Spanish researchers show how roof gardens can reduce pollution and energy use

Research Lead

Researchers from the Polytechnic University of Madrid (UPM) have built a roof covered with plants and a watering system that insulates the roof and reduces energy consumption by the building’s heating and cooling systems.

The roof of the building in Colmenar Viejo, Madrid, was divided into 20 modules, and different substrates and plants were tested for their insulating properties.

Plants such as sedum (Sedum praealtum) or aptenia (Aptenia cordifolia) provide the best insulation, “because they have a thick leaf and are resistant to frosts and heat”, said Francisco Javier Neila, Professor at the UPM indicated.

In terms of a substrate that helps rainwater to drain quickly so the plant does not drown, the best solution was pine bark crushed and mixed with sewage sludge.

The substrate lies onto of porous concrete, which acts as a sieve for excess water that drains into a tank. The water collected in the way rises up to the roof through capillary action, enabling even irrigation. Underneath the concrete is a waterproof sheet.

Each layer includes a sensor that measures temperature and humidity. The researchers left some of the modules unplanted to demonstrate the effectiveness of the ‘ecological roof’.

Ecological roofs reduce pollution, absorbing lead and other organic components. They also reduce noise levels.