Green Roofs- Sustainability And Limits

Green roofs have been quite popular for a long time and are becoming more prominent in modern ‘eco-friendly’ building design. How sustainable are green roofs exactly, and how helpful are they?

Types

Let’s start with the two types of green roofs, intensive green roofs, and extensive green roofs.

The name itself explains the differences between the two. An intensive roof has plants that require more maintenance and support. These include the ones you usually see on the fancy tall buildings with green terraces. These usually feature great plant diversity and may include more than just small plants, or even trees, which is why intensive roofs are a popular choice for parks, vegetable gardens, and podium decks. This type is less cost-effective, as compared to the extensive green roofs.

An extensive green roof requires much less maintenance and houses smaller plants. They usually have a shallow soil profile as compared to the intensive one. Extensive green roofs are ideal for large buildings and apartments, especially for flat surfaces. The choice of plants usually includes desert grasses and succulents that need less care and maintenance.

Advantages

Some (really cool) advantages of green roofs include:

Improvement in the lifespan of the roof: It is estimated to extend the life of a roof by two or three times beyond its typical lifespan.
Improvement in the drainage system: Green roof systems can help reduce stormwater runoff and improve stream water quality. It’s a great way to prevent floods, especially in cities.
Improvement in air quality: Green roofs can reduce air pollution by absorption of pollutants and gasses like carbon dioxide.
Much more aesthetically appealing than traditional roofs.
Environmental benefits: Green roofs help in improving the biodiversity of the place. They can also help moderate heat island effects.

Weston Residence - Specht Novak | Image © Jasper Lazor

Specht Novak designs residence nestled in a valley by the Saugatuck River

The Weston Residence features multiple green roofs planted with year-round, region-specific succulents providing sustainable advantages.

Disdvantages

A couple of drawbacks (as there are with anything) include:

Cost of construction: Green roofs require proper irrigation setup, drainage system, waterproofing, and often reinforcement as well, which will significantly increase the cost.
More weight loads: In addition to the systems mentioned above, before adding a green roof, one must take into account the weight of the soil, as well as the weight that might be added during rain or snowfall. This will tell the designer if the roof needs any additional structural reinforcement. Fortunately, most flat roofs can handle this additional load, but most other types will need to be given additional reinforcement.
Cost of maintenance as compared to traditional roofs: With the additional systems, soil, plants, and reinforcement, green roofs do cost more than your regular roof. Although, they prove beneficial in the long run, and despite the increased cost.

Off-Grid Guest House - ANACAPA Architecture | Image © Erin Feinblatt

Off-Grid Guest House With 360-Degree Views Of The Pacific Ocean

The residence is fully powered by a photovoltaic energy system, and includes a private well and water treatment system among other strategies

A few pointers

Considering getting a green roof? Following are the important pointers before you start.

Building code restrictions
Roof slope
Environmental effects
Drainage
Extra weight

An extra, but just as important point to consider is to make sure the installation and functioning do not require toxic or environmentally unfriendly. This includes choosing the right fertilizer, avoiding chemicals like Formaldehyde, and overuse of plastics.