Organizers for the Paris Olympics are working to keep athletes cool at the 2024 Olympic Games, but it doesn’t involve air conditioning. Instead, they plan to implement an underground solution.

During the Olympics, between July and September 2024, 15,600 athletes and sports officials and 9,000 athletes and their supporting teams during the Paralympics will be staying at Athletes Village, located next to River Seine in the popular district of Seine-Saint-Denis. Temperatures will be kept in check for the athletes with an underground water-cooling system. After the games, Paris will turn the 125-acre village into an eco-friendly, zero-carbon residential and commercial neighborhood. The first of the 6,000 new residents will move in starting in 2025.

The decision to use the system is part of the organizing committee’s goal to cut the carbon footprint of the Paris Games by half. This led to staging the most sustainable Olympics to date with the special geothermal technology to keep everyone at the games cool, even during a potential heat wave, which during the summer in Paris — a city already known for sparse air conditioning — is likely.

“I want the Paris Games to be exemplary from an environmental point of view,” said Paris Mayor Anne Hidalgo in a press release. Hidalgo has resolved to tackle climate change with an action plan that aims to drastically reduce greenhouse gas emissions and make Paris carbon neutral by 2050. Compared to a conventional project, she said, the carbon impact will be reduced by 45% for the Athletes Village during the construction phase and over the entire Olympic cycle.

Leaders in Paris are confident the water-cooling system will provide the heat relief needed. In anticipation of the hot weather to come, organizers have been studying heat waves block by block in Athletes Village, even simulating conditions in certain parts of the village that are most exposed to the sun. This allowed the organizers to test the effectiveness of the cooling system with an objective to keep the indoor temperature between 73°F and 79°F.

According to Laurent Michaud, the director of the Olympic and Paralympic Villages, the geothermal system will ensure that the temperature in the athlete apartments does not rise above 79°F at night, even during a potential heat wave. To ensure this, organizers have conducted tests in rooms that are located on the highest floors of the residences, are facing south, and exposed to direct sun on two sides, also factoring in directions of winds in the region and the water temperature in the Seine. To develop temperature forecasts, organizers have worked closely with France’s national weather agency.

“Despite outdoor temperatures reaching 41°C (106°F), we had temperatures at 28°C (82°F) in most of these rooms,” Michaud told The Associated Press (AP), describing the results of a heatwave simulation. “In other rooms, we clearly had lower temperatures.”

In addition to the underfloor geothermal cooling system, the insulation built into the buildings in Athletes Village will allow residents to keep the cold obtained during the night throughout the day. To achieve this, Michaud said athletes will have to follow some basic rules such as making sure the window blinds are shut during the day.

This green transition happening at Saint-Denis City Hall, Paris’ northern suburb where the main Olympic Village will be located, is headed by Laurent Monnet, who said that all rooms should be 11°F cooler than the outside temperature, without an a/c unit.

Yet this doesn’t please all Olympic hopefuls. In fact, some have already expressed concern about the lack of a/c.

Monnet said that athletes should adapt and help contribute to the fight against climate change.

“We need athletes to set an example when they use the buildings,” Monnet said. “We can build the most virtuous village we want; it is also the use that will be made of it that will weigh on our carbon footprint.”

One athlete who has endorsed the Paris sustainability plan is Eluid Kipchoge, two-time Olympic champion and marathon world record holder. The Kenyan runner has long been vocal regarding climate change, environmental justice, and the impact of global warming.

“It’s a good thought, because we all need to reduce our carbon,” Kipchoge quoted to the AP.

Kipochoge called on fellow athletes to do their part in helping combat climate change by reducing their carbon impact during competition, training, and every other aspect of their life, saying, “We are all going to go through the same scenario.”

Organizers do want to be kind to the environment, but they also don’t want to endanger the health of the athletes. The director of the Olympic Village, Michaud, said some athletes — especially in Paralympic events — have difficulty regulating their body’s core temperature, and if they reside in rooms in which it proves impossible to keep 79°F at night, national delegations will be able to install a portable a/c system. Basically, it will be on a case-by-case basis, as long as the devices comply with the organizing committee’s technical criteria.

Though technically athletes are allowed to bring their own a/c, Hidalgo said she’s against it, aside from those with special needs.

“I can assure you that we will not change course and that there will be no changes to the construction program of the village regarding air conditioning,” Hidalgo said.