Rooftop greening offers many advantages, both in terms of sustainable development and in terms of protecting biodiversity and the urban environment.
Rainwater management
The increasing urbanization of towns and cities is creating more and more impermeable surfaces, which do not absorb rainwater. Green roofs make it possible to reduce and regulate the quantity of rainwater reaching a building and then discharged into the public drainage system;
Part of the rainwater is absorbed by the vegetation complex (substrate and vegetation) until it reaches saturation point, and is then consumed by the plants through evapotranspiration. Once saturated, the vegetation complex slows down the evacuation of water into the networks. The green roof absorbs rainfall peaks (“delay effect”), thus limiting sewer clogging during violent storms.
LE PRIEURE has developed complementary solutions for managing rainwater on roofs: ALVEO and OASIS. These solutions are dimensioned by our GEPETO software and accompanied by a hydraulic study.
Thermal comfort
The various layers of the green roof complex (drainage, filter, substrate and vegetation) provide an additional layer of thermal insulation on the roof, protecting the building from the cold in winter and combating the urban heat island effect in summer. The evapotranspiration, shading and reflection mechanisms of the plants making up the green roof can reduce the temperature of a building in hot weather.
Environment Canada’s 2004 study of Toronto showed that greening 6.5 km2 of the city’s roofs would :
- lower room temperature by 1 to 2°C in the hottest periods
- eliminate 2.18 tonnes of greenhouse gases and 30 tonnes of pollutants every year.
Acoustic comfort
The plant complex’s layers of substrate and vegetation dampen impact noise (rain, hailstones, etc.) and reduce the perceived volume of airborne noise.
Extends the life of roofs
By protecting the waterproofing membrane against thermal shocks and aggression (UV, punching), green roofs help extend the life of roofs.
Improves quality of life for city dwellers
A veritable “green lung” in the city, the green roof helps combat pollution: plants release oxygen, absorb carbon dioxide and bind dust in the air. Bringing nature back into the urban environment also means that buildings blend in better with their surroundings: the city is more beautiful and the living environment more pleasant for city-dwellers.
Promotes biodiversity
By reintegrating green spaces into the urban environment, green roofs restore ecological functions degraded by urbanization. A layer of substrate, diversified planting adapted to the local climate and the creation of refuge zones encourage the return and development of urban flora and fauna.
