ARTICLES

GREEN ROOFS: FEATURES AND BENEFITS OF GREEN ROOFS

Roofs, Thermal insulation

Living roofs for residential well-being and energy efficiency

25 Oct, 2019

New buildings keep getting constructed in residential areas. This overbuilding has a series of negative consequences for individuals and society that technology is seeking to check.The solutions that are also being introduced in Italy include green roofs.

Green roofing for new urban ecosystems

The GreenROOF roofing system, co-engineered with ISOPAN DAKU, consists of green areas on the roofs of buildings, be they residential or manufacturing/commercial.

They are urban ecosystems that fulfil multiple, increasingly urgent, needs.

The loss of ground, due to the construction of more extensive and building-dense urban centres, has led to a drastic decrease in green areas in the cities.

One of the most obvious consequences, which is now visible to everyone, also in Italy, is the reduced ability of the soil to retain water.

This has dramatic effects in case of exceptionally intense rainfall or what is known as a “water bomb”, a cloudburst over a populated area that causes localised damage.

 

Green roofs and the management of rainwater

In the cities, where the soil is made impermeable by overbuilding, water, which is not filtered and retained by the earth, runs on the surface; the result: urban runoff. Moreover, when the amount of rain exceeds the sewage flow rate limits, the water is forced to remain on the surface, resulting in the phenomenon of runoff.

The speed at which the water flows often causes collected water bodies to spill over and diffuses pollution from heavy metals and particulates found on the tarmac.

Furthermore, when green areas are replaced by concrete, plants’ ability to produce oxygen and retain polluting dust - an extremely important function - also decreases.

The proof of these issues has led to the research and development of technological solutions that may be in a position to remedy the reduced size of green areas.

The application of living roofs combines the need to manage rainwater with the well-being of looking at a natural landscape, the need to reduce urban runoff with the need for sustainable construction.

Depending on its features, rooftop landscaping of buildings may result in a green roof or a hanging garden.

 

Extensive or intensive green roofs

There are two types of green roof.

Extensive use of plants results in green roofs that, albeit being unusable, require little maintenance, limited use of water, and vegetation whose development is limited.

Conversely, the intensive use of plants creates true hanging gardens, whose accessibility is a fundamental requirement for the performance of the maintenance required.

The variety of plants and the usability of hanging gardens mean that the building acquires a new dimension.

 

Waterproofing

There are two ways in which waterproofing is of importance when it comes to green roofs

On the one hand, the flat roof, which is best suited to hanging gardens and green roofs, requires thorough waterproofing.

This is the most critical aspect of this type of solution, which can be successfully resolved by resorting to adequate materials and paying particular attention to the joints and critical points during the installation.

At the same time, a green roof protects the waterproofing layers on the rooftop of buildings, sheltering them from sunlight and weathering.

 

Thermal insulation and soundproofing

The construction of a green roof offers a relevant benefit when it comes to thermal insulation and soundproofing.

The sequence of the various layers - draining, waterproofing, plants - placed on the concrete slab makes it possible to reduce the temperature of the roof, which is the part most exposed to sunlight.

A green roof also generates a higher heat flow offset compared to other types of roofing.

Moreover, the amortisation of vibrations by the green surface and the sound absorption provided naturally by the plants reduce ambient noise.

 

Environmental impact

The presence of green areas in the urban system is an effective method for mitigating the heat island effect; a microclimatic phenomenon resulting in higher temperatures in more urbanised areas and, therefore, in higher consumption of energy for cooling.

 

Water retention

The ability of the various layers that make up the green roof to retain water is the reason this solution has become so popular around the world.

Climate change and urbanisation have resulted in increasingly frequent and dangerous extreme weather events.

Green roofs are one of the most effective ways to counteract these issues, as they reduce the quantity of water that is released and slow it down, making it possible to exceed the maximum flow moment in the case of “water bombs”, which generally do not last very long.

The performance of the systems is verified and certified in accordance with the UNI 11235/15 standard.

 

Against pollution

Green roofs reduce air pollution, exactly as they normally do for the soil because the plants are able to trap carbon dioxide and fine particles.

 

Creation of new spaces

Green roofs are places that can be enhanced and used in more interesting and valuable ways compared to the simple roofing for buildings.

At a time where available space at ground level is increasingly reduced, using the roofs to create a space of social value is a not-to-be-missed opportunity, which, at the same time, offers new possibilities for architectural expression.

 

Added value for buildings

Aside from the significant aesthetic impact on buildings, rooftop landscaping actually increases their commercial value. 

In fact, as we have seen, they have an impact on energy efficiency, sustainability, the residential well-being of buildings, aspects that are increasingly appreciated by the market.

So-called living roofs limit the environmental impact of buildings and have a history that is lost in the mists of time.

Thanks to their numerous benefits and the possibilities presented by extensive green, they now are also being introduced to Italy.

Tax and administrative interventions, put in place to support this type of solution, can further contribute to their popularity, as has already happened in other countries.

Written by

Cesare Arvetti - Research & Development Department
Cesare Arvetti - Research & Development Department

Isopan expert with more than 10 years’ experience in the dry construction sector. Architect Cesare Arvetti supports leading architectural and design studios to identify the solutions that are best suited to the needs of individual projects.

Visit the author's page

Subscribe to the newsletter

Leave your data to keep updated in Manni Group products, services and activities