Lyon becomes first French city to classify overheated homes as unfit for habitation
Lyon is set to become the first French city to treat excessive indoor heat as grounds for declaring a home unfit for habitation, as part of a comprehensive strategy to address bouilloires thermiques – properties that reach dangerous temperatures during summer heatwaves.
Green mayor Grégory Doucet, who was narrowly re-elected in March 2026 with 50.67% of votes, announced the initiative on July 15, describing it as fulfilling a campaign pledge. The timing is particularly significant given that France experienced a devastating summer in 2026, with 52 days of heatwave conditions and more than 7,300 excess deaths – for the first time affecting all age groups from 15 years upward since monitoring began in 2004.
The proposal addresses a critical gap in French housing law. While current regulations require rental properties to maintain a minimum temperature of around 18-19°C during winter, there is no maximum temperature standard for existing homes. Housing decency assessments conducted by regional health agencies or municipal health departments currently examine issues such as dampness, inadequate heating and electrical safety, but not dangerous heat levels.
How the system would work
Under Lyon's plan, tenants would gain the right to report excessively hot homes to the city's health department, triggering a property inspection. Rather than applying a rigid temperature threshold, officials say they would primarily assess whether a dwelling is capable of cooling down, examining factors such as the absence of shutters or blinds to block sunlight.
Landlords failing to implement improvements after inspection could receive formal notices and potentially face financial penalties. The approach draws on international precedent, particularly from British Columbia, Canada, which introduced building code requirements in 2024 mandating that at least one living space in new dwellings must maintain a temperature of 26°C or less under summer design conditions. Health Canada reinforced this threshold in June 2026, recommending 26°C as an upper indoor temperature limit to protect older adults from heat-related illness and death.
Scale of the problem
The initiative responds to a housing crisis affecting millions of French residents. According to a 2025 study by the Foundation for the housing of the disadvantaged, approximately one-third of homes in France qualify as bouilloires thermiques, and more than 40% of tenants suffered from heat in their homes during summer 2024. In Lyon's Presqu'île district, tenant group Locataires Ensemble found that 62% of surveyed homes met the thermal kettle criteria.
The problem has already proven deadly. Between 2014 and 2023, France recorded 37,825 heat-related deaths, with the largest impacts in 2022 (approximately 6,969 deaths) and 2023 (approximately 5,167 deaths). A study by IGNES, an alliance of building professionals, projects that two out of three homes will be exposed to heatwaves by 2030, indicating the crisis will intensify.
Support for low-income owners
Recognising that many affected buildings are historic or architecturally protected – Lyon has around 150 listed apartment blocks, particularly in areas such as Vieux-Lyon and La Croix-Rousse – the city plans to establish a support fund. This would help low-income property owners and social landlords install equipment such as fans and window blinds.
Eligibility criteria and funding sources remain under development, with the fund expected to launch in spring 2027. Officials acknowledge that retrofitting old buildings presents unique challenges requiring targeted financial assistance.
Broader context and future prospects
Lyon's initiative builds on existing French housing policy addressing energy performance. The Climate and Resilience Law established a phase-out schedule for poorly insulated rental properties classified as passoires thermiques (thermal sieves): G-rated homes have been banned from rental since January 2025, with F-rated properties to follow in 2028 and E-rated homes in 2034.
Since 2021, France's DPE energy performance certificates have included a summer comfort indicator displayed with smiley faces (good, average or poor), though this does not affect the overall A-G energy rating. Lyon's proposal would go further by giving summer overheating genuine regulatory weight.
Energy renovation specialists have welcomed the plan as a French first. Mayor Doucet hopes Lyon's approach will prompt the national government to update housing decency rules nationwide, potentially extending similar protections to tenants throughout France.
