The retrofit concerned 250 homes in four buildings erected in the 1980s. Priority had to go to the most effective insulation and energy efficiency solutions under the terms of the Climate Plan. “First of all, we worked on the buildings’ external thermal insulation and choice of heating. Two of them were fitted with new, high-efficiency gas boilers, with a yield of over 110% and reduced CO2 emissions”, explains structural works inspector Bruno Fricard, who helped draw up the technical specifications with the project manager.
Other renovation work was carried out in the communal areas and to ensure fire safety compliance–changing the ventilation and smoke-extraction systems.
The operation required advanced insulation studies, says architect Dominique Desmet from Equateur Architecture. “The main problem was that the four buildings were designed by four different architects, so we needed to research specific insulation principles for each one, within the framework of the Climate Plan, fire safety and budget. I think I can safely say that I compiled the most exhaustive detail booklet on external insulation ever produced by an architect! It’s a useful database for everyone and RIVP can use it for reference in other projects.”
Georges Frasca, director of GTM Bâtiment’s retrofit unit, emphasises the complex architecture of the facades. “There were far more building-specific details than for a standard retrofit.”
A certain amount of preparation was needed for the 18-month retrofit of an inhabited building. There were public meetings to explain the nature and process of the work involved, and the resulting disturbances. After the workmen moved in, communication became even more important. Franck Charvet, manager of the RIVP Grenelle agency, says: “When the tenants are faced with the reality of the process, you need to offer support and reassure them about safety, because of the scaffolding; you have to make choices if there are issues with the work carried out in their home. And you have to support the liaison staff on the front line.”
Ms Estevès, the caretaker, admits that it wasn’t a particularly restful time: “Yes, there was a bit more to do. This kind of work is very messy. And you always have to deal with the usual malcontents, even though there was a complaints log for tenants in my office.”
Franck Charvet relates a story that sums up the support role that everybody had to play: “One day representatives of the Caisse des Dépôts, a French financial organisation, came to visit the site. Everybody there simply couldn’t believe their eyes to see one of the workmen on his scaffolding watering a tenant’s flowers!”
Lower charges, greater comfort
The efficiencies gained from the retrofit have led to the buildings’ energy requirements falling by two-thirds from 300 kilowatt hours per square metre to just 90 kWh/m2 per square metre per year. This change has not gone unnoticed by the tenants. Clarisse Crevier, who has lived in one of buildings for 20 years, says: “There is no comparison with what it was like. So much heat was lost and you couldn’t get properly warm. Now that the loggia has been closed off and double-glazing put in, it’s not just the insulation that has improved but noise levels as well. Financially, it makes a big difference too: between the end of 2012 and the end of 2013, I saved €500 on my gas bill! And it looks really good. You would never believe that this is a social housing project.”
Reducing energy charges is a priority for RIVP, which has been tracking charges for a selected panel of tenants since the end of the retrofit.
Everybody agrees that the retrofit project was an enriching human experience. Bruno Fricard talks about the chemistry between the different operators, emphasising their professionalism and responsiveness in finding the best solutions. Franck Charvet highlights the team spirit and commitment of everybody involved.
For Georges Frasca: “A project like this is first and foremost about people. If you don’t work together, you can’t do it. And this was a really successful project in every way—technically, aesthetically and personally.” Dominique Desmet agrees: “Everybody I dealt with at RIVP was open-minded and did things in the right way to make it work.”
©OECD Observer No 304, November 2015