Novel technology to improve green roofs

Expertise in basic plant and soil science, funded and fostered by NERC at the University of Sheffield, underpins a unique systematic approach to designing a range of growing media tailored for use on green roofs. The research has developed a novel product: a cutting-edge technological improvement that solves a neglected engineering challenge.


Due to water-management legislation for modern buildings and other planning demands, the green roof market has grown considerably in recent years. Green roof technology can aid sustainable urban drainage through the attenuation of rainwater, improve air quality and increase biodiversity in urban habitats. Building and engineering of green roof structures is now very advanced, but the composition of the substrate (a mix of materials that the plants grow in, including organic matter and minerals such as broken brick) has changed little in 40 years.


Using their soils science and plant nutrition knowledge, plant biologists Dr Gareth Phoenix and Dr Duncan Cameron of the Department of Animal and Plant Sciences investigated whether they could engineer a range of substrates that were good for plant growth, but that also had a range of nutrient-supply and water-holding capacities. They collaborated with industrial partner Boningale Ltd, an SME that supplies plants to the UK landscape industry.

The result is a new range of substrates that are tailored to provide good plant growth and water-holding capabilities under different climatic and rainfall conditions in different areas of the UK. Using regional zoning developed by the Met Office, Boningale provide the right kind of substrate depending on the climate of where it will be used. Customers can also specify whether the priority is growth, water retention and so on, resulting in a bespoke substrate.

Economic impact

It is a new market for the company. Maggie Fennell, Green Roof Project Manager at Boningale, said: “This project is exciting for Boningale because it will provide reliable, scientific answers to questions that are very important to green roof designers and clients. It will enable us to establish our reputation as a leader by guiding the industry towards green roofs with much higher environmental performance, putting the expertise at the University into the hands of practitioners.”

Dr Cameron is optimistic that improved substrates will have a big impact on the growth of green roof technology: “Green roofs that are more effective, cheaper and easier to apply lead to economic savings for business. Companies are more likely to adopt green roof technology, which in turn brings environmental benefits to cities.”

Partnership research is continuing: Boningale Ltd is co-funding a PhD at E-Futures, the University of Sheffield's Doctoral Training Centre for Interdisciplinary Energy Research. This work is expanding the key lines of research to relate to expected changes in the UK climate and could result in further refined substrate products. Dr Phoenix said: “Further research could lead to more products that will improve choice and make substrates even more targeted to the need, and with a capacity to cope with the demands of future climates.”

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