Energy savings: Heat homes, cool the planet
When it comes to energy efficiency, France is lagging behind its European neighbours, trailing Germany, Sweden, the United Kingdom and the Netherlands. Nearly seven million French people live in residences known as "passoires énergétiques" or energy sieves. These homes have an energy rating of F or G, meaning it's too cold in winter, too hot in summer and importantly, it adds considerably to the country's carbon footprint.
A 'thermal photo' stroll
Paris has pledged to make all of its buildings energy efficient by 2050. To do so, the city will need to accelerate the pace of renovation 20-fold in the years to come. It's a steep challenge, heightened because in a city like Paris, architectural heritage is an additional factor to consider.
Using a thermal camera, Down to Earth accompanied Nabil Zenasni from the Paris Climate Agency on a stroll down a typical Paris street. The camera reveals which buildings are releasing large quantities of heat, with red and orange indicating heat loss, and blue suggesting proper insulation. For example, Hausmann-style heritage buildings will often release heat through the doors and windows if they have not been renovated. ''We started imposing building insulation in Paris in 1974. The overwhelming majority of buildings in Paris were built before that time, so that means an enormous number of buildings are not insulated,'' Zenasni explains.
Rehabilitate or demolish?
The teams in charge of renovating Paris's buildings systematically ask themselves an important question. "Do we renovate or do we demolish and rebuild?" says Hélène Schwoerer, deputy director of Paris Habitat, a public organisation that manages the city's low-cost housing. For heritage reasons, insulation work needs to be completed from the interior. For example, it is forbidden to modify the brick facade of a 1930s building. Insulation efforts are instead focused on using bio-sourced materials such as hemp and wood.
''Here we are talking about heritage buildings that can be part of a sustainable city, that we can change and evolve. I hope that with the work done today, we have begun a new life cycle of 50, 60 or even 70 years,'' Schwoerer concludes.
A facade made of algae
Could the city change its face in 70 years? That's one idea put forward by Anouk Legendre, an architect with the agency XTU.
Her team has designed bio-facades which are like flat aquariums with water and microalgae inside, with the added benefit of improving energy efficiency.
''It's a buffer space that protects from the heat and the cold, which optimises the building's insulation and reduces consumption by half,'' the architect explains.
For heritage reasons this type of project wouldn't work on Paris's historical buildings, but it can be applied to new constructions or more modern buildings such as the business towers in the La Défense district. There are already several projects underway, with the most recent a residential building in central Paris.
Additional heat captured by the bio-facade can be used in the building, for example for hot water tanks, and the microalgae that multiples inside can provide a source of food and potentially medicine for the city of tomorrow.
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