regulatory changes requiring buildings within a designated zone to connect to the system allow district heating and cooling projects to realise widespread energy efficiency gains cities can also improve the conditions for distributed clean energy investments by providing lowinterest loan programmes which enable property owners to install renewable energy technologies in some cases repayable through property taxes as in several united states cities or through ordinances requiring installation of renewable energies in new buildings such as barcelona s solar thermal ordinance oecd access to the longterm finance required for regional clean energy investments can for instance be considerably facilitated by tapping regional financial markets