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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.


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


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), Weber 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 Weber 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



  • 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, Weber 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 – ©Weber Tradical®

Case study 06 – An energy-efficient house in the Doubs

Only 1,500 kg of wood pellets required for heating

In our ‘Feedback on heating costs’ series for hempcrete houses, this is the sixth conclusive case study.

In Roche-Les-Blamonts, where temperature and weather can fluctuate considerably within the same day, there is nothing better than Tradical® Hempcrete to counterbalance these variations and ensure that indoor temperatures remain stable, leading to greatly reduced energy consumption whatever the season:

The profile of this low-energy house

  • Surface area: 100 m²
  • Altitude: 420 m
  • Climate zone: H1c


Construction system

  • The building rests on a 40/60 granular fill which contains all the networks. A drained hardcore layer was placed on top of this.
  • The main house, adjoining garage and extension are all built using Tradical® Hempcrete.
  • This eco-friendly building has benefited from an innovative timber framework made of vertical wall panels, making it easier to coat the structure with the lime-hemp composite.
  • This composite material was projected on the exterior, over lost formwork. Timber cladding was then added to finish the façades.
  • A hot water tank was installed for DHW
  • The house is heated by a wood pellet stove


Bio-based hempcrete insulation in five areas


  • Tradical® Hempcrete insulating walls, where R = 4.7 m²K/W for a thickness of 40 cm
  • A Tradical® Hempcrete insulating roof, where R = 5 m²K/W for a thickness of 30 cm
  • A Tradical® Hempcrete insulating screed, where R = 2.1 m²K/W for a thickness of 20 cm


  • Tradical® Hempcrete insulating layer in the unused attic space, where R = 2.1 m²K/W for a thickness of 20 cm


  • Tradical® Hempcrete insulating walls, where R = 2.4 m²K/W for a thickness of 20 cm


A very low environmental impact

Bilan CO2Label Bâtiment BiosourcéVolume Béton Chanvre Tradical®
19 t de CO2 captéEligible niveau 368 m3


Summer comfort with no air conditioning required

Example for July 2016

  • Outdoors: an average temperature of 15°C at night and 30°C in the day
  • Indoors: a daytime average temperature of 25-26°C with high outdoor temperatures


Thermal comfort in winter

  • Outdoors: an average temperature of 0°C at night and 9°C in the day
  • Indoors: a daytime average temperature of 22-23°C


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In addition to this article, why not also read the five other case studies published in early 2017

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.

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

Build with hempcrete with Weber Tradical, your expert in hempcrete, lime render and more

Contact us!

Weber Tradical®: contact@weber-tradical.com

Case study 04 – High-performance architecture

This bioclimatic house in the Périgord region, with a gross floor area of 170 m², was built by DB Chanvre using a timber frame system combined with an insulating wall, an insulating ground floor slab and an insulating first floor screed, all made with TRADICAL® HEMPCRETE.


The idea of offsetting the framework towards the interior is to enable all the timber framework elements to be coated as the Tradical® Hempcrete is cast.

This method ensures the build is thoroughly self-insulated thanks to continuous casting, which also provides uniform thickness:

  • on the façade-side without any interruption
  • where façades join together
  • where vertical walls join with floors

ADVANTAGES: no thermal bridges and no loss of thermal performance and vapour-regulation properties.

Maison béton de chanvre

A hempcrete house – the project

Temperature monitoring shows that indoor temperatures remain constant, regardless of the season, yet heating costs are cut and no air conditioning is needed. It is proof that the Tradical® Hempcrete system is as effective in summer as in winter.


Construction system

  • A 30 cm thick Tradical® Hempcrete wall was sprayed directly onto storey-high Fermacell panels fastened to the interior of the framework.
  • A ground floor slab was laid comprising a drained hardcore layer of limestone and clay pebbles, a 20 cm thick Tradical® Hempcrete layer, a lime-based floor screed and a terracotta covering layer.
  • A first floor screed was laid consisting of a 15 cm thick Tradical® Hempcrete screed cast on poplar floorboards and then covered with a lime-washed chestnut flooring.
  • A passive solar floor-to-roof window area was installed, along with a humidity-controlled double-flow CMV.
  • A thermodynamic heat pump was installed to provide domestic hot water (COP 3.8 at 7°C)
  • An 8 kW heat storage and wood pellet-fired stove was installed (without ventilation) at the centre of the house
  • Exterior joinery was made of local lime-washed chestnut and on the south-facing side, of aluminium.
  • A rainwater harvesting system was installed
Plan Rdc de la maison Trijau

Ground floor plan of the house

Temperatures are dynamically regulated by Tradical® Hempcrete

Example for February 2017

Regardless of the temperature variations, with lows of -5°C and highs of 20°C

  • Indoors: the average low was 18.8°C and the average high 23°C
  • Outdoors: the average low was 5°C and the average high 13.8°C

With a very high level of thermal comfort and well-being

performance béton de chanvre Tradical hiver 2017

Tradical Hempcrete performance levels in winter 2017

Exeample for July 2016

Regardless of the temperature variations, with lows of 9°C and highs of 33.3°C

  • Indoors: the average low was 20.2°C and the average high 23.8°C
  • Outdoors: the average low was 15.8°C and the average high 26.5°C

With a very high level of thermal comfort and well-being

Performance du béton de chanvre Tradical été 2016

Tradical® Hempcrete performance levels in summer 2016

Heating energy consumption

The house is in the Périgord, but in the north of the department where the climate is more continental, with cold winters. For six to seven months of heating, depending on the year (October to March/April), the budget is €300 incl. VAT.

Thermal performance

performance thermique chaux + chanvre

Thermal performance of the lime + hemp blend

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Weber Tradical® : contact@weber-tradical.com

Build with hempcrete with Weber Tradical, your expert in hempcrete, lime render, lime salt petre and more


Case study 03 – Energy performance of a ‘Passive House’

The house was designed and built by Daniel Bayol of DB Chanvre, who specialises in this type of building.

Located in Vidauban (in the Var department), this modern house is positioned so as to make the most of the sun throughout the day, with very large south-facing windows.

  • Natural light floods in.
  • The sunshine is ideal for exploiting the heat storage capacity of the mud brick wall, which also serves to structure the indoor space.
  • The wide overhanging eaves that run right round the building serve to protect windows and the mud brick wall from over-exposure to the sun during the hottest period (from May to September). This means that the house does not get too hot when the sun really starts to blaze, as it can do in this region.

This is truly a bioclimatic house, where everything has been designed to get the best out of the positioning of the house and the materials used to ultimately reduce energy consumption and environmental impacts as much as possible.

Ossature bois porteuse poue cette maion passive

The timber load-bearing frame used in this passive house

Temperatures are dynamically regulated by the hempcrete

For example, when we visited the house at the end of January:

  • Outdoors it was 8°C
  • Indoors it was 19°C
  • Indoor relative humidity was 50%

With a very high level of thermal comfort and well-being

Eclairage naturel et grand espace intérieur pour définir cette architecture contemporaine

The interior where natural light has pride of place

Heating energy consumption

The heating bill for 2015 was €133 incl. VAT for the winter season running from November to end of March.


Passive House certification

  • The primary energy consumption (CEP) threshold for this certification stands at 120 kW/m²/year
  • The CEP for this 122 m² house is 113 kW/m²/year, or 6% less than the reference figure.


Construction system

  • Timber framing
  • Tradical® Hempcrete: thickness of 30 cm
    applied to walls via mechanical projection over three days. R=3.5 m²K/W
  • Double-flow CMV
  • Internal wall made of mud bricks to store the heat from the sun
  • Cellulose wadding
  • Solar thermal panels

Environmental Impact

43 m3 of Tradical® Hempcrete stores 3.6 t of CO2
Eligible for Level 3 Bâtiment Biosourcé (bio-based building) certification

Performance ratings

Maison passive en béton de chanvre

Six qualities that define this passive house

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Weber Tradical®: contact@weber-tradical.com

Weber Tradical, your expert in hempcrete for houses

mur isolant béton de chanvre Tradical

Case study 02 – Monitoring heating costs

This hempcrete house is yet another example of energy efficiency. The figures prove it.
Located in the Haute-Garonne department, the house was designed with an environmentally friendly approach in mind:

  • Natural insulation with Tradical® Hempcrete insulating walls
    (R = 3.5 m²K/W for a thickness of 30 cm)
  • A Tradical® Hempcrete insulating roof
    (R = 5 m²K/W for a thickness of 30 cm)
  • Masonry stove
  • Solar DHW

Completed in 2011, the house has provided us with a precise snapshot of energy consumption. Note that for all hempcrete constructions, heating energy consumption is higher during the first year of use before becoming more stable in the following years, as the table below shows.

Outcome per yearYear 1Year 2Year 3
Wood consumption2 steres of logs
+ 2 m3 of chestnut
1.5 steres of logs
+ 2 m3 of chestnut
2 steres of wood
Energy performance57 kWh/m²/year50 KWh/m²/year30 kWh/m²/year
Heating costs250 €200 €150 €

Overall energy performance

The outcome is 50 kWh/m²/year, taking account of DHW and ancillaries in particular

Bilan consommation IC2E

Energy consumption byIC2E

Temperature readings show good indoor thermal comfort in winter and summer.

  • In winter: 22/23°C indoors in the daytime when outdoors it is 0°C at night and 9°C during the day
  • In summer: 25/26°C indoors in the daytime when outdoors it is 15°C at night and 30°C during the day

Case study 01 – Heating energy consumption

It is winter, and January through to February is the ideal time to do the rounds of the houses built a few years ago using Tradical Hempcrete and discover how truly energy efficient they are in terms of heating.

The calculations for designing projects that conform with Thermal Regulations are theoretical,
so when you are holding an actual reduced heating bill in your hands, it feels great!
It underlines the benefits of the Tradical Hempcrete insulating system, which go above and beyond the R value alone.

The house we are (re-)visiting today is located in Mimeure, in the Côte d’Or department. It was completed in 2011, RT 2015-compliant.

‘At the beginning,’ says Mme Doile (project owner), ‘the idea of an eco-friendly house drove me to find out more by going to green building trade shows. Then I met a builder, Mr Babic, trained to work with Tradical Hempcrete, which helped me develop my project.’


‘I wanted an energy-efficient house to limit heating costs, bearing in mind the future and the ever-increasing cost of fuel.’


‘Six years on and I can safely say I have rarely felt cold in my house.’ ‘When I go away for a few days, I come back to an indoor temperature of 15°C, which immediately rises to a comfortable temperature once the heating gets going.’

Mme Doile showed us round her house around midday on 8 December 2016:

  • outdoors it was 4°C,
  • indoors the temperature with no heating was about 20°C
  • despite an outdoor temperature of -4°C in the early morning.

At the design phase, the engineering consultants included an electric heating system in their calculations. However, this heating source has never been used. The house is heated exclusively by a 6 kW stove with an external air supply. The north-facing bedrooms were cosily fitted with tripled-glazed windows, whereas the ideally placed, large south-facing living room windows only required double-glazing.

The outcome is that today, 4 to 5 steres of wood a year are enough to heat the house! 

See the project profile

Weber Tradical®contact@weber-tradical.com

Weber Tradical, your expert in hempcrete for houses