90% of housing unsuitable for extreme heat: alarming errors in DPE calculations revealed

A study conducted by IGNES and the Pouget Consultants firm reveals that 9 out of 10 homes in France are not adapted to high temperatures[1]. This in-depth analysis of the energy performance diagnosis (DPE), commissioned by IGNES, highlights worrying failures in the calculation of the "summer comfort" indicator, a key parameter for assessing the ability of a home to cope with high temperatures.

According to the report, the indicator that assesses the adaptation of a dwelling to heat waves is incorrectly calculated in 26% of cases. Among the errors identified, dwellings that are insufficiently protected from the sun or without an insulated roof, although located on the top floor, are sometimes rated "good" or "average". However, according to the calculation rules, they should be systematically classified as "insufficient"[1].

The study also reveals an inconsistency in the assessment of roof insulation. About 32% of the homes studied have a roof considered insulated for winter, but judged not insulated for summer, or vice versa.

In a context of global warming, the poor adaptation of housing to heat waves is becoming a major concern. IGNES urges public authorities to quickly bring together building professionals to improve this indicator and better prepare the French housing stock for future heat waves.

For Baudouin de la Varende, co-founder of Ithaca: "The Energy Performance Diagnostic (DPE) is based on calculation rules to model energy consumption and greenhouse gas emissions for everything related to heating, but not for everything related to summer comfort. The summer comfort indicator, currently entered manually, is therefore not the result of a calculation rule on existing systems and materials. It also does not take into account energy consumption (of an air conditioner for example). The performance mentions on summer comfort indicated on the DPE are therefore very approximate to say the least. Also, the DPE does not value thermal inertia (bio-sourced materials and solar protection), discouraging their installation. It is therefore urgent to create a specific indicator for summer comfort that would make it possible to truly inform the consumer and redirect funding towards effective solutions such as solar protection, sustainable materials, or air mixers."

[1] Boiler housing: between errors and inconsistencies, the DPE once again criticized - Challenges