Living Roofs: What are Intensive & Extensive Green Roofs?

As we begin to adopt new technologies to green up our urban spaces, planners and designers are opening to the idea of greening up more roof spaces. Whether it is the unused flat roof on top of a multi-storey carpark, or the bare rooftop of an old skyscraper, the untapped potential in these “wasted” spaces are arguably ripe for the picking. Therein lies the opportunity to convert these spaces into green roofs, whether intensive or extensive.

When it comes to green roofing, the abovementioned terms intensive & extensive are often bandied about. But how many of us are really able to distinguish between the two kinds of green roofs? In this post, we shall attempt to lay these doubts to rest – here’s a brief comparison between intensive green roofing & extensive roofs. (TLDR; scroll down to the last image)

An extensive green roof on metal deck completed by Belalang outside a meeting room in Johor Bahru.

INTENSIVE GREEN ROOFS are described in the Guidelines for the Planning, Execution and Upkeep of Green Roofs (published by the German Landscape Research, Development and Construction Society, or FLL for short) as “…the planting of shrubs and coppices, as well as grassed areas, even an occasional tree.” and it also mentions that “Regular attention is needed to maintain sites of this type in good order, in particular regular watering and feeding is required“. In simple terms, intensive green roofs allow for the widest range of plants and shrubs to be planted on the roof area, restricted only by the property’s design intent and structural constraints. The inclusion of grasses that are trafficable also allows users to step onto these green roofs for leisure activities such as picnics or strolls.

That said, the substrate needed to sustain these plants are usually deeper, which translates into a massive weight addition to the building’s structure. Deeper growing medium also means that planters have to be specifically created to suit the location of these plants. Lastly, an intensive design is usually accompanied by a high up-front cost (taking into consideration the structural load and creation of planters) as well as incur more substantial maintenance efforts to ensure a thriving green roof.

Intensive green roof at Accapella Residence in Seksyen 13, Shah Alam

EXTENSIVE GREEN ROOFS on the other hand, are limited by their thin built-up and inherent system traits to provide a shorter list of species. The reason for this being that extensive green roofs advocates the lowest form of maintenance, hence the usage of hardy local species that require close to zero attention upon installation. This also means that these roofs are usually located in areas to which the public have limited to no access.

The FLL in Germany classifies extensive green roofs as “… cultivation of vegetation in forms which create a ‘virtual Nature’ landscape and requires hardly any external input for either maintenance or propagation”. Being inaccessible and catering to a narrower range of species for this kind of green roof are tradeoffs to the following attributes:

  1. Lowest form of maintenance due to hardy local plants
  2. Lightweight (As reference, the GaiaMat extensive green roof is 6 times lighter than convensional roof turfing systems)
  3. Lower up-front cost
  4. Able to retrofit different roof types- RC flat roof, Metal decks and even glass roofs.
Extensive green roof completed by Belalang in 2019 using hardy species in PJ, Selangor

To sum it all up, here’s a table comparing both roofing systems, extracted from the Green Roof and Wall Policy in North America – Regulations, Incentives and Best Practices (2019):

We hope this helps to clarify any doubts on what we call Extensive and Intensive green roofing! For enquiries on using our GaiaMat (extensive) or the GaiaTurf (intensive) green roof system, please do drop us a message in the contact form (<< click here).

Green Walls – taking us back to nature

Since the dawn of civilization, humankind has maintained an unspoken attachment to nature as it is from nature that our ancestors derived their essentials to survive- food, water and shelter. It was only during recent centuries that rapid population growth and urbanization forced a chasm between us and natural elements such as the forests and rivers.

Despite all our progress in technology, there remains an innate biological connection which we cannot ignore- this proven concept is called Biophilia (Something we will expand on in future posts). To maintain this closeness to nature, many have adopted building elements and designs that incorporates some form of biophilia or connection to nature- from the Hanging Gardens of Babylon to the lawn/gardens we have these days in front/behind landed houses. Such is the importance of this connection between nature and humans that when buildings started going skyward and concrete jungles outgrow and bulldoze through actual jungles, the demand for more green in our urbanscape increased manyfold.

One of the many completed green wall projects using our GMS system in the Jewel, Singapore.

One of the many ways to merge the hard concrete & steel with softer greenery while utilizing the limited space in our cities is to incorporate green facades. This is where green walls come into the picture. While green walls are now appearing left, right and center, the idea of having this vertical green element has been around since the early 20th century. As pointed out by this article we are referencing from the Landscape Architects Network website,

The simplest way is to picture it as a cliff: the synthetic medium is the interface to which the cliff growing plant species can hang onto.

And this is the exact philosophy behind the creation of the GaiaWall– a breakthrough soil-free vertical green system that mimics nature in providing a cliff on which epiphytes and selected plant species can grow onto the synthetic growing medium. After the initial growing phase, these plants will be able to merge with the media itself (about 50mm thick) to form a more organic and robust ecosystem.

Without using the usual potted system, the Gaiawall advocates a way for plants to thrive without soil.

Basically, what scientists are saying is that biophilic design, including green walls, can reduce stress, improve cognitive function and creativity, improve our well-being and expedite healing. Besides that, studies by the Tokyo Institute of Technology showed that green walls are good thermal insulators and they have been proven to lower energy loss in buildings (from mechanical cooling). They also act as a sponge in absorbing dust & heavy metal particulates from the air. In many cases, noise abatement properties of green walls allow inhabitants to cut out most of the noise from traffic. However, the foremost role living walls play in the modern urban landscape is the creation of new green spaces in our land-scarce cities.

With the rapid development of a diverse range of living green systems for building facades, it is important to weight the pros and cons of each before adopting them as none of them are designed as a “one-size-fits-all”. For those who live in Malaysia, we at Belalang Inovasi are ever-ready to assist you in that regard. In the process of making our cities greener and taking us back to nature, it is also key to bear in mind that green walls are only part of a wider strategy and we should always keep our minds open to innovation and ideas that will continue to improve our daily lives.