Green roofs save money

Traditional Icelandic farm houses had turf roofs where flowers grew. Results from a new study indicate that this type of roof may see a comeback in urban areas in the near future. “In many cities the amount of precipitation is a serious problem, more so in other countries than Iceland. Enhancing drainage systems is difficult and expensive, and discovering new means of dealing with drainage is vital. In our research we sought to discover whether green roofs reduced the strain on drainage systems in cases of heavy rainfall”.

This is how Ágúst Elí Ágústsson describes his master’s thesis where the potential of green roofs to reduce and delay the flow of precipitation from buildings. Green roofs are defined as roofs where vegetation can grow. “Green roofs are often discussed as an element of sustainable precipitation solution, reducing surface water in built areas, for example by binding water in the soil.”

A substantial part of Ágúst‘s work went into the design and implementation of the experiment. “The green roofs needed to be designed and constructed. We collected drainage from four different types of green roofs to see how much water flowed from each roof compared to the amount of precipitation.”

The measurements took place in Iceland from January to April 2015. On average the experiments showed that 20 to 50% of the precipitation was retained on the roofs. “This shows that 20 to 50% less water would flow from a green roof than a conventional one. The results therefore indicate that green roofs can be used to reduce the amount of drainage from buildings in Iceland.” 

Ágúst chose this research subject because he feels it is interesting and important. “While studying in Gothenburg I learned a little something about sustainable precipitation solutions and so my interest in this field was sparked. When I saw the advertisement for this project I decided to jump at the chance.”  

Ágúst says that the study is important because it increases our knowledge of how green roofs can best be utilised in Iceland, but such knowledge is scant here despite the prevalence of turf roofs in the past. “The study has been well received and hopefully this option will be more positively received than it has been hitherto.”

Supervisors: Hrund Ólöf Andradóttir, Associate Professor at the Faculty of Civil and Environmental Engineering and Reynir Sævarsson, Project Manager for Drainage and Waterworks at Efla Consulting Engineers.