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On this project, a contemporary design completely transformed the original space. The large volumes made it easy to totally redesign the different areas for living and circulating. The variety of perspectives, the materials and textures used, and the aesthetic attention paid to conduit and duct features are a pleasure to behold.
And it’s all reversible.
The success of the project also came from using materials with thermal and moisture-regulating properties that work in perfect harmony with the existing building. We all know thermal comfort that one-metre-thick walls can bring! Here, it was just a question of adding to the existing potential.
JMA: The work site, located in a village in the Ardèche, consisted of a large second floor room with a church-like barrel vault. The room was 20 m long by 8 m wide and 8 m high. The place had been used as a dormitory until 1950 before being abandoned and falling into disrepair.
The vault was in poor condition, but you could still see traces of the light blue paint or wash with a burgundy border on the lower edges. A large crack ran along the apex from one end of the room to the other. Before I took on the project, the roof above the vault had already been completely rebuilt and tie rods had been installed to consolidate the vault. A previously installed chimney flue made of clay flue liners ran up the centre of the room; it had been used to evacuate the smoke from a ground floor fire place.
My client owned all the buildings around this room.
JMA: The building work had six main phases:
Phase 1: Remy Larmande (builder from the Ardèche department)
The entrance to the apartment was changed by creating a new opening leading in from the stairwell in the neighbouring building and by building a landing and staircase.
Phase 2: JMA-Bâtiment Conseil and Art Pierre Tradition (Sylvain Delisle)
PHASE 3: Remy Larmande
PHASE 4: JMA-Bâtiment Conseil and Art Pierre Tradition (Sylvain Delisle)
PHASE 5: Remy Larmande
PHASE 6: JMA-Bâtiment Conseil and Sandrine Gourju
JMA: The idea was to insulate (without thermal bridges) the external walls up to a certain height (5 m at most) to be able to keep the vaulted ceiling. The hemp solution meant the insulation thickness could be adapted and tapered off at the base of the vaulted ceiling. By using machine projection, we were able to leave the mix in the trucks below, just outside the building (the room was accessed via a narrow staircase in an adjoining house). With ‘conventional’ insulation, all the equipment would have had to be brought up. The project owner contacted me as he wanted a healthy solution. The first solution that came to mind, of course, was hempcrete combined with a hemp and lime render. This solution also enabled us to have the same colour everywhere, on the hempcrete and on the non-insulated walls. The colour of Tradical® PF 80M Hemp Render suited my client, although I also offered either a limewash or Tradical® Décor finish to change the colour and aspect.
JMA: We decided that insulating the vault (with a hemp and lime solution) was ‘unnecessary’ in view of the height of the ceiling and the vault’s thickness – above the vault (under the roof) there’s a thick layer of rubble acting as a loading force. The owner wanted to the room to be a light as possible and was quick to agree to the idea of a white-coloured vault.
The substrates were prepared and any cracks and damaged areas were repaired (filled and meshed) at the same time. If we had applied a coating of something like limewash on this heterogeneous substrate, the end result would not have been very harmonious. So, I suggested finishing the vaulted ceiling with Tradical® Décor applied with a sponge effect. To avoid any unsightly joins, the entire 200 m2 surface area was completed in one go in a single day by three people working with mobile scaffold towers.
JMA: The Tradical Hemp Render was applied to the walls first. The thickness applied was gradually tapered off between the heights of 4 m and 4.5 m up from the floor. The render was floated and smoothed right up to the top to make it easier to cover the join between this material and the vault.
Before applying the Tradical® Décor finish, the hemp render had to be protected from splashes to avoid stains. Timber battens were fixed all around the walls using a rotating laser level set to the required height (about 4.3 m up from the floor). A plastic sheet was then stapled to the battens and hung down to the floor. The battens acted as dividers between the wall and the vaulted ceiling.
JMA: The existing substrate was the original lime and sand render (18-19th century) coated with a limewash. Some parts had been repaired with plaster. At a later time, the base of the walls had been coated with lead paint. When we were preparing the substrates, I sanded the surfaces entirely.
JMA: Yes, we repaired several damaged areas, such as where water had infiltrated due to old leaks in the roof and where the height of the window openings had formerly been reduced, causing cracks where the wall met the vault. The vault itself had a crack running along its entire length.
However, the apartment being on the second floor was a real advantage as we didn’t have any of the issues of rising damp that frequently occur in stone walls. So, there was no saltpetre.
The only part of this building that sometimes suffers from damp is the basement. That meant we had a building in good overall health.
JMA: I talked to my client about how regulating the level of humidity indoors helps to provide thermal comfort. Hempcrete is perfect for regulating humidity.
We didn’t have access to any information on prior energy consumption for the building, so we can’t really make a comparison. What I can say though, is that for the whole duration of the works, through winter and summer, the indoor temperatures remained very pleasant. In summer, during the hottest part of the day, the sun doesn’t heat the apartment and in winter, when the weather is at its coldest, the indoor temperature remains comfortable without having to turn the heating on. The high thermal inertia of the walls was respected by using self-insulating hempcrete applied to the inside of external walls.
In terms of noise, there was a lot of echo before work started, but once the hempcrete had been cast on the walls, the acoustics became very pleasant. There was no more echo and the coat of Tradical® Décor applied to the vault improved the acoustics even more by providing a clearer sound (prevents reverberation).
JMA: A modern electronically-controlled pellet stove was installed. One pallet of bags of pellets was ordered before the end of the renovation work. The lime-hemp renders finished drying with the help of this heating system and by airing the place daily.
JMA: The hot water for domestic use is heated using an electric water heater. As the apartment can be rented out and therefore used by people for short periods of time, we opted for straightforward solutions for domestic hot water, heating and so on, to make it easier in terms of servicing and maintenance.
Thank you, Jean-Marie, and we look forward to hearing about your next project!
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