Dutch engineer aims high with latest green roof design

A Dutch engineer has created a new kind of rooftop garden that he says can store more water than existing green roofs and supply it to plants rooted in shallow beds of soil.

Joris Voeten unveiled his design on top of a former naval hospital in Amsterdam on Friday. Voeten says it also requires less power by relying on an irrigation system that uses insulation material instead of pumps.

Roofs adapted so plants can grow on them produce a cooling effect on buildings and the air immediately above them. To promote the practice, the city of Amsterdam offers subsidies.

Voeten says readings taken on a very hot day showed a temperature difference of up to 40 degrees Celsius — 72 degrees Fahrenheit — between his new roof garden and a conventional roof covered in waterproof sheeting.