A condominium engages in energy renovation to move from class E to class B

The energy renovation of condominiums remains a difficult decision

Co-owners shrink from the costs to be incurred, especially when they have modest incomes or are not the occupants of their accommodation. The return on investment can be very long. In Rennes (Ille-et-Vilaine), the Galicie residence has nevertheless taken the plunge. This 95-unit condominium, more than half of which is rented, has just completed its transformation after several years of planning.

Renovation project

“The first thoughts date back to 2014,” recalls Kévin Verger, manager for Foncia, syndic of the co-ownership. This building in the South Hospital district, delivered in 1969, needed renovation. A renovation of the dilapidated facades is essential. A project management team has been formed around the Rennes agency Séverine TouchetArchitecte DPLG led by Séverine Touchet, architect and engineer, specializing in the rehabilitation of existing buildings. She works with the colorist of the City of Rennes on a pre-selection of color ranges in order to bring this neutral and pale façade back to life. “The only reliefs of this long U-shaped R+3 building are made up of the projecting concrete walls at the level of the twelve stairwells, describes Séverine Touchet. We proposed to punctuate these entries with color.” Two shades of mauve and blue are offered to the group of co-owners appointed to form the works commission. Three different mauves will punctuate the entrance halls, associated with two beiges and a white for the common parts and a gray for the base.

From renovation to facade insulation

“As France's leading trustee, Foncia has chosen to be a player in the energy transition, by informing union councils and co-owners about the challenges and benefits of energy renovation, emphasizes Kévin Verger. Long reluctant to undertake such work, which is perfectly understandable because it is often quite high amounts, they are showing themselves to be more and more sensitive to the usefulness of such interventions, especially when it is explained to them that they will gain in quality of life. »

At the Le Galicie residence, in parallel with the architectural studies, an energy audit is carried out by the Acceo/E2C design office and the condominium is selected by Rennes Métropole with five other residences as part of a energy renovation named "City of tomorrow" managed by the Caisse des Dépôts et Consignations, and having the "purpose of financing innovative projects, demonstrators and examples of what will be the city of tomorrow". In addition to public state aid, there are grants from the community of municipalities to carry out the renovation, on condition that the BBC Renovation label is obtained after the works.

The project is therefore evolving towards a global energy renovation. The simple renovation is replaced by thermal insulation from the outside, completed by the insulation of the upper floor of the basement and the roof terrace and associated with the complete renovation of the building's ventilation system. The original exterior joinery has been replaced by some co-owners but there are still 10 to 15% of single-glazed wooden windows. Since we cannot impose on all the co-owners the replacement of the joinery of their accommodation, the project management team made sure to reach the level of energy performance of the BBC label by equipping the roof terrace with solar panels. heaters intended to produce part of the domestic hot water. The collective boiler room has been renovated and thermostatic taps are fitted to all the radiators.

All of these measures allow the building to go from energy class E to class B and thus obtain the expected funding.

"Depending on the income of each co-owner, the aid can cover 30 to 50% of the cost of the work, or even 90% for a few people with very modest incomes", describes Kevin Verger. The decision to start the work is voted at the General Assembly of co-owners in December 2018.

Plaster on rock wool

On the façade, the solution recommended by the architect is the StoTherm Mineral ITE system which uses incombustible rock wool insulation. To achieve a thermal resistance R of 3,7 m2K/W, the insulating panels will have a thickness of 140 mm. The floated finishing plaster used is StoSilco K based on siloxane resin, which is particularly resistant to bad weather.

The Rennes-based company SNPR wins the façade works contract and starts a project in September 2019 that will last nearly two years. Accustomed to working with Sto products, the company, on the strength of its experience, strictly respects the recommendations of the project manager.

“Sto is one of our main suppliers,” says Hervé Rouault, manager of the facades sector at SNPR. We appreciate its wide range of products, the sales advice, the short delivery times, the products adapted to the installation conditions thanks to summer and winter versions…”

The wedged-dowelled fixing of the mineral insulation panels is carried out with Sto-Mortier glue B and dowels with rosettes. A coat of StoLevell Uni base coat reinforced with fiberglass mesh is then applied, followed by a second pass of the same coat. The ground floor surfaces are reinforced with armor reinforcement embedded in a first pass of plaster. The StoSilco K1.5 float finish coating is available in three shades from the StoColor System color chart depending on its location on the facade: white and two shades of beige.

X-black technology

The facades, unheated stairwells, do not require insulation. They are therefore the subject of a technical facelift in class I3 facade impermeability, including a StoPrim primer coat, an Irtop SC undercoat and a floated finish coat Irtop SK 1.5, to obtain the same grain. of finishing plaster than the isolated parts. The mauve shades chosen (33400, 33401 and 33402 from the StoColor System color chart) being strong, the coating benefits from Sto's exclusive X-black technology which reduces its solar absorption coefficient and limits heat absorption in summer.

The bases, undersides and balcony nosings are coated with a class D2 microporous paint with a StoColor Jumbosil matt finish.

Winter and summer comfort

In the fall of 2021, when the work was not fully completed, the co-owners confided their satisfaction to Kévin Verger. In addition to the aesthetic aspect of their residence, which was their initial objective, they now appreciate the increased comfort of their accommodation, summer and winter alike. They noticed that it was less hot there during periods of summer heat and many of them did not need to turn on their radiators at the start of the heating period.

Technical specifications

• Type of building: rehabilitation of collective housing building
• Location: Square de Galicie and Avenue de Pologne, 35000 Rennes
• Facade area treated: 5 m200
• Client: represented by Foncia Rennes
• Project manager: SARL "Séverine Touchet - Architect DPLG"
• Thermal design office: ACCEO/E2C
• Organizations: Rennes Métropole, ecoTravo, Caisse des dépôts, CEE, Anah
• Applicator company: SNPR
• Date of receipt: end of 2021
• Solutions used: StoTherm Mineral system, StoSilco K coating, Irtop SK waterproof coating with X-black technology, StoColor Jumbosil paint