Zinc Roofs Give Paris Its Signature Look. But They Are a Nightmare in Heat.

They are an essential part of Paris, like the Eiffel Tower and Notre Dame.

The city’s blue-gray rooftops that gleam like a sun-battered ocean have inspired Impressionist painters, novelists, filmmakers and selfie-taking tourists.

The secret to their uniformity is zinc, which covers almost four-fifths of the city’s rooftops.

But during heat waves, increasingly common in Paris as the earth warms, those zinc roofs become sizzling frying pans, exceeding 158 degrees Fahrenheit (70 degrees Celsius). For people living directly under, they become suffocating heat blankets.

“All of these apartments, especially on the top floors, will become uninhabitable in the coming years,” said Dan Lert, deputy mayor in charge of the city’s ecological transition and its climate change plan.

He added, “We will have to accept that the Parisian landscape needs to change.”

The people charged with protecting Paris’s heritage do not agree, and they are in control. Overlapping heritage rules cover 97 percent of the city. Changes, even minor ones, need to be appraised by a small but powerful office inside the Ministry of Culture called the Building Architects of France, whose decisions in many cases are binding.

Though there is no campaign to do away with the zinc roofs, there have been many requests to make them less heat-absorbing.

The office’s position is that the zinc roofs of Paris should not change in structure, form or usage.

“When you’re on the roofs of Paris, there is this kind of gray sea that is absolutely sublime,” said Jean-François Hébert, who oversees the architects’ office as the ministry’s director of heritage and architecture. “It is obviously a very important and historical element for Paris.”

That position has made the heritage architects unpopular, he said, but they are the ones who protect against what he called “ugly France.”

Mr. Lert, the deputy mayor pushing for climate-change adaptations, said the office blocked or restrained one-third of proposed projects to protect buildings from heat waves in the city. Mr. Hébert said that was exaggerated, but that the office does not have statistics on this.

As of 2024, only 26 buildings in Paris won approval to insulate from the outside, according to a fact-finding report by French lawmakers. (They did not say how many applied.)

The problem, several experts said, is that insulating from the inside is not always feasible, nor is it the most effective way to combat the radiating heat of the sun-baked roofs. And, according to Mr. Lert, the case-by-case deliberations on projects by the heritage architects are too slow given the pace of climate change in Europe, which scientists warn is warming faster than the global average.

In 2019, Paris had a new high of 42.6 Celsius, or nearly 109 Fahrenheit, and city officials have begun to prepare for when it could hit 122.

“This is an emergency. It’s a major health issue,” said Mr. Lert, pointing to a recent study investigating the deadly 2003 heat wave, which revealed that living directly below rooftops multiplied the risk of death more than four times.

“It’s not about making Paris ugly,” Mr. Lert said. “It’s about protecting the health of its inhabitants.”

The roofs are relatively new to the city. Before the 1850s, many buildings in Paris had peaked roofs covered in slate and clay tile shingles, according to Julien Bigorgne, an engineer specializing in adaptation to climate change.

Zinc, relatively cheap, light and malleable, was the perfect roofing material, able to be folded into the Mansard shape, which offered space for small, uninsulated rooms at the top, Mr. Bigorgne explained.

“They were always uncomfortable, but that wasn’t considered a problem,” he said. “Servants lived there.”

But since the 1970s, those maid’s rooms, known as chambres de bonnes, have increasingly been converted into apartments with cathedral ceilings and skylights, worsening the heat problem, Mr. Bigorgne said.

With no upstairs neighbors, and views across the city, they became prized real estate.

Until heat waves, that is, when the temperature under those roofs can rise above 104 degrees and remain high into the night.

Residents describe strategies like soaking in cold baths, eating only uncooked food to avoid using the stove, or simply escaping somewhere cooler. Few have air-conditioning units, which are uncommon in Paris and the subject of much discord.

Evenings are the worst, said Julien Mellul, from his top-floor apartment in the 17th arrondissement. During a heat wave in early July, an indoor thermometer by his front door didn’t slip below 86 degrees until after 5 a.m.

“That’s what’s so miserable — you can never cool down,” said Mr. Mellul, 44, who runs an IT management company.

There is little question that the roofs are precious to many beauty-loving Parisians. In December, the profession of zinc roofer was named an intangible cultural heritage by UNESCO. But even the president of the union that includes roofers, Edouard Bastien, said something must be done, and said workers have already adapted by adding insulation beneath roofs during routine renovations.

“We are not dogmatic,” he said. “The question that lawmakers must resolve is what is it possible to do.”

One proposed solution sits atop the former town hall in the city’s center: a wooden deck lined with planters erupting with strawberries, thyme, rosemary and lavender. It’s the work of Roofscapes, a company formed in 2020 by three French architecture students at MIT.

They’ve set thermal sensors under the zinc roofs, and under their wooden decking that provides shade. On one day when Paris hit 96 degrees, the temperature under the wooden deck was 87, while below the exposed zinc it was 116.

The idea also offers something rare in Paris, green space for hanging out.

“We have an opportunity with all these untouched surfaces to do something that is virtually impossible anywhere else in a city like Paris,” said Eytan Levi, a co-founder of Roofscapes. “There’s a new way you can live.”

The city has issued an international call for innovative solutions to the roofing problem, and the heritage architects’ office is a partner in the experimental program.

Mr. Bigogne, the adaptation engineer, says if people aren’t allowed to change the roofs from the outside, they will push to install air-conditioning. And that could cause a whole other set of heritage concerns, with vents emerging from facades or roofs.

“We just have to say it honestly,” he said. “We need to understand the consequences, because in essence, people can’t live under those roofs unless we’ve put in place solutions.”