Wien has a strong track record of high energy standards in social housing and corresponding high levels of subsidised housing, comprising almost 60% of all homes. Each year the city supports the construction of 5,000 to 7,000 social apartments, approximately 85% of the volume of new homes built annually (Covenant of Mayors, 2013). Since 2007 strict environmental standards and legal regulations for construction new social housing have been in place. These standards require a maximum energy consumption of 30 kWh/m²/year for heating. However, many new developments exceed this, reaching Passivhaus standard (less than 15 kWh/m²/year). As a result of these standards in 2010, 20 to 30% of the new homes built in Vienna were to Passivhaus standard (Covenant of Mayors, 2013).