Installing a green roof can dramatically reduce energy use and costs - as well as supporting biodiversity, reducing flooding and combating climate change. Roofs offer an opportunity for more green spaces in the heart of the city That was the message for delegates at an afternoon seminar organised by CIRIA, the Construction Industry Research and Information Association. Firms that have installed green roofs have reported a 25% reduction in energy use in the floor directly under the roofs, and reduced usage at a lower percentage in other floors.