Do plants on green roofs burn during heat waves? FALSE!!!

This video debunks the myth with concrete, actionable evidence and advice for architects, urban planners, and public project owners.

Why this video is useful if you are looking for the “definition of heatwave”

When you type in "heatwave definition," you get the meteorological framework (thresholds, duration, vigilance). But to make decisions and design in cities, we must extend this definition of heatwave to its operational impacts on materials and living environments. This is the purpose of this film: to translate heatwaves into concrete consequences for green roofs and show how well-designed solutions allow plants to survive the drought... and then recover, while contributing to the cool island.

On properly designed systems (useful reserve, appropriate plant palette) and with very low but well-managed irrigation, plants survive the stress period without tipping into lethal stress—then recover quickly when the rains return or with micro-inputs. In other words, the right question is not “do they burn out?”, but “what settings guarantee their resilience during the heatwave?”

What you will see in the movie

The interview with Pierre Georgel (President of ECOVEGETAL) filmed in 2025, at the heart of the summer fieldwork: he explains how green roofs are surviving the heatwave, what is suffering, what is holding up, and why the recovery is rapid.

Rooftop irrigation plans at ECOVEGETAL headquarters: a very concrete illustration of the ideal structure of a green roof with water retention mats, wicking mats to raise the water by capillarity, etc.

Visuals to help understand the “useful reserve” that keeps the roof in place during a prolonged episode.

The 3 keys to remember (to review, memorize, apply)

Micro-watering: During heatwaves, favor very short and repeated waterings rather than massive watering. The goal is not to "overwhelm" the population, but to prevent the shift to irreversible watering, with a minimum of water.

Useful reserve: design the roof with retention layers (mats/drains/tanks) that store water at the source. It is this “buffer” that allows it to “hold” and cushion the heatwave.

Suitable palette: Select resilient plants (sedums, certain grasses) capable of dormancy and rapid recovery after drought. As long as they remain alive, they evapotranspire and contribute to a local cool island.

How does this extend the “heatwave definition”?

The definition of a heatwave isn't just meteorological: in cities, it translates into significant thermal and water constraints. A well-designed green roof isn't just "resistant": it cushions peaks, stores, transpires, cools the air, and protects the lower layers. It literally becomes an infrastructure for managing the urban climate crisis.