Created in 1952, ‘La Cigale’ is a housing cooperative comprising 273 apartments in two buildings located in Geneva, on the corner of the Rue de Vermont and the Rue du Vidollet. 57 years after the buildings’ construction and with the aim of preserving their asset, the members of the cooperative took the decision to renovate their two buildings.
In this context, Brolliet, which is responsible for managing the cooperative, and its partners, put forward a renovation solution which was both entirely innovative and exemplary in terms of energy savings. The objective was both clear and ambitious: to achieve a 70% reduction in the buildings’ heating requirements thanks to improved energy performance and less dependency on fossil fuels, with the aim of obtaining Minergie-P® certification. This solution comprised a highly efficient building envelope coupled with an innovative heating system combining heat pump, ice accumulator and solar thermal roofing.
Having quickly received unanimous validation from the members of La Cigale, this unique sustainable renovation project began in early 2013 and was completed the following year. Renovating two buildings dating back to the 50s, with the objective of obtaining Minergie-P® certification, proved to be a considerable challenge, one which was met with a great success, thanks to the commitment of all partners involved. In addition, the scale of the volumes handled in the context of this project makes it the largest Minergie-P® certified sustainable renovation project ever undertaken in Switzerland. It should also be noted that all the social, ecological and financial solutions that were implemented make it a pioneering experience, supported by the Federal Office of Energy, and fully reproducible.
Finally, in recognition of the innovation, commitment and sustainable solutions put in place, the La Cigale project received two prestigious awards:
The 2014 Canton of Geneva Award for Sustainable Development The 2014 Swiss Solar Award
HISTORY Created in 1952, ‘La Cigale’ is a housing cooperative comprising 273 apartments in two buildings located in Geneva, on the corner of the Rue de Vermont and the Rue du Vidollet.
57 years after their construction, a full renovation of both cooperative buildings’ façades and a new heating system was undertaken.
In this context, Brolliet, which has been responsible for managing the Cooperative since its creation in 1952, and its partners, submitted a sustainable renovation proposal to the ‘La Cigale’ buildings’ members. The objective was both clear and ambitious: to achieve close to a 70% reduction in the buildings’ heating requirements thanks to improved energy performance and less dependency on fossil fuels, with the aim, therefore, of obtaining Minergie-P® certification.
Unanimously accepted by the cooperative’s members, Brolliet took on the role of pilot and leading consultant for this operation and set up a group of experts including architects François Baud and Thomas Früh, BG Ingénieurs Conseils SA, Signa-Terre SA, Geneva Industrial Services (SIG) and UBS to manage investment and fundraising.
PROJECT Every possible measure was taken so that the major renovation operation would create the least possible impact on the quality of life of ‘La Cigale’ members. In this context, work lasted only one year, from 2013 to 2014, and mobile scaffolding was put up and relocated as the prefabricated elements and loggias went up. This innovative solution enabled all renovation work to be implemented from outside the buildings, allowing all residents to remain in their apartments throughout the duration of the work.
In order to meet the set energy objectives, the cooperative selected a highly innovative heating concept designed by Energie Solaire SA comprising a hot water and heating generation system combining a heat pump, ice accumulator and solar thermal roofing covering 1700 m². It utilises low-temperature solar contributions and is therefore able to cover over 80% of the renovated buildings’ heating requirements using solar energy. The heat pumps use ‘Vitale Vert’ energy from SIG, enabling the ‘La Cigale’ buildings to be supplied with 97% renewable energy. Finally, a small natural gas source is conserved to provide backup heating in exceptional weather conditions, thereby guaranteeing tenant quality of life.
Rent levels, which were also taken into account, were a key element in the conception of this project in order to respect the cooperative’s operating philosophy. This involved a financial plan implemented by Brolliet in order to restrict, as far as possible, the repercussions of the work on members and keep rent levels below market average, i.e. approximately -50%.
By virtue of its size, the Minergie-P® ‘La Cigale’ renovation project is unique in Switzerland. And the work carried out had a considerable impact, representing 98% of the Minergie-P® surface area of transformations in the Canton of Geneva!
Despite the cost of such a renovation, estimated at CHF 18.5 m, obtaining Minergie-P® certification on such high volumes makes this project the first of its kind in Switzerland. In addition, the active partnership between the different stakeholders and members of ‘La Cigale’, all the social, ecological and financial solutions implemented make the renovation of ‘La Cigale’ a pilot experience, fully reproducible in Switzerland.
THE BUILDING ENVELOPE / HEATING / FINANCIAL ASPECTS IN ORDER TO MEET THE GENERAL OBJECTIVES, WORK WAS PRINCIPALLY FOCUSED ON THE FOLLOWING ASPECTS: Building envelope Heat generation Heat recovery through ventilation Energy consumption metering Implementation process in an occupied site
THE BUILDING ENVELOPE The building envelope which separates heated areas from non-heated areas was designed to be sustainable, energy-efficient and aesthetic.
Comprehensive insulation on the façades, roofing and ground floor, including replacing windows and French windows, ensured excellent building insulation and a marked increase in comfort levels.
The creation of loggias, principally to eliminate thermal bridging on balcony slabs, creates a buffer area, increasing passive solar gains.
It became essential to develop construction methods enabling work to be carried out on an occupied site, keeping negative impacts to a minimum and conserving comfort levels for residents as far as possible.
With this in mind, the renovation project utilised prefabricated elements, considerably reducing assembly times on site.
HEATING Heating and domestic hot water generation is, for the main part, provided by solar energy and ambient air exchanges.
The system comprises heat pumps combined with approximately 1700 m² of unglazed solar thermal sensors and an iced water accumulator enabling the use of latent heat linked to phase changes (water/ice).
Installation of dual-flow ventilation with high-efficiency heat exchanger in each walkway.
Introduced into living areas via a new network of the shafts integrated within the new envelope and recovery of air through the existing network from the sanitary areas.
Heat recovery is essential in buildings reaching this level of performance, with air renewal consuming the majority of heating requirements. Work was closely monitored by SIG to ensure alignment between the energy concept and the work completed.
To ensure continuous optimisation of the system, metering and consumption monitoring was put in place and will also be operated by the University of Geneva as part of research financed by the OFEN.
A screen is set up in each building indicating the consumption of the walkway and the whole area, with all stakeholders being able to benefit from remote controls for any type of screen.
FINANCIAL ASPECTS Cost of work: CHF 19’900’000.-
Estimated subsidies: CHF 2’000’000.-
A decision was taken from the outset to limit rent increases to respect the principles and ethics of the cooperative.
Long-term guarantees are in place, conserving a rental level per room at approximately 50% below market average.
The effective increase is less than CHF 50 per room per month, thanks to offsetting through fixed cost reductions.
Once the building has been renovated, the results will also depend on the residents’ ability to take onboard certain behavioural changes.
To this end, there was a focus on explaining both the concept to the residents as well as the practical aspects of living in these ‘new apartments’. This involved:
Setting up an information centre to answer questions Creating entertaining diagrams Creating a “code of conduct” Setting up multimedia screens in building lobbies
