Green Roofs, a trending and eco-friendly solution for thermal regulation of your building

Did you know that around 40% of the energy produced worldwide is destinated for construction and maintenance of buildings?

Many architects are now using different techniques in order to reduce energy consumption and build well-isolated buildings. One iconic and efficient method to improve the thermal performance of the structure is the concept of green roof. This building technique adjust the temperature around the building ( especially in hot summer days) , improving the efficiency of HVAC systems installed.

The use of greenery on the tops of the buildings is also seen as a mitigator of urban heat island effect, improves air quality in the city, decrease sound pollution, preserves biodiversity and increases longevity of roofing membranes, by limiting strong heat variations that undermine the material.

The green roof: an ancient practice

Even though it could seem a modern technique, the early green roofs were used on Babylon’s hanging gardens and in the Ziggurats of Mesopotamia. Also, the discovery of mysteris Villa in Pompeii revealed that roof gardens were also present in Roman architecture.

In Norway we can still see the use of green coverage on Sood roofs, typical of vernacular architecture. They were not conceived to impress but to provide insulation and mitigate the damage to the roof from the rainfalls. Birch bark was used as a water resistant material instead of modern bitumen.

In more recent times, architect Le Corbusier included green roofing in the five points of modern architecture, thus starting a new trend that continues to this day.

Types of green roofs

There are two types of green roofs: 

  • Extensive: With soil thickness less than 10-15 cm, generally inaccessible because of fragile roots of plants, they present a low biodiversity, they don’t need irrigation and their cost is moderate. They can be implemented on sloped roofs as well.

    You can install this type of green roof on existing buildings as they do not require a pre-engineered structure to support their weight ( which is around 60 -150 kg/ m2)

  • Intensive: With soil thickness more than 15 cm, usable for recreational purposes, they generally present high biodiversity but they need drainage and irrigation systems. Despite their cost is much higher than extensive green roofs, they act better in terms of insulation and storm water management.

How it works

The thermal insulation value provided by green roofs varies depending on the plants cultivated on it. For instance, Sedum ( one common type of plant used for roof coverage) is very efficient in terms of solar radiation shading and it is compatible with drier climates. However it has a low thermal resistance value.

Ryegrass, is better for air circulation but it does not provide the best solar shading.

Vinca is halfway between the previous two, offering better shading and convective heat transfer.

The best plants varieties to use

The thermal insulation value provided by green roofs varies depending on the plants cultivated on it. For instance, Sedum ( one common type of plant used for roof coverage) is very efficient in terms of solar radiation shading and it is compatible with drier climates. However it has a low thermal resistance value.

Ryegrass, is better for air circulation but it does not provide the best solar shading.

Vinca is halfway between the previous two, offering better shading and convective heat transfer.

Alessandro Azzolin
Alessandro Azzolin
Digital marketing intern, with interests in different cultures. My priority is the preservation of ecosystems.
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