PhD project: Risk assessment of blue-green/-grey roof solutions

Blue-green roofs are roofs wherein vegetation and water detaining substrates are combined for stormwater management as functional layers on top of the roof. In theory, this makes green roofs a subset of blue-green roofs, but in practice the terms are used synonymous for green roofs utilized for stormwater management. A blue-grey roof is roof that functions like a blue-green roof, but where the plants are replaced by permeable paves and the underlying substrate layers are made up of non-organic water detaining materials. 

The risk imposed by a blue-green roof solution will include the serviceability and service life of a building or building component, including the blue-green roof itself. There are associated economic risks as well, even if a building defect is discovered before any damages occur, as repairs would be needed. However, there are also positive risks, such as a higher building value, and a possibility of saving money if stormwater fees are instated in the future. 

The PhD study is motivated by a scoping literature review (Andenæs et al., 2018) showing that the risk aspect of green roof operation is scarcely treated in academic literature.

The objectives of Erlend Andenæs’s PhD project are to:

• Review the state of the art concerning the design and construction processes of blue-green/-grey roofing solutions currently and previously utilized on buildings in Norway and internationally.

• Determine the most important failure modes and their consequences for blue-green/-grey roofs, and how to avoid or mitigate them.

• Thoroughly assess the various building-related challenges and risks associated with green, blue-green and blue-grey roof solutions.

• Develop methodology/framework for risk assessment of roof-related issues for new builds or refurbishments.

The supervisor team is Prof. Tore Kvande (NTNU), Prof. Tone Merete Muthanna (NTNU) and Chief Scientist Berit Time (SINTEF).