speaking from experience, it’s great in terms of acoustics and provides a cosy, mellow atmosphere.

‘There’s something about hempcrete, but you can’t quite put your finger on it. It’s just very restful.’


Weber: How do you go about recommending this material to your clients?

AM: I just offer to use the material and most of the time my clients accept! I’ve had to find builders who know how to handle it though: some building projects were a bit difficult to manage as this material requires real expertise. Thankfully, more and more builders are hempcrete-trained now and have acquired experience. Hempcrete first appeared about 30-40 years ago, so it’s relatively new.

It’s the material we get the most positive feedback on from our clients!


Weber: Have you got an anecdote to share with us?

AM: Yes. Once, I met clients who were intrigued by the thermal regulations for building their house. I explained to them that they didn’t actually need to install central heating. They remained sceptical.

The moral of this story is that today, regulations oblige you to insulate your house, but not enough for you to get rid of your heating completely. If we were to insulate just a little more with materials such as hempcrete, we could greatly reduce the need for heating and air conditioning!

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Insulating attic spaces to keep your house inherently cool

Roofs are often the cause of reduced thermal efficiency in summer and winter. Insulating attic spaces is first thing to do when you renovate. Your energy bills plummet immediately when you remove the need for air conditioning in summer.

We discussed the subject with Dominique Burg, a specialist in eco-friendly materials for renovations working from an office in the Quercy area in south-west France. The environmentally preserved Quercy area has naturally led him to opt for hempcrete solutions, to stay in keeping with his clients’ preferences.

He also works on new builds. The house he is currently building is ideal for testing different casting methods to increase his efficiency on projects involving this material in the future.

  • 1/2 Entreprise SEE Burg
  • Interview with Dominique Burg on 14 May 2018: Weber Tradical®


Weber: Why is a well-insulated attic so important for you?

Dominique Burg: We get a lot of sunshine in our region, with average temperatures of around 30°C in summer. To keep indoor spaces cool, I’m a strong advocate of installing insulation that’s effective for that period of the year and can counter overheating.

Having an attic you can use as a pleasant living space is a real plus for house owners. My approach is therefore to offer an environmentally friendly solution that cuts back on energy costs.

Hempcrete has proved to be the ideal solution for insulating attic spaces under these conditions.


Weber: Have you ever tried other solutions? On earlier projects for example?

DB: Yes, I have actually tried using lightweight insulating materials such as cellulose, wool and so on, but they don’t work in summer. If you don’t have air conditioning, converted attic spaces just can’t be used. And let’s not forget that air conditioning is not only high-maintenance but also uses a lot of electricity.

It’s absurd to have an energy bill that’s larger in summer than in winter. The real issue is how to keep the temperature down indoors. What people want in a home is a good living atmosphere.

Hempcrete is as effective in summer as in winter.


Weber: How are you organised in terms of casting?

DB: We made the most of this building project to try out the different ways of casting hempcrete, the main aim being to gain in efficiency on projects in general. We compared the times for casting hempcrete using a mechanical projection solution and a solution involving a mobile concrete mixing station with a telescopic chute.


Weber: What were the main differences between these two processes?

DB: We had to install the equipment for mechanical projection quite high up to reduce the length of the pipe and ensure it was level as much as possible. This was to obtain the maximum possible output of 3 m3 per hour.

As for the mobile concrete mixing station, the procedure was completely different as we were mixing large quantities of hempcrete – up to 40 m3 per hour. The Tradical® lime + Chanvribat ® hemp + water mix was very high quality. The real output was actually dictated by the speed at which the hempcrete could be cast for the roof.


Weber: What did you do in terms of lost formwork?

DB: Here again I made the most of it to try out two very different solutions. In the first case, the lost formwork consisted of storey-height panels. The advantage is that you can apply the finish directly on these substrates. In the second case, I used battens made of poplar. This is a stronger substrate and also has the benefit that you can dissociate the finish from the lost formwork and thus the hempcrete.


Weber: What else is on the programme for the rest of the house?

DB: We’re going to compare the same two casting methods for creating 120 m² of insulated walls and insulating Tradical® hempcrete screeds. We’re also going to apply a lime and sand render to finish the exterior of the house. The interior is going to be decorated using a mix of moisture and heat-regulating hemp renders and lime plus mud renders. Heating will be provided by a masonry stove.

The house will soon be ready to show off its energy efficiency over the summer and throughout the following seasons!


Project profile 

  • Project owner and main contractor: Dominique Burg
  • Town: Saillagol, France
  • Surface area: 160 m2
  • Altitude: 300 m
  • Climate zone: H2c
  • Insulation: The roof, wall and screed are cast with Tradical®Hempcrete
    • Using Tradical®Thermo + Chanvribat®
      • An approved material blend that complies with the performance requirements laid down by French professional rules.
      • Certified fire-resistance rating
      • Certified lambda value of 0.056 W/m.k for attic insulation and 0.076 W/m.k for wall insulation.


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