Green roofs – where traditional roofs are replaced with plants and a watering system – optimise the energy consumption of buildings and have other advantages, say Spanish researchers.
According to a study by Francisco Javier Neila and colleagues at the Polytechnic University of Madrid (UPM), green roofs could reduce the temperature in urban areas and noise pollution, as well as serving as excellent insulation for individual buildings.
“Roof areas with plants optimise better the heating and cooling of a building than a normal structure, regardless of how well insulated it is,” says Neila.
The roofing system studied by the researchers consists of a layer of plants such as sedum or aptenia – depending on the local conditions – planted on a special substrate that allows water to drain away (in this case bark mixed with sewage sludge), a porous concrete layer that allows water to rise up from tanks and a waterproofing sheet to prevent leaks.
Green roofs are becoming an attracting building material, say the researchers, but they remain expensive.
“The situation is being resolved [in Germany] with tax benefits, council taxes, increase in suitability for building, which means it does not cost developers so much to invest in this option,” says Neila.