In Avranches, the hassle of thermal renovation of "remarkable heritage"

About twenty kilometers from Mont Saint-Michel, a UNESCO World Heritage Site, the city center of Avranches is undergoing a revitalization operation to bring back activities.

But renovating a 19th-century building 100 meters from the Saint-Gervais Basilica in Avranches is expensive, as Aline Duguet knows. Lime plaster was imposed on two facades of her building, as well as a wood-clad entrance topped with a brown zinc roof, explains the 54-year-old owner. That's an additional ten thousand euros, linked to the recommendations of the Architects of Buildings of France (ABF), tasked by the Ministry of Culture with protecting heritage.

100 meters away, the renovation of a former butcher's shop founded in 1945, with the creation of five housing units, could only get underway thanks to substantial financial assistance from the town hall.

Insulating the walls, floors, roof, changing the heating system, installing ventilation, the building should go from a G rating (very energy-intensive) to B in the energy performance diagnosis.

For the interior of the former business and the three pre-existing dwellings, the owner, Claude Nouet, is free.

But the exterior must remain as identical as possible to the past, which is controlled by the ABF and the town hall, which apply heritage preservation rules to all buildings located within 500 meters of a historic monument - in this case, the basilica.

Wood and lime

A third of housing in France is thus affected by these restrictions, which aim to preserve the aesthetics of French-style towns and villages. Up to 89% in Nancy and 94% in Paris, according to a Senate report. "Far too many projects are still being stopped or slowed down" by the ABFs, criticizes Dan Lert, deputy mayor of Paris.

In Avranches, at Mr. Nouet's, the disappearance of the butcher's shop window will give way to windows of the same size and aligned with the other openings in the facade, surrounded by wooden cladding.

Elsewhere in France, ABFs sometimes refuse to install shutters or solar panels and impose traditional materials (zinc, wood, etc.).

Avranches does not want to "apply stupid and nasty rules" and is trying to be flexible: "We are not absolutely anti-PVC or aluminum" for windows, explains mayor David Nicolas, who is looking for "an appropriate response" that avoids "too much dissonance."

"More expensive"

The issue is aesthetic as much as technical: we must avoid damaging an old building with modern techniques.

Problem: these requirements are not always compatible with those of energy renovation, especially when it comes to measuring the energy gain permitted by the work, a calculation on which the granting of subsidies depends.

"Some materials, particularly insulation materials, did not have associated technical resistance," which distorts the DPE, explains Clara Marchal, project manager at Urbanis, which supports Avranches homeowners. But more and more technical data sheets are being published.

But ABF recommendations "almost systematically cost more," she says, pointing out that "an apartment in an old town center necessarily involves constraints and additional costs" compared to a new one.

The accumulation of constraints sometimes blocks projects: impossibility of insulating the facade from the outside, higher cost, insufficient energy gain to obtain aid and even the need to go through the Ministry of Culture if the heritage is classified by UNESCO, as is the case in Le Havre.

"When we give an unfavorable opinion" on work, "for us it's a failure, our DNA as architects is to carry out projects," defends Fabien Sénéchal, president of the national association of ABF, who deplores "often being seen as a scarecrow."

Aware of the complexities created by the multiple regulations, Avranches has developed a work guide and organizes monthly meetings with the ABFs. A system that allows them to rediscover their "vocation of advising owners," says Mayor David Nicolas.