green flat roofs – the way to go for tomorrow roofing

urbanscape trend: green roofs

Although pitched roofing still is de facto for new buildings, this is the case mostly because it’s cheaper. But from a usability point of view flat roofs offer much more.

In a study on flat roofs I can see many things that would suggest that these kind of roofs will be the way to go for tomorrow. The flat roof technology has improved big time over the latest years and the bad reputation it developed should be certainly cleared. Let’s see a few facts - flat roofs provide:

· Reduced energy costs in hot urban environments
· The ability to reduce storm water run‐off, reducing stress on urban sewer systems and decreasing runoff related pollution of natural waterways
· Trap rain-dissolved pollutants from air in the vegetated roof’s soil
· Dust reduction
· Air quality improvement
· Noise pollution reduction
· Extended life expectancy
· Flat roof design can be very flexible (recreational or decorative designed spaces, solar panel easier installation, etc)
· Easier to install than pitched roofs because of their flat structure
· Flat roofs are also considered low maintenance. Because there are no slopes or valleys, they are easier to clean and maintain than a pitched roof
· Green flat roofs also prevent the heat island effect by absorbing the heat and evaporating water as a way to expell it from the roof.

As the cost is concerned I don’t think flat roofs cost more or less than pitched roofs, it all depends on the design and materials used. Even if the flat roofs have less surface to cover and thus lowers the cost, the ceiling of the space below should be strengthened to be walkable so the costs are higher for this particular part. The disadvantages of flat roofs are generally derived from poor installation techniques, poor outdated materials, installers’ qualification and experience.

There are a few requirements that a flat roof must comply with: strength for snow loads, walking, etc, waterproof,  heat and UV repellent and must provide insulation for the space below.
Arguably the most exciting development in sustainable roofing is green roofing. Although new green roofing products are being developed more frequently than ever before, the structure is mostly covered by a:

· High‐performance waterproofing layer
· Root‐resistant compound (if waterproofing layer doesn’t already provide this function)
· Drainage system that draws away excess moisture
· Fine soil particle filter that prevents drain‐system clogging
· Specially engineered lightweight soil
· A surface layer of vegetation

Here’s a sketch that provides an easier to understand visual description:

, where 1- vegetal mass; 2- engineered soil; 3- fine soil particle filter; 4- drainage membrane; 5- root-resistant membrane; 6- waterproofing membrane; 7- roof structure.

As the world turns to green roofing from U.S. Food and Drug Administration building in Washington D.C., to Heinz Corporate headquarters in Pittsburgh and all over Europe ( Germany accounts 14% of green roofs from total buildings and growing a steady 10% per year  ) more and more opportunities arise. Vertical farms will have their structure based on the technology green roofs, gardens in skyscrapers will offer future citizens local organic food and green alleys and parks in between floors will offer entertainment. Lots and lots of potential. Just have a look below at some projects:

Designed by Reinier de Jong, Tuin project is an array of two storey dwellings that also accommodate a garden:

This one is Chris Jacobs’  vertical farm concept, more info you can find on his website.

“The Living Tower”, designed by SOA architects :

School of Art, Singapore, an existing one:

This green roof in LA, designed by architect Alexis Rochas provides dozens of species of vegetables for restaurant Below:

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