"Reaching the carbon neutrality target set by Switzerland will require tripling the renovation rate that has been practiced for many years (between 0.8 and 1%)," says Philippe Thalmann, professor of environmental economics at EPFL.
The buildings that are easiest to retrofit for energy efficiency have been, and the measures that are easiest to implement have also been applied to the others. Thanks to these efforts, combined with milder winters, CO2 emissions from residential and non-residential buildings decreased by 44 % in 2022 compared with 1990.
However, there is still a way to go, since the Climate and Innovation Act, approved on 18 June 2023 by 59 % of voters, provides that buildings will emit 82 % less CO2 in 2040 than in 1990, and zero in 2050. In addition, the energy consumption of buildings per m² must fall by 35 % by 2050, compared with 2020.
It can be estimated that around 75 % of the energy reference area remains to be renovated to reach the zero CO2 objective by 2050, i.e. a pace of 3 % per year. This implies tripling the renovation rate practiced for many years (between 0.8 and 1 %). Yet today, three quarters of the construction sector's activity concerns new buildings, compared with only one quarter dedicated to renovation. This ratio must therefore be reversed, unless, all of a sudden, 600 000 people are found ready to work in the construction sector.
If three times more workers are mobilized for the energy renovation of the building stock, this implies that three times fewer workers will be able to continue building new buildings. This poses a major challenge, in a context where there is a strong sense of a housing shortage and and where the population continues to grow.
In such a context, I see only three possibilities :
The considerable existing residential and activity areas argue in favor of the third option. In 1990, the total energy reference area dedicated to housing amounted to 346 km² for a population of 6.67 million inhabitants, i.e. 51.9 m² per person. With that same standard, the current 530 km2 could house 10.2 million inhabitants.
However, many social, legal and economic obstacles stand in the way of a more efficient use of the existing housing stock. To begin with, it is necessary to reconcile the interests in favor of construction in order to respond to the housing shortage. Fundamental economic and social transformations are therefore necessary.
Option No. 3 also offers additional advantages: it helps preserve agricultural and natural areas, reduce travel, and promote a more social way of living. Is it really ideal that half of urban dwellings are occupied by a single person? By transforming buildings during their renovation so as to reduce private spaces and increase shared areas, it would be possible to offer each resident more square meters while reducing the overall area per inhabitant.
Let's take an example. In a typical building of 1800 m2 (energy reference area, SRE), 1500 m2 are privatized within the apartments and 300 m2 are shared for circulation, the laundry room and the bike storage room. This building houses 30 inhabitants, which corresponds to an area of 60 m² per person: 50 m² private and 300 m² shared, for a total of 350 m².
After transformation, this building privatizes only 25 m2 per inhabitant. By now housing 40 inhabitants, 1 000 m² are dedicated to private spaces, while 800 m² are available as shared spaces. These spaces include a large kitchen, a dining room, a guest room, a play area, a coworking space, storage areas, etc. The area per inhabitant becomes 45 m²: 25 m² private and 800 m² shared, for a total of 825 m².
Can this model be economically viable? In principle, yes. If the same building houses 40 people instead of 30, it becomes possible to increase rental income while reducing the rent per person. The owner thus recoups the cost of the renovation and transformation of the building. Everyone wins !
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