Since 2008, citizens can apply for a green roof subsidy from the city of Rotterdam in the Netherlands to partially cover the otherwise large costs of installing such interventions. The goal of the program is to achieve a total of 800.000 square meters of multi-functional roofs with greenery, water retention systems, and solar panels by 2030. In order to be eligible for the subsidy, roofs must be able to retain 30 ml of water per square meter. In return, building owners (private individuals, home owners associations, organisations, contractors and property owners) can get up to €500 for every cubic meter of water collected through the green roof. The city also pushes the construction green roofs on top of municipal property. By increasing the total surface of roofs covered with soil and greenery, the municipality aims to enhance water retention capacities as well as heat absorption during heatwaves. Green roofs, by acting as isolators, also increase the overall durability of the underneath building, and the new green spaces offer opportunities for various uses, such as gardening and food production. The access to subsidies is conditional upon the selection of plants which include native and non-native species particularly beneficial to biodiversity.