Rehabilitation of social housing: The Bel Air residence comes to life with personalized coatings

In Sannois (Val d'Oise), the Bel Air residence has looked great since the renovation of its facades. Owned by CDC Habitat, a subsidiary of Caisse des Dépôts, it houses 143 housing units in five buildings built in 1975. The leading landlord in France had already modernized the housing units. "The energy performance of the five buildings still needed to be improved by insulating the facades", explains Thierry Brocheriou, operational group manager at the Project Management Department. The objective is to achieve a BBC Effinergie Rénovation performance level, NF Habitat certification.

A consultation was launched at the end of 2017 in order to conclude a design-build contract for this exterior thermal insulation work.

Respect for the original architecture

Among the three groups selected to propose an offer, the team made up of the Agence Olivier Cabanes Architecte (AOCA), the company Demathieu Bard and the Sogeti design office was selected. A strong point of his proposal is respect for the original architecture. The five R + 4, R + 7 and R + 9 buildings are animated by prefabricated concrete edges which punctuate the facades and assert their verticality. Placed at the corners of buildings and between rows of windows, these vertical elements have two concave faces that connect them on either side to the facade wall.

How to provide thermal insulation from the outside on such reliefs without altering the appearance of the facades? Olivier Cabanes finds the solution with the brand new offer proposed by Sto: expanded polystyrene panels bent on demand. Depending on the radius of curvature requested, the curved plates are produced from a block of polystyrene by removing excess material. These curved surfaces will be coated with the same plaster as the facade while the flat projecting part will be coated with aluminum. "Its changing color depending on the amount of sunlight, from white to gold, recalls the play of light on the enamels which originally covered the spandrels and blind gables of buildings", underlines the architect.

Water repellent effect

Familiar with social housing rehabilitation operations, Olivier Cabanes is often dissatisfied with the coatings applied as part of thermal insulation from the outside of buildings: "They get dirty in a few years". For this operation, he therefore chooses a product that promises to be more durable: StoLotusan K plaster. This facade cladding with a self-cleaning function reproduces the microstructure of the lotus leaf which has a microstructured surface, considerably reducing the contact surface of the water. Raindrops bead off the surface, dragging dirt with them.

On the Sannois site, StoLotusan K plaster is applied as a finish to a StoTherm Classic external thermal insulation system. After several masonry repairs, the expanded polystyrene insulating panels are glued to the concrete support and then fixed using dowels. A masking coating (StoArmat Classic plus) is applied to the insulation and a fiberglass reinforcing mesh is embedded in its thickness. Finally, the StoLotusan K sandstone finish plaster covers the whole.

Room for creativity

Another proposal from the AOCA-Demathieu Bard-Sogeti team won over the client: to animate four blind walls with prefabricated plaster elements. Another Sto innovation! The Sto-Ecoshapes concept consists of gluing these elements on the facade on an ITE Sto system or on vertical masonry. The architect determines the format, color and texture of the rendering elements. He thus realizes his unique pattern and creates his layout plan in complete freedom. It can combine facade facings with traditional plaster and play with more or less contrasting joints. In short, the concept lends itself to very original façade compositions, at a controlled cost.

Olivier Cabanes proposes to create four different patterns that bring an identity to each building and involve the client as well as the Town Hall of Sannois in the choice of patterns and colors. Two of the motifs emphasize the verticality of the buildings by assembling long rectangular plaques in three different shades. A more kinetic layout reproduces cubes by associating diamonds of three shades and three different textures. Finally, a fourth wall is dressed with rafters in three shades.

Careful implementation

“This proposal seduced us, explodes Thierry Brocheriou, because it allows an original creation of the architect, while being quite economical. But it needs to be implemented by a very careful company. "

Consulted by the company Demathieu Bard who was looking for a subcontractor to carry out all the facade work, Sto proposed the company PMR (Plaquette Maçonnerie Ravalement) which has proven, for nearly fifteen years , of its competence in the installation of platelets. The founder and manager of this 38-person company, Murat Delikaya, and the works supervisor, Firat Doner, appreciate the assistance of an application technician sent by Sto for the first days of the installation of the Sto-Ecoshapes system. .

"The installation of the elements was carried out by three journeymen," describes the works foreman. The glue and the jointing mortar are one and the same product tinted in the mass. This is spread with a notched trowel on the support (the masking mortar for the ITE reinforcement) then the prefabricated elements are placed in the fresh mortar and pressed using a roller. The joints are then smoothed using a slightly damp brush before a second pass with a dry brush. "

“We are proud to have carried out the first application of Ecoshapes products on a large site in France, adds Murat Delikaya. And our companions found this technique pleasant to work with. "

Information

• Type of building: renovation of social housing
• Location: rue des Maraîchers, 95118 Sannois
• Surface of facade treated: 6.000 m²
• Client: CDC-Habitat
• Design-production group: Agence Olivier Cabanes Architect AOCA, company Demathieu Bard, BET Sogeti
• Applicator company: PMR
• Construction date: August 2019 - February 2020
• Solution used: StoTherm Vario insulation system, StoLotusan K plaster, StoColor Lotusan® paint and prefabricated Sto-Ecoshapes plaster elements for heating. Class D2 renovation