Green Roofs

Here is an update on some of the green roofs I was involved with last year and checking out some new ones whilst in Brazil. These are all ‘low-tech’ as in the same method I showed everyone last month on the Open Day. The roof I had a look at in Lenny Kravitz’ farm was made with a much deeper substrate – around 200mm of soil on top of a layer of both sand and gravel. This was to facilitate it’s use for not only grasses and succulents but any type of planting. Bruce who has created it had the great idea of keeping guinea pigs on top to keep the grass down. He keeps them unfenced and with little earth covered homes for protection. Only one has fallen off so far (he was fine!) and all in all they are very happy little creatures, with so much room to run around and which also produce such great fertiliser.


An intensive green roof with the added benefit of keeping guinea pigs

Close up of the houses and the happy little pigs

What is a ‘Green Roof’?

Also known as ‘living roofs’, green roofs serve several purposes for a building, such as absorbing rainwater, providing insulation, creating a habitat for wildlife, and helping to lower urban air temperatures and combat the heat island effect. There are two types of green roofs: intensive roofs, which are thicker and can support a wider variety of plants but are heavier and require more maintenance, and extensive roofs, which are covered in a light layer of vegetation and are lighter than an intensive green roof.

Here is an example of two green roofs at the bio-architecture institute of Tibá.

What are the benefits?

  • Use the roof to grow fruit, vegetables and flowers
  • Reduce heating and cooling loads on a building
  • Increase the lifespan of a roof
  • Reduce storm-water runoff
  • Filter pollutants and CO2 out of the air
  • Filter pollutants and heavy metals out of rainwater
  • Easy to retrofit your existing roof or create a new one in less then a day
  • Can be flat or inclined and combined with other types of roofs

Check out this informative paper by German earth building expert Gernot Minke on his research into the practical uses of Green Roofs.

Inclined Green Roofs – Gernot Minke

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