"Adapting" existing buildings today would make it possible to face the environmental challenges of tomorrow, according to our partner The Conversation.
This path is mentioned in a prospective work by ADEME including 4 scenarios that would make it possible to achieve carbon neutrality by 2050.
This analysis was conducted by Albane Gaspard, in charge of building and real estate prospective studies, and Jean-Christophe Visier, building and real estate prospective adviser.
Thermal renovation, adaptation to aging and climate change… the 21st century requires unprecedented investment in the management of our existing building stock to adapt it to the challenges of tomorrow.
But what about new construction?
Building is not an innocuous act from an environmental point of view.
Indeed, even if new buildings are today very energy efficient once built, the major part of their environmental impact relates to the construction.
It is estimated, for example, that construction products and equipment represent 65 to 85% of all carbon emissions linked to the life cycle of a new building.
The consequences in terms of soil artificialization should also be underlined: between 2006 and 2014, the surface area dedicated to housing grew faster than the population.
In this context, the question arises: can building needs be met by making better use of the existing stock?
As part of "Transition(s) 2050", a vast prospective work, the Ecological Transition Agency (Ademe) has developed 4 scenarios, from the most sober to the most technological, which would make it possible to achieve carbon neutrality at the horizon 2050. The most frugal scenarios explore ways to meet the need for buildings other than new construction.
8% vacant units
First, let's try to shed some light on the debate.
In France, INSEE notes in 2021 that 8% of dwellings (i.e. 3 million) are vacant, that is to say unoccupied for various reasons (rental, pending inheritance settlement, without specific assignment, etc. ).
Admittedly, having a zero vacancy rate is not an option, because it would no longer be possible to move, but the recent increase in short-term vacancies opens up avenues for reflection.
The panorama of the under-occupation of the stock is reinforced when we also take into account dwellings inhabited on an occasional basis, for example second homes (10% of the stock), or dwellings considered to be under-occupied (88% of individual and 45% of collective housing).
Thus, if overcrowding is a very real phenomenon and with deleterious social consequences, the underpopulation of part of the French housing stock is also an issue, in particular with regard to the challenges of the transition.
In the tertiary sector, there is little data on vacant offices and their potential for transformation into housing.
The outlook for their occupancy rate is largely disrupted by the current transformation of practices, and in particular teleworking.
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4 million new homes by 2050
In this panorama, the most frugal scenario of the 4 developed by Ademe provides for the new construction, between 2015 and 2050, of 4 million housing units.
The scenario where new construction is pushed to its maximum, by imagining a vast program of deconstruction-reconstruction of housing rendered obsolete (particularly because of metropolisation) involves creating 12 million – more than three times more, so.
By way of comparison, note that over the past thirty years we have built around 11 million homes.
The calculation is based on several assumptions.
First, a demographic slowdown, echoing INSEE projections.
The context is indeed very different from that of the post-war years, marked by a demographic boom.
Then, a slowdown in de-housing, which would curb a historic trend.
Three phenomena have contributed in recent decades to the decline in the number of people per household and are now tending to stagnate: the decline in the number of large families, the tendency to divorce and the departure from their parents of many baby-boom children.
The aging of the population could partly take over.
The over 75s, whose proportion in the population will double by 2050, rising from 9% to 16%, live more often alone in large dwellings.
The life choices of the elderly are therefore also an issue of ecological transition.
In territorial rebalancing scenarios, it is thus possible to transform second homes into main homes, for example to accommodate new retirees or teleworkers, or to use them all year round by combining use by tourists or seasonal workers. and student use.
We can also imagine reinvesting in vacant housing currently located in derelict areas.
Reinvesting in these areas involves rebalancing activity, an ambitious challenge in terms of regional planning.
Reuse the existing, a variety of solutions
Making better use of what already exists is therefore an avenue to explore.
How to make it happen in practice?
For this, it will be necessary to adapt to the diversity of households and territories.
In peri-urban areas, where housing is often homogeneous and made up of largely under-occupied individual houses and owner-occupiers, it is necessary to diversify the stock to create rental accommodation and small housing designed for populations who appreciate this peri-urban way of life.
One mayor describes it this way:
“I needed housing for hospital employees.
I needed housing for old people who can no longer keep their big barracks, and for young people who are still 26 years old with mom and dad.
»
The remodeling of individual houses is an option to be developed in these areas.
In very tense urban areas, the difficulties of access to housing are significant.
The transformations of use allowing to better value each square meter are possible (student shared accommodation, tourist rentals, residential division, transformations of offices, etc.).
The main challenge concerns the rules for sharing this rare space.
The public authorities try with difficulty to maintain balances which allow the various actors who make the life of a territory to be able to live together.
In low-density predominantly rural areas, the challenge is to make these areas attractive by relying on existing buildings that are often available but sometimes obsolete.
What leads?
The renovation of degraded buildings and blocks, the revitalization of trade, crafts, services, or the development of cultural activities based on an existing heritage to be reinvented.
In these areas, the risk would indeed be to think of new construction as a way of attracting at the cost of significant artificialisation when it can be used in very small doses as a catalyst, for example, to rethink a town center .
Towards a new building economy
Building only when necessary and after optimizing the existing will have consequences on the economic sector of new construction.
For example, if finishing companies can imagine a future where renovation will take a more important place, structural work assets will see their activity strongly impacted.
Our file “<strong>ENERGY TRANSITION</strong>”
What growth drivers?
Alongside the massive renovation of the stock, which is essential for any trajectory of carbon neutrality by 2050, it is a set of new activities that must now be imagined: mass restructuring of obsolete or vacant housing, changes in the use of offices into housing, but also deconstruction or production of services for occupants… Thus, the new construction sector is undoubtedly at the dawn of a major transformation that we must anticipate now.
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This analysis was written by Albane Gaspard, in charge of prospective studies for building and real estate, and Jean-Christophe Visier, prospective adviser for building and real estate – CSTB (both at the Ecological Transition Agency [ADEME]).
The original article was published on
The Conversation website
.
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Declaration of interests
● Jean-Christophe Visier is an employee of the Scientific and Technical Building Center and is seconded part-time to the Ecological Transition Agency.
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